Issue 2 Spring 2018
INSTITUTE OF WATER JOURNAL ISSUE 2
We are pleased to present our second issue of The Institute of Water Journal The Institute of Water Journal is a peer-reviewed, technical journal with the sole aim of providing relevant and valuable learning and knowledge on the themes of science, engineering and the environment being applied in a water context, together with thought leadership, innovation and technical developments in other areas such as regulation, customer service and skills development. The Journal contains papers and case studies from authors working across these fields, including regulators, academics and their students, water company personnel and supply chain organisations, including consultants.
Authors are encouraged to consider carefully how readers may be able to readily apply what they have learned from each paper to their role in the water industry, as provision of excellent continuing professional development (CPD) opportunities is absolutely central to the ethos of the Institute of Water. Every paper has been peer-reviewed by a panel of experts from the Institute of Water, industry regulators and key academic partners: you can read more about the panel on page 60. In order for a paper to be accepted for publication in the Journal, the panel must be satisfied that it: •
Provides relevant and valuable learning for water industry professionals
•
Presents new and innovative thinking or research outputs or a different slant on an existing approach
•
Contains information and knowledge that many readers will be able to readily apply to their role as part of their Continuing Professional Development
CONTENTS 4
Innovative demand forecasting methods for more resilient water resource plans ARTESIA CONSULTING LTD
12
Mayflower Water Treatment Works; a voyage to a new world of water treatment SOUTH WEST WATER
18
The Lancashire Cryptosporidium event of 2015 - lessons learned for the water industry DWI
but not heard Obtaining evidence 24 Seen 41 how can better customer for “evidence based communications help improve water and wastewater services? OFWAT
management”: The taste and odour problem DWR CYMRU WELSH WATER, CARDIFF UNIVERSITY
Assessment of risk Flow Cytometry to 46 28 Using to water treatment improve understanding of chlorination processes in drinking water treatment SCOTTISH WATER
Reverse Auctions 36 Using to support delivery of catchment off-sets ENTRADE
from phytoplankton in reservoirs using long term data sets ATKINS, ANGLIAN WATER
we missing the big 56 Are picture on water efficiency? CCWATER
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ARTESIA CONSULTING LTD INNOVATIVE DEMAND FORECASTING METHODS FOR MORE RESILIENT WATER RESOURCE PLANS
Innovative demand forecasting methods for more resilient water resource plans Rob Lawson Director, Artesia Consulting Ltd
Abstract How we use water depends on how people use a range of fixtures and appliances each day, subject to factors as diverse as social norms, affluence, culture, religion, lifestyle, values, plumbing, the weather, the price of water, and the age and number of occupants (Artesia 2017). This paper focuses on the methods used to predict household consumption - that is how much we use as individuals or households - over the next 25 to 50 years. In particular the paper presents the established approach to micro-component forecasting, based on estimating the ownership, frequency of use and volume per use of water using devices in the home. This is compared with an improved approach that has been developed and applied for the current round of draft Water Resources Management Plans, which builds on micro-component models and includes the relationships
between micro-component consumption and household occupancy, based recent empirical research, to estimate future water demand. The pros and cons of the two methods are presented and discussed and recommendations are made for future data collection and for consumption forecasting in general.
Introduction
religion, lifestyle, values, plumbing, the weather, price of water, and the age and number of occupants (Artesia 2017).
Water companies in England or Wales are legally required to supply water to people and businesses within their areas, as set out in Section 37A-37D of the Water Industry Act 1991. Each company’s strategy to meet this obligation is set out in their water resources management plans (WRMPs) which describe how they intend to maintain the balance between water supply and demand. These plans take a long term view, covering at least 25 years, with some extending as far as the end of this century. The next set of final WRMPs will be published in early 2019 and companies have already completed extensive work to update their supply and demand forecasts.
These factors have driven major change in household water use – such as the increased frequency of personal washing, from infrequent (e.g. weekly) baths to daily showers over the last thirty years or so. Understanding these long-term changes in water use is essential if companies are going to meet their obligations and ensure the resilience of future water resources systems.
However, forecasting in general is a challenging endeavour (for example, Tetlock and Gardner (2015)), and this is particularly true of household consumption forecasting. How we use water depends on how people use a range of fixtures and appliances each day, subject to factors as diverse as social norms, affluence, culture,
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Key words: Household consumption, demand, micro-components, occupancy. "If you can look into the seeds of time, and say which grain will grow and which will not, speak then unto me." Macbeth, Act 1, Scene 3.
This paper focuses on the methods used to predict household consumption – that is how much we use as individuals or households. It describes the methods used by UK water companies over the past 15 years and summarises some of the new methods that have been developed and applied in preparation for the next round of WRMPs in 2019. Alternative methods are also presented and discussed. The paper concludes with recommendations for further work and a call for a greater focus on understanding demand.
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Methods used in the past
For example, where per-capita consumption (PCC) is defined (e.g. UKWIR 1997) as:
Prior to 1995 a ‘predict and provide’ approach was taken towards water resource planning and efforts generally focussed on supplyside options (Parker & Wilby, 2013). Shortly after that Herrington (1996) produced what is generally regarded as a seminal study of household demand. This report was one of the first widely read pieces on the micro-component forecasting method and provided the basis for the method which has been used almost universally by UK water companies over the past 15 years.
PCC = ∑i(Oi x Vi x Fi) + pcr
Herrington states that “A detailed picture of past, present and future domestic use may be constructed with the aid of knowledge and assumptions concerning ownership of appliances, frequency of use of appliances or habits, volumes of water used and household occupancy rates”, and indicates that “this sort of exercise make[s] for more rational and more thoughtful demand forecasting”. Later (p33) Herrington (1996) states that the forecasts derived are based on “copious helpings of judgement”, informed by numerous literature sources, which are laid out in transparent detail.
The above equation enables PCC to be forecast (a similar equation can be used to model per household consumption – PHC). By applying this together with the population (or property) data, a water demand forecast is formed. The forecast changes in each of the variables needs to be defined, which means that microcomponent models based exclusively on the ‘OVF’ variables requires practitioners to assign values for O, F and V for each microcomponent (and often sub-micro-component) for each year of the forecast. Most micro-component models produced for the 2014 WRMPs related these changes in numerous variables to reflect future changes in technology, policy, regulation, and behaviour. In general no relationship with occupancy was identified, and the differences between metered and unmetered micro-component consumption was estimated.
Micro-component models quantify the water used for specific activities (e.g. showering, bathing, toilet flushing, dishwashing, garden watering, etc.) by combining values for ownership, volume per use and frequency of use.
Where ‘O’ is the proportion of household customers using the appliance or activity for micro-component ‘i’ ‘V’ is the volume per use for ‘i’ ‘F’ is the frequency per use for ‘i’ pcr is per capita residual demand
A typical OFV-based forecast, created for the WRMP14 of an anonymous water company in England, is presented in Table 1. Table 1 - Variations in OFV for example micro-component forecast from WRMP14 Micro-component
Sub-component?
Ownership
Volume/use
Frequency/use
Toilets
Yes, by six flush volumes
Varies over time, by flush volume and meter status
Varies by flush volume but not over time or by meter status
Fixed
Bathing
Yes, by four shower types and bath
Varies over time, by shower type or bath and meter status
Varies over time by shower type or bath but not by meter status
Varies over time by shower type or bath
Washing machines
No
Varies over time and by meter status
Varies over time
Varies over time by meter status
Dishwashing
Dishwasher and hand-washing
Varies over time and by meter status
Varies over time
Varies over time and by meter status for dishwashers only
Taps (not dishwashing)
No
Assumed 100%
Varies over time and by meter Not analysed status
External use
No
Fixed
Fixed over time but varies by meter status
Note: This is a real example but is anonymised to represent typical level of complexity in OFV micro-component forecasts. In this example, initial ownership values are based on recent regional survey data. The forecast variations in micro-component variables are mainly taken from the Market Transformation
Fixed
Programme (Defra 2011). Differences between micro-component consumption in metered and unmetered households is estimated and assumed to be driven by either ownership of more efficient toilets and showers and frequency of use for washing machines or dishwashers.
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ARTESIA CONSULTING LTD INNOVATIVE DEMAND FORECASTING METHODS FOR MORE RESILIENT WATER RESOURCE PLANS
This methodology has been used by most water companies in their plans over the last 15 years, mainly because this method was mandated by the Environment Agency for water resources planning until the last round of plans, published in WRMP14 (Environment Agency et al, 2012). This approach was reviewed by UK Water Industry Research in preparation for the current (WRMP19) round of plans (UKWIR, 2015). Interviews with practitioners were conducted in this study, which highlighted the perceived strengths and weaknesses of the micro-component methodology. Table 2 includes some relevant quotes from this research. Table 2 - Practitioner views on micro-component forecasting Comments against micro-components “Main challenge was lack of data.” “M/comp was too data intensive for our needs” “M/comp involves too much judgement” “Main challenge was the lack of data to inform forecasts” “Lot[s] of judgement needed” “Key challenges in m/comp modelling was data” “The main challenges were associated with data” “M/comp is reasonable if data is there”
The project indicated that whilst the OFV micro-component method is transparent and clear, and also logical; there was a lack of empirical data on to estimate current rates of appliance ownership, their frequency of use and the volumes of water used. The UKWIR work also highlighted the reliance on Market Transformation Programme (MTP) forecasts of future micro-component use (Defra, 2011). These forecasts were last updated in 2011 and rely on older estimates of the ‘stock’ of products in use and other key variables such as current and forecast housing numbers. Therefore the OFV micro-component method was not always underpinned by valid (empirical) data, and did not necessarily treat the factors that explain household consumption in an explicit way.
An opportunity for another approach The UKWIR project on household consumption methods for WRMP19 reviewed a range of forecasting techniques from the use of existing data to regression modelling and micro-simulation (UKWIR 2015). The review included the current micro-component methodology and emphasised that the ‘OVF’ approach (as illustrated in Table 1) is not an intrinsic or essential part of micro-component modelling. The guidance suggested alternative methods including rates of change or statistical models based on factors that influence consumption, as well as expert judgement.
“Very data intensive” “Much of the base data for m/comps is now old” Comments in favour of micro-components “There is nothing underpinning [trend-based forecasts] – which is where the comfort blanket of m/comps comes in.” “Nothing fundamentally wrong with m/comps. Would be better if there was some flexibility on its application.” “Whatever is used needs to provide clarity – m/comps does this.” “M/comps advantages are that it takes account of behavioural and technological changes and enables flexibility in judgement choice of assumptions.” “M/comps is good at evaluating change going forward. For comparing between now and the future it is as good as any method.” “[We] expect to stick with m/comps in higher risk WRZs as unlikely that anything better will be available.”
This research updated the criteria for the review and selection of household consumption forecasting methods. Of relevance to this paper were the criteria that forecasts should be:
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•
Underpinned by valid data;
•
Empirical validation;
•
E xplicit treatment of factors that explain household consumption;
•
Transparency and clarity; and
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Logical and theoretical approach
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An improved approach to micro-component forecasting has been developed based on this guidance, and has been applied successfully to several water company household forecasts. The following section summarises this method and highlights its pros and cons compared to the more familiar and widely used OVF approach (in the UK at least).
The improved micro-component forecast The preceding section highlighted the importance of data in microcomponent forecasting. Data collected over time will allow trends to be investigated and forecast. Data will also allow relationships between micro-component consumption (e.g. toilet flushing or shower volumes) and other variables (e.g. property type, occupancy) to be explored and analysed. A recent UKWIR project into customer behaviour and water use collected empirical micro-component water use data from a sample of 62 metered properties in England and Wales (UKWIR 2016). Occupancy and demographic data for these properties were also collected via survey. Artesia Consulting also has a database of micro-component data collated from households not billed on a meter from other anonymous studies (without associated property of demographic data).
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One of the only other published datasets of micro-component data is from a study from 2002-2004 (WRc 2005). This study and the UKWIR (2016) study provide two historic data points for microcomponents. The revised approach to micro-component forecasting used these two main sources of data in two ways, to reflect how household consumption is affected by a combination of the household composition and the water using devices in the home: •
The first part explored and developed relationships between micro-component consumption and household occupancy.
•
The second part used the two historic data points and the MTP
forecasts (which remain the only reliable and comprehensive source of micro-component forecasts) to produce consumption trends to reflect the effect of technology, behaviour, policy and regulation. This method also enables practitioners to include company-specific water use data in their analysis where available. The first part was based on the observation from empirical evidence that the consumption associated with certain micro-components had a relationship with household occupancy, as illustrated in Figure 1.
Figure 1 - Each micro-component daily use plotted against occupancy
Each of the micro-components were investigated to determine whether the daily volume per use, frequency of use or ownership varied significantly with occupancy. The following microcomponents showed relationships where occupancy was a significant factor: •
WC flushing;
•
Shower use;
•
Bath use;
•
Tap use; and
•
Washing machine use.
For each of these micro-components (WC, Shower, Bath, WM and Taps) a linear model was developed using occupancy as the predictive factor. Figure 2 shows the variation of WC flushing frequency per day with occupancy, with the frequency of use per day plotted against occupancy. The model is a log relationship of frequency of use against occupancy with the following equation: Frequency of use (uses/day) = 6.143 + 3.744 * ln (occupancy) Equation 1
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ARTESIA CONSULTING LTD INNOVATIVE DEMAND FORECASTING METHODS FOR MORE RESILIENT WATER RESOURCE PLANS
Figure 2 - Variation of WC flushing frequency (uses per day) with occupancy
Relationships for the other four micro-components influenced by occupancy were also identified. By deriving these relationships, it was possible to use forecast changes in occupancy (which also varies depending on household metering status) to predict the rate of change in this first part of micro-component consumption. The model can then be used with ownership and frequency estimates to calculate the microcomponent daily use (and hence the per household consumption ‘PHC’) for the starting year of the forecast for the following property segments. This is based on the occupancy assigned to each property type, in the base year through to the final year of the forecast: •
Unmeasured households;
•
Existing measured households;
•
Optant measured households; and
•
New build measured households.
Figure 3 - Histogram of WC flush volumes from 2002/04 and 2015/1
The latest MTP projections for WC flushing volumes in 2030 for the reference scenario is 4.8 litres/flush (Defra 2011). Figure 4 shows the mean 2002/04 (WRc 2005), the 2015/16 flush volumes and the flush volume from the MTP scenarios in 2030. The blue line shows the linear fit from the 2002/04, 2015/16 and MTP Reference scenarios. If we assume that the market transformation continues at the current rate (a reasonable assumption for baseline forecasts, as there are no planned regulatory changes in WC flush volumes), then the flush volume in 2028 will be approximately 5.1 litres (shown by the intersect of the grey lines in Figure 4). This provides some confidence in the MTP Reference scenario for WC flush volumes. Figure 4 - Historic, current and future flush volumes
Consumption for the smaller micro-components (which are not statistically related to occupancy) are assumed not to vary with occupancy. The second part of the updated forecasting approach was to assess trends in micro-components to account for developments in water-using device technology, policy and behavioural factors using a combination of historic micro-component data and future projections from the Market Transformation Programme. Using historic data (WRc 2005, UKWIR 2016) it is possible to create a histogram of the volumes per flush from 2002/04 and 2015/16. These are shown in Figure 3. This shows that for 2002/04 the mean flush volume was 9.4 l/flush, with a range of flush volumes from 5 litres to > 15 litres. In 2015/16 the mean flush volume had reduced to around 7.3 litres with a range from 3 litres to about 13 litres per flush. The reason for the reduction in flush volumes from 2002/04 to 2015/16 is due to the replacement of larger volume WC cisterns with smaller volume cisterns, due to the introduction of a six litre maximum flush volume in the water regulations in 1999 (HMSO 1999).
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Trends for toilet volume per flush have been created (see Figure 5) using: •
The base year volumes per flush in Table 5 for different property types;
•
The 2030 projection for WC flush volume from the MTP reference scenario;
•
An assumption that all property types will have achieved the MTP Reference scenario between the forecast base year and 2030 (for the baseline forecast assuming no change to current WC flush regulations)1; and
•
An assumption that the volume per use will then remain relatively constant until 2045.
We also assume that ownership and frequency of use for WC flushing remains constant.
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Figure 5 - Trends for WC flush volumes
From these trends, annual rates of change (as a percent of the previous year’s consumption) have been produced for each of the property types. These are then added to the occupancy component forecast.
Pros and cons of the OFV and improved micro-component approaches Table 3 presents the pros and cons of the OFV and the improved micro-component approach. Table 3 - Pros and cons of OFV and improved micro-component approaches OFV Method
Improved approach
Pros
Cons
Pros
Cons
Explicit consideration of individual m/comps
Requires lots of inter-related assumptions to be made.
Key link with a principal explanatory variable (i.e. occupancy).
Still relies on MTP data or other assumptions for future trends.
Logical
No clear link with changes in occupancy or other factors affecting household consumption.
Can be easily updated using new base year data.
Transparent
Forecasts rely mainly on MTP.
Uses empirical micro-component data to validate trends in behaviour, technology and policy/regulation.
No clear factors influencing differences in consumption between meter segments.
Updated population, property and occupancy forecasts (by meter segment) can also be incorporated readily.
Table 3 indicates that the improved method presented in this paper provides a more statistically robust approach to micro-component forecasting and can be updated more readily that the OFV approach. This presents an opportunity for water companies to update their household demand forecasts more frequently and to produce future WRMP forecasts much more readily than possible in the past. It is worth noting that although the OFV method has been widely used to forecast household demand by water companies over the past 15 years, there has been very little analysis of the accuracy of these forecasts, compared to what actually happened. Such analysis would be useful to understand the accuracy, and therefore the value of both previous OFV forecasts and the forecasts made for this round
of plans using the improved method.
Summary This paper has described how the micro-component approach to household consumption forecasting was developed in the UK, mainly through the analysis of ownership, frequency of use and volume per use of specific water using devices in the home. This is known as the ‘OFV’ approach. The paper has also presented an improvement to the OFV approach, based mainly on recent empirical data that illustrated statistically significant links between occupancy and micro-component consumption for several domestic water uses.
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ARTESIA CONSULTING LTD INNOVATIVE DEMAND FORECASTING METHODS FOR MORE RESILIENT WATER RESOURCE PLANS
The main differences between the two methods are: •
•
The OFV method assigns values of ownership, volume per use and frequency of use for each micro-component each year (or every five years). Assumptions are made on the effect of metering on either ownership of more efficient fittings or the frequency of use of devices. Generally there is no relationship with occupancy. The improved approach establishes consumption using a OFVbased model at the start of the forecast, but then predicts the change of key micro-components based on an occupancy model (which varies by meter segment), and then applies an annual rate of change to each micro-component based on the analysis of historical data and future predictions.
The advantage of the improved approach is that once the occupancy relationships and other trends are established, the models become much simpler to implement. There is less scope for human error and the models can be readily coded into modelling packages such as R, and can be refreshed on an annual or more frequent basis. This in turn makes the forecast ‘live’ and useful between WRMPs. Both the original OFV and improved forecasting methods rely on good data to establish estimates of micro-component consumption at the start of the forecast (i.e. the ‘base year’ in water resources planning terms). National data collected in 2015/16 (UKWIR 2016) have provided a useful but relatively small sample for analysis. Company-specific data will also improve the calibration of the model to reported consumption values. Both methods also rely on good forecasts of future trends in consumption driven by policy and regulation. The need for improved data and forecasts for forecasting are considered further in the following section.
Discussion and recommendations The improved approach links micro-component consumption forecasts to household occupancy. This relationship is based (initially at least) on national data from a relatively small sample of properties. Increasing the sample of properties at a national level will provide increased confidence in the consumption-occupancy models, and may enable statistically significant relationships between occupancy and the remaining micro-components (i.e. those shown not to have a significant relationship with occupancy) to be identified. In the absence of local data there can be a difference between modelled and reported consumption in the base year. This is most likely due to differences in occupancy-consumption relationships in the national sample and the relationship for a given water resources zone. This could be due to the make-up of a particular zone compared to the national sample (e.g. more/less urban, different demographics, etc.). In companies with multiple WRZs it is possible to statistically test the modelled consumption against reported values and this has given a very good level of confidence that the model is working well. Nevertheless, local micro-component data
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will help to validate data from national studies. The consumption forecasts in the Market Transformation Programme have underpinned OFV micro-component forecasts and remain an important part of the improved method. However these forecasts have not been updated since 2011 and only extend to 2030. Although recent empirical data (UKWIR 2016) has demonstrated that the MTP forecasts to be relatively accurate to date, updates will be required in the next few years to extend the forecasts out to 2050 at least, and to update the estimates of current stock levels and consumption rates. Updates should also reflect the potential impact of Brexit on policy and regulation as well as economic prospects. Based on these points, and others from elsewhere in this paper, the following recommendations are made: Recommendation 1: The accuracy of household consumption forecasts made using the OFV and improved methods in WRMP19 should be tested by comparison with actual demand in the next few years. Such comparisons will provide insights into the modelling process and allow future models to be improved. Should the improved method, which has been shown to have several advantages over the OVF approach prove to be sufficiently accurate, then this approach could be used as a new standard micro-component methodology. Recommendation 2: In any case the accuracy of either method depends on good data. Therefore it is recommended that a larger national study to improve the national data set on microcomponents be carried out and then repeated every five years. This study should aim to collect micro-component consumption from a representative sample of properties, with a sample size to provide robust results for occupancy-based modelling. The monitoring method used in recent empirical studies (i.e. UKWIR 2016) would be appropriate. The monitoring should be accompanied by surveys to (primarily) establish occupancy. This study should be repeated regularly in order to develop a time-series of microcomponent consumption. Recommendation 3: In order to improve regional estimates of household demand, individual water companies should aim to collect representative and statistically robust micro-component and occupancy data from households in their region. This could be augmented by the national studies described in Recommendation 2. Recommendation 4: A national study should be completed to update the current Market Transformation Programme projections for household water using devices. These updated forecasts should be based on more recent data on appliance ownership and reflect current economic conditions and forecasts, for example for rates of new home completions and home refurbishment rates. The forecasts should consider likely future regulatory scenarios for water use in the home.
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Recommendation 5: New research, as outlined in recommendations 2-4 should be completed well before the next round of draft WRMPs start being prepared, in 2021-2, so that results can be readily included in future plans. References 1.
This is a reasonable assumption given the rate of change in actual data presented in Figure 4.
Bibliography Artesia (2017) Planning for the future: a review of our understanding of household consumption. Ref AR1170. October 2017. Unpublished report to Water UK Defra (2011) accessed via http://efficient-products.ghkint.eu/cms/product-strategies/subsector/ domestic-water-using-products.html#viewlist on 22/11/17
Environment Agency, Ofwat, Defra & Welsh Government (2012) Water resources planning guideline. The technical methods and instructions. October 2012. Developed by Environment Agency, Ofwat, Defra and the Welsh Government. Ref: GEHO0612BWPE-E-E Herrington, P. (1996) Climate Change and the Demand for Water. HMSO, London. HMSO (1999) The Water Supply (Water Fittings) Regulations 1999. Schedule 2, para 25(c). Accessed via: https://www.legislation.gov.uk/uksi/1999/1148/schedule/2/made on 29/11/17. Parker, J.M. & Wilby, R.L.W (2013) Quantifying Household Water Demand: A Review of Theory and Practice in the UK. Water Resources Management (2013) 27:981–1011. DOI 10.1007/s11269-0120190-2 UKWIR (2015) WRMP19 Methods – Household Consumption Forecasting Supporting Guidance. Report Ref. No. 15/WR/02/9 WRc (2005) Increasing the Value of Domestic Water use Data for Demand Management, WRc, March 2005 UKWIR (2016) Integration of behavioural change into demand forecasting and water efficiency practices, UKWIR 16/WR/01/15
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SOUTH WEST WATER MAYFLOWER WATER TREATMENT WORKS; A VOYAGE TO A NEW WORLD OF WATER TREATMENT
Mayflower Water Treatment Works; a voyage to a new world of water treatment D.Metcalfe & C.Rockey South West Water, Exeter
Abstract South West Water (SWW) is in the process of developing a new water treatment works (Mayflower WTWs) which will use novel pretreatment technologies. The novel processes were tested extensively during long term pilot trials to establish the technical feasibility of the process and to optimise its operation. These trials showed that the removal of high molecular weight organic compounds was essential to good operation and efficiency of the ceramic membranes. In terms of water quality the combination of suspended ion exchange (SIX) and inline coagulation (ILCA) pretreatment could significantly enhance the removal of organic compounds and disinfection by product precursors relative to conventional water treatment works (WTWs) processes. The enhanced removal of dissolved organic carbon (DOC) in the first stage of pre-treatment improves the efficiency of downstream processes and disinfection. The pilot findings were used to optimise the full scale design, build and commissioning phases of Mayflower WTWs.
Highlights •
SWW needed to replace the existing Crownhill WTWs with a new facility
•
Novel pre-treatment using SIX® and CeraMac® was tested at bench and pilot scale
•
Large organic compounds caused significant membrane fouling with SIX alone
•
SIX with inline coagulation (ILCA) was required to optimise membrane operation
•
SIX/ILCA significantly reduced DOC and DBP concentrations including brominated DBPs
•
Pilot data was used to inform and enhance the full scale design
Key words: Ceramic membranes, Suspended ion exchange, Inline coagulation, Organic compound characterisation, DBPs, Innovation
Introduction - Drivers for investment in water quality and supply South West Water had a long term strategic goal to replace Crownhill WTWs, which supplies the city of Plymouth and the surrounding area. The existing site was built in the 1950s and uses conventional treatment (coagulation, sludge blanket clarification, rapid gravity filtration and super chlorination disinfection) to treat three water sources; an upland reservoir and two direct river abstractions which are typically used during the summer.
compounds geosmin and 2-methoisoborneol led to a requirement to install a granular activated carbon (GAC) plant. Delivering this additional treatment at the existing site would have been extremely challenging and inefficient •
Increasing DOC concentration and variability in the raw waters (as observed across much of northern Europe) led to a desire to future-proof the process to ensure robust removal of organic compounds/disinfection by product (DBP) precursors at all times
•
The South West of England is an intensively farmed region containing around a third of the cattle in the U.K, which leads to an elevated Cryptosporidium risk. In light of this, changing regulation, and a number of recent national events, a robust process for Cryptosporidium removal was required
•
An alternative more strategic location on the edge of Dartmoor was available and plans to develop a new facility had been part of a long term strategic goal for the organisation since privatisation
The existing site / process had a number of issues including: •
The site was constrained due to urban creep which resulted in potential security issues, limitations upon the chemicals that could be used and limited space for any process improvements
•
Pesticide detections and the presence of the taste and odour
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SWW had a number of key goals for a process upgrade; enable a move to a strategically more preferable site, provide enhanced DOC and DBP control, provide an absolute barrier to Cryptosporidium within a compact, robust and automatable modern treatment process whilst keeping consumers bills down in the long term. The SIX® (suspended ion exchange) CeraMac® (ceramic microfiltration) process developed by PWN Technologies (Netherlands) was identified as potentially meeting these needs. This process could completely remove the need for front end coagulation and pH control and provide an absolute barrier to Cryptosporidium, potentially providing a simple but robust process (waste, process control etc.). One of the key differentiators of the SIX process, from other suspended ion exchange (e.g. MIEX®) processes, is that it utilises “single pass” regeneration; where all of the resin is regenerated following a defined contact time with the water (e.g. 30 minutes). This provides more stable / higher adsorption kinetics and reduced potential for resin biofouling in comparison with processes where only a small portion of the resin is regenerated at a time (Galjaard et al. 2009). Although a larger volume of brine is produced the overall efficiency of the approach was expected to be higher. Ceramic membranes have been used in industry for many years and in the last 20 years they have been used within municipal water treatment applications. They offer some key benefits over polymeric membranes including; longer lifetime (>20 years), no integrity failure, physical and chemical resistance, operation at significantly higher flux, lower propensity for organic fouling etc. (Lee & Kim, 2014). Whilst their application outside of Japan (in water treatment) has been limited until the last few years, there has been a significant increase in ceramic membrane research over the last couple of decades and several full scale plants using ceramic membranes are in the process of coming online. The CeraMac process (PWN Technologies) uses vessels containing multiple ceramic microfiltration membrane elements, which operate by dead end filtration. Figure 1 - Number of peer reviewed publications per year using the search terms "Ceramic Membranes" and "Water Treatment" for the period 1991 - 2017 (Scopus)
Initial bench scale testing Following the identification of the SIX CeraMac process, initial bench scale testing was performed to establish the efficacy of anion exchange resins for the removal of the dissolved organic compounds present in the SWW raw water. These tests involved stirring known quantities of resin with raw water for set contact times (jar tests), to replicate the SIX process. These tests showed that the organics in the upland reservoir source were amenable to ion exchange as 65-70% of the DOC could be removed even when raw water DOC concentrations were very low (1.75mg/l). This performance was encouraging being that it outperformed what was possible with coagulation, which typically has a DOC removal efficiency of less than 60% for the reservoir water (Metcalfe et al. 2015). Further jar tests suggested that relatively low resin doses could yield good DOC removal (Figure 2) however; higher doses would potentially be required during periods of poorer raw water quality. Figure 2 - Resin jar tests at various resin concentrations and contact times. UVT was used as a surrogate parameter for DOC with previous tests establishing a linear relationship (UVT (%) x -0.1107 + 11.251 = DOC (mg/l))
A model was developed from the jar test data to determine the required resin dose and contact time to reach a given target UVT. This model suggested that for the Burrator source ~10g/l resin for 20 minutes contact time would effectively remove DOC to around 1mg/l. The tests were encouraging and an important step on gaining support for progressing with an innovative solution for the replacement of Crownhill WTWs, but the data was known to have significant limitations such as; virgin resin has higher activity than used resin (Walker & Boyer, 2011), jar tests do not accurately reflect full scale conditions and desorption kinetics and long term resin performance effects could not be evaluated.
Why perform a long term pilot scale evaluation? The ultimate investment in a new treatment facility needed to be comprehensively assured. The SIX CeraMac process was very novel with only one other pilot scale process operational at the time the
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research commenced. Subsequently, one full scale SIX CeraMac plant has been built at Andijk, Netherlands. A long term pilot scale trial was therefore essential to monitor and optimise the performance of the different treatment processes over an extended period (two years).
separator efficacy and associated resin loss rates etc. Importantly, this testing would provide SWW with hands on experience of operating the process and give the opportunity for accidental and intentional hazard and operability studies (HAZOP) to assess potential failure and recovery modes.
This would also allow for the collection of a large water quality and operational data set, capturing the variable raw water conditions for the 3 water sources. A containerised pilot plant which was capable of 150m3/day was used for testing (Figures 3 and 4).
Figure 3 - SIX / CeraMac Pilot Plant at Crownhill WTWs
It was important to establish the long term performance of the resin, the dose rate and contact time requirements, the resin loss rate and the optimised regeneration conditions. The jar test data previously collected provided information about the quantity of resin required to achieve a certain treated water DOC, but it was not possible to know the effect of the residual DOC upon the membrane operation without pilot testing. Membrane processes require piloting to establish the optimal membrane cleaning regimes, the sustainable flux rate (surface loading rate), irreversible fouling rates and subsequent frequency of clean in place (deep clean) etc. This data could assist any subsequent full scale design by establishing the optimal number of membranes, the sizing of dosing pumps, tanks etc. Long term operational data would also allow SWW to fully understand the performance of the membranes under different conditions (e.g. during river spate conditions).
Figure 4 - Process flow diagram for the SIX CeraMac plant (prior to modifications to include inline coagulation)
Further to this, piloting a large scale continuously flowing system would allow other aspects of the process to be tested and improved, for example, optimising air distribution for the SIX process (where the resin is mixed with the water using air), testing the lamella
Impact of residual doc on membrane performance One of the initial drivers of piloting SIX CeraMac was to get away from coagulation and front end pH correction systems. SIX potentially offered a very simple, single dose for the removal of DOC and contaminants. Therefore, the initial pilot testing focussed upon the use of SIX (primarily for the removal of DOC to reduce membrane fouling and DBP formation) as the only pretreatment, followed by CeraMac. Initial SIX tests gave promising results with DOC removal broadly in line with what was expected and similar or better than that which could be achieved with coagulation for the reservoir source water (typically lower than 60% DOC removal, Metcalfe et al. 2015). Membrane fouling rates during these early tests were higher than anticipated which would lead to an increased frequency for
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membrane cleaning and uneconomic operation. It was expected that further optimisation would yield improved results on the reservoir water, however, when the raw water was of poor quality, membrane fouling rates became unsustainable when operating at the relatively high flux rates (>100l/m2/h). Research was performed to establish the compounds which were responsible for this fouling in an effort to provide insights which would better allow SWW to optimise the process. Liquid Chromatography – Organic Carbon Detection (LC-OCD) analysis in combination with other analyses revealed that the majority of the fouling was caused by organic compounds. LC-OCD is a specialist organic characterisation technique which separates organics by their apparent molecular weight and measures the organic carbon, UV absorption and organic nitrogen concentration of each fraction (Huber et al. 2011). Several findings came out of this analysis / research as reported by Metcalfe et al. (2016):
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•
SIX was very effective for the removal of low to mid molecular weight (MW) organic compounds, however, the removal of high MW (HMW) compounds was very limited (Figure 5)
•
The residual HMW compounds were adsorbed by the membrane during filtration
•
As the concentration of HMW organic compounds increased in the raw water, more DOC was adsorbed to the membrane. Membrane fouling became unsustainable during periods of elevated HMW organic compound concentrations due to increased adsorption to the membrane
Coagulation preferentially removes HMW organic compounds (Figure 5) and is therefore complimentary to SIX. Tests were conducted using coagulation pretreatment alone and this showed that the LMW organics not removed by coagulation were not adsorbed to the membrane and the membrane fouling rates were much lower than those obtained using SIX pretreatment (Metcalfe et al. 2016). Therefore, optimised coagulation / flocculation of the HMW organic compounds provided a means to minimise membrane fouling. Initial trials using SIX combined with a coagulant pretreatment yielded very low membrane fouling rates and significantly enhanced DOC removal relative to using SIX or coagulation pretreatment alone (Figure 5). As SIX removes the majority of the DOC present in the raw water, only a small coagulant dose was required to coagulate the remaining organic compounds (primarily HMW compounds). This appeared to be a promising process, however, utilising a full coagulation / clarification process would have conflicted with a number of the goals for the project especially in terms of footprint, rapidity of the process, sludge formation, cost etc. Figure 5 - LC-OCD chromatograph - organic carbon detection traces for different pretreatment processes
SIX pretreatment followed by inline coagulation with a reduced dose of coagulant were performed. The results were promising and subsequent long term pilot trials showed that membrane fouling could be controlled, even whilst operating the membranes at high flux on poor quality direct river abstractions. Following SIX pretreatment, adding a small amount of coagulant for a short contact time was sufficient to flocculate the HMW organics, preventing them from interacting strongly with the membrane and enabling their removal during routine membrane cleaning.
Enhanced removal of doc and impact on disinfection by product formation As a by product of the need for coagulation (to control membrane fouling) in combination with SIX, significantly enhanced DOC removal was achieved. This is because these processes preferentially remove opposite organic fractions, when they are combined very high organic removal rates could be achieved (Figure 5) which subsequently lead to significantly lower formation of trihalomethane (THM) and haloacetic acid (HAA) DBPs. Whilst THM and HAA were measured, the overall reduction in DOC, dissolved organic nitrogen and reduced chlorine demand is expected to reduce a wide range of other unregulated DBPs. During this pilot work it was shown that DOC and DBP reductions of 50-62% could be achieved relative to the existing conventional process, as described by Metcalfe et al. (2015). These findings are corroborated by previous studies (Humbert et al. 2007) who have studied the application of combined ion exchange and coagulation for the removal of organic compounds. In addition to a greater removal of DOC leading to reduced DBPs, the anion exchange resin used in the SIX process also removes some bromide, which helps to reduce the formation of brominated DBPs; DBPs which are considered more toxic than their chlorinated analogues. The additional removal of DOC that was possible with this process is also expected to lead to more efficient operation of downstream processes (such as granular activated carbon adsorption, disinfection etc.) as well as reducing chlorine demand and re-growth within the distribution network.
Full scale design considerations
Previous research with ceramic membranes had used inline coagulation successfully (Meyn et al. 2012). Inline coagulation is a very compact process where the coagulant and alkali / acid is injected and mixed for a short contact time before all of the floc is loaded onto and removed at the membrane surface. Trials using
During piloting a moderate / high resin dose was typically applied however, it became apparent that lowering the maximum resin dose (at maximum flow) could yield significant savings in TOTEX (total expenditure; the sum of capital and ongoing operational expenditure). This provides an example of how the experience gained through the pilot work helped SWW to optimise the
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design of the plant. In this case experience indicated that using coagulation and SIX in combination gave two dose variables which could be optimised to meet the required treated water quality. Pilot analyses indicated that a better balance between resin and coagulant dose would be to use a lower maximum resin dose and a consequently slightly higher coagulant dose.
helped to get everyone engaged with the process by allowing Treatment Technicians and Scientists to gain hands on experience of running the plant.
Further pilot tests were performed to check that the higher coagulant doses would not have a detrimental effect on membrane fouling. The ceramic membranes are known for having a very high solids loading capacity and this was confirmed by challenging the membrane by running with no SIX, a high coagulant dose and long filtration runs during river spate (poor quality) conditions. The membranes performed well during these periods with no significant increase in fouling rate, suggesting that the increased solids loading which would occur due to reducing the SIX dose was not a problem for membrane operation. This allows flexibility to optimise the resin dose as required to achieve the required target treated water quality e.g. using a low resin dose during period of good raw water quality, increasing the dose as the source water quality declines.
Figure 6 - Mayflower WTWs under construction
All of the data from the pilot work was reviewed and challenged by the design team to assist in the initial design; number of membranes, sizing of tanks, dosing pumps, control philosophy etc. As design progressed and logistical or economic design challenges presented themselves, the experience gained through long term piloting assisted SWW in making informed decisions about the best course of action. Where necessary further pilot scale tests could be performed to establish the best solutions.
Conclusion The pilot plant assisted in gathering key data for design, it also helped to dispel myths about the new treatment process and provide an opportunity to engage fully with operational staff. Concerns about how the process would perform with our raw waters, during river spate conditions or cold water conditions were broken down by deliberately challenging the process and seeing the operation during such conditions. Furthermore, the pilot facility
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Mayflower WTWs is currently under construction / commissioning and will be operational during 2018 (Figure 6).
Acknowledgments This research has been carried out within the Interreg 2 Seas project DOC2C’s. The DOC2C’s project is a joint European collaboration with project partners from the water industry and universities in the 2 Seas Area to research and to exchange the results on Dissolved Organic Carbon (DOC) removal. The DOC2C’s consortium consists of PWN Technologies R&D (NL), South West Water (UK), De Watergroep (BE), Lille University (FR) and Delft University of Technology (NL). The authors would also like to thank PWN Technologies, Cranfield University, SWW operational staff and H5O designers for their support during pilot work and design (particularly Milo Mackin, James Rushforth, Mark Wood, and Alastair Steven) and the forward thinking Board at SWW for supporting the pilot trials. References Galjaard G, P.C. Kamp, E. Koreman. (2009). SIX – A New Resin Treatment Technology for Drinking Water. Water Practice and Technology, 4 (4) Huber, S.A., Balz, A., Abert, M., Pronk, W., 2011. Characterisation of aquatic humic and non-humic matter with size-exclusion chromatography - organic carbon detection - organic nitrogen detection (LC-OCD-OND). Water Research, 45 (2), pp. 879-885. Humbert, H., Gallard, H., Jacquemet, V., Croué, J.-P., 2007. Combination of coagulation and ion exchange for the reduction of UF fouling properties of a high DOC content surface water. Water Research, 41 (17), pp. 3803-3811. Lee, S. and Kim, J., 2014. Differential natural organic matter fouling of ceramic versus polymeric ultrafiltration membranes. Water research, 48(1), pp. 43-51. Metcalfe D., Rockey C., Jefferson B., Judd S., Jarvis P., 2015. Removal of disinfection by-product precursors by coagulation and an innovative suspended ion exchange process. Water research, 87, pp. 20-28. Metcalfe, D.C., Rockey, C., Jarvis, P., Judd, S., (2016). Pretreatment of Surface Waters for Ceramic Microfiltration. Seperation and Purification Technology. 163, 173-180. Meyn, T., Altmann, J., Leiknes, T., 2012. In-line coagulation prior to ceramic microfiltration for surface water treatment-minimisation of flocculation pre-treatment. Desalination and Water Treatment, 42 (1-3), pp. 163-176. Walker, K.M., Boyer, T.H., 2011. Long-term performance of bicarbonate-form anion exchange: Removal of dissolved organic matter and bromide from the St. Johns River, FL, USA. Water Research, 45 (9), pp. 2875-2886.
INSTITUTE OF WATER JOURNAL ISSUE 2
SHAPING THE
FUTURE
IDEAS DISCUSSION & DEBATE The future of the water industry | Glasgow Caledonian University | 21-22 June 2018 Institute of Water Annual Conference Chaired by Douglas Millican, CEO, Scottish Water
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DWI THE LANCASHIRE CRYPTOSPORIDIUM EVENT OF 2015 - LESSONS LEARNED FOR THE WATER INDUSTRY
The Lancashire Cryptosporidium event of 2015 - lessons learned for the water industry Jacqueline Atkinson
Marcus Rink
Principal Inspector
Chief Inspector of Drinking Water
Abstract In August and September 2015 a major drinking water quality emergency occurred in north Lancashire, when more than 700,000 consumers in Blackpool, Preston, the Fylde Coast and surrounding areas were required to boil their water. This was in response to the detection of Cryptosporidium oocysts in water supplied from Franklaw water treatment works, at a maximum detected concentration of 0.119 oocysts per 10 litres, a level never previously recorded at the works. The source of the oocysts was later found not to have arisen from the source water, but from a planned change to the motive water arrangements for chlorination, bringing contaminated water from a service reservoir into the later stages of the works bypassing treatment designed to remove Cryptosporidium. The absence of a risk assessment, the use of a reservoir for process water post-treatment, the recycling of water within the works and the restarting of the works after contamination was discovered, were all in contravention of good practice identified in the reports of the group of experts published during the 1990s. Had the recommendations of these reports been followed, the consequences of the incident could have been much reduced, and it may have been avoided completely.
Introduction In August and September 2015 a major drinking water quality emergency occurred in north Lancashire, affecting more than 700,000 consumers in Blackpool, Preston, the Fylde Coast and surrounding areas. The incident began when United Utilities, the water company responsible for supplying the area, identified the presence of the protozoan parasite Cryptosporidium in water leaving Franklaw water treatment works. Water suppliers have a statutory duty to supply wholesome water. This means it must not contain any parasite at a level which could be a potential danger to human health, including where no standard has been set. Where this condition is not met a supplier must inform consumers before the supply is made.
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Highlights •
In August 2015, the detection of the parasite Cryptosporidium in water supplied from Franklaw treatment works led to more than 700,000 consumers being advised to boil their tap water before consumption.
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The incident developed into a major water supply emergency, and affected consumers for four weeks, causing widespread public concern and disruption.
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A number of key lessons to be learned have been identified as a result of this emergency that are applicable to all water suppliers.
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An expert group on Cryptosporidium in water supplies was established in 1990, and its published recommendations continue to set the bench mark for recognised good practice, that should be followed by all water suppliers.
Key words: Cryptosporidium, drinking water supplies, risk management, emergency planning
In response, United Utilities advised all consumers supplied with water from Franklaw to boil their tap water before using it for drinking and food preparation. The event was escalated to an emergency under the requirements of the Civil Contingencies Act 2004 because it was a situation which threatened serious damage to human welfare due to the disruption of a supply of water, and involved the Civil Contingencies Secretariat and DEFRA. The incident was managed at a strategic level by the Strategic Coordination Group (SCG) chaired initially by the Lancashire Police with representatives from the local authorities, Public Health England (PHE), NHS England and the Drinking Water Inspectorate (the Inspectorate, or DWI). This was the largest incident of its kind in Britain since 1989, when the water industry in England and Wales was privatised and the DWI
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was established to regulate drinking water quality in England and Wales. Cryptosporidium is a protozoan parasite found in humans and many other species of animals, including cattle and sheep, other mammals, birds, fish and reptiles. Some species, particularly C. hominis and C. parvum, predominate in causing human disease known as cryptosporidiosis1. Many communities support a background level of cryptosporidiosis, but their presence in raw water supplies is most frequently associated with sewage contamination or run-off from farmyards and farmland used for grazing livestock. They occur in the environment in the form of tiny resistant bodies called oocysts, which are excreted by infected humans and animals. In the United Kingdom, the first recorded outbreak of waterborne human cryptosporidiosis occurred in Ayrshire in 1988, associated with Camphill and Greenhead water treatment works2. In March 1989 there was an outbreak of cryptosporidiosis in Swindon, Oxfordshire associated with Farmoor water treatment works2.
a concentration of 0.119 per 10L. These results were exceptionally unusual for Franklaw works and the concentrations were similar to oocyst concentrations detected during previous documented incidents where an outbreak had occurred6. The company decided, in consultation with health professionals, to advise the consumers supplied by Franklaw to boil their tap water before consumption (Figure 1). This advice was in place for up to four weeks for some consumers. Figure 1 - Map of the area covered by the boil water advice (reproduced with permission of United Utilities Water Ltd)
Following these outbreaks, an expert group was established, chaired initially by Sir John Badenoch and later by Professor Ian Bouchier, who published three reports in 19902, 19953 and 19984. The purpose of these reports was to set out what is known about the organism, its occurrence in the environment and its importance as a human pathogen. The reports made recommendations covering water treatment, catchment protection, asset protection, management of outbreaks, responding to the presence of oocysts in water supplies, emergency planning, sampling and laboratory analysis. These recommendations remain the bench mark of good practice for managing risks associated with Cryptosporidium in water supplies, and in response the water industry in England and Wales has invested heavily in improvements to water treatment works to address risks associated with this parasite.
The cause of Cryptosporidium contamination at Franklaw As is normal practice at many surface water treatment works, where there is a risk of Cryptosporidium being present in the raw water supply, United Utilities had in place at Franklaw continuous sampling for Cryptosporidium at a dedicated sampling point on the outlet of the works. This comprised a continuous filtration unit containing a replaceable compressed foam pad filter designed to entrap any oocysts present5, maintained in continuous operation with replacement of the filter approximately three times per week. On 4 August 2015, a filter which had been in place since 31 July 2015 was removed and sent to the laboratory for analysis. Oocysts were detected in the filter at a level equivalent to a concentration of 0.031 oocysts per 10 litres (10L). The filter that was put in place on 4 August was analysed on 5 August, and on 6 August it was confirmed that oocysts were also present in this filter, equivalent to
There was a sequence of significant events at Franklaw during the month preceding the first detection of oocysts in the final water. In early July 2015, a leak was identified on one of the major trunk mains supplying water out of Franklaw into the distribution network, on the Franklaw site. Operations to isolate a section of this trunk main to repair the leak began on 25 July. This main was used to supply the works’ service water (used for domestic services, chemical make-up, motive water and other purposes), and therefore the supply to the service water system was switched to a different main, fed from Barnacre service reservoir which is off-site. This introduced a planned change to the treatment process, because service water is used for chemical dosing and is therefore an integral part of the treatment process. Problems were encountered with the work to repair the leak, and the ring main which transports
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service water around the site subsequently depressurised a number of times. This change to the service water supply lasted until 31 July, when it was switched to a different outlet main from Franklaw.
What became apparent was the most likely point of contamination at Franklaw was within the process stream, somewhere in or around the second stage filters.
Crucially, water from Barnacre service reservoir was introduced into the treatment process stream immediately before and during the period when the first filter containing oocysts was in situ on the works outlet.
The treatment processes at Franklaw (Figure 2) consisted, at the time, of conventional chemical coagulation followed by clarification, rapid gravity filtration, chlorination for oxidation of manganese followed by second stage filtration for manganese removal, and final disinfection with chlorine and contact in a dual-compartment contact tank. Investigations ruled out raw water quality and problems with clarification and rapid gravity filtration, with oocysts being detected downstream of the treatment processes that are important for removal of Cryptosporidium.
United Utilities began investigating the source of the Cryptosporidium immediately, but whilst a number of defects were found with assets associated with Franklaw works and the supply system, and several potential sources of oocysts were identified, the actual source of the contamination was not conclusively identified.
Figure 2 - A simplified diagram of Franklaw treatment processes at the time of the incident
As the incident progressed, oocysts were detected in most of the service reservoirs in Franklaw’s distribution network. Cryptosporidium hominis was identified in two service reservoirs, and in water supplied from Barnacre service reservoir. United Utilities was unable to find where the oocysts in the process were
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coming from, and, in order to expedite lifting the boil water advice, decided to install ultra violet treatment at reservoirs in the Franklaw distribution system to inactivate oocysts present, with flushing of the system to remove contaminated water.
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It was not until later in 2015, many weeks after the boil advice was lifted, that investigations at Barnacre service reservoir identified that the reservoir was leaking, and that there were sources of Cryptosporidium in the local environment with hydraulic pathways into the service reservoir, that could introduce contaminated water into the treated water stored inside.
Lessons to be learned - Contingency planning, emergency planning and resilience of supply systems Perhaps the most noteworthy feature of the Franklaw incident was the large population advised to boil their tap water before using it for drinking and food preparation. Franklaw works was the sole supply of drinking water to more than 700,000 consumers. The population affected was swelled because the incident coincided with the peak holiday period for the Fylde Coast, with large numbers of visitors present in the area. There was not an outbreak of cryptosporidiosis associated with this incident. This was confirmed by Public Health England who conducted epidemiological studies7. Nevertheless it caused major disruption to consumers and widespread public concern. Issuing written advice to more than 300,000 properties supplied by the works stretched United Utilities’ emergency plans to the limit. The advice to boil water was in place for up to one month for some consumers. The incident also had a serious effect on local businesses, in particular hotels and catering establishments, food production companies, medical services and nurseries. All schools in the area were provided with bottled water prior to returning from their summer break, but had the incident occurred outside the school holiday period, the provision of sufficient quantities of bottled water may have presented a further logistical challenge for the company. Before the company decided on 6 August to advise consumers to boil their tap water, Franklaw had been taken out of supply for planned maintenance during the evening of 5 August. The company was already aware of the first highly unusual Cryptosporidium result at this time, yet took the decision to restart the works as planned. The need to maintain a supply of water took priority over water quality considerations even in the knowledge of the potential risk to public health. The second positive result was available to the company during the morning of 6 August, after operations to restart the works had commenced. It was some hours later that the decision to issue the boil advice was taken. When a water company is aware of the presence of a pathogen in the water supply, it should be understood that to protect consumers, the parasite must either be eliminated from the water supply by an appropriate treatment process, or inactivated by some means such as boiling, UV light or provision
of alternative supplies. The means to deploy these measures should be included in a water supplier’s emergency plans to ensure that appropriate steps can be taken to protect public health before a works is returned to supply. As would be expected, the company made every effort to publicise the advice immediately on its website, and made use of social media, local press, TV and radio. The company had arrangements in place to deliver written advice to affected properties. These plans were stretched to the limit for the number of properties covered, and it took five days for all properties to receive written advice. A number of consumers who were interviewed by the Inspectorate or responded to questionnaires confirmed that they felt confused by the advice, struggled to make direct contact with the company and received mixed messages about whether the water was safe to drink or not. United Utilities’ contingency plans for responding to a microbiological emergency at Franklaw were not adequately designed to deal with the large number of consumers affected. The emergency plans did not prepare the company to effectively and rapidly communicate protective advice to 700,000 people, nor did they include adequate arrangements to rezone the network and restore wholesome supplies within a short space of time. The first Badenoch report published in 19902 emphasises the importance of water companies having emergency plans that include arrangements for communicating with consumers, local authorities and public health professionals; and that these plans should be regularly tested and kept up to date. This and the followup reports3,4 also include recommendations about investigative monitoring for Cryptosporidium during emergency situations. Since the incident, United Utilities has undertaken a thorough review of its incident management arrangements, communications with consumers and stakeholders during an emergency and deployment of recovery plans. These lessons are applicable to all water suppliers, and to support dissemination of key learning points, the Inspectorate published its report on the incident6 to make it available to the wider water industry and stakeholders. The following important lessons are applicable across the industry: •
Water quality and sufficiency emergency plans should be appropriate for the size of the treatment works and the number of consumers dependent on the works as the sole source of supply.
•
Issuing protective advice to large numbers of consumers is difficult and labour-intensive. Consumers are at risk of illness whilst the arrangements for issuing advice are being put in place. There is a need to ensure the right balance between drinking water quality and public health considerations against the need to maintain a supply of water at all costs. Water suppliers should consider carefully whether temporary shutdown
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of a treatment works may reduce the risk of consumers being made ill, even at the risk of losing the water supply to those consumers. Health professionals consulted when there is a developing water quality emergency must be fully appraised by the water supplier about the relative risks. •
Arrangements for issuing protective advice to consumers should aim to ensure delivery of written advice to all affected properties within 24 hours of the start of an emergency.
•
Water suppliers should review their supply arrangements to ensure that sufficient resilience is built in to supply systems, for example increasing connectivity of networks and building in duplication of assets, to minimise the duration of emergencies and the number of consumers directly affected. Companies should consider these needs in their medium to long-term asset management strategies and business plans.
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Plans for responding to drinking water quality emergencies should consider the need for provision of temporary water treatment, and how it will be procured.
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Water suppliers’ emergency sampling responses should allow for the speedy deployment of large-volume sampling for Cryptosporidium at key sampling points, for example raw water, points within treatment processes, final water and in distribution systems, to aid and expedite decision-making about the cause and extent of contamination. Water suppliers should hold or have access to an adequate stock of portable sampling equipment for these purposes (Figure 3).
Figure 3 - Mobile Cryptosporidium sampling equipment (reproduced with permission of United Utilities Water Ltd)
materialising. This is a duty under the Water Supply (Water Quality) Regulations 20168, which requires that companies’ risk assessments for their supply systems are continuously reviewed and updated. The importance of risk assessment to protect consumers from the risk of Cryptosporidium was recognised by the expert groups, and recommendations are made in their published reports. The first Badenoch report2 confirms that “when operated normally and assuming no more than background levels of oocysts in raw water sources, current water treatment processes appear able to prevent contamination of supplies.” It goes on to state: “It also seems likely that water supplies may be more susceptible to oocyst contamination when there has been a major planned change in a water treatment process …” The report also comments on risks associated with service reservoirs. The Ayrshire outbreak of 1988 cited in the report was caused by contaminated farm runoff entering a break pressure tank. Water from this tank was pumped to one of the local treatment works from where it was supplied to consumers without further treatment. Badenoch clearly states that “..good practice regarding the maintenance of service reservoirs should ensure their hygienic safety. Service reservoirs, particularly roofs, may leak inwards. Leakage in of oocysts poses a particular risk to the population served ….as there is no further barrier to the oocysts reaching consumers’ taps”. The Inspectorate prosecuted a water company in 2014 for an event in 2012 where Cryptosporidium was detected in a service reservoir due to faecal ingress from the environment and with striking similarities to the case cited by Badenoch9. The evidence of risk associated with service reservoirs, from both the direct detection of Cryptosporidium and detection of indicators of faecal contamination reported by the Inspectorate every year10 is a clear indication of real risk. United Utilities had a programme for inspecting service reservoirs internally and testing for ingress, but it was the same frequency for all reservoirs and no risk assessment was made before the planned change to introduce service reservoir water into the treatment process at Franklaw. United Utilities also continued to recycle treated backwash water at Franklaw to the works inlet, when it is clearly stated in the first Badenoch report that with oocysts present, the situation is transformed to become potentially dangerous. The lessons learned are applicable to all water suppliers: •
Risk management and asset management Whenever a major change is made to the operation of a water treatment works, suppliers should carry out a full risk assessment before work is commenced in order to identify all likely hazards and to implement steps to prevent serious consequences from
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Water suppliers should know about the condition of their assets, in particular tanks and reservoirs containing treated water, where there is a risk of ingress. Inspection and maintenance regimes should be at a frequency appropriate to the risk. For example, if an underground service reservoir is surrounded by higher ground with grazing livestock and septic tank discharges, it would be reasonable to assume that risks associated with the potential ingress of contaminated water may be greater than they might be at reservoirs in different locations.
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•
Water suppliers should ensure that all tanks and reservoirs that are used for treatment or storage of drinking water can be easily removed from supply for cleaning and maintenance.
•
Up-to-date and accurate information about the condition of assets, and the operational status of underground pipes and valves is critical for risk management of water supply systems. The lack of accurate, current information about the condition and status of operational assets is likely to render inadequate any risk assessment undertaken prior to a planned operational change.
•
Water suppliers should continue to follow the recommendations made by the groups of experts on Cryptosporidium to ensure that water treatment processes are operated correctly, with appropriately alarmed online continuous monitoring for turbidity at critical points (such as outlets of rapid gravity and slow sand filters), and that wash water is not recycled to a works’ inlet when there is an increased risk of oocysts being present.
economic losses. The loss of consumers’ confidence in the quality of their tap water was immense. Responding to the incident, restoring wholesome supplies and compensating affected consumers and businesses incurred huge costs for United Utilities, and the company suffered significant reputational damage as a result. United Utilities is working with the water industry to raise awareness of the lessons to be learned. Water suppliers should respond by taking these lessons into account when planning for the future to ensure that continuous supplies of wholesome water can be maintained under all circumstances, building resilience and robust asset maintenance strategies into their long-term plans. Information about the DWI’s investigation of this incident, the findings and recommendations are contained in the Inspectorate’s final report6, which is published on the DWI website at www.dwi. gov.uk. References
Summary The reports of the group of experts on Cryptosporidium in water supplies were published two decades ago. The recommendations made in these reports continue to set the bench mark of good practice for water suppliers, to ensure that consumers are protected from risks associated with this parasite. Whilst there was no outbreak of cryptosporidiosis associated with this incident, consumers were exposed to a significant risk to health. The issuing of advice to boil water to more than 700,000 people caused widespread anxiety and inconvenience, as well as
SHAPING THE
FUTURE
1.
Cryptosporidiosis. Davies, A. P. & Chalmers, R. M. 2009. BMJ 339, b4168.
2.
Cryptosporidium in Water Supplies, Report of the Group of Experts, Chairman Sir John Badenoch, July 1990.
3.
Cryptosporidium in Water Supplies, Second Report of the Group of Experts, Chairman Sir John Badenoch, October 1995.
4.
Cryptosporidium in Water Supplies, Third Report of the Group of Experts, Chairman Professor Ian Bouchier, November 1998.
5.
The Microbiology of Drinking Water (2010) - Part 14 - Methods for the isolation, identification and enumeration of Cryptosporidium oocysts and Giardia cysts, Standing Committee of Analysts.
6.
Report of the Drinking Water Inspectorate’s Investigation into the Cryptosporidium Contamination of Franklaw Treatment Works in August 2015, Drinking Water Inspectorate, 25 October 2017, www.dwi.gov.uk
7.
Potential Impact of media reporting in syndromic surveillance: an example using a possible Cryptosporidium exposure in North West England, August to September 2015. Elliot et al, Surveillance and Outbreak report, 15 December 2015.
8.
The Water Supply (Water Quality) Regulations 2016 SI 2016/614.
9.
Broadway (Worcestershire) 2012, Drinking Water Inspectorate press release, January 2014, www. dwi.gov.uk
10. Drinking Water 2016, Summary of the Chief Inspector’s report for drinking water in England. July 2017, www.dwi.gov.uk
IDEAS DISCUSSION & DEBATE The future of the water industry | Glasgow Caledonian University | 21-22 June 2018 Institute of Water Annual Conference Chaired by Douglas Millican, CEO, Scottish Water
Book Now www.InstituteOfWater.org.uk
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OFWAT SEEN BUT NOT HEARD – HOW CAN BETTER CUSTOMER COMMUNICATIONS HELP IMPROVE WATER AND WASTEWATER SERVICES?
Seen but not heard - how can better customer communications help improve water and wastewater services? Dylan Spedding Principal, Corporate Communications. Ofwat
Introduction There is no product or service that everyone will use every day – except water. But not one of the companies that deliver it in England and Wales are in the top 50 for customer service. It doesn’t seem like a big issue until you imagine the public reaction to news – real or fake – that, for example, water was somehow unsafe to drink. At the same time, water companies face calls to build bigger, quicker and more infrastructure – while also finding smarter ways of delivering services and keeping bills affordable. These challenges may seem unconnected, but is there a joined up solution? Better customer communications has an increasingly critical role to play within the water sector. This article explores key reasons why that is the case.
Using communications to develop closer relationships with customers The water sector is facing the greatest challenge to its legitimacy in almost three decades. The Labour manifesto for the 2017 UK General election1 included a promise to renationalise water and a number of other industries. But headlines such as “Some of the UK’s privatisations, notably in water, have failed2” (Financial Times) and “The scandal of privatised water is going to blow3” (The Spectator) show this is far from simply a party political challenge. It is much more fundamental than that. The current debate might feel as if it came out of nowhere. After all, if you look at what the sector has achieved for customers and
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society since privatisation there really is a good story to tell. A litre of water delivered and taken away costs less than a penny, with customer satisfaction at about 90%4. But if you listen to a group of customers talking about water issues it doesn’t take long before someone says something along the lines of: ‘I don’t know why we pay for water when it just falls from the sky’. Of course, customers do understand that collecting, treating and transporting water costs money. And that somewhere along the line someone needs to pay for those costs. But what those conversations are telling us is how differently people think about water. Water is not the same as consumer goods, or even energy or banking. It’s thought of as a human right. For many, there is a sense that water companies are not being run in the interests of the people who depend on their services. And that not only are public interests somehow in conflict with the interests of shareholders – but the latter’s interests are winning out. Clearly regulation should – and is – having a role in aligning the interests of shareholders and companies with those of customers and wider society. But, this isn’t always how the sector is perceived. Changing perceptions is where better customer communications can help. As a sector, we need to communicate: •
the value we add;
•
the resilience of our service;
•
the way we are innovating to meet customer expectations; and
•
how we are supporting customers in situations of vulnerability and those struggling to pay.
How water companies choose to engage with customers and communities now, and throughout the 2019 price review, will be seen as a symbol for how responsive the sector is to the changing environment in which we all operate.
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Using customer communications and relationships to help tackle challenges
Communications is one of the most important tools for achieving that; making sure that customers are engaged, involved and participants in water services.
The second reason communications is increasingly important is as a means of driving change and innovation within companies and the sector.
But it’s not a one-way street, whereby companies tell customers what they are doing and then ask if they agree.
Regulators and economists are increasingly recognising the power of communications – witness, for example, the growth of nudge economics. At Ofwat we have recognised and used communications as part of our regulatory toolkit for many years. And it will only continue to grow in importance in our increasingly complex and interconnected world. In June 2017, Ofwat’s then-Chief Executive Cathryn Ross, gave a lecture at the London School of Economics about the future of independent economic regulation5. She highlighted her view that communications can have more impact for customers than some price control mechanisms. Communications can drive behaviour change: transforming what customers think, feel, believe and do. And customers’ active participation at scale can deliver real impacts, and help to achieve business objectives. Of course, communications and engagement professionals at companies also know the potential of communications to: •
raise awareness of the value of water among customers and employees;
•
encourage customers to save water and change what people put down sinks and loos;
•
reduce unnecessary calls, help customers take early action to reduce the risk of debt or change the behaviour of audiences such as farmers and local authorities; or
•
collaborate with others to create new social norms or a means of prompting specific water-related behaviours.
Many of those same professionals also recognise communications as a means by which they can ensure customers are: •
heard;
•
given the opportunity to participate in planning and creating services;
•
encouraged to take an active role in the delivery of those services by, for example, adopting good behaviours around water efficiency and other issues; and
•
understand more about water and their role within the water sector.
But the key question is whether company Boards and executive teams are clear about the role of comms in achieving these things too. At Ofwat we often talk about customers being at the heart of everything we do. And we want this sector to do the same.
Instead it’s a dialogue, based on listening to customers, understanding them and feeding that back into the business. That might mean: •
adopting new channels to talk to customers;
•
talking about the things that are important to them – rather than important to the company; and
•
letting them set the agenda, rather than trying to control it.
And while the sector has come a long way, we will be looking for a real step change in the way companies engage with their customers in their plans for 2020-25. We want to see companies recognise their customers as active participants in the water sector, not passive recipients6.
Using communications to help transform services by 2025 The third reason why communications is important is in transforming services by 2025. And in 2019, at the 2019 price review (PR19) we’ll be setting the price, service and investment packages that will encourage companies to do that. Companies must submit their plans for services from 2020 to 20257 to us by 3 September 2018. PR19 has its roots in the step-change improvements we made at the 2014 price review, but we want it to go further. Much further. We’re being explicit about the four areas that we want customers to benefit from in this price review. And good customer engagement is critical to all of them.
1. Great customer service Water companies have made great strides here over the years. We really want to see companies in this sector going way beyond getting the basics right and really delivering against the expectations of customers in the 21st century. That doesn't mean thinking like a water company. It means thinking like a customer. And not just thinking like someone paying a water bill. But thinking about the real people the companies serve. People have busy lives, with competing demands on their cash, with multiple affiliations to different communities. It means thinking about how a water company can make life better and easier for individuals, families and communities. We’re already seeing other utility companies moving into that space, so why not water companies?
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OFWAT SEEN BUT NOT HEARD – HOW CAN BETTER CUSTOMER COMMUNICATIONS HELP IMPROVE WATER AND WASTEWATER SERVICES?
We’re not just talking about reducing complaints, or getting it right first time in resolving issues, which of course do matter. We’re talking about: •
different services;
•
different ways of accessing those services; and
•
plurality in channels of communication.
In essence: more personalised, more targeted. It will require companies getting a lot smarter in how they learn about what customers want and how they want it. There is so much more companies could be doing to collect information about their customers.
Of course, this data is from customers and they expect it to be used wisely. But there is massive potential here to deliver better service and build trust. And communications is an important route in to understanding and responding to customer expectations. How companies listen to customers, the channels that they use to talk to them and how they use what they tell customers to shape the story about what outcomes customers will deliver is all deeply rooted in communications practice. That is why we’re making how companies have communicated part of the assessment of their business plans for the first time.
Ofwat’s expectations for how companies will communicate with their customers at PR19
2. Resilience in the round The second of our themes is resilience. This is one of the words that will most dominate the next review. And rightly because it is one of the things that matters most to customers. We all depend on the vital public services the sector produces. We rightly expect them to be reliable. And we expect to have confidence that they will continue to be provided into the future. You may already have heard that we take a broad view of resilience.
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If you look from the customer perspective, what matters is all those risks to the reliability and long term resilience of water and waste water services. And those risks are many and various. Which is why we refer to 'resilience in the round’. And customers and communities are part of operational resilience too. Customers are themselves part of the value chain. Their behaviour and decisions have a huge impact on how much water we need to supply and how much waste water treatment is needed.
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And incident response and recovery and excellent communications are all critical to mitigating the impact of service disruption, which is important for operational resilience too. Communicating with customers during a major incident Good communications with customers is critical. But never more vital than during a major incident. Delivering services where the impact of failure could be death, the sector is well drilled at managing major incidents. In recent years we have seen some companies falling short in meeting the expectations of their customers in how they communicate during those incidents. For example, it is surprising in an increasingly social media-dominated world and news cycle that there is such variability in response times by water companies to customer complaints on Twitter8. In 2015, United Utilities experienced a Cryptospiridum contamination incident that resulted in the company issuing a boil water notice to 300,000 homes and businesses. The incident lasted several weeks and, by its own admission9, has led to the company taking a number of remedial actions to improve its services in future – including the way it communicates with customers, particularly those that are most vulnerable. The company is also embarking on a programme of engagement with customers and other stakeholders to learn any wider lessons.
3. Affordable bills for all Our third theme is affordability. And it is worth being clear here that what we are talking about here is affordability for all - not only for those customers who need specific assistance. Concentrating concerns about affordability on that smaller group risks tipping more people into a position of struggling to pay their bills. We think there is scope at the next review to really improve affordability for everyone. Because we think there is really substantial scope for costs to come down. We want to see more evidence of engagement with customers about their preferences; as well as more efforts to engage with vulnerable customers and those who are hardest to reach.
And there are also pressures for change from customers, whose expectations, based on their experience in other sectors, are rising. Customers these days expect a great service and a hassle free experience – at a time and via the channel of their choosing. But more than that they expect a more personalised service, better information, more control12. And competition for customers is still pretty limited in the sector. We know, for example, that the sector can make better use of data to drive greater customer service and satisfaction13, including collaborating more closely with companies in other sectors that face similar challenges on shared solutions. As a public service, the water sector should care deeply about its legitimacy. And that legitimacy depends on meeting those expectations. So this is a very real driver for innovation.
Seeing and hearing We have said repeatedly that PR19 will be a tough review for companies. •
More stretching outcomes
•
Lower financing costs
•
A tougher efficiency challenge
•
A higher bar on the quality of business plans.
But it will be a review with massive opportunities. And one of the biggest opportunities lies with the way companies use all their communications tools to listen and respond to customers and communities. And this needs to happen for individual companies and, going forward, as a sector. Many of those opportunities - particularly in the customer participation space - are ones that we probably haven’t even conceived of yet. But one thing is clear, those companies that recognize they need to see and hear their customers will be the ones to make the most of those opportunities. And that will improve water and wastewater services for us all. References
One of our priorities for this review is to see levels of bad debt come down – so that those who do pay are not shouldering the burden of those who don’t10. Reaching and engaging with these customers is going to require new ways of communicating and very possibly new partnerships11.
4. Innovation that delivers benefits for customers Our final theme is innovation. This underpins everything we want to see achieved through PR19. But the real driver for more innovation going forward is that companies simply cannot do things in the way they always have and continue to deliver those vital public services we all depend on at a price we can all afford.
1. Our Manifesto: For The Many, Not The Few, UK Labour Party, May 2017 2. ‘A welcome, if thin, vision of a free-market Britain’, Financial Times, 2 October 2017 3. ‘The scandal of privatised water is going to blow’, The Spectator, September 2017 4. discoverwater.co.uk, November 2017 5. The future of independent economic regulation - keynote lecture by Cathryn Ross at London School of Economics, Ofwat, 22 June 2017 6. ‘Tapped In - From passive customer to active participant report’, Ofwat, March 2017 7. Delivering Water 2020: our final methodology for the 2019 price review, Ofwat, 13 December 2017 8. How the UK’s Water &Sewerage Suppliers Perform for Customer Service on Twitter, HelpHandles, 27 September 2017 9. Conclusion of court hearing following 2015 cryptosporidium incident, United Utilities, 10 October 2017 10. Debt management and other retail costs: research and recommendations, Ofwat, September 2017 11. ‘Making better use of data: identifying customers in vulnerable situations’, UKRN, October 2017 12. UK Customer Satisfaction Index, Institute of Customer Service, July 2017 13. ‘Unlocking the value of customer data: a report for water companies in England and Wales’, Ofwat, June 2017
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THOM ET AL USING FLOW CYTOMETRY TO IMPROVE UNDERSTANDING OF CHLORINATION PROCESSES IN DRINKING WATER TREATMENT
Using Flow Cytometry to improve understanding of chlorination processes in drinking water treatment Claire Thom
Laura Murray
Nichola Hepburn
Water Science Team Leader
Process Scientist
Process Scientist
Paul Weir
Elise Cartmel
Susan Lee
Project Manager Water Science
Chief Scientist
Microbiology Laboratory Team Manager
Abstract This study demonstrated the application of flow cytometry in assessing the disinfection efficacy of chlorination processes at various drinking water treatment works. Intact and total bacterial cell counts were measured at different points in the process at 10 water treatment works throughout Scotland, during a day of normal operations. Cell counts in the untreated (raw) and treated (final) waters were also monitored weekly at the same sites for one year. Intact cell removal across chlorination processes ranged from <0.1-3.08 log cells mL-1 and total cells- <0.1-1.79 log cells mL-1. Bacterial cell removal was strongly correlated with the Ct value (mg.min L-1 free chlorine). Many sites with poor Ct relied on residual disinfection in treated water storage tanks to reduce cell counts. Raw water loadings and upstream process capabilities were less strongly correlated to the efficacy of chlorination, but further analysis is needed to assess these impacts. There is evidence of seasonal variation of cell counts, as there were significant differences in removal performance across the year from weekly monitoring of intact cell counts in the raw and final water. Final water concentrations varied from <10^2 and 10^4 intact cells mL-1 between sites, although Heterotrophic Plate Counts (HPCs) were commonly
Introduction Improving drinking water compliance and public health is of paramount importance to the Water sector. In Scotland, chemical compliance continues to improve year on year, however bacteriological compliance has begun to plateau (Drinking Water Quality Regulator for Scotland, 2016). Improving understanding of
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0 cfu mL-1. It was highlighted by this study that a complex range of factors influence bacterial removal and survival throughout drinking water treatment, and this supports the use of flow cytometry as a tool for assessing chlorination processes.
Highlights •
Flow cytometry is a useful tool in assessing disinfection performance in drinking water treatment.
•
Intact cells were highly variable between treatment works with similar processes.
•
Cell removal across disinfection correlated strongly with the Ct (Free Chlorine mg.minL-1).
•
Sites with poor Ct had a high level of residual cell removal in treated water storage.
•
Evidence of seasonal differences in cell counts in both treated and untreated water.
Keywords: Drinking water quality, Flow cytometry, Heterotrophic bacteria, Ct value, Chlorination
disinfection processes is a key activity in increasing bacteriological compliance, with many bacteriological sample failures due to inefficiencies in this process (Figueros & Borrego, 2010). The process of disinfection is achieved by the addition of a strong oxidising agent, which inactivates pathogens. In Scotland this is achieved primarily using chlorination. Liquid sodium hypochlorite is added to treated water, which then flows through a Chlorine Contact
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Tank extending contact time with the disinfectant. The production of highly reactive hypochlorite acid (HOCl-) ions disrupts the polarised cell membrane, ultimately destroying the cell. This process is described by the Chick-Watson law, which defines the kinetics of disinfection as a product of the disinfectant residual and contact time and is expressed as the Ct value in mg.min L-1 of free chlorine. The rate of this process is dependent on the pH and temperature of the water with ideal conditions pH <8 and >10°C (Chick, 1908). Preparation of the water prior to disinfection is also an important factor in the efficacy of the disinfection process (World Health Organisation, 2011). The most common treatment processes employed in Scotland are coagulation and flocculation of raw water using a metal salt under optimum pH conditions followed by rapid gravity sand filtration (RGF) as a physical particle removal stage. Some sites also employ an intermediary clarification stage using sedimentation or flotation processes (Figure 1). Primary treatment processes are particularly important in treating surface waters which have higher organic loadings. Figure 1 - Conventional water treatment process in Scotland Raw Water
Screening Coagulant
Traditionally, coliforms have been used as the primary indicator of contamination of drinking water (Standing Committee of Analysts, 2009), with Heterotrophic Plate Counts (HPCs) as a supplementary indicator of general microbiology (Bartram, et al., 2004; Robertson, 2003). Unlike coliforms, HPCs are not necessarily a risk to public health, but give an understanding of treatment process efficiencies (Carter, et al., 2000). The limitations of HPCs have been well documented (World Health Organisation, 2011), with HPCs being affected by many factors including but not limited to: hydraulic conditions; surface area; surface material; surface roughness; disinfectant residual and culture media (Chowdhury, 2012; Allen, et al., 2004). Direct microscopy has quantified that <1% of bacteria are culturable by HPC methods due to most bacteria being in a viable but non-culturable state (VBNC) (Van der Kooj, 2003). This has led to the development of culture independent methods which give a more accurate and rapid assessment of general heterotrophic bacteria. Flow cytometry is one of the most promising culture independent methods which facilitate a direct count of heterotrophic bacteria. Several robust methods have been widely tested in the water industry, evaluating: absolute cell numbers, process efficiencies and regrowth potential (Hammes, et al., 2008; Berney, et al., 2008; Hammes, et al., 2010; Hammes & Egli, 2005; Vital, et al., 2012). The majority of studies have been carried out in Central Europe where a disinfectant residual is not maintained and hence focussed on total cell counts. However, assessment of the regrowth potential of intact cells (cells which are presumed to be viable due to the presence of an intact polarised membrane) has only been carried out in small study of 3 chlorinated drinking water systems (Gillespie, et al., 2014).
pH Correction Flocculation Tanks
or Dissolved Air Flotation Tanks
Sedimentation Tanks
Materials and methods
Rapid Gravity Filtration Sodium Hypochlorite Chlorine Contact Tank Orthophosphoric Acid pH Correction Treated Water Storage
Distribution
This study aimed to assess the reduction of intact cells across the disinfection processes of 10 surface water treatment works in Scotland, as well as the concentrations of intact cells at the final outlet of treatment. This investigation was completed to develop understanding of the efficacy of chlorination processes in reference to: raw water cell loadings; quality of water prepared for disinfection; the Ct value; and HPCs.
Sampling Locations & Procedure Samples were taken from ten water treatment works (WTW) across Scotland, which used coagulation, clarification and filtration as primary treatment processes. Samples were taken from: the inlet to the treatment works (raw water); the outlet of the filtration process; the inlet and outlet of the chlorination process; and at the final water outlet. Samples were taken from designated sample lines, which are designed for water quality monitoring. Sites were sampled on a day of normal operations in 2016, with five samples taken at each point. Samples were collected in sterile 500mL PVC bottles (Aurora Scientific; UK) pre-dosed with sodium thiosulphate to quench residual free chlorine. Sample taps were flushed prior to sampling for three minutes, flame sterilised using a blow torch for 30 seconds and
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THOM ET AL USING FLOW CYTOMETRY TO IMPROVE UNDERSTANDING OF CHLORINATION PROCESSES IN DRINKING WATER TREATMENT
flushed for a further 3 minutes to prevent sample line contamination. Samples were then stored at 5±3°C for transportation to the laboratory, and analysed within 24 hours. Weekly monitoring of intact and total cell counts during 2016 was also carried out in both the raw and final waters. Analysis was completed from the routine microbiological samples taken at the raw and final waters at those treatment works; other relevant tests carried out were HPCs and testing of free chlorine residual using Hach™’s pocket colorimeter, following manufacturer’s instructions.
Flow Cytometry For the enumeration of total cells, 10000x SYBR Green (Life Technologies Ltd., stock, cat no. S-7567) was diluted in dimethyl sulphoxide (DMSO, Fisher Scientific) to a working stock of 100x 2.5µl of working stock was added to 250µl of each sample to give a final SYBR Green concentration of 1x. For the enumeration of intact cells 5 parts 100x SYBR Green was added to 1 part Propidium Iodide (PI) (1 mg mL-1, corresponding to 1.5 mM; cat no P3566; Life Technologies Ltd.) to give final concentrations of 3µM PI and 1x SYBR Green. 3µl of this mixture was added to 250µl of each sample. Samples were gently mixed and incubated for 15 minutes at 30°C. 50µl of each sample was then analysed using BD Accuri’s C6 flow cytometry system (Becton Dickinson UK). Negative control samples were also analysed for both intact and total cell staining mixtures using ultra-pure deionised water (sterilised at 121°C for 15 minutes). Samples were subject to excitation by a laser at 488nm and subsequent light scatter was detected at 533nm (FL-1, green fluorescence) and 670nm (Fl-3, red fluorescence) and plotted two dimensionally for green fluorescence. Sample plots were analysed under a template created for the C6 system (Gatza, et al., 2013; Gillespie, et al., 2014), with a single fixed threshold gate applied to discriminate background fluorescence from bacterial cells. This generated two plots for each sample, one used to calculate total cells mL-1 (dead and intact cells) and the other intact cells mL-1. In samples where total fluorescence events were >105/50µl, samples were diluted 1:10 using sterile ultra-pure water. Highly coloured or turbid samples (e.g. raw water) were also diluted 1:10 and filtered using 11µm filter paper (grade 1, Whatman, UK) prior to analysis. For the purposes of this study, a lower detection limit of 200 intact cells mL-1 (5 events in 50µl) was employed in accordance with other studies on intact cells (Hammes, et al., 2008; Hammes, et al., 2010).
Heterotrophic Plate Counts The HPCs were analysed from the same sample bottle as the intact and total cell counts within 24 hours of sampling. Following the Standing Committee of Analysts (SCA) procedures, 2 x 1mL of sample was added to sterile petri dishes with 18±3mL of molten Yeast Extract Agar (Oxoid, Fisher Scientific UK, cat No. CM0019B) and swirled gently to mix. Agar was prepared as per manufacturer’s instructions and added at 30°C, post sterilisation at 121°C for 15 minutes. One sample was then incubated at 37°C for 48 hours and the other at 22°C for 72 hours. Colonies were then manually counted as colony
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forming units (cfu) per mL (Standing Committee of Analysts, 2012).
Results Cell counts across the chlorination process At the filter outlet, intact cells ranged between 1.584 x 104 mL-1 and 3.85x 105 mL-1 at different sites (Figure 2). At the outlet of the chlorine contact tank (CCT,) intact cells were reduced between <0.05 and 3.05 log intact cells mL-1. When compared to the overall level of cell matter, intact and disrupted (total cells mL-1), the removal followed a similar pattern. Total cells were reduced between <0.05 and >2 log cells mL-1. Sites which exhibited the lowest level of intact cell removal generally ranked similarly in total cell removal. However, site 2 had an average removal of 1.16 log intact cells mL-1 and a total cell reduction of <0.05 log cells mL-1. Most sites with <3.5 x 105 total cells mL-1 at the filter outlet also had a lower level of cell removal of both intact and total cells. Although at site 7, removal of >3 log intact cells mL-1 was achieved from 3.11 x 105 cells mL-1 at the filter outlet. At site 8, no cell counts from the CCT outlet were taken as this was not in operation as a portion of the clean water storage tank (CWT) is used to disinfect water at this site. Site 6 had a slight increase in intact cells across the CCT, but this was less than the standard deviation of filtered cells (1249 intact cells mL-1) and was not considered significant. Figure 2 - Mean intact (a) and total (b) cells mL-1 across the chlorination process at ten conventional Water Treatment Works across Scotland and their log removal values (log cells mL-1). Cells were measured on a day of normal operations in 2016 at the end of physical treatment (Filter outlet) and at the outlet of the Chlorine Contact Tank (CCT Outlet). Sites ranked lowest to highest log unit removal. Error bars are 1 standard deviation of the mean.
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In the context of the overall intact cell removal from the raw water to the works outlet (Final), sites with higher log removal across disinfection had a higher overall cell removal (Figure 3). Sites 3,4,6,8 & 10 removed <1 log intact cells mL-1 across chlorination and reduced cells by <3.5 log intact cells mL-1 overall. Removal of cells across coagulation and filtration processes was lower on average than across chlorination - 0.63-1.62 log intact cells mL-1. The amount of removal achieved by physical processes had a moderate correlation (Pearson= 0.54) to the amount of removal achieved by chlorination although this was not significant (p=0.134). Sites without a clarification stage post coagulation and flocculation of raw particles had a lower median cell count at the outlet of filtration, 9.93 x 104 intact cells mL-1, whereas those with a sedimentation or clarification stage had a median value of 2.38 x105 intact cells mL-1 (Figure 4). A list of the type of clarification employed at each site can be found in Table 1.
Figure 3 - Log intact cell removal from Raw (untreated) to Final (disinfected) water at ten water treatment works across Scotland. Sites were ranked from lowest overall removal to highest. Removal was divided into three areas: Raw-Filtered water, Removal across Chlorine Contact Processes (Disinfection Log Removal) and residual removal in treated water storage (CCT Outlet Log Removal), all in log intact cells mL-1.
Table 1 - A list of sites analysed, listing their Clarification process, if any. Sites either employed: Direct Filtration (no clarification); Sedimentation processes, either using lamellas or horizontal sedimentation basins; or Dissolved Air Flotation (DAF). Site 9 uses an Actifloâ&#x201E;˘ system, which combines coagulant and ballasted sand, which then undergo sedimentation across lamellas to remove particulate matter. Site
ClariďŹ cation
1
Direct Filtration
2
Horizontal Sedimentation Basins
3
Dissolved Air Flotation
4
Direct Filtration
5
Horizontal Sedimentation Basins
6
Direct Filtration
7
Direct Filtration
8
Direct Filtration
9
Actifloâ&#x201E;˘
10
Lamella Sedimentation
Some sites also had a high level of residual removal of intact cells after residence in the contact tank due to the persistence of the free chlorine residual. At this point in the treatment process, pH is increased to >8 and then water is stored in the CWT prior to distribution. Sites with greater intact cell removal across chlorination generally had a lower removal post CCT, e.g. site 7 had a chlorination removal of 3.08 log intact cells mL-1 with a residual reduction of 0.18 log intact cells mL-1. Site 8 did not have a dedicated CCT and relied entirely upon disinfection in the CWT and had the lowest overall reduction, 2.35 log intact cells mL-1. This site had the 2nd highest residual removal, 1.71 log intact cells mL-1. The highest residual removal was achieved at site 10, 1.77 log intact cells mL-1.
Figure 4 - A box plot of intact cells mL-1 at the filter outlet for the ten water treatment works measured, by upstream process type. Clarification plants include a sedimentation or flotation stage to remove flocculated particles, direct filtration plants do not.
When disinfection removal was compared to the minimum Ct value achieved at those WTW (Table 2) there was a clear correlation between the Ct value and the amount of intact cell removal (Figure 5). Sites where the minimum Ct was >20mg.min L-1 achieved removal of >2 log intact cells mL-1. Conversely sites with a minimum Ct of <5 mg.min L-1 had a log removal of <1.25 intact cells mL-1 and significantly more cells remained at the end of the process. A Pearson correlation of intact cell removal and Ct value are positively correlated, 0.921 (p=<0.05).
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THOM ET AL USING FLOW CYTOMETRY TO IMPROVE UNDERSTANDING OF CHLORINATION PROCESSES IN DRINKING WATER TREATMENT
Table 2 - Results of historical Ct calculations carried out at the ten water treatment works across Scotland. Disinfection temperature and pH are used to offset the Ct value (Correction Factor) based on the available percentage of HOCL- ions under these conditions. 1
2
3
4
5
6
7
8
9
10
Maximum Plant Flow ls-1
Parameter
Measure
1886
237
1157
1041
1493
972
3200
428
1000
179
Residual Free Chlorine
mg l-1
0.85
0.5
1.5
0.95
0.9
1
0.73
0.95
0.85
0.75
Contact Time
min
90.0
12.5
6.3
10.1
33.1
35.0
38.4
18.7
33.3
11.6
Disinfection Water Temperature
째C
7
14
10
14
10
3.4
8.9
10
15.5
8.9
Disinfection pH
pH units
6.1
6.3
9.3
8
6.3
7.8
6.1
8.25
7
6.2
Correction Factor
%
97.68
95.6
2.4
33
96.1
47.5
97.5
33.0
81.2
96.1
Ct value
mg.min L-1
74.73
5.95
0.23
3.18
28.59
16.60
27.36
5.88
22.98
13.86
Figure 5: A bubble plot of mean intact cell removal across disinfection for ten water treatment works across Scotland, plotted against their Ct value (mg min L-1). Ct was calculated at maximum works flow. Bubble size represents the amount of intact cells left after disinfection (cells mL-1). Site 8 is not shown as no dedicated chlorine contact tank exists.
individual standard deviations and confidence limit of 95% of the mean. Site 8 was not monitored for raw water in 2016 and therefore value is blank.
Final water intact cells
Cell count weekly monitoring Raw water intact cell counts were also monitored weekly throughout 2016. When these were compared to final water cell counts measured on the same day, mean cell removals varied between 3.13 and 4.11 log intact cells mL-1 (Figure 6). Most sites had a higher mean intact cell removal across 2016 than on the day of intensive process sampling. Site 6 in particular have a much higher mean across weekly monitoring compared to the day of intensive sampling (4.04 log intact cells mL-1). Sites 1, 5, 7 and 10 ranked similarly to the day of intensive sampling, but the intact removals were significantly higher. Across all data, raw water cells had a minimum of 7.84 x 104 intact cells mL-1 and a maximum of 5.34 x 106 intact cells mL-1, with a median value of 1.48 x 106 intact cells mL-1, indicating variation between sources. Figure 6 - An interval plot of mean log removal of intact cells mL-1 from Raw to Final based on weekly samples for ten water treatment works across Scotland in ascending order. Intervals were based on
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Intact cells were monitored weekly at the final water outlet at the 10 Sites over 2016, alongside HPCs at 22째C and free chlorine residual (mg L-1). HPC values were commonly 0 cfu mL-1 at all sites (Figure 7). Mean HPCs at 22째C were <1 for all sites except 4 and 8, 1.86 and 3.81 cfu mL-1 respectively. HPCs did not have any correlation to the final water cell counts at any sites (Pearson correlation= 0.092, p= 0.00). Figure 7 - Individual value plot of colony counts at 22째C (cfu mL-1) at the ten water treatment works sampled.
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Final water cell counts between the ten sites varied significantly (Figure 8). Most sites had a median intact cell count of <500 cells mL-1, except sites 8 and 4. Sites with higher median cell counts also had increased variability. Site 4 had the highest median value of 780 intact cells mL-1, with a range of 0- 3120 intact cells mL-1. Site 5 with the lowest median value, also had the lowest range: 0- 320 intact cells mL-1. When all cell count results are analysed by month, this variation is spread seasonally (Figure 9). In 2016, mean cell counts increased in the first 3 months of the year to the highest mean value: 757 intact cells mL-1 (Âą68.2). Cells then decreased in April and May before increasing again between June and August 2016. Cells then returned to 337 cells mL-1 (Âą27.7) in November 2016 and remained low for the remainder of the year. Figure 8 - A box plot of intact cells mL-1 measured at the outlet of 10 water treatment works in ascending order by site.
Discussion Cell removal across chlorination processes
Mean free chlorine residuals for the months in 2016 also have a seasonal pattern (Figure 9). Free chlorine levels were 0.68-0.74 mg L-1 in all months in 2016. Free chlorine was at its lowest in May 2016 (0.68 mg L-1) increasing by month to its highest value (0.74 mg L-1). This does not correspond with the cell count trend. Despite increased chlorine in the summer months intact cells continued to increase. Figure 9 - Mean a) intact cells mL-1 and b) free chlorine residual (mg L-1) at the works outlet of all sites measured in 2016 by month. Intervals represent individual standard deviations (95% confidence for the mean).
Intact cell removal across the chlorination process was strongly influenced by the minimum Ct value for the site. Sites with poor Ct had the lowest level of removal and consequently the highest number of intact cells left at the end of the process. This supports the use of flow cytometry to validate Ct calculations, sites where Ct was >20 mg.min L-1 had significantly less intact cells. The Ct values quoted are the minimum that is achieved at each site at maximum works flow. In practice Ct values will be significantly higher, as most works were significantly below capacity on day of sampling. The World Health Organisation (WHO) recommend a Ct of 1 mg l-1 of free chlorine for 30 mins (below pH 8) is sufficient to inactivate three log units of bacterial and viral pathogens in treated water, with disinfection of protozoa unachievable in practice. Different bacteria are inactivated by varying Ct levels, with most bacterial pathogens requiring <2 mg.min L-1 (World Health Organisation, 2004; World Health Organisation, 2011). From these results it is suggested that significantly higher levels of Ct are required to reduce heterotrophic bacteria by three log units in drinking water. It is hypothesised that fluctuations in Ct due to flow, as well as pH and temperature will influence the removal of intact cells (Nocker, et al., 2007; Haas & Karra, 1984; Virto, et al., 2005), although further monitoring of these parameters across the chlorination process alongside cell counts is required to verify this. Sites where the level of removal was lower during chlorination had a much higher residual removal of intact cells in the treated water storage tank due to the persistence of free chlorine residual. This was reversed in sites with high removal of cells during chlorination. This residual removal is therefore important in reducing cell numbers in sites with poor Ct. However despite this high level of removal, it should be noted that chlorination post CCT is occurring at much lower rate due to increases in pH prior to storage of treated water. This residual Ct will be significantly lower, and may not be sufficient to inactivate bacterial pathogens (LeChevalier, 2013; Nocker, et al., 2013).
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THOM ET AL USING FLOW CYTOMETRY TO IMPROVE UNDERSTANDING OF CHLORINATION PROCESSES IN DRINKING WATER TREATMENT
Intact cell count removal during chlorination was not significantly affected by cell removal across upstream processes on the day of sampling across all sites, despite significant differences in filter outlet cell counts. However it is interesting to note that sites where a supplementary clarification stage existed had a higher median cell count at the filter outlet. This may be due to higher loadings leading to higher removal, but also due to biological activity in the filter increasing cell removal across the process. Rapid sand filters have a moderate level of biological filtration (Bar-Zeev, et al., 2012). A recent study highlighted the potential for significant bacterial activity in rapid sand filters when treating groundwater, and proposed that mineral coatings which formed on the sand grains over time increased microbial colonisation (Gulay, et al., 2014). It is difficult to make comparisons to other studies using flow cytometry to assess treatment performance, as most have focused on total cells and different treatment processes. Removal of 103 total cells mL-1 across primary ozonation processes, and regrowth across Granular Activated Carbon (GAC) filters to 105 cells mL-1 have been reported (Hammes, et al., 2008). Although total cells at the outlet of filtration in this study were similar, coagulation and filtration processes use very different mechanisms. Unlike coagulants, ozone is a powerful bactericide and GAC filters are more active biologically than sand filters.
may explain the higher average removal values from the weekly monitoring on sites compared to the day of sampling. Other studies have reported significantly lower raw water cell counts, 1x106 total cells mL-1 (Lake Switzerland) (Hammes, et al., 2008).
These results highlight the complexity of bacterial survival and proliferation throughout drinking water treatment. The influence of raw water cell counts, upstream processes and Ct on the removal of intact cells across the chlorination process may change with an increased data set. Only five samples were taken at each process stage across a single day, and with evidence of variation in raw and final cell counts it is predicted that chlorination cell removal changes over time. A validated method for online monitoring of cell counts has been developed, using the same staining methods (Besmer, et al., 2016; Besmer, et al., 2014). This technique is proposed as useful in developing this research further. In addition this study represented only a small proportion of surface water treatment systems in Scotland. Increasing the number of sites which are monitored may refine understanding of the impact of these parameters.
The variation of final water cell counts within sites was distributed seasonally. Peaks of intact cells were evident in spring and summer months (March-April and June-August) when comparing all data. Changes in temperature and precipitation may lead to the aforementioned variation in raw water cell counts and removal across the treatment process. Temperature and rainfall are significant factors in affecting bacterial concentrations in surface water sources (Le Chevalier, 1990). The monthly mean values of free chlorine did not correlate with the increases in cell counts across all sites. Other studies propose that disinfectant residual is a significant factor in limiting intact cells, where values of >0.5 mg L-1 limit cell growth (Gillespie, et al., 2014). As free chlorine residuals were significantly higher, this may affect any correlation and other factors like raw water loadings and treatment performance may be more significant in affecting final water intact cells.
Final water cell counts Final water intact cells also had significant variability both within and between the sites monitored. Variability of final water intact cells in this study was lower than in a study of three drinking water systems in Scotland, where cells varied between 102-105 cells mL-1 (Gillespie, et al., 2014). The differences may be due to the fact that chloraminated systems were not included in this study. Chloraminated water produces higher levels of intact cells in the final water compared to those with a free chlorine residual, but an overall lower regrowth potential (Gillespie, et al., 2014). Chloraminated water uses ammonium bound to the majority of the free chlorine residual and is therefore a less powerful oxidant (Haas, 2000). It has also been suggested that chlorine and chloramine act upon different cell membrane proteins (Watters, et al., 1989). Sites using monochloramine residuals may limit residual cell removal post chlorination in comparison to those using free chlorine and therefore may have a higher final water intact cell count.
Weekly monitoring samples Significant variation in cell removal from raw water to final was evident from weekly monitoring samples. This significant variation in cell removal is achieved across the year at all sites assessed in this study, and this was reflected in differences in the raw water cell counts. Raw water cell counts may change seasonally, as many Scottish surface waters exhibit seasonal shifts in colour and organic levels (Evans, et al., 2005). A study of Scotlandâ&#x20AC;&#x2122;s raw surface waters reported Dissolved Organic Carbon (DOC) concentrations of <8.3 mg L-1 and colour of <76 Hazen (Valdivia-Garcia, et al., 2016). However results from Scottish Waterâ&#x20AC;&#x2122;s routine monitoring of raw water routinely return values of 50 mg L-1. The maximum value of intact cells from a surface water source in this study was 5.34x106 cells mL-1 demonstrating that high organic availability in Scotlandâ&#x20AC;&#x2122;s surface waters may contribute to higher raw cell count concentrations, and
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The HPC results did not correlate to intact cell counts in this study. Weak correlations between HPCs and total cell counts in drinking water have been identified in assessments of total cells in drinking water (Siebel, et al., 2008). Hammes et al (2008) also reported that HPC trends followed that of total cells, although there was a high standard error associated with HPCs-30%. The lack of correlation between HPCs and intact cells in this study may be due to the lower concentrations of both. Most sites commonly returned 0 cfu mL-1 making statistical analysis of the data-set difficult. However, both Sites 4 and 8 had the highest median intact cell concentrations as well as the highest HPCs, suggesting that HPCs could correlate to intact cell counts where concentrations are above a certain threshold.
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Flow cytometry Flow cytometry methods have become well established in the water industry over the past five years. SYBR Green / Pi staining is a robust method of enumerating cell counts which is significantly more accurate than HPCs, and allows the enumeration of the high proportion of viable but not culturable bacteria (Hammes & Egli, 2010). However, it should be noted that although an intact polarized cell membrane is important to bacterial viability, this is not the sole factor; therefore cells may be intact but not viable (Hammes, et al., 2010). For example, Ultra Violet (UV) disinfection mechanisms inactivate pathogens by disrupting DNA replication, without disrupting the membrane (LeChevalier, 2013). To assess removal of viable cells across disinfection some studies have employed the use of amplification techniques like quantitative PCR (Nocker, et al., 2007) while others have used a combination of flow cytometric and cell sorting methods to isolate cells which are active enzymatically (carboxyfluorescein diacetate, CFDA) in addition to having an intact cell membrane. This method reported considerably lower values for cell removal across the entire treatment process, 2.11-2.89 log units of viable intact cells (Hoefel, et al., 2005). This suggests that although higher intact cell removals were found across treatment processes in this study, not all of the removed cells may have been viable. This further highlights the complexities in assessing bacterial survival and proliferation throughout the drinking water treatment process.
Conclusions Flow cytometry is a robust method of assessing the chlorination of drinking water, but a complex range of factors influence bacterial removal. Intact cell removal was highly variable between sites at all stages of the process, although it should be noted that although cells were intact they were not necessarily viable. The removal of intact cells strongly correlated to the minimum Ct value for the site, and suggested that Ct values >20mg.min L-1 were required to reduce heterotrophic bacteria by three logs. Sites where Ct was low relied on the persistence of the free chlorine residual to reduce intact cells to similar levels, although at a much lower rate. More work is required to assess the influence of upstream process capability and the high raw water loadings experienced in comparison to other studies, especially as weekly monitoring had significant variations in cell removal throughout the year. Intact cells in final waters were low compared to other studies, potentially due to the high free chlorine residual. Seasonal variation was evident across the whole data-set between March and April and again between June and August. The HPCs did not correlate to the final water cell counts, demonstrating the value of flow cytometry in moving beyond traditional analytical methods in assessing drinking water quality. Acknowledgements Thanks to Ryan Cheswick and Andrew Upton for their advice and help with research, and to the Microbiology team at Scottish Water for help with analysis. Thanks also to Jemma Beedie for her help with proof reading.
References Allen, M. J., Edberg, S. C., & Reasoner, D. J. (2004). Heterotrophic plate count bacteria-what is their significance in drinking water? International Journal of Food Microbiology, 92(3), 265-274. Bartram, J., Cotruvo, J., Exner, M., Fricker, C., & Glasmacher, A. (2004). Heterotrophic plate count measurement in drinking water safety management: report of an Expert Meeting Geneva, 24–25 April 2002. International Journal of Food Microbiology, 92(3). Bar-Zeev, E., Belkin, N., Liberman, B., & Berman, T. (2012). Rapid sand filtration pretreatment for SWRO: Microbial maturation dynamics and filtration efficiency of organic matter. Desalination, 286, 120-130. Berney, M., Vital, M., Hulshoff, I., Weilenmann, H., Egli, T., & Hammes, F. (2008). Rapid, cultivationindependent assessment of microbial viability in drinking water. Water Research, 42(14), 4010-4018. Besmer, M., Epting, J., Page, R., Sigrist, J., Huggenberger, P., & Hammes, F. (2016). Online flow cytometry reveals microbial dynamics influenced by concurrent natural and operational events in groundwater used for drinking water treatment. Scientific Reports, 6(1). Besmer, M., Weissbrodt, M., Kratochvil, B., Sigrist, J., Weyland, M., & Hammes, F. (2014). The feasibility of automated online flow cytometry for in-situ monitoring of microbial dynamics in aquatic ecosystems. Frontiers in Microbiology, 5. Carter, J. T., Rice, E. W., Buchberger, S. G., & Lee, Y. (2000). Relationships between levels of heterotrophic bacteria and water quality parameters in a drinking water distribution system. Water Research, 34(5), 1495-1502. Chick, H. (1908). An Investigation of the Laws of Disinfection. The Journal of Hygiene, 8(536). Chowdhury, S. (2012). Heterotrophic bacteria in drinking water distribution system: a review. Environmental Monitoring and Assessment, 184(10), 6087-6137. Drinking Water Quality Regulator for Scotland. (2016). Annual Report on Drinking Water Quality. Edinburgh: DWQR. Evans, C., Monteith, D., & Cooper, D. (2005). Long-term increases in surface water dissolved organic carbon: Observations, possible causes and environmental impacts. Environmental Pollution, 137(1), 55-71. Figueros, M., & Borrego, J. J. (2010). New perspectives in monitoring drinking water microbial quality. International Journal of Environmental Research and Public Health, 7(12), 4179-4202. Gatza, E., Hammes, F., & Prest, E. (2013). Assessing water quality with the BD Accuri™ C6 flow cytometer. White Paper. BD Biosciences. Gillespie, S., Lipphaus, P., Green, J., Parsons, S., Weir, P., Juscoviak, K., et al. (2014). Assessing microbiological water quality in drinking water distribution systems with disinfectant residual using flow cytometry. Water Research, 65, 224-234. Gulay, A., Tatari, K., Muscovic, S., Matieu, R., Albrechtsen, H., & Smets, B. (2014). Internal Porosity of Mineral Coating Supports Microbial Activity in Rapid Sand Filters for Groundwater Treatment. Applied and Environmental Microbiology, 80(22), 7010-7020. Haas, C. (2000). Disinfection. In R. Letterman (Ed.), Water Quality & Treatment, A Handbook of Community Water Supplies (5th ed.). New York: McGraw-Hill, Inc. Haas, C., & Karra, S. (1984). Kinetics of microbial inactivation by chlorine-I Review of results in demandfree system. Water Research, 18(11), 1443-1449. Haas, C., & Karra, S. (1984). Kinetics of microbial inactivation by chlorine-II Kinetics in the presence of chlorine demand. Water Research, 18(11), 1451-1454. Hammes, F., & Egli, T. (2005). New Method for Assimilable Organic Carbon Determination Using FlowCytometric Enumeration and a Natural Microbial Consortium as Inoculum. Environmental Science & Technology, 39(9), 3289-3294. Hammes, F., & Egli, T. (2010). Cytometric methods for measuring bacteria in water: advantages, pitfalls and applications. Analytical and Bioanalytical Chemistry, 393(3), 1083-1095. Hammes, F., Berger, C., Egli, T., & Koster, O. (2010). Assessing biological stability of drinking water without disinfectant residuals in a full-scale water supply system. Journal of Water Supply: Research and Technology—AQUA, 59(1), 31. Hammes, F., Berney, M., Wang, Y., Vital, M., Koster, O., & Egli, T. (2008). Flow-cytometric total bacterial cell counts as a descriptive microbiological parameter for drinking water treatment processes. Water Research, 42(1-2), 269-277. Hoefel, D., Monis, P., Grooby, W., Andrews, S., & Saint, C. (2005). Profiling bacterial survival through a water treatment process and subsequent distribution system. Journal of Applied Microbiology, 99(1), 175-186. Le Chevalier, M. (1990). Coliform regrowth in drinking water: a review. Journal-American Water Works Association, 82(11), 74-86. LeChevalier, M. (2013). Water Treatment and Pathogen Control: Process Efficiency in Achieving Safe Drinking-water. Water Intelligence Online, 12. Nocker, A., Burr, M., & Camper, A. K. (2013). Pathogens in water and biofilms. In S. L. Percival, M. V. Yates, D. Williams, R. Chalmers, & N. Gray (Eds.), Microbiology of Waterborne Diseases. Academic Press. Nocker, A., Sossa, K. E., & Camper, A. K. (2007). Molecular monitoring of disinfection efficacy using propidium monoazide in combination with quantitative PCR. J. Microbiol. Methods, 70, 252-260. Robertson, W. a. (2003). The role of HPC in managing the treatment and distribution of drinking water. In Heterotrophic Plate Counts and Drinking-Water Safety (pp. 137-145). London: WHO IWA Publishing. Siebel, E., Wang, Y., Egli, T., & Hammes, F. (2008). Siebel, E., Wang, Y., Egli, T. and Hammes, F., 2008. Correlations between total cell concentration, total adenosine tri-phosphate concentration and heterotrophic plate counts during microbial monitoring of drinking water. Drinking Water Engineering and Science, 1(1), 1-6. Standing Committee of Analysts. (2009). The Microbiology of Water 2009: Part 4- Methods for the Isolation and Enumeration of Coliform Bacteria and Escherichia coli (Including E. coli O157:H7). London: Her Majesty's Stationery Office. Standing Committee of Analysts. (2012). The Microbiology of Drinking Water 2012: Part 7-Methods for the Enumeration of Heterotrophic Bacteria. London: Her Majesty's Stationery Office. Valdivia-Garcia, M., Weir, P., Frogbrook, Z., Graham, D., & Werner, D. (2016). Climatic, Geographic and Operational Determinants of Trihalomethanes (THMs) in Drinking Water Systems. Scientific Reports, 6(1). Van der Kooj, D. (2003). Managing regrowth in drinking water distribution systems. In Heterotrophic Plate Counts and Drinking-Water Safety (pp. 199-232). London: IWA Publishing. Virto, R., Manas, P., Alvarez, I., Condon, S., & Raso, J. (2005). Membrane damage and microbial inactivation by chlorine in the absence and presence of a chlorine-demanding substrate. Applied and Environmental Microbiology, 71(9), 5022-5028. Vital, M., Dignum, M., Magic-Knezev, A., Ross, P., Rietveld, L., & Hammes, F. (2012). Flow cytometry and adenosine tri-phosphate analysis: Alternative possibilities to evaluate major bacteriological changes in drinking water treatment and distributio. Water Research, 46(15), 4465-4676. Watters, S. K., Pyle, B. H., LeChevalier, M. W., & McFeters, G. A. (1989). Enumeration of Enterobacter cloacae after chloramine exposure. Applied and Environmental Microbiology, 55(12), 3226-3228. World Health Organisation. (2004). Process Efficiency in Achieving Safe Drinking Water. In W. H. Organisation, M. W. LeChevalier, & A. Kwok-Keung (Eds.), Water Treatment and Pathogen Control. London, UK: IWA Publishing. World Health Organisation. (2011). Microbial Aspects. In Guidelines for Drinking Water Quality (4th ed.). Geneva: IWA Publishing.
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ENTRADE USING REVERSE AUCTION TO SUPPORT DELIVERY OF CATCHMENT OFF-SETS
Using Reverse Auctions to support delivery of catchment off-sets James Peacock Product Manager, EnTrade
Abstract Water companies are experiencing increased levels of pollution in water sources, and sewage discharges are facing tighter restrictions to meet higher environmental standards. Since privatisation, water companies have invested over £100 billion on improving assets and meeting tougher European standards. This asset led approach has been necessary, but increasingly water companies are looking to catchment led approaches to deliver better water quality.
Poole Harbour Poole Harbour is a high profile site in the Wessex Water region and has some of the highest levels of biodiversity in UK. It is an important bird habitat, protected as a RAMSAR site, a SSSI and as a SAC/SPA.
Since June 2016, Wessex Water have been working with EnTrade, trialling a reverse auction platform to help deliver nitrogen offsets through catchment management. This approach invites farmers and others to bid for funding for environmental improvements to offset capital works that Wessex Water would otherwise build. In this article, we discuss experiences of this approach to reducing pollutant loadings, and discuss benefits as well as lessons learnt. Key words: Nitrogen; phosphorus; catchment management; reverse auction; payment for ecosystem services
Despite significant investment to reduce nutrient inputs from sewage treatment works in the catchment, further reductions are required to meet Water Framework Directive standards. At the last price review, the regulators asked us to reduce the amount of nitrogen we discharge in to the catchment over the AMP by 40 tonnes.
The last forty years have seen a marked increase in levels of nitrate flowing from the catchment in to the Harbour. The catchment is currently at risk from eutrophication from nitrate pollution, and Wessex Water is one of the contributors to this.
Additional or upgraded sewage treatment is becoming less costbeneficial, particularly as we address smaller sites. For example, nitrogen removal at Dorchester sewage treatment works would cost around £6m to install and £0.4m annually to operate, but remove less than 2% of the total annual load to Poole Harbour from all sources.
Levels of nitrates have been increasing in the Poole harbour catchment for 50 years
Source of nitrogen in the Poole Harbour catchment – 66% is from agriculture
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The majority of nitrate losses comes from agriculture in the catchment, and therefore this is where the best opportunities for reduction are. Costs for a catchment management approach will be substantially less than an asset approach even on a whole life basis. For example in Poole Harbour the 40 tonne nitrogen saving can be achieved for a quarter of the cost of an asset approach. Catchment management measures also have a lower overall carbon footprint, and can provide additional benefits such as biodiversity gain. We decided to use a reverse auction as an alternative way to deliver this 40 tonne of nitrogen saving as a fair way to set the price. Oil Radish – a type of cover crop grown over winter to reduce nitrogen leaching
Reverse auctions Reverse auctions are not new. They work best for simple commodities, and have been popular in procurement for 30 years. They help to find the market price for a commodity, in our case ecosystem services. This means the price paid for services should be fair to buyers and sellers, and based on supply and demand in the market.
Auction design When designing an auction, there are a number of considerations to make. These decisions require a balance between the overall price obtained and engagement with farmers and other stakeholders. The main considerations are shown in the Table1.
Scheme
Description
EnTrade approach
Information disclosure
If average or the maximum accepted bid is published, or the distribution of bids received the previous bidding rounds, this could influence collusion or strategic bidding.
Reveal threshold price and position but not exact range of bids
Single vs multiple objectives
Single objective is more straightforward, but may inadvertently increase in another type of pollutant. Multiple objectives can be complicated but focuses on solutions that can maximise environmental benefits without causing negative environmental impacts.
Single objective, as the focus here is on nitrates, with a view to expanding to multiple objectives in the future.
Discriminatory vs Uniform Pricing
Discriminatory pricing, so that we pay what With uniform price everyone is paid the same as the highest bidder, whilst with discriminatory pricing you are people bid. paid the exact price you bid. Under a discriminatory pricing format, bidders with low opportunity cost may overstate their true cost in order to secure a profit. Bidders with higher opportunity cost may bid more closely to their true opportunity cost in order to ensure that they are accepted.
Hard vs Soft Close
Hard-close would encourage bidders to wait till the last minute to submit a bid that they know would beat the winning bid, giving others insufficient time to respond. Soft-close would automatically extend the finish time for bids that are made within a pre-specified time to prevent ‘sniping’ attempts.
Reverse auctions have also been used before for environmental improvements, such as the schemes at Chesapeake2 in the US and Lake Taupo3 in new Zealand. Systems are also available for simple offsets, and basic reverse auction systems are available. Other schemes have run one-off reverse auctions – for example the Fowey River auction run by South West Water in 2012-134.
Hard close as this would be seen as the fairest and simplest system.
At Wessex Water, we were keen to see if we could deliver the auction through an on-line platform. We felt that developing this was critical to demonstrating the scalability of a reverse auction. There was no system that brings together reverse auctions with catchments analysis, and this is what we wanted to try with Poole Harbour and EnTrade.
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ENTRADE USING REVERSE AUCTION TO SUPPORT DELIVERY OF CATCHMENT OFF-SETS
What does EnTrade do? We wanted to design a system that allows farmers to bid to put in nitrate reducing measures, such as growing cover crops on fields that would otherwise be bare and for arable reversion. As reverse auctions are new in catchment management, we wanted to make the process as simple as possible for farmers. We therefore wanted to build a system, which calculates estimated savings based on details entered by the farmer for particular measures, and gives real time results from the auction. Taking the platform on-line also gave us an opportunity to address the admin burden of catchment management.
Measures - Cover crops One way to deliver nitrogen savings is to grow cover crops over the winter period. Cover crops are crops sown in the autumn after a commercial crop, where the next commercial crop would not be grown until the spring. The cover crops reduce leaching by taking up residual nitrogen held in the soil and by providing ground cover over the winter, when most leaching occurs. In our reverse auction, bids are ranked on the basis of value for money - Cost effectiveness. Cost-effectiveness is made up of two components: •
the fee paid to the grower for growing a cover crop and
•
the effectiveness of that cover crop in reducing the amount of nitrogen leached.
Taking account both gives us an overall £/kg nitrogen, the basis for the ranking in the auction. A number of factors affect the effectiveness of a cover crop in reducing nitrogen leaching. These include: •
level of residual nitrogen in the soil,
During an auction, a farmer selects the type of cover crop they will grow and the date they expect to grow it. The system then takes this date and calculates effectiveness (in kgN/ha) using a derived curve function for the selected cover crop, shown above. Farmers enter details of their bid, and EnTrade calculates the effectiveness of their bid automatically
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•
climate,
•
rainfall,
•
soil type,
•
geology,
•
date cover crop is sown and
•
variety of cover crop.
Date of sowing and choice of cover crop are directly in the control of the grower, and therefore we use these factors to influence the estimate of effectiveness. The conceptual understanding is that the earlier a cover crop is sown the greater the effectiveness, but the impact of sowing date will differ between crops. Residual soil nitrogen is not used as a factor as this could create a situation where a grower increases levels of residual soil nitrogen in the autumn to improve their standing in the auction - an unwanted outcome.
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Farmers can adjust their bid at any point throughout the auction, and once closed the buyer of the offsets can calculate the most costeffective combination of bids to meet their given target.
in the platform. This data then is fed back in to the platform to continuously improve the calculations, and therefore the accuracy of the estimates.
Results
Analysing samples for soil mineral nitrogen (SMN) to validate impact of environmental measures
EnTrade have now run six auctions with Wessex Water, United Utilities and Natural England since June 2016. These auctions have included arable reversion, cover crops and buffer strips. In total 150 tonnes of nitrogen reduction measures have been bid through the platform, from nearly 50 farmers. There have now been over 1000 bids across 3200 hectares in 475 fields. In Poole Harbour, the auction approach has resulted in an overall cost per kg of nitrogen saved of £1.40 per kg N (£76 per hectare) for cover crops. This is 20% less than the overall average of all bids of £1.68 (£97 per hectare), showing the value of the auction process. In addition to this, this reverse auction approach moves from a flat fee on a per hectare basis, to a payment based on the overall saving of the measure. By providing instant feedback to farmers on the effectiveness of the measures they are proposing, the overall cost can be reduced. We found a further 20% saving when compared with the approach of just taking the cheapest on a cost per hectare basis. This gives a broad range on a cost per hectare basis, from £38 to £125 per hectare, which is more difficult to administer, but a lower cost overall. In addition to the nitrate savings achieved, the measures put in by farmers have also had biodiversity and soil erosion benefits. We have achieved this by working with soil scientists and biodiversity experts from our catchment management team, to make sure we make the most of the funding. In future auctions we will aim to quantify these additional natural capital benefits, which could be enhanced by combining further funding from other sources. Monitoring The major drawback with using catchment management to tackle water body pollution is that there are greater uncertainties around its effectiveness – there is no end pipe where you can take a sample. To address this, we have implemented a significant sampling and testing programme that supports the calculations used in EnTrade and to confirm the actual impacts of the completed measures. This has involved analysis in all fields and leachate analysis in a representative cross-section and sites associated with the auctions. For the first auction, the farmers carried out their measures during the autumn and winter of 2016/17. Our catchment advisers conduct follow-up visits to ensure that the work is being carried out, and we make payment once we were satisfied of this. The planting of cover crops by farmers had an over 90% success rate, and our sampling results have shown that the measures have been successful in delivering the required savings, very close to the estimated savings
Engagement We have been oversubscribed in the majority of auctions we have run so far. We devised EnTrade as an auction as it allows us to find a fair market price, for both buyers and sellers. However, the auction approach was not universally popular initially. It was seen by some as a ‘race to the bottom’, rather than a system that produces a fair price for all. As we have been oversubscribed for the majority of our auctions, we have only been able to contract with 40% of the bids entered in to the system. In order to drive price reduction through the auction process, we require a greater supply of bids than the demand for nitrogen savings. However, this must be balanced against the desire to engage with as many farmers as possible. We have found in our feedback surveys that 70% of farmers who use the system are positive about it for our first auction. This increased to 90% in the most recent auction. We are currently carrying out some work to find out about the eligible farmers who have not bid. In order to help farmers through the process and further understand the impacts of their measures, we carried out an awareness raising campaign. This was done with farmers through live talks and discussion, leaflets and through the system itself. We also carried out many site visits to discuss with the farmers how to use the system. Some users were not confident with technology so this too needed to be managed, but all farmers who wanted to take part were able to place a bid.
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ENTRADE USING REVERSE AUCTION TO SUPPORT DELIVERY OF CATCHMENT OFF-SETS
The system itself was also an important educational tool. Farmers were able to change the options of their bid â&#x20AC;&#x201C; such as sowing date and type of cover crop, to produce the most efficient measure, and therefore the best price. Future developments Wessex Water will also be trialling EnTrade for delivery of phosphorus savings in its Brinkworth Brook catchment in 2018. This module will take in to account background loadings of phosphorus in different areas of the catchment and different impact of measures. Other water companies have also expressed an interest in trialling the platform. EnTrade will be trialled for delivery of funding through non-auction routes in January 2018. This will involve funding for fertiliser spreader calibration in the Poole Harbour catchment, where impact is made across many fields. This will test the system to see if it can be used beyond auction allocation funding, for example in reducing pesticides.
Similarly, EnTrade could be used for other agri-environment support, in particular after Brexit, with Natural England interested in its applications. We are also investigating how we can increase automated verification that measures have been put in place, through photos, satellite imaginary and blockchain technologies. References 1. Environment Agency (2012) Reverse Auctions for Diffuse Pollution in the South East, Environment Agency, Bristol, Ref: 26554/R 2. Rees, G. & K. Stephenson. (2014). Transaction Costs of Nonpoint Source Water Quality Credits: Implications for Trading Programs in the Chesapeake Bay Watershed, Report to the Office of Environmental Markets, Office of the Chief Economist, United States Department of Agriculture. Washington DC. 3. Connor, J.D., MacDonald, D.H., Morrison, M. and Cast, A., 2009. Evaluating policy options for managing diffuse source water quality in Lake Taupo, New Zealand. The environmentalist, 29(4), p.348. 4. Everard, M. (2014) Integrating integrated water management. Proceedings of the ICE - Water Management, 167 (9). pp. 512-522. ISSN 1741-7589
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PERKINS ET AL OBTAINING EVIDENCE FOR “EVIDENCE BASED MANAGEMENT”: THE TASTE AND ODOUR PROBLEM
INSTITUTE OF WATER JOURNAL ISSUE 2
Obtaining evidence for “Evidence based management”: The taste and odour problem Perkins, RG
Andrade, T
Pearson, P
Froggatt, T
School of Earth and Ocean Sciences, Cardiff University & Catchment Management Team, Dŵr Cymru Welsh Water
Catchment Management Team, Dŵr Cymru Welsh Water
Catchment Management Team, Dŵr Cymru Welsh Water
Catchment Management Team, Dŵr Cymru Welsh Water
Abstract This article explains how scientific evidence generated through Welsh Water and academic collaboration is driving forward our ability to safeguard drinking water quality and improve customer acceptability. This is investigated in the face of increasing risk from climate change, specifically focusing on the issue of taste and odour in drinking water supply. Earthy and musty taste and odour complaints have been attributed primarily to the production of volatile organic compounds, methylisoborneol (MIB) and geosmin, in water supply reservoirs by filamentous cyanobacteria. One of
Introduction In recent years there has been a UK-wide increase in customer complaints regarding drinking water supply due to earthy and musty taste and odour (Drinking Water Inspectorate data). The cause of this has been linked to volatile organic compounds (VOCs), in particular 2-Methylisoborneol (MIB) and 1,10-dimethyl-trans-9decalol (geosmin). MIB and geosmin are natural, harmless organic compounds produced by a wide range of organisms, including cyanobacteria, actinomycetes, fungi and higher plants. In water supply reservoirs, the main producers are the cyanobacteria1,2,3, in particular the filamentous species such as Oscillatoria and Dolichospermum (formerly Anabaena)3,4,5. The problem to the Water Industry is that, when the cyanobacteria are damaged or die, geosmin and MIB are released and hence get into the water supply system, either in the reservoir or during treatment. Their removal then requires treatment, including the use of activated granular or powdered carbon (GAC and PAC respectively) filtration. There is an urgent need to determine the triggers for geosmin and
the key triggers of production has been identified as the relative abundance of ammonium compared to other nitrogen sources, principally nitrate. When other nutrients, e.g. phosphorus, are available to specific strains of cyanobacteria, and environmental conditions of temperature and light are favourable, rapid growth stimulates production of MIB and geosmin. These compounds are stored internally by the cyanobacteria cells, but can be released into the water column later, causing elevated concentrations that may not be removed at the water treatment works. In order to prevent this issue exacerbating due to climate change, catchment management interventions, well evidenced by sound scientific research, are urgently needed.
MIB production. Cyanobacteria like warm shallow water systems, typical of those predicted under climate change scenarios and resulting from reduced river abstraction legislation. Shallower reservoirs are often associated with increased nutrient supply, e.g. through release of phosphate from muddy bottom sediments that store nutrients over time (internal loading)6,7. Cyanobacteria are extremely good at outcompeting algae for phosphate, resulting in rapid growth and potential cyanobacteria blooms, which is exacerbated by warmer water enabling faster growth8. Will treatment keep up with increased taste and odour risk resulting from climate change? Will treatment remain cost effective or environmentally sustainable as PAC/GAC costs and carbon footprints for their use rise? A robust solution to these issues is likely to incorporate catchment management, working with land users and managing catchments and reservoirs to prevent geosmin and MIB production in the first place. Catchment management, like all management intervention, needs to be evidence based. To be effective in mitigating geosmin and MIB problems, we need the evidence required to determine the triggers for the production of these compounds and then to determine the actions required to reduce their presence prior to abstraction to
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PERKINS ET AL OBTAINING EVIDENCE FOR “EVIDENCE BASED MANAGEMENT”: THE TASTE AND ODOUR PROBLEM
water treatment works. Dŵr Cymru Welsh Water (hereafter Welsh Water), in collaboration with a Natural Environment Research Council (NERC) internship from Cardiff University, has been investigating this by analysing findings from catchment surveys and reviewing scientific research on geosmin and MIB. An early outcome has been the establishment of the UK Water Industry Taste and Odour Working Group at the start of 2017. The following outlines how initial findings are helping frame our current understanding of the problem and how the Working Group collaboration can generate the evidence for catchment management intervention. The biology of MIB and geosmin production 2-Methylisoborneol (MIB) and trans 1,10-dimethyl-trans-9-decalol (geosmin) are tertiary alcohols existing as a monoterpene and a sequisterpene respectively9. They are produced by a wide range of organisms, including fungi, streptomycetes and cyanobacteria4, although cyanobacteria are considered to be the primary source in aquatic environments where photosynthetic growth is possible1,2,3. MIB and geosmin producing cyanobacteria are commonly found within water supply reservoirs in the form of shoreline benthic biofilms (e.g. Oscillatoria7) or as plankton (e.g. Dolichospermum3, previously known as Anabaena). Both compounds produce an earthy and musty odour which can be detected by humans at very low concentrations, 5 ng l-1 for MIB and 10 ng l-1 for geosmin3,10. MIB and geosmin are produced by the mevalonate (MV) and 2-methylerythritol-4-phosphate isoprenoid (MEP) metabolic pathways3,4. They are precursors for a range of important cellular compounds in cyanobacteria, such as sterols and pigments1,3,4, with the MV pathway for sterol production in the cytosol compared to photosynthetic pigment synthesis via the MEP pathway in plastids3. Synthesis of geosmin and MIB in actinobacteria has been attributed to the MEP pathway4, which appears to be the dominant pathway during rapid growth11. These pathways are also found in cyanobacteria3,4, and periods of high productivity, rather than high biomass correlate with high MIB and geosmin production12, and high MIB has been reported at times of high ATP synthesis13. Previous studies attempting to correlate MIB and geosmin with biomass or cell counts have had little success11, and correlation with primary productivity would likely be more successful. It is highly likely that MIB and geosmin production are the result of periods of rapid growth phase by cyanobacteria when exposed to favourable nutrient supply and environmental conditions which stimulate synthesis of MIB and/or geosmin. Furthermore most studies, along with UK Water Industry sampling, have measured solely dissolved extracellular forms of MIB and geosmin, however both compounds also occur as intracellular dissolved and particulate bound forms, likely released by cyanobacteria during later, slower growth phases and not at the time of production associated with rapid growth phase3,14. This is of paramount importance as it disassociates the triggers of MIB and geosmin production from the time of peak concentrations detected.
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The role of nutrient ratios: a case study Plas Uchaf and Dolwen Reservoirs is a mid-altitude site (approx. 150m above sea level) in North Wales which has had significant geosmin and MIB production in spring and late summer, despite being an oligotrophic to mesotrophic site based on data for algal biomass (chlorophyll a) and total phosphorus (TP). Water inputs to Plas Uchaf include a compensation flow from Dolwen and pumped abstraction from the River Aled. Raw water from Plas Uchaf is taken by gravitational flow to Glascoed Water Treatment Works (WTW). Spatial differences in cyanobacteria taxa have regularly been recorded with Oscillatoria from the shallow end and Dolichospermum in the main basin of Plas Uchaf. Analysis of historical datasets for Plas Uchaf and Dolwen Reservoirs, has indicated a steady increase in geosmin and MIB since 2012 (Figure 2) with data suggesting two sources, a benthic biofilm of Oscillatoria (MIB and geosmin producer15) in the shallow top end of the Plas Uchaf reservoir and a planktonic bloom of Dolichospermum (geosmin producer15,16) in the deeper main body of the reservoir. Analysis revealed a negative relationship between both MIB and geosmin with total nitrogen to total phosphorus ratio (TN:TP), but a positive correlation (r2 = 0.945 and 0.824 for MIB and Geosmin respectively, n=5, p < 0.01) with ammonium (Figure 4). Data agree with literature, with geosmin production by Dolichospermum positively correlated to low TN:TP5 and high ammonium concentration, but inhibited by nitrate5,15. Findings indicate significant spatial variability within Plas Uchaf regarding nutrient regimes, MIB and geosmin production and source taxa of cyanobacteria. This is likely due to locations of inflows, abstraction point, localised water currents and stratification which redistribute external nutrient loadings13, and determine the magnitude of internal phosphorus loading6,7. Spatial patterns in N and P are well known to induce spatial differences in plankton community17. Figure 1 - MIB and geosmin concentrations in the raw water abstracted from Plas Uchaf water supply reservoir since January 2012.
INSTITUTE OF WATER JOURNAL ISSUE 2
Figure 2 - The inverse relationship between MIB (A) and Geosmin (B) and the ratio of total nitrogen to total phosphorus (TN:TP) in Plas Uchaf water supply reservoir (note the log scale).
The only significant change in nutrient supply between the two years was an 85% reduction between 2015 and 2016 in the ammonium concentration in the compensation flow from Dolwen to Plas Uchaf (Figure 4). There is a strong evidence base therefore that the relative supply of ammonium compared to nitrate and phosphate, is a primary trigger for geosmin and MIB production. This fits our understanding of cyanobacteria physiology, as they outcompete algae for ammonium and are more productive at times of adequate phosphate availability. Figure 4 - The difference in ammonium concentration between 2015 and 2016 for five sample points (SP1 to 5) in Plas Uchaf water supply reservoir and the input from Dolwen (DOL). Letters refer to the level of significant difference (one factor ANOVA with post hoc Tukey test) between years, a = p < 0.05, b = p < 0.01.
Figure 3 - The relationship of MIB and Geosmin with ammonium concentration at five sites within Plas Uchaf water supply reservoir in 2015 and 2016.
We analysed this further comparing two years in which the magnitude of geosmin and MIB production differed; in 2015 Plas Uchaf had high levels of geosmin and MIB, whereas in 2016 there was a significantly lower production of both compounds in the site.
Taking the knowledge forward: evidence for catchment management Differences in water mixing and other aspects of hydrology, balances in nutrient supply from external and internal sources, environmental conditions such as wind exposure, temperature etc. all lead to lakes and reservoirs behaving very differently from each other and, importantly, often behaving differently from year to year. Our findings from Plas Uchaf lead to important advances in our understanding of when and how geosmin and MIB are produced at this site and provide the evidence for catchment management intervention specific to this site. However what is lacking is a deeper understanding of how the triggers outlined above interact. We need to improve our knowledge to develop an overarching model that can be applied to a wide range of reservoirs. That means expanding our evidence base and studying a wider range of sites. There are two key sources of data to facilitate this, existing data in the form of previous site monitoring, and data creation through modified and improved catchment sampling. Early on in the analysis within Welsh Water, it was seen that the best solution was a UK-wide collaboration. The taste and odour issue is one that is experienced by many Water
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PERKINS ET AL OBTAINING EVIDENCE FOR “EVIDENCE BASED MANAGEMENT”: THE TASTE AND ODOUR PROBLEM
Companies and, of key importance, appears to be an expanding and increasing problem within the UK (Drinking Water Inspectorate data). Welsh Water, in collaboration with the NERC internship of one of the authors (Perkins), therefore established the UK Water Industry Taste and Odour Working Group. Sharing of the findings to date by Welsh Water and then by other Water Companies has already provided a better understanding of the magnitude of the problem, with a commonality being that MIB and Geosmin production and associated taste and odour problems are spreading through the UK and are of increasing frequency and magnitude. It was agreed that the Welsh Water experience of catchment and reservoir sampling and analysis could be used to define two phases of collaboration to address the need for a wider range of sites throughout the UK to provide the knowledge to drive a more generalised model as outlined above. The first phase of collaboration within the Taste and Odour Working Group has been the initialisation of data sharing. Each Working Group member has agreed to determine a key study site providing a wide range of water quality data including MIB and geosmin concentrations. This exercise is aimed at catching existing data and knowledge and hence is limited by previous sampling strategies, analysis methods and laboratory detection limits. The second phase of collaboration, data generation, is the establishment of a catchment and reservoir sampling protocol. Examination of existing data and findings in literature has enabled us to determine what the optimal range of variables needed, and their levels of detection, are for determining causal relationships between triggers and geosmin and MIB production. This is the most powerful dataset to support evidence based management intervention. This phase is the exciting next step of the Working Group collaboration, taking the research at UK level in to 2018 and beyond. This aspect of the work programme will then lead on to application within evidence based catchment management. Identification of sources of ammonium specific to catchments will enable interventions to be developed by working closely with stakeholders to reduce such inputs; an example might be changes in farming practices to reduce ammonium rich land management practices at key times associated with cyanobacteria productivity. Reducing nutrient stimulus for MIB and geosmin production would therefore reduce the need for more costly solutions trialled within the UK and abroad, which have included the use of barley straw, ultrasound, and recently the increased use of forced reservoir mixing (e.g. turbine mixers such as ResMix following on from bubble curtains etc.) which have been reported to have had variable success (UK Water Industry Taste and Odour Working Group member communications).
Conclusions To summarise our findings to date, when there is sufficient light and water temperature is warm enough to support increased rates of cyanobacteria productivity, elevated ammonium is likely to stimulate the metabolic processes that produce geosmin and/or MIB. When these triggers don’t align, cyanobacteria may grow more slowly and achieve high biomass, but are far less likely to produce large amounts of MIB and geosmin. We now understand the role of relative nutrient abundance in this process, but there is a real need to take this forward through collaborative research to determine how this interacts with environmental factors in order to generate two important results: i) catchment management intervention to reduce MIB and geosmin production and, ii) early warning for MIB and geosmin production where preventative intervention isn’t possible. Acknowledgements This work was partly funded by a Natural Environmental Research Council Innovation award to RP. References 1. Jůttner F, Höflacher B, Wurster K (1986) Seasonal analysis of Volatile Organic Biogenic Substances (VOBs) in freshwater phytoplankton populations dominated by Dinobryon, Microcystis and Aphanizomenon. J. Phycol. 22:169–175 2. Yagi O, Sugiura N, Sudo R (1985) Chemical and biological factors on the musty odor occurrence in Lake Kasumigaura. Jpn. J. Limnol. 46: 32–40 3. Watson, Sb, Monis P, Baker P, Giglio S (2016) Biochemistry and genetics of Taste-and Odorproducing cyanobacteria. Harmful Algae 54: 112-127 4. Jůttner F and Watson SB (2007) Biochemical and ecological control of geosmin and 2-Methylisoborneol in source waters. AEM 73:4395-4406 5. Harris T, Smith V, Graham J, Van De Waal D, Tedesco L, Clercin N (2016). Combined effects Of Nitrogen to Phosphorus and Nitrate to Ammonia ratios on cyanobacterial metabolite concentrations in eutrophic Midwestern USA reservoirs. Inland Waters 6:199-210 6. Perkins RG and Underwood GJC (2000) Gradients of chlorophyll a and water chemistry along an eutrophic reservoir with determination of the limiting nutrient by In Situ nutrient addition. Wat. Res. 34:713-724 7. Boström B, Andersen JM, Fleischer S, Jansson M (1988) Exchange of phosphorus across the sediment-water interface. Hydrobiologia 170:229-244 8. Reynolds CS (1984) Phytoplankton Periodicity: The interactions of form, function and environmental variability. Freshwat. Biol. 14:111-142 9. Bentley R and Meganathan R (1981) Geosmin and Methylisoborneol biosynthesis in Streptomycetes: Evidence for an Isoprenoid pathway and its absence in non-differentiating isolates. FEBS Lett. 125:220–222 10. Griffiths NM and Fenwick Gr (1977) Odour properties of Chloroanisoles-effects of replacing Chloroby Methyl groups. Chem. Senses Flavour 2:487 11. Seto H, Orihara N, Furihata K (1998) Studies on the biosynthesis of terpenoids produced by actinomycetes. Part 4. Formation of BE-40644 by the mevalonate and nonmevalonate pathways. Tetrahedron Lett. 39: 9497–9500 12. Zimmerman LR, Ziegler AC, Thurman EM. 2002. Method of analysis and quality-assurance practices by US Geological Survey organic geochemistry research group-determination of geosmin and methylisoborneol in water using solid-phase microextraction and gas chromatography/mass spectrometry. US Department of the Interior, US Geological Survey Scientific Investigations Report 2002–337. 13. Behr M, Serchi T, Cocco E, Guignard C, lSergeant K, Renaut J, Evers D (2014) Description of the mechanisms underlying geosmin production in Penicillium expansum using proteomics. J. Proteomics 96:13-28 14. Wu JT and Jůttner F (1988) Effect of environmental factors on geosmin production by Fischerella muscicola. Wat. Sci. Technol. 20:143-148 15. Saadoun IMK, Schrader KK, Blevins WT (2001) Environmental and nutritional factors affecting geosmin synthesis by Anabaena SP.. Wat Res 35:1209-1218 16. Smith JL, Boyer GL, Zimba PV (2008) A review of cyanobacterial odorous and bioactive metabolites: impacts and management alternatives in aquaculture. Aquaculture 280:5-20 17. Perkins RG and Underwood GJC (2001) The potential for phosphorus release across the sediment– water interface in an eutrophic reservoir dosed with ferric sulphate. Wat Res 35:1399-1406
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INSTITUTE OF WATER JOURNAL ISSUE 2
APPLICATION OF THE SCIENCES ACROSS THE WORLD OF WATER
ONE DAY SCIENCE CONFERENCE THURSDAY 3 MAY 2018 NATIONAL STEM CENTRE, YORK BOOK NOW @WWW.INSTITUTEOFWATER.ORG.UK instituteofwater.org.uk
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ATKINS ASSESMENT OF RISK TO WATER TREATMENT FROM PHYTOPLANKTON IN RESERVIORS USING LONG TERM DATA SETS
Assessment of risk to water treatment from phytoplankton in reservoirs using long term data sets Peter. W. G. Daldorph
Robin Price
Stuart Knott
Atkins Limited
Anglian Water Services
Anglian Water Services
Abstract Water treatment problems associated with large phytoplankton populations in surface water reservoirs can be severe, potentially threatening the security of supply. Such events, however, tend to occur infrequently which makes planning for them difficult in terms the development of mitigation strategies and the operational response when they occur.
these have changed over time. The reservoirs show distinct patterns regarding the level of risk, the stability of risk over time and the degree to which shifts in risk have occurred in relation to external influences. The relevance of these findings is discussed in relation to business planning, future monitoring and further development of risk analysis methods.
Highlights
Long term historical data can be a valuable resource for analysing the treatment risk associated with phytoplankton and how this changes over time. Such analysis can also be used to inform business planning of measures to reduce risk, in the catchment, reservoir and treatment works.
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Analysis of long term algal count data from three Anglian Water reservoirs to assess treatment risk
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Average weekly values compared to risk thresholds
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Rolling mean and 95 percentile values calculated to assess long term changes in populations
This paper presents long term (30-50 years) data on phytoplankton cell counts at three of Anglian Water’s surface water reservoirs; Grafham Water, Rutland Water and Ardleigh Reservoir. Cell counts are compared with treatment risk thresholds for key taxonomic groups (e.g. cyanobacteria) to estimate their return periods and how
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Return period of exceedance estimated
Introduction Surface water reservoirs are affected by a wide range of pollutants including hazardous organic substances such as pesticides and pharmaceuticals, bacteria, viruses and pathogens such as Cryptosporidium. Consequently, advanced treatment is often deployed including Dissolved Air Flotation, Granular Activated Carbon and Ozone which ensures a reliable supply of high quality drinking water. Occasionally, however, large blooms of phytoplankton can challenge these treatment processes by physical blockage of filters and the release of extracellular products that interfere with coagulation and
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Key words: Pytoplankton, Water Treatment, Risk, Cyanobacteria, Return Period
adsorption processes which can thus reduce the output from the treatment works (Knappe et al. 2004, Ewerts et al. 2013). In severe circumstances, it may be necessary to redirect supply from other sources which reduces the overall yield of the water supply system. The frequency at which severe treatment problems related to phytoplankton occur varies greatly between reservoirs because it is influenced by many factors including the nature of the catchment and the hydromorphology and hydrodynamics, the processes in the treatment stream and hydraulic loading on the treatment works. Generally, severe treatment problems are infrequent and many years may pass during which no significant treatment problems occur. Such infrequent but severe events present a problem for planning
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and investment for water companies because it is difficult maintain expertise in how to react to such events (e.g. treatment and supply) as well as the understanding of their causes and, therefore, how measures can be developed to make them less frequent.
by group specific thresholds (Table 1), a lower threshold above which some treatment problems might occur and a higher threshold above which severe treatment problems might occur based on long-term experience of treatment at these works.
A further complication is that the likelihood of severe phytoplankton blooms changes over time. Catchment measures can reduce inputs of nutrients to upstream rivers (e.g. phosphorus removal at wastewater treatment works and improved agricultural practices) whilst climate change is likely to affect patterns of algal succession and therefore the frequency of severe events (Kosten et al. 2012, Paerl & Paul, 2012).
It is important to note that the aim here is to estimate risk. It does not follow that treatment problems always occur above these thresholds, only that there is a higher level of risk. The development of treatment problems is also dependent on the species of algae within each taxonomic group and its physiological state.
Assessment of the current and ongoing risk of severe phytoplankton booms that adversely affect water treatment is, therefore, important to help maintain and develop operational systems and prioritise investment in measures. In this paper, a phytoplankton risk assessment methodology is presented using long term data sets of algal cell counts at three of Anglian Water’s reservoirs, Rutland Water, Grafham Water and Ardleigh reservoir.
Methodology All existing data on chlorophyll-a, algal cells counts and nutrients were collected from a range of sources, including paper and electronic records held by Anglian Water, the Environment Agency as well as information published in the scientific literature. Because the data covered a period of up to 50 years, the information was held in many formats. Electronic databases went back to the early 1980s whilst earlier paper records were in the form of data entry tables and graphs which were digitised. Inevitably, changes in sampling and analysis protocols occurred during this period. Documentation of this, however, no longer survives so there has been no attempt to assess changes in data quality (in general this is likely to have improved over time as quality control systems have been put in place). Algal cell counts were separated into key taxonomic groups; Cyanobacteria (blue green algae), Bacillariophyceae (diatoms), Chlorophyceae (green algae), Dinophyceae (dinoflagellates), Cryptophyceae etc. Weekly average cell counts were calculated from all sampling locations (raw water and within reservoir samples) to maximise the data period covered. The water treatment risk associated with algae is not only related to the size of the population but also the nature of the treatment processes and degree to which each taxonomic group can cause treatment problems. Treatment risk = Algal Load x Treatment Vulnerability x Treatment Difficulty Quantification of Algal Load is based on cell count data, whilst Treatment Difficulty of each key taxonomic group is defined broadly
Treatment Vulnerability (i.e. differences in the treatment works that may affect their ability to treat algal laden water) is not considered in this paper as it would require further detailed analysis. Treatment risk is compared by calculating the proportion of time exceeding the thresholds and the proportion of years in which the thresholds are exceeded. The latter metric provides a measure of the ‘return period’ of potential problems. In order to assess whether levels of risk are changing further metrics are first calculated; the ten year rolling average and 95 percentile cell count which is also used to identify a period over which algal cell counts are sufficiently stable to assess long term risk. Table 1 Treatment risk thresholds associated with different taxonomic groups of phytoplankton. Taxa
Lower Threshold
Higher Threshold
Cyanobacteria Blue green algae)
100000
250000
Chlorophyceae (Green algae)
20000
50000
Bacillariophyceae (Diatoms)
15000
30000
Chrysophyceae
10000
25000
Cryptophyceae
15000
30000
Dinophyceae
5000
10000
Xanthophyceae
10000
25000
Results Analysis of long term change in algal activity Figure 1 shows an example of the long-term data for algal cell counts and chlorophyll-a that was used in this research; in this case a longterm record for Grafham Water for the period 1970 to 2017 (i.e. 47 years) with some gaps. Similar data is available for Rutland Water (1985 to 2017) and Ardleigh Reservoir (1981 to 2017). This data illustrates the large inter year variability of the algal counts and the requirement for long term data to assess risk. For each of the three reservoirs, ten year rolling average and 95 percentile values were calculated for three key algal taxonomic groups, Cyanobacteria, green algae and diatoms. For each group,
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ATKINS ASSESMENT OF RISK TO WATER TREATMENT FROM PHYTOPLANKTON IN RESERVIORS USING LONG TERM DATA SETS
the degree to which long term change is evident was assessed to determine whether risk is increasing, decreasing or remaining stable. A period was then identified over which algal activity was sufficiently similar to that observed in the last ten years to assess ongoing risk (shown by the grey boxes on the charts (Figure 2 to 4). At Rutland Water (Figure 2), the populations of Cyanobacteria were found to be sufficiently stable over the period 1997 to 2016 to assess current risk (i.e. 19 year data series). During the period between 1985 and 1997 Cyanobacteria populations were larger. In contrast, populations of green algae and diatoms appear to be increasing after showing a decline from the early period with an increase in the statistics of 3 to 4 times since the 1990s. In these cases, therefore, it is not possible to estimate a current steady state risk. The trajectory of increasing risk is, however, an important observation for future planning. Grafham Water (Figure 3) shows substantial long term change in the size and composition on the phytoplankton populations. Populations of Cyanobacteria increased after the first ten years of the data period and then declined from the early 1990s with a period of stability in the statistics covering the period 1988 to 2016. Green algae also showed a period of increased populations but this occurred approximately ten years after the period of high Cyanobacteria counts. Diatom counts have shown a longer term increase over the data period. Ardleigh Reservoir shows a substantial decline in the counts of all three groups of algae (Figure 3) with much reduced populations from the late 1990s onward. Populations of Cyanobacteria and green algae were particularly low in the later period although there is evidence of a recent increase in diatoms and green algae albeit far below the earlier recorded values. In addition to showing the gross changes in algal populations, this analysis forms a basis for assessing the current ongoing level of risk of excessive populations. Figure 5 shows the percentage of years in which average weekly values at some point of the year exceeded the moderate and high thresholds over the period in which populations are perceived to be stable (i.e. the grey boxes in Figure 2 to 4). Where populations were not found to be stable the last ten years were used. Where risk is clearly shown to be increasing the axis is marked with an upward arrow. This analysis shows the comparative risk at the three reservoirs. For Cyanobacteria, Grafham Water and Rutland Water have the greatest current risk whereas for green algae and diatoms, Grafham Water has far the highest risk. When translated into return periods, Grafham Water has a return period of 14 years for exceedance of the moderate threshold and 29 years for exceedance of the high threshold. For both moderate and high threshold, Rutland Water has a return period of 18 years. This approach can also be used to assess shifts in population of
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particularly problematic species. Figure 6 shows the rolling mean and 95 percentile values for Microcystis, Aphanizomenon and Anabaena in Grafham Water which shows distinct shifts in their relative abundance.
Discussion The analysis presented in this paper provides a simple means to estimate the ongoing likelihood of excessive algal populations. Increasing or decreasing trends in algal cell counts can also be identified as well as a return period for populations exceeding threshold values. The concept of considering these issues in terms of a return period is important because it provides a basis for long term planning. This contrasts with the more reactive approach which tends to currently prevail in which â&#x20AC;&#x2DC;unexpectedâ&#x20AC;&#x2122; treatment problems occur followed by a response in terms of planning and investment in measures whereas during prolonged periods without problems, interest in the issue wanes. For example, several reservoirs may have recently suffered from problems associated with algal blooms. Investment to mitigate the risk is best be directed to those reservoirs with the higher longterm risk which cannot be evaluated based solely on those recent events which to some extent are determined by chance. The primary advantage of the proposed approach is to ensure that investment planning is based on risk rather than be a reaction to problems as they occur which is less likely to direct investment to where it is required. Investment may, for example, include improvements to the treatment processes (e.g. the installation of micro-strainers or dissolved air flotation or GAC/ozone to remove algal toxins), reservoir management (e.g. installation of artificial aeration or chemical dosing to remove phosphorus in pre-reservoirs or lagoons) or wider catchment management measures (phosphorus removal at wastewater treatment works), all of which can be highly expensive. The analysis can also show whether risk is increasing or decreasing, for example, as a result of climate change. The response in this case might be to invest in ongoing monitoring of the changes in phytoplankton abundance where at other sites where the risk is low or declining, monitoring might be reduced. It is important to note that the return period estimates are only valid if there are no recent or planned changes in management of the reservoir systems. For example, if substantial increases in reservoir output are planned, the likelihood of problems with algae is likely to change because of the reduced retention time. The analysis presented in the paper applies fixed algal cell count risk thresholds at all the reservoirs. The vulnerability of treatment works is, however, also a function of the treatment processes in place and the hydraulic loading of each of the treatment barriers.
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The risk assessment methodology would be improved if different thresholds were calculated for each reservoir to reflect differences in vulnerability. This might involve a review of the treatment processes in place along with an analysis of how the treatment works have coped with high algal loads in the past. This might include an analysis of backwash frequency, changes in output and the degree to which algal cells have penetrated each treatment barrier in relation to algal loads. More subjective information on how well treatment works have coped with algae as perceived by the works manager would also be informative. Improvements to recording such information and how it is reviewed might also be considered because, although often available, such data is generally used for shorter term operational management. Further analysis of this nature would provide a better evaluation of risk to again provide a better basis for investment in mitigation in the treatment processes, reservoir and catchment. Another aspect that might be considered to improve the methodology is to identify which species of algae are particularly problematic for treatment. Within the Cyanobacteria, for example some species are believed to interfere with treatment more than others but such information tends to be anecdotal and not recorded in a consistent way. Gathering such information from operators alongside a review of the scientific literature would, therefore, be useful with the aim of proving a treatment risk score for key common taxa which could be incorporated into the methodology. Development of improved methods to assess treatment risk associated with algae could form part of the Drinking Water Safety Planning process that each water company is required to undertake to meet the requirements of the Drinking Water Inspectorate and further development of the methodology is justified in this context. The causes of the observed long-term changes in algal populations
at the three reservoirs are not considered in this paper because they are complex and would require a wider consideration of data related to the controlling influences on algal populations such as nutrient inputs, climate and the introduction of measures such as aeration systems. The potential impact of climate on algal populations in water supply reservoirs is, however, an important consideration in relation to future risk. Higher water temperatures and longer growing seasons for algae linked to climate change are likely to increase treatment risk, particularly related to Cyanobacteria that are believed to be favoured by these changes (Kosten et al. 2012, Paerl & Paul, 2012). The analysis presented in this paper is reliant on the collation of long term algal cell count data and the maintenance of monitoring during periods when few problems occur. Monitoring is particularly important for low frequency severe events because it provides the only way to assess the ongoing risk and evaluate the benefits of investment in potentially expensive mitigation measures in the catchment, reservoir or treatment works. Acknowledgements The data presented in this paper is based on the work of many field and laboratory scientists at Anglian Water and the Environment Agency over a period of almost fifty years and we wish to thank them for their painstaking work. In particular, we would like to thank Amanda Pinkney and Leon Stone who help greatly in compiling the long-term data. References Drinking Water Inspectorate (2005) A brief guide the Drinking Water Safety Plans. http://www.dwi.gov. uk/stakeholders/guidance-and-codes-of-practice/Water%20Safety%20Plans.pdf Ewerts, H.E, Swanepoel, A du Preez H.H. (2013) Efficacy of conventional drinking water treatment processes in removing problem-causing phytoplankton and associated organic compounds Water SA. 39, 5 Knappe D, Belk R.C., Briley B, Gandy S, Rastogi N, Rike A, Glasgow H, Hannon E, Frazier W, Kohl P & Pugsley S (2004) Algae Detection and Removal Strategies for Drinking Water Treatment Plants (Research Report / Awwa Research Foundation) Kosten, S., Huszar, V., Be´cares, E., Costa, L., van Donk, E., Hansson, L.-A., Jeppessn, E., Kruk, C., Lacerot, G., Mazzeo, N., De Meester, L., Moss, B., Lurling, M., No¨ ges, T., Romo, S., Scheffer, M., 2011. Warmer climate boosts cyanobacterial dominance in shallow lakes. Global Change Biology, cyanobacterial dominance in shallow lakes. Global Change Biology 18(1):118 – 126 Paerl H.W, & Paul V.J (2012) Climate change: Links to global expansion of harmful cyanobacteria. Water Research, 46, 5, 1349 – 1363
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Figure 1 - Example of algal cell count data (Grafham Water) compared to moderate and high thresholds. Chlorophyll-a data is also shown for comparison.
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Figure 2 - Rolling mean and 95 percentile values for algal cell counts for the previous ten years for Rutland Water
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Figure 3 - Rolling mean and 95 percentile values for algal cell counts for the previous ten years for Grafham Water
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Figure 4 - Rolling mean and 95 percentile values for algal cell counts for the previous ten years for Ardleigh Reservoir
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Figure 5 - Return period for exceedance of the moderate and high treatment thresholds (upward arrows indicate that risk is increasing)
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Figure 6 - Rolling mean and 95 percentile values for algal cell counts for key species of Cyanobacteria at Grafham Water
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CC WATER ARE WE MISSING THE BIG PICTURE ON WATER EFFICIENCY?
Are we missing the big picture on water efficiency? M Keil
L Cotton
A Millan-Villaneda
K Gibbs
Head of Policy & Research
Consumer Research Manager
Policy Manager
Senior Policy Manger
Abstract Confronting the mounting pressure on our water resources is a challenge the water industry cannot afford to ignore. The water sector as a whole – water companies, Water UK, CCWater and other organisations such as Waterwise - has been promoting water efficiency for many years. Water saving messages to consumers tend to focus on simple ‘top tips’ for using less water, but the struggle is to engage consumers in these messages to help them stick and have a lasting impact on personal water use.
This paper describes CCWater research to explore perceptions of the bigger environmental picture of water resources both now and in the future, to see how water consumers connect this to water saving messages and their personal water use. It identifies that low awareness of the current bigger picture of water resources and how things may change for future generations is a key gap in public awareness. The research concludes that getting the message across about the ‘big picture’ is a vital starting point to set the context for water saving messages. This would help people to understand why it is important to use water carefully as well as how, and help create more meaningful engagement with water saving messages.
Introduction
people with the issues in order to create long term behaviour change and reductions in personal water use.
In 2016, Water UK published its long-term planning framework for water resources1, highlighting the huge challenges facing the industry around future water supplies. Not least is the ability of the industry to maintain reliable water supplies that consumers generally take for granted when faced with significant impacts from climate change and population growth. Water UK’s report brought into sharp focus the urgency and need for action to be taken now to address these issues, including the need for additional water resources.
The aim of our study was to provide robust evidence for us to develop our messaging and communications to consumers on water saving and resilience, so we could encourage consumers to take action. We also wanted it to help us provide good practice and lessons learned on this issue to the industry, governments and others as water companies develop their plans as part of the 2019 Price Review.
Since the Water UK report was published, household water use has increased; our December 2017 report on water supply resilience2 found that water consumption in England and Wales increased again in 2016-17, by 1.2%, to an average of 141.2 litres per person, per day. In the Methodology for the 2019 Price Review3 Ofwat proposed to make per capita consumption one of the industrywide performance commitments – setting a clear expectation that the industry must find ways of engaging and enabling household consumers to use less water. And in June 2017, Waterwise published it’s Water Efficiency Strategy4, setting out its ambitions for a more water-efficient UK to help meet the challenges of future water resources. It is in this context that the water sector must maintain reliable water supplies into the future and find effective ways of engaging
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Method In June 2017, our research partner, Community Research ran four day-long deliberative research workshops in London, York, Neath and Norwich. These were attended by 93 water customers in order to explore their attitudes towards awareness of the bigger picture around the future availability of water and attitudes to water use. Participants were recruited to ensure representation from a range of different types of water customers (including some non-bill payers), including age, gender, life-stage, socio-economic background as well as metered and unmetered customers. On recruitment, participants were also asked to rate how far they agreed with six statements relating to water use, water resources and broader environmental engagement to identify attitudes towards these and ensure a good mix for each workshop. The locations for the workshops were chosen
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to represent some of the larger water companies, a wide geography and a mix between water stressed and non-water stressed areas.
framework, that by 2050, demand for water in the UK could outstrip the amount of water available by up to 22%. Another said:
Each workshop consisted of a mix of small group discussions at tables (of around eight participants) facilitated by a moderator and information provided from the front via quizzes and animations. Participants were drip-fed information about a wide range of issues affecting water supplies now and in the future. Broadly, the information and discussions covered:
“22% is absolutely frightening. Even 5% would be scary - 30 years isn’t a lot of time to put things right.”
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Responses to a range of past messaging on environmental related issues e.g. recycling, energy and water use (to identify awareness of messages and inclination towards environmental issues/behaviours).
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Spontaneous discussions during which current attitudes and behaviours in relation to water and the future supply of water were explored (to establish baseline awareness and engagement with water specific issues).
•
Five short sessions where information on the following topics was provided, each followed by moderated round table discussions to explore awareness, reactions and effect on baseline views. The order of the topics was designed to take people on an informative journey starting with the basics of where water comes from and things that affect its availability in the environment, moving on to societal factors for water demand and water use, and finally onto the role and activities of water companies and how they manage water supplies: - - - - -
The water cycle and the impact of water shortages. The impact of extreme weather conditions. The impact of population growth. The impact of household consumption. Water company actions.
The outputs of the discussions were used to inform a report including a typology based on attitudes to water use, and an infographic with key tips for developing communications which is aimed at organisations which communicate with water consumers about water use. The full report Water saving: helping customers see the bigger picture5 is available for download from CCWater’s website.
Findings The research found low awareness and misconceptions about water resources. As participants became more informed, they generally became more concerned about the future reliability of their water supplies, and how they would be able to use water. “Shocking and frightening for future generations - we’ve got to be more careful”. This comment was made by a water customer when they were informed of this conclusion of Water UK’s long-term planning
These were typical of the reactions of many who found the bigger picture of water resources of real concern once they became aware of the population and climate change pressures on water resources and supplies. Many were also alarmed by the scale and speed of the challenge. Even the few people who had known there might be issues with our water resources in the future were surprised at how quickly things could change from water seemingly being plentiful into a resource with an underlying shortage. Customers were surprised that more frequent and heavier rainfall would not necessarily result in increased water supply. Learning that water companies are not always able to capture and store rainwater – especially when it falls in short, intense, downpours - made many people rethink their existing view that because we get so much rain there can’t be a problem. This led them to question why the industry had not yet found a solution to the problem. The rate of population growth was also a concern for customers. Although many were aware that the population is increasing, they were shocked to discover how quickly this was happening: scenarios predict a population growth for England and Wales of between 6.6 million and 16 million by 2040. This information was made all the more relevant by showing population forecasts for the region that people lived in. It hit home and forced many of the participants to make the link to the likely increased demand for water and the current forecasts for available water supply. The perception that water companies were losing large amounts of water at the same time as asking customers to use less was galling for many of the participants. The average is 121 litres per property lost through leakage every day. Indeed, the latest figures in our report on water supply resilience show that the amount of water lost through leakage rose by a further 1% in 2016-17. Participants consistently underestimated the overall household use of water and were shocked by the amount used for daily, frequent uses such as toilet flushing - 30% of overall household consumption - and felt people should be more aware of these figures. More generally, the perceptions of many participants of their personal water use and claimed environmental behaviours were subject to cognitive dissonance or inconsistencies in thinking and behaviours. This was evidenced at the first workshop where participants were grouped according to their claimed attitudes at recruitment e.g. one table was for those engaged with water use, the environment and water resources, another was for those who fairly disengaged and
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CC WATER ARE WE MISSING THE BIG PICTURE ON WATER EFFICIENCY?
the other was for those somewhere in the middle. It quickly became apparent that each table was a mix of these attitudes and more importantly related behaviours once they were explored. This has implications for segmentations which aim to help target messages about water use as it is very challenging to define segments which reflect how people really behave; they may be in different segments for different aspects of water use and be unaware of the trade-offs
they make in their behaviours which lead to these inconsistences. Despite the challenges of segmentation, a broad typology of attitudes to water and water use was developed and can be seen in Figure 1. Based on the research, it’s likely that people are in different sectors for different aspects of water use, though this would need to be further tested.
Figure 1: The broad typology of attitudes to water and its use.
CARE ABOUT WATER 1. Care about water and use it carefully
D: Could do more E: Need more support
A: Concerned about future supplies
F: Underestimators
4. Don't care about water and don't use it carefully
2. Don't particularly care about water but use it carefully
G: There'll always be water
B: Cost conscious
H: Confident of future solutions
C: Waste not want no attitude
USE WATER CAREFULLY
DON'T USE WATER CAREFULLY
3. Care about water but don't use it particularly carefully
DON'T CARE ABOUT WATER
Conclusions Our research shows that a focus on messages to raise awareness of what the problem is and why it matters, rather than diving straight into the detail of how consumers should go about changing their individual water use behaviour, may be more effective in engaging them. Getting the message across about the ‘big picture’ is a vital starting point irrespective of typology of attitudes to water. As it stands, people who are saving water often don’t have a clear understanding of why they are doing so unless it is to save money - they just know they are ‘supposed’ to.
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The findings give us the confidence to believe that it is possible to engage meaningfully with the public on these issues by using a combination of factual, targeted information and a compelling call to action. At the very least, if people have a better understanding of why they are being asked to reduce their water consumption, they may be more receptive to such messages. Perhaps more importantly, they may also be more open to water companies investing in solutions to these issues - and more accepting of the bill impact that may come with this. By explaining to consumers the future challenges and their implications, what the sector and governments are doing to address them, and what we as consumers can do to help, we can prepare the ground for a much more engaging, coherent and persuasive conversation about why our water use matters.
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The key messages from the research are presented in the infographic in Figure 2, below.
Acknowledgements CCWater would like to thank the Community Research Team: Rachel Lopata, Lucy Brady, Kathryn Rathouse, Andrew Darnton and Suzannah Kinsella. References 1. Water UK: Water resources long term planning framework 2015-2065 (2016): https://www.water. org.uk/water-resources-long-term-planning-framework 2. CCWater: Water, water everywhere? Delivering a resilient water system 2016-17 (2017): https:// www.ccwater.org.uk/wp-content/uploads/2017/12/Water-water-everywhere-Delivering-a-resilientwater-system-2016-17.pdf
3. Ofwat: Delivering Water 2020: Our final methodology for the 2019 price review (2017): https:// www.ofwat.gov.uk/wp-content/uploads/2017/12/Final-methodology-1.pdf 4. Waterwise: Water Efficiency Strategy (2017) http://www.waterwise.org.uk/wp-content/ uploads/2018/02/Waterwise-National-water-strategy-report.pdf 5. Consumer Council for Water: Water saving: helping customers see the bigger picture (2017): www. ccwater.org.uk/wp-content/uploads/2017/10/Water-Saving-helping-customers-see-the-biggerpicture.pdf
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The Institute of Water was founded in 1945 and is the only professional body which caters exclusively for the UK water sector. Our vision is for the UK water industry to be served by the best people. Our aim is to inspire our members to reach their potential through learning, networking and professional development.
Our members are committed to the water industry and its customers, to our vision and values and to developing their careers. We are inclusive and non-hierarchical and our members are drawn from water companies, suppliers, contractors, consultants and regulators. Membership offers anyone who works in water (regardless of their qualifications or discipline/department) the opportunity to broaden their knowledge and develop within the sector.
Benefits of membership include: Professional Registration We are licensed to award Professional Registration in Engineering (Chartered Engineer, Incorporated Engineer, and Engineering Technician), Science (Chartered Scientist, Registered Scientist and Registered Science Technician) and Environment (Chartered Environmentalist and Registered Environmental Technician).
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Our editorial panel Robin Price CSci Vice President Science, Institute of Water Head of Water Quality, Anglian Water Robin’s career in the water industry began in 1992 when he started a PhD at the University of Birmingham researching the impact of ozone treatment on algal-laden water and downstream water treatment processes. The PhD was sponsored by Anglian Water and, at the end of his studies, Robin was offered a 1 month contract by their Innovation team looking at the biology of activated carbon adsorbers.
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Over 20 years later, Robin’s scientific career at Anglian Water has taken him through the research and development, regulatory and operational teams, and Robin is currently Head of Water Quality, responsible for process science, public health liaison, water quality risk management along with water quality policy, strategy and regulation within the Water Services directorate. Robin’s role on the Institute of Water Board is to champion the professional development of scientists across the industry, particularly focused on developing Chartered Scientist and associated qualifications, working closely with the Science Council. Robin also chairs the Institute’s Membership and Standards Committee, and is the Board Diversity Champion.
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Ian Barker CEnv Vice President Environment, Institute of Water Managing Director, Water Policy International Ian Barker is Water Policy International Ltd’s founder and Managing Director. With over 35 years’ experience in the water sector he identified the need for an independent consultancy able to cover the spectrum from policy formulation through to practical, integrated water management solutions and for an independent, authoritative voice on water policy and strategy. Ian has worked within the water industry since before privatisation in 1989, when he opted for a career with the environmental regulator, rather than with one of the privatised companies. Since then, in a range of senior national roles at the Environment Agency, he aimed to ensure that the water companies (and others) could deliver environmental protection and improvement, whilst still reconciling their wider responsibilities. Ian is a Visiting Professor at the University of Exeter’s Centre for Water Systems, and is an Expert Advisor to the OECD on water governance, regulation and management.
Sam Phillips CEng Vice President Engineering, Institute of Water
Marcus Rink CSci Chief Inspector, Drinking Water Inspectorate Marcus Rink was appointed as the Chief Inspector of Drinking Water in August 2015 after thirteen years with the Drinking Water Inspectorate at all levels. As Chief Inspector he provides independent scrutiny of the water industry ensuring the safety and quality of water and public confidence through a robust regulatory framework. His role encompasses a range of statutory and nonstatutory functions, discharging the duties of the Secretary of State and the Welsh Government to ensure companies meet their regulatory requirements and Local Authorities take action in respect of private supplies. His career spans over 30 years with the Health Authority, ADAS, Public Analysts, Analytical Laboratories and the DWI providing a diverse insight into management, regulation, enforcement, health and the technical aspects of drinking water. Marcus is a member of the EU expert group advising on the Drinking Water Directive, the advisory EU microbiology expert group and the Chair of the Standing Committee of Analysts who produce independent methodology for water and environmental laboratories.
Prof Dragan Savic FREng, CEng Professor of Hydroinformatics, University of Exeter
Sam is a graduate of Queen’s University Belfast. In 1981 he joined Ferguson McIlveen LLP, Consulting Engineers and worked mainly on water engineering projects, becoming an Associate in the firm in 1988 and a Partner in 1992. He became a Director with Scott Wilson when it acquired Ferguson McIlveen in 2006 and when URS acquired Scott Wilson in 2010 he became Director responsible for Water & Infrastructure Engineering. Sam has over 30 years’ experience as a consulting engineer and has worked on a wide variety of projects in UK, Ireland, Africa and the Russian Far East. He is married and has one daughter. Sam is now retired and in addition to his work for the Institute of Water, is a Board member of the North West Zambia Development Trust and a passionate advocate for its work.
Lynn Cooper CPFA, CEnv Chief Executive, Institute of Water Lynn left her native Glasgow in 1983 with an Accountancy degree and qualified as an accountant with Sunderland and South Shields Water Company in 1987. She remained with the company when it became North East Water then Northumbrian Water until January 1997 when she moved to the Institute of Water as General Secretary. She was appointed as Chief Executive and a Board Member in December 2007. Lynn is a Founding Director of the Society for the Environment, where she served as Treasurer for 8 years, and is a Chartered Environmentalist. In her spare time Lynn coaches middle to long distance runners and enjoys helping people to be the best they can.
Professor Savic is the UK’s first Professor of Hydroinformatics, having held this post at the University of Exeter since 2001. His research interests cover the interdisciplinary field of Hydroinformatics, informatics/computer science and environmental engineering. Applications are generally in the environmental engineering/science areas, including water resources management, flood management, water & wastewater systems and environmental protection & management. Professor Savic has lectured extensively throughout the UK and abroad where he has given research presentations at many institutions on all continents. He is currently a Visiting Professor at the Universities of Bari (Italy) and Belgrade (Serbia), UNESCOIHE (Delft, The Netherlands) and Harbin Institute of Technology (Harbin, China). Professor Savic is a founder and co-director of the Centre for Water Systems, an internationally recognised group for excellence in water and environmental science research. He is a Chartered Civil and Water Engineer with over thirty years’ experience in research, teaching and consulting.
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