Water Journal December 2010

Volume 37 No 8

DECEMBER 2010

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The Industry's Most Widely Used Water Modelling Software

Major water network operators like Brisbane City Council, ActewAGL Water Division, SA Water, and Barwon Water all rely on Bentley products every day

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Jo"mal of 1he .....,;,n Water Assoc;a1;on ISSN 0310-0367 Volume 37 No 8 December 2010

contents

I

REGULAR FEATURES From the AWA Chief Executive

The State We're In

My Point of View

T Mollenkopf

4

C Davis

5

Crosscurrent

6

Industry News

12

AWA News

23

Conference Reviews

40

Darling Walk Development - see page 12

Specialist Networks Committees 2010-2012 - see page 24

AWA CONTACT DETAILS Australian Water Association ABN 78 096 035 773 Level 6, 655 Pacific Hwy, PO Box 222, St Leonards NSW 1590 Tel: +61 2 9436 0055 Fax: +61 2 9436 0155 Email: info@awa.asn.au Web: www.awa.asn.au DISCLAIMER Australian Water Association assumes no responsibility for opinion or statements of facts expressed by contributors or advertisers.

COPYRIGHT AWA Water Journal is subject to copyright and may not be reproduced in any format without written permission of the AWA. To seek permission to reproduce Water Journal materials, send your request to media@awa.asn.au WATER JOURNAL MISSION STATEMENT 'To provide a journal that interests and informs on water matters, Australian and international, covering technological, environmental, economic and social aspects, and to provide a repository of useful refereed papers. ' PUBLISH DATES Water Journal is published eight times per year: March, April, May, July, August, September, November and December.

EDITORIAL BOARD Chair: Frank R Bishop; Dr Bruce Anderson, AECOM; Dr Terry Anderson, Consultant SEWL; Michael Chapman, GHD; Robert Ford, Central Highlands Water (rtd); Anthony Gibson, Ecowise; Dr Brian Labza, Vic Health; Dr Robbert van Oorschot, GHD; John Poon, CH2M Hill; David Power, BEGA Consultants; Professor Felicity Roddick, RMIT University; Dr Ashok Sharma, CSIRO; and EA (Bob) Swinton, Technical Editor.

AWA

EDITORIAL SUBMISSIONS Water Journal welcomes editorial submissions for technical and topical articles, news, opinion pieces, business

National Water Week 2010 - see page 28

information and letters to the editor. Acceptance of editorial submissions is at the discretion of the editor and editorial board.

• Technical Papers and Features Bob Swinton, Technical Editor, Water Journal - bswinton@bigpond.net.au AND journal@awa.asn.au Papers 3,000-4,000 words and graphics; or topical articles of up to 2,000 words relating to all areas of the water cycle and water business.

Submissions are tabled at monthly editorial board meetings and where appropriate are assigned referees. Referee comments will be forwarded to the principal author for further action. Authors should be mindful that Water Journal is published in a 3 column 'magazine' format rather than the full-page format of Word documents. Graphics should be set up so that they will still be clearly legible when reduced to two-column size (about 12cm wide). Tables and figures need to be numbered with the appropriate reference in the text e.g. see Figure 1, not just placed in the text with a (see below) reference as they may end up anywhere on the page when typeset.

• Industry News, Opinion pieces and Media Releases Anne Lawton, Managing Editor, Water Journal - journal@awa.asn.au • Water Business and Product News Lynne Bartlett, National Relationship Manager, AWA - lbartlett@awa.asn.au

ADVERTISING Advertisements are included as an information service to readers and are reviewed before publication to ensure relevance to the water sector and objectives of the AWA. Lynne Bartlett, National Relationship Manager, AWA - lbartlett@awa.asn.au Tel: +61 2 9467 8408 or 0428 261 496 AWA BOOKSHOP Copies of Water Journal, including back issues, are available from the AWA Bookshop for $12.50 plus postage and handling.

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Maroondah Dam at Healesville, Victoria. Photograph by Lynton Crabb. Picture supplied by Bureau of MeteO(Ology. Turn to page 14 to read about the Bureau's new water storage information website and iPhone app.

water

DECEMBER 2010 1

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ref e r eed paper

ASSESSING HEALTH RISK OF RECLAIMED WATER USING HUMAN CELL CULTURE M L Ackland, A A Michalczyk, D Freestone, F Stagnitti Abstract For risk analysis of reclaimed water, current animal and toxicity test ing may not detect subtle effects such as interactions that could contribute to complex diseases such as cancers that develop over a long period of time.

There is a need for assays that can be validated against known human physiological processes. We have previously validated sensitive human cell cu lture assays for t heir responsiveness to agents that induce carcinogenesis in vivo. In t his initial study we analysed the effects of t hree batches of reclaimed water on human colon ic cells. At concentrations of up to 10-fold, they had no significant effect on the cellular markers, indicati ng an overall lack of biological activity. The assay has potential but needs to be refined to maximise it s sensitivity.

Introduction Sustainable management of water requires an understanding of t he health effects of water from different sources and an estimation of the pot ential risk of adverse effects following exposure to the water. Recent advances in water treatment technolog ies have substantially improved the quality of reclaimed water and several studies have provided good arguments for more extensive use of reclaimed water including for potable use (1). The effects of rec laimed water in

water Future Features MARCH - Sewer Processes; Smart Systems; Metering APR IL - Membranes and

relation to human health, however, remai ns a content ious issue. The key issues and challenges of reclaimed water re-use arise from incomplete characterisation of the diversity and variability of chemical substances in source waters and chemical substances that may be formed during t reat ment or distribution of water (2) and the limitat ions of toxicit y testing (3).

Microbial risks are generally well understood and read ily mitigated in modern re-use schemes through hightechnology engineering (4). Health risks from chemicals, on t he other hand, have been difficult to quantify because: (i) there is potentially a very large number of chemicals to consider, (i i) the concentration of chem icals in different re-use streams differs considerably, (iii) the interact ive effects of combinations of chemicals are very difficult to characterise, and (iv) t he diseases that can arise from exposure to environmental agents can be chronic with long latency periods, for example, cancers. Many bioactive agents have been reported to be present in reclaimed water, including pesticides, organohalogens, phthalates, aromatic compounds, and surfactants.

Also present are hormones from natural sou rces including humans and animals and those synthesised as drugs (5).

These hormones along wit h other pollutants are classified as endocrine disruptors as they can interfere with the normal endocrine functioning th rough mimicking or blocking normal hormone action. It is not proven to what extent t hese may pose a health risk in rec laimed water. A study t hat measured the levels of 13 estrogenic endocrine-d isrupting compounds in reclaimed water established that overall, consum ption of reclaimed water did not contribute significantly to the total amounts of estrogenic endocrine-disrupting

Desalination; Stormwater Use

MAY - Resou rce Recovery; Biosolids; Efficiency, WICD, Education

The development of a sensitive risk assessment tool for cancer.

compounds ingested, relative to overall dietary intakes (6). Wh ile it may be possible to ascribe a specific cellular effect to individual chemicals in reclaimed water, t he cumu lative effect of multiple bioactives on humans cannot be predicted using this approach. This is due to t he possible complex interactions between different bioactives. Thus, to establish the physiological effects of reclaimed water it is necessary to evaluate the combined effects of the bioactives at the relevant concentrations.

Currently the main methods for testing of wat er involve toxicity tests using animals or in vitro toxicity assays. The in vivo toxicological evaluation of chemical contaminants is normally undertaken using animal test ing, most commonly rodents including mice, rats or hamsters and fish (7, 8). While t his approach wi ll undoubtedly be fru itful, the genetic and phenotypic differences between mice, other animals and humans is a limiting factor.

An alternative to animal toxicological studies is t he use of in vitro bioassays.

The Ames test, for example, uti lising specially developed strains of the bact erium Salmonella typhimurium , is used as a screening test for mutagenicity and other types of genotoxic effects that indicat e profound cellular disturbance.

Combinations of tests to measure more specific toxic effects including estrogenic activity, arylhydrocarbon receptor response, neurotoxicity, dioxin-like activity and phytotoxicity have also been employed (9, 10). A combined in vitro assay to screen water produced from several Australian water recycling schemes has been developed. This includes Caco2 and liver cytotoxicity tests, a mixed function oxidase test , Ames for mutagenicity, a micronucleus assay for genotoxicity, a Luciferase reporter assay to detect activation of estrogen, and rogen, glucocorticoid, t hyroid and progesterone receptors, an acetylcholinesterase assay as a measure of neurotoxicity and a cytokine assay (11).

water DECEMBER 2010 49

chemicals of concern

refereed paper

Table 1. Advantages and disadvantages of different toxicity tests.

Water test

Advantages

Disadvantages

in vivo animal toxicity tests

• Can test for whole body effects and specific organ effects

• Effects in animals may not be similar in humans • Ethical issues associated with animal use • Costly • Time consuming • Requires specialised facilities and trained animal technicians

in vitro microbiological tests

in vitro human cell culture tests

• Quick

• Insensitive test that measures DNA damage or cell death

• Not costly

• Effects in microbiological agents may not be similar in humans

• Can test many samples at once

• Does not indicate whole body effects

• More rapid than animal testing

• More costly than microbiological tests

• Less costly than animal testing

• Requires more specialised facilities and equipment than

• No ethical issues

microbiological testing

• Effects are human-specific

• Does not indicate whole body effects

• Sensitive tests can detect subtle biochemical changes • Different types of human cells can be tested individually • Many sensitive biochemical assays available

Human cell culture models provide important insights into biochemical processes occurring in cells. The strength of the cell cu lture model is that it provides a well -defined environment for investigating cell-specific effects of one or more bioactives. The detectable changes can be more subtle t han mutational effects or overall toxicity effects. Cells taken from human t issues can be grown in culture and used to mimic in vivo processes. Human cell culture models can be used to model the biology of normal and diseased states.

For example, we have generated a threedimensional cell culture model of the human mammary g land to study lactation. Thi s model was the first of its kind to show milk-specific protein synthesis upon stimulation with lactational hormones (12) and has been used by us as well as international groups to study breast cancer progression and metastasis (13). The mammary cell culture model can undergo the same changes that are observed in cancer in vivo (14, 15). Other t issuespecific cells that we have cu ltured include human skin (16), placental tissue (17), human mouthwash cells (18) and human gut cultures (19). On the basis of our previous studies using cultured human cells and the advantages of this approach over animal toxicity test ing and microbiological assays, we propose that this approach could be applied to testing the biological effects of reclaimed water.

Table 1 summarises the advantages and disadvantages of t he d ifferent methods that can be used for testing t he effects of reclaimed water.

50 DECEMBER 2010 water

Cancers caused by environmental factors can take many years to fully develop (20). Our assays are sufficiently sensitive to detect early changes that are known to precede the fully developed metastatic cancer that include, for example, increases in cell proliferation , migration, invasion and loss of cellular organisation. The cell culture models are sensitive enough to detect within days or weeks, changes that take months or years to occur in the body. Consistent w ith our previous find ings on the effect of flavonols on gut cell metabolism, we wou ld expect to detect changes w ithin days rather than weeks of exposure to bioactive agents. For example, o ur study on t he effects of quercetin and kaempferol on gut cells indicated that 5 days was the time at w hich the maximum difference in DNA synt hesis in treated cells relative to control cells was observed (19).

The aim of this study was to utilise the human colonic cell line, HuTu80, as a, novel tool for measuring the effect s of reclaimed water in promoting carcinogenesis. Our approach is based on previous studies where, in testi ng the effects of bioactives present in food, we have used different human cell culture models for the study of normal and cancer cel ls (12, 19). These studies have validated the responsiveness of the human cell culture model to external bioactive agents t hat may be present in reclaimed water. Our studies and those of others indicate that subtle cellular changes can be monitored in these models and that t hey may be usefully applied for the analysis of the effects of reclaimed wat er.

Materials and Methods Secondary treated effluent samples Three batches (100 L each) of secondary treated effluent, comprisi ng a mixture of municipal domestic and industrial waste, were obtained from three sewage treatment plants. The secondary treatment in vo lved anaerobic and aerobic biological treatm ent (21 ). Follow ing secondary treatment, the effluent underwent disinfection. Batches 1, 2 and 3 were co llected on October 19 and 27 and November 8, 2006, respectively, and a physico-chemical analysis of each is provided in Table 2. The samples were filtered using 0.22 µm filters (M illex GP Syringe Driven Filter Units, Millipore, Melbourne), to sterilise and remove microorganisms and, for some assays, concentrated by room temperature evaporation by up to 10 fold. Their pH was 7 .8 and conductivity ca. 1800 EC.

Cell culture Confluent cu ltures of human colonic HuTu80 cells were cultured in 75cm2 culture flasks in RPMI medium supplemented with 10 per cent FBS (CSL, Austral ia) and incubated at 37°C in 5 per cent CO2 in air. After two days, cells seeded at an initial concentration of 0.5 X 106 were exposed to reclaimed water concentrations of 1, 2, 5 and 10 fold in culture medium containing 2 per cent foetal bovine serum for periods of one and two weeks before being harvested. Control cu ltures were exposed to RPMI culture medium containing 2 per cent foetal bovine serum in which t he pH and conductivity had been adjusted t o that of the medium with the filtered secondary t reated effluent.

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Functional cell assays The following tests, described in detail in our cited references, were carried out using each batch of water, following exposure of the cells to reclaimed water for periods of one and two weeks. (a) Cell viability HuTu80 cells were trypsin ised and a Trypan blue viable cell count carried out as previously described (19) , using a haemocytometer. The total cell count was determined.

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(c) Cell death Apoptotic HuTu80 cells were detected as we have previously described (16), using t he expression of active caspase-3 as a marker for end stage apoptosis. (d) Cell migration The cel l migration assay is based on a technique where cel ls grown in different media concentratio ns of reclaimed water were seeded onto 22mm2 glass coverslips and allowed to incubate for two days. A strip of cells was then removed from the confluent culture and the rate of closure of t he gap over a period of 18 hours was measured. We have previously utilised this technique to show increased cell migration in breast cancer cells in the presence of EGF (14). (e) Cell adhesion

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HuTu80 cells were fixed in 4 per cent paraformaldehyde, permeab ilised with 0.1 per cent Triton X-100 and then immunolabelled with Ki67 antibody which was detected with f luorescent-tagged secondary antibody (Alexa 488, Molecular Probes, Eugene, Oregon, USA) as previously described (1 9).

Nuclei were co unterstained with et hidium bromide. Cells were viewed using a laser scanning confocal microscope and the proportion of labelled nuclei per high power field (X60) for 20 fields was determined.

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Figure 1. Effect of different concentrations of reclaimed water on viability (log 10 percentage) after one and two weeks incubation in RPMI culture medium containing 2 per cent foetal bovine serum and reclaimed water concentrations from Oto 10-fold. Error bars represent 1 SD. Back-transformed means are presented above bars. which is accumulated in cells undergoing DNA synthesis (19) (Figure 2). Results indicated that t he proportion of labelled cells was similar at Week 1 and Week 2 for cells that had been exposed to control cu lture medium and 1x, 2x, 5x and 1Ox reclaimed water medium (P>0.2).

Cell death Western blot analysis followed by probing with an antibody to active caspase-3 (16) indicated that extracts of HuTu80 cells treated with different concentrations of reclaimed water ranging from 1x to 1Ox had the same band intensity as the co ntro l

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HuTu80 cells were trypsi nised, counted and seeded into diameter 6-well plate. Aft er incubation for 20, 30 min, 1 and 6 h, t he proportion of attached cells was determined by measuring the proportion of cells remaining in suspension.

Data analysis Treatment effects were investigated using analysis of variance .

For the cell adhesion analysis, a blocking design wit h reclaimed water batch nested withi n t ime was used. Separate analyses were carried out for the Week 1 and 2 viability studies, with reclaimed water batch being modelled as t he on ly blocking factor in each case. In order to meet the assumpt ions of ANOVA, particularly stable variances and normality, al l viabil ity data were log 10-transformed. The P < 0.05 criterion was applied to all post hoc significance tests (Fisher's least sig nificance difference). All analyses were performed in the statistical package Genstat (version 9, Lawes Agricultural Trust, IACR-Rothamsted).

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Results Viability After 1 and 2 weeks of exposure to culture medium containing reclaimed water, no significant effect (P = 0.291 and 0.201 , respectively) was observed for the analyses of HuTu80 cell viability (Figure 1).

DNA synthesis lmmunofluoresence microscopy detected the relative number of cel ls labelled with the nuclear proliferation antigen Ki67 ,

Figure 2. Effect of different concentrations of reclaimed water on the expression of nuclear proliferation antigen Ki67. Ki67-labelled cells are shown in green and unlabelled cells (ethidium bromide) shown in red. Representative images showing control cells (Ox) and cells exposed to 10x reclaimed water are shown for one and two weeks of treatment. No significant differences in the proportion of cells labelled with Ki67 were seen with treatments of 1x, 2x, 5x or 10x of reclaimed water (data not shown).

water DECEMBER 2010

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chemicals of concern ext racts, indicat ing no significant effect of reclaimed water in stimulation of apoptosis (P>0.05). For each treatment, the results were expressed as the proportion of the untreated sample (Figu re 3).

Cell migration HuTu80 cells were grown in medium containing different concentrations of reclaimed water for one week and two weeks before seeding onto glass coverslips for two days. The relative capacity of cells to migrate was measured by the closure of the gap created by removal of a strip of cells after 18 hours (13). No significant differences in the gap were seen between any concentrations of wastewater, either at one or two weeks.

Cell adhesion Cell adhesion was determined by the number of cells attached to t he substrate following the seeding of cells treated with different concentrations of reclaimed water for 1 and 2 weeks.

Water concentrations did not have a significant effect on cell adhesion (P = 0.976) (Figure 5). Cell adhesion varied significantly (P < 0.001) from the time that cells in suspension were allowed to attach to the substrate over the 6-hour test period with adhesion being significantly higher at 6 h than al l other periods, and 2 h being higher t han 0.5 and 1.0 h. No significant difference (P = 0.229) in adhesion was observed between batches of water.

Discussion A major obstacle to implementing re-use of reclaimed water is the gap in knowledge of the risks associated with its use.

Health risks from chemicals have been difficult to quantify on account of t he numerous chem icals present in reclaimed water and their potential interactions. Of concern is t he presence of bioactives t hat may contribute to cancer. In this article we report the development of a risk assessment tool that could be used as an indicator to assess t he biological effects of water, particularly in relation to cancer.

In our preliminary study presented here, we selected a range of indicators to investigate t he biological effects of reclaimed water on cultured human cells. These indicators include cell proliferation, DNA synthesis, cell death, migration and adhesion . Such indicators have previously been shown in vitro to be altered by agents that promote carcinogenesis (18).

We would predict t hat HuTu80 cel ls would respond to bioactives, such as endocrine disruptors, if t hey were present at biological concentrations. No significant effects of the three reclaimed water samples were detected , even when t he water was concent rated up to 10-fold. Further optimisation of the assays could reduce t he standard deviations, which were quite large.

refereed paper

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In summary, we describe t he use of a human cell culture model of the gut for testing of concentrations of secondary treated effluent as an indicator of the health effects of water, particularly in relation to cancer. Considerable variations in the tested parameters were seen in t he cel lular responses; however, no significant effects were demonstrated even at 10-fold concentrations. The system could be further developed to improve its sensitivity and utility as a tool to evaluate the health effects of reclaimed water.

52 DECEMBER 2010 water

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Figure 4. The migration of HuTu80 cells into the gap over a period of 18 hours was measured in cells treated with different concentrations of reclaimed water. The gap distance was measured at 10 points along the length of the gap after cells had been labelled with ethidium bromide (red) to indicate the position of the nucleus and vimentin (green Alexa 488), a cytoskeleton stain. The error bars represent the SEM obtained from triplicate analyses carried out in three independent experiments.

Future studies would benefit from the use of reclaimed water controls. Water samples could be concentrated by at least 1000-fold to increase t he concentrations of putative bioactives to physiological levels of hormones (1 o-8 M) that induce cellular responses in vivo . Future work could focus on refin ing the most appropriate set of cellular markers to employ and develop a "fingerprint" that would provide an overall indicator of the biological effects of different water samples, at the gene and protein levels withi n cells. It would also be informative to be able to ascertain the effects of samples on a variety of cell types, for example gut, liver, kidney, breast and prostate. The project would requi re the expertise of an experienced scientist 35

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There are many other cellular indicators that are altered in cancer, for example cell-matrix adhesion molecules, matrix metalloproteinase activity and signal transduct ion mechanisms.

These are just a few of the markers that could be used to develop a more sensit ive test.

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Acknowledgment Sarah Wilkinson for technical assistance.

The Authors

Professor Leigh Ackland is Deputy Director of the Centre for Cellular & Molecular Biology, School of Life and Environmental Sciences at Deakin Uni versity, Burwood, Melbourne, Victoria.

E-mail: leigha@deakin.edu.au, Website: http://www. deaki n. edu. au/scitech/ les/ staff/acklandl/ Dr Agnes Michalczyk is a Research Fellow at the Centre for Cellular & Molecular Biology, David Freestone is a PhD student at the Centre for Cellular & Molecular Biology and Professor Frank Stagnitti is Pro Vice-Chance llor Research at the University of Ballarat, Vic toria Australia.

References (1) Khan Sand Roser G (2007) Risk Assessment; Health Effects Studies of Indirect Potable Reuse Schemes and Refilling the Glass, Centre for Water and Waste Technology School of Civil and Environmental Engineering University of New South Wales.

(2) Chapman H (201 0) Theme 2: Risk Management and Validation, Australian Water Recycling Centre of Excellence Discussion Paper.

(3) Australian Government National Water Commission Quantitative Chemical Exposure Assessment for Water Recycling Schemes (2010).

(4) Toze S (2006) Reuse of effluent water benefits and risks Agricul Water Manage 80, 147-159.

(5) Ying G-G, and R Kookana 2002 Endocrine d isruption: An Australian perspective Water 29:53- 57 .

(6) Leusch FOL, Moore MR and Heather F. Chapman HF (2009) Balancing the budget of environmental estrogen exposure: the contribution of recycled water. Water Science and Technology 60.4: 1003-1012.

(7) Young F (2009) Safety of recycled water for end users determined by a mouse in vivo multigenerational study: Flinders University, SA, Melbourne Water/Yarra Valley Water, Australian Water Quality Centre, Water Quality Research Australia.

(8) Leusch FOL, Khan SJ and Chapman HF (2007).

Chemical contaminants in water: Can we m easure everything? p. 296-303 in Water Reuse and Recycling (2007) (Khan SJ, Stuetz RM and Anderson JM, Eds), UNSW Publishing & Printing Services, Sydney, Australia. ISBN 978 0 7334 2517 2.

(9) Reungoat J , Macova M, Escher Bl, Carswell S, Mueller JF and Keller J. (2010) Removal of micropollutants and reduction of biological activity in a full scale reclamation plant using ozonation and activated carbon filtration .

Water Research, 44; 625-637.

COMMERCIAL FIBREGLASS WOUND VESSELS

{10) Macova M, Escher Bl , Reungoat J, Carswell S, Chue, KL, Keller J and Mueller JF. (2009) Monitoring the biological activity of micropollutants during advanced wastewater treatment with ozonation and activated carbon filtration. Water Research, 44; 477-492.

(11) Leusch FOL, Humpage, AR, Froscio SM, Khan SJ, Coleman HM, Quale PA and Chapman HA. (2010) Combining an in vitro bioassay battery w ith t argeted chemical analysis to detect "unknown" organic contaminants in recycled water. Presented at Ozwater' 10, 8-10 March 2010, Brisbane, Old, Australia.

(12) Ackland ML, Michalczyk, A, and Whitehead, RH (2001) PMC42, A Novel Model for the Differentiated Human Breast Experimental Ce// Research 263: 14-22.

(13) Ackland 2003 Ackland L, Newgreen D, Price J, Fridman M , Waltham M, Arvanitis A, Minichiello and Thompson A. (2003) Epidermal growth factor-induced epithelio-mesechmyal transition in human breast carcinoma cells.

Lab Invest 83:435-448.

(14) Lebret, C, Donald F. Newgreen, Mark C. Waltham, John T. Price, Erik W. Thompson and M . Leigh Ackland . (2006) Myoepithelial Molecular Markers in Human Breast Carcinoma PMC42-LA cells are induced by extracellular matrix and stromal cells. In Vitro Cell Develop Biol-Animal 42: 298- 307.

(15) Lebret SC, Newgreen OF, Thompson EW, Ackland ML. (2007) Induction of epithelial to mesenchymal transition in PMC42-LA human breast carcinoma cells by carcinomaassociated fibroblast secreted factors.

Breast Cancer Res 9:R19.

Capable of processing up to 396 m3/ hr.

Suitable for commercial, industrial, municipal and water treatment applications.

MULTICYCLONE CENTRIFUGAL FILTER No fi lter media to clean or replace. 3m3/hr to 30m 3/ hr Suitable for commercial and water treatment applications.

CARTRIDGE AND BAG FILTERS Capable of withstanding up to 600kPa.

(16) Wilson D, Varigos G and Ackland ML. (2006) Apoptosis may underlie the pathology of zincdeficient skin. lmmunol Cell Biol 84, 28-37.

Suitable for commercial and water treatment applications.

(17) Hardman B, Manuelpillai U, Wallace E, Monty F, Kramer D, Mercer J and Ackland ML. (2005) Expression, Localisation and Hormone Regulation of the Human Copper Transporter hCTR1 in Placenta and Choriocarcinoma Jeg-3 Cells. Placenta 27: 968-977.

(18) Michalczyk A, Varigos G, Smith Land Ackland ML. (2004) Fresh and cultured buccal cells as a source of mRNA and protein for molecular analysis. Biotechniques 37(2):262-4, 266-269.

ELECTRONIC COAGULATION

(19) Ackland ML, van de Waarsenburg Sand Jones R. (2005) Synergistic antiproliferative action of the flavonols quercetin and kaempferol in cultured human cancer cell lines. In Vivo 19 (1 ): 69-76.

Precipitates and coagulates a wide range of contaminants.

(20) Wolff, MS, et al. (1993) Blood levels of organochlorine re sidues and risk of breast cancer J Natl Cancer Inst 85:648-652.

Suitable for grey water recycling applications.

{21) Smith, P.G. and Scott. J. G. (2005) Dictionary of water and waste management. 2nd edition.

Elsevier and IWA Publishing . Amsterdam, NL and London, UK. (22) Hugo, H, Ackland ML, Blick, T , Lawrence MG, Clements JA, Williams ED and 'Thompson EW (2007) Epithelial- mesenchymal and mesenchymal-epithelial transitions in carcinoma progression J Cell Physiol 213(2):374-83.

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chemicals of concern

refereed paper

CONTAMINANTS OF CONCERN IN RECYCLED WATER J Lampard, F D L Leusch, A Roiko, H F Chapman Abstract This paper reviews significant research pertaining to exposure sources for five contaminants known to be in raw wastewater. For all five contaminants invest igated the estimated daily intake calculated to result from consumption of recycled water was several orders of magnitude below the estimated daily intake associated with other exposures such as food.

Introduction In the early 2000s many Australian stat e governments began considering reclamation of wastewater as a means of combating water scarcity issues associated with drought, cl imate change and population growth. This has generated sign ificant debate in parliament, the media and in the community over the potential of human health effects associated with exposure to recycled water. In 2007 the Cooperat ive Research Centre for Water Quality and Treatment (CRCWQT, 2008) conducted a survey across five Australian capital cities examining commu nity views on recycled water. Half of the 3000 respondents expressed an unwillingness to drink recycled water. Encouragingly, 74 per cent of all respondents said they would be willing to drink recycled water if they co uld be assured of its safety.

To provide a clearer understanding of the potent ial exposures consumers face from recycled water, this paper reviews the most significant research pertaining to exposure sources for five contaminants known to be in raw wastewat er and therefore potent ially present in treated water. The paper does not purport to provide a comprehensive meta-analysis of the existing literature for each contami nant, but provides a snapshot of the most significant exposure sources for each contam inant compared with the predicted exposure resulti ng from consumption of recycled water. Five compounds were selected representing four groups of contaminants identified as being of interest by t he scientific community, water industry providers and/or the general public: • Pharmaceuticals and personal care products

54 DECEMBER 2010 water

- 17a-ethinylestradiol (EE2) the active ingredient in the contraceptive pill and a known endocrine disruptor, - galaxolide (HHCB), a musk fragrance t hat has been detected in human breast milk; • Phthalates - di-2-et hylhexyl phthalate (DEHP), a plasticiser used extensively in household , medical and food packaging products; • Herbicides - Atrazine, which is used extensively in Australia for weed cont rol; and • Disinfection by-products - N-Nitrosodimethylamine (NOMA), which can be produced during drinking water disinfection and also occurs naturally.

Effects of the Compounds Chosen Pharmaceutical and personal care products Concern regarding the health effects of pharmaceuticals in wastewater first emerged in the mid to late 1960s (Snyder et al., 2003), however the role of pharmaceuticals and personal care products as pollutants received limited attention until the 1990s. Prior to this t ime the majority of water quality and risk assessment research focussed on persistent chemicals such as pesticides and industrial chemicals. In contrast to pesticides and industrial chem icals, which have temporal and spat ial variability associated with their release into the water cycle, PPCPs directly and continuously enter the water cycle globally via human excretion (Daughton and Ternes, 1999) and have been termed "pseudo-persistent". PPCPs also enter the water cycle from medical treatment facilities (Daughton and Ternes, 1999), the disposal of expired or unused medication via toilets or burial in landfill, and accidental spills at pharmaceut ical manufacturing plants and the disposal of illicit drugs (Reddersen et al., 2002). An

Alternative sources of exposure.

extensive range of studies has been published since 2000 regarding the detection, removal, environmental impact and potential health consequences associat ed with PPCPs in water. While antibiotics have received the most scientific attention (Daughton and Ternes, 1999) hormones, in particular estrogens, have generated the most public concern.

17a -Ethinylestradiol (EE2; CASRN 57-63-6) The synthetic estrogen EE2 is an active ingredient found in oral contraceptive pills. Some studies have linked low concentrations of EE2 in wastewater effluent to reproductive changes in male fish (Jobling et al., 1998, Filby et al., 2007), wh ile other studies have proposed EE2 may only be partially related to observed increases in vitellogenin in male fish (Desbrow et al., 1998). This uncertainty has generat ed debate at the scientific level and concern at the community level.

Concentrations of EE2 from monitoring studies for wastewater effluent in England ranged from undetectable (<0.2ng/L) t o 7ng/L (Desbrow et al., 1998). In Australia concentrations ranging between 0.01 ng/ L-1.30ng/L have been detected in wastewater treatment plant (WWTP) effluents in subtropical and temperate regions (Williams et al., 2007).

Galaxolide (HHCB; CASRN 1222-05-5) Polycyclic musks are the most commonly used musk fragrances in personal care products and detergents accounting for 60 per cent of global synt hetic musk sales (Rimkus, 1999). Of t he seven polycyclic musks, galaxolide (HHCB) has the highest prod uction worldwide. Its only known use is as a fragrance in personal care products and household detergents (Ford et al., 1999). Products contain ing HHCB include cosmetics, perfumes, shampoos, soaps, moisturising creams, laundry detergents, fabric softeners, household cleaners and air fresheners (Rimkus, 1999, HERA, 2004, Slanina, 2004).

Human skin patch trials and oral gavage studies in rats suggest that HHCB is not toxic to humans (Epstein, 1974 and Moreno 1975, cited in Opdyke,

BJ

chemicals of concern

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1976). However concerns regarding the human health risks assoc iated with HHCB have emerged followi ng its detection in human breast milk (Muller et al., 1996, Zeh ringer and Herrman, 2001 ), plasma (Hutter et al., 2005) and adipose tissue samples (Muller et al. , 1996, Rimkus and Wolf, 1996). HHCB has also been seen to bioaccumulate in the muscle and adipose tissue of fish (Draisci et al., 1998, Eschke et al. 1994, cited in Mersch-Sundermanno et al., 1998). HHCB has been detected in wastewater and in rivers downstream from WWTPs at concentrations up to 150ng/ L (Mu ller et al., 1996, EPHC/NHMRC/NRMMC, 2008).

Plasticisers Di-2-Ethylhexyl phthalate (DEHP; CASRN 117-81-7) Di-2-Ethylhexyl phthalate (DEHP), t he most highly used plasticiser worldwide (Latini, 2005) is a synthetic chemical that makes polyvinyl chloride (PVC) products flexible (ATSDR, 2002). Wide use of DEHP began in Japan and the United States of America during the 1930s (Huber et al. , 1996) and it is ubiquitous in the environment due to its use in an extensive range of products and its ability to be released into the air and food. Products containing DEHP include food packaging films, intravenous tubing, blood storage bags, household, plumbing and construction products, some chi ldren's toys, baby pants, wet weat her clothing , shower curtains, swimming pool liners, garden hoses, furn iture and automobile upholstery, tablecloths, wall coverings, floor ti les, pavements, and wire and cable insulat ion (ATSDR, 2002, Huber et al., 1996, Warns, 1987). DEHP is highly lipophilic and does not bind to polymer, which increases its likelihood to leach from plastic food packaging into food in the presence of fats, oils and lipoproteins (ATSDR, 2002, CPSC, 1985).

Reviews of t he limited data available on potential human toxicity have found no evidence to suggest toxicity associated with oral or intravenous exposure to DEHP for humans (!ARC, 2000, ATSDR, 2002, EC, 2002). However, DEHP has been shown to be carcinogenic in mice and rats. The carcinogenic potential of DEHP for humans is contradicted by a number of international bodies (IARC, 2000, USEPA, 2000). The USEPA (2000) classifies DEHP as a 'probable human carcinogen' citing t he evidence of carcinogenicity in rats and mice wh ile the International Agency for Research on Cancer (2000) proposes t here is 'inadequate evidence( ... ) to evaluat e carcinogenicity for humans' . The ATSDR

(2002) argues that data from animal studies conducted prior to 2002 do not provide sufficient evidence to suggest environmental exposures to DEHP wi ll cause adverse health effects in humans to justify the need for further epidemiological investigations. DEHP has been detected in secondary treated effluent at concentrations up to 182Âľg/ L (Marttinen et al. , 2003, Fromme et al., 2002).

Herbicides 1.3 Atrazine (CASRN 1912-24-9) Atrazine is a synthetic herbicide used selectively to control broadleaf weeds in agricultural cropping and non-selectively to control weeds in public, industrial and residential areas (ATSDR, 2003). Atrazine is one of the two most extensively used herbicides in Australia and the most frequently used in the United States (Radcliffe, 2002). Use in Australia is primarily industrial for maintaining roadsides, railroads etc. with agricultural uses including t riazine-tolerant canola, sorghum, maize, sugar cane, forestry and the maintenance of irrigat ion channels (APVMA, 2008, Radcliffe, 2002). In 1998 the Australian government cancelled licensing for atrazine to be used for home gardens and non-agricultural purposes (APVMA, 2008). Prior to this it was used broadly for maintenance of residential lawns, golf cou rses and sporting fields.

The actual risk atrazine presents to human health remains unclear despite many toxicological and epidemiological st udies. It has been identified as a mild skin and severe eye irritant, however its carcinogenicity stat us is unclear.

Numerous studies have been cond ucted on workers exposed during application, and the exposure experienced by their fam ilies coming into contact with clothing and other exposed items, however results remain inconclusive (APVMA, 2008, Hopenhayn-Rich et al. , 2002, Gammon et al. , 2005, Garcia, 2003). With the progression of epidemiological and toxicological research over the past 15 years at razine's carcinogenicity classification has been clarified from ' possible human carcinogen' to 'not a likely human carcinogen/ not classifiable' since 1988 (APVMA, 2008, US EPA, 1994). Atrazine has been detected in wastewater effluent at concent rations up to 20.9ng/ L (Hua et al., 2006).

DBPs and Industrial 1.4 N-Nitrosodimethylamine (NOMA; CASRN 62-75-9) NDMA is formed as a result of both anthropogenic and natural processes.

NDMA is also a by-product of many industrial processes including drinking water treatment, leather tanning and t he production of rubber products and tyres (Mitch et al. , 2003). During drinking water treatment NDMA forms as a result of a reaction between the disinfection chemical , usually chlorine, and organic matter, t he higher the level of organic matter in the water being disinfected the higher t he level of NDMA (Mitch et al. , 2003). NDMA also forms naturally in air, soil and water due to chemical, biolog ical and photochemical processes (Liteplo and Meek, 2002). It is also generated in animals and humans during metabolism when stomach acids react with the nitrite and nitrate in food (Fristachi and Rice, 2007). NDMA is a component of rocket engine f uel and in Australia can be found in herbicides containing oxyfluorfen as the active constit uent (APVMA, 2007).

Initial concerns regarding the health effects of nitrosamines, including NDMA, emerged in t he 1960s with detection of NDMA in beer, cured meats, rubber products including baby bottle nipples and tobacco smoke (Haorah et al., 2001).

NOMA is a member of a fam ily of potent carci nogens and is considered a probable human carcinogen (Mitch et al., 2003). It is very toxic if inhaled or swallowed at high concentrations (ATSDR , 1989). Five deat hs have been linked to NDMA exposure, three via ingestion and two via inhalation (Mitch et al., 2003). Concerns about NDMA in drinking water arose in the mid 1990s when it was detected at high concentrations in surface and well waters near a rocket testing site in the US and also in chlori nated drinking wat er supplies in Canada (Mitch et al. , 2003).

NDMA has been detected at 24ng/ L in drinking water (Fristachi and Rice, 2007).

Methods Concentrations Data pertaining to t he highest concentrations of each of t he five selected contaminants detected in sewage and drinking water was drawn from international scientific literature, databases and published government reports. In the limited instances where multiple data sets were available for det ection of a contaminant in sewage or drinking water, the highest detected concentration was used to calculate predicted exposure based on the principle of worst case scenario.

For ot her exposure sources estimated daily intake data from documented exposures for each contam inant was obtained from international scientific

water DECEMBER 2010 55

Q

chemicals of concern literature, databases and publicly avai lable government reports. Where multiple dat a sets were available for an exposure source the highest exposure concentration t hat most reflected a pot ential exposure scenario in Austral ia based on probable dietary intake or socio-economic factors was selected .

Concentrations relating to occupational exposure associated with the prod uction of any of the contaminants were not included in t his study as they are not reflective of probable exposure by the general population.

Table 1. Acceptable daily intake (ADI) for a 70/kg adult (µg/day).

Contaminant

ADI from water (µg/d)•

17 a -Ethinylestradiol (EE2)

0.003

Galaxolide (HHCB)

3600 20

Di-2-Ethylhexyl phthalate (DEHP)

40

Atrazine

0.02

N-Nitrosodimethylamine (NOMA)

Derived by multiplying the guideline values (µg/L) in (EPHCINHMRC/NRMMC, 2008) by a standard water consumption of 2Uday.

a

Predicted concentrations of the selected contaminants were calculated by applyi ng a 3-log (i.e. 99.9 per cent) removal to the highest reported concentration of each contaminant found in secondary-treated sewage. The 3-log removal is conservatively based on the minimal expected removal of the contaminant throughout the multiple stages of t reatment that occu r between the point of wastewater effluent t o t he tap (Snyder et al., 2003 , Snyder et al., 2007).

Estimated daily intakes Estimated d aily intake from recyc led water was calculated by mult iplying the predicted concentration in recycled water by an ass umed water consumption of 2L per d ay. To enable comparisons between all exposu re sources estimated daily

intakes were calcu lated for a 70kg adult and data are presented as µg/day. T he predicted daily intake associated with recycled water for each contaminant was also eval uated against an acceptable daily intake derived from the Aust ralian Guidelines for Water Recycling: Man aging Health and Environmental Risks (Phase 2), (EPHC/NHMRC/ NRMMC , 2008) as outlined in Tab le 1.

Results & Discussion Estimated daily intakes for each contam inant v ia n umerous exposure pathways are presented in Table 2.

17a -Ethinylestradiol (EE2) The most sig nificant EE2 exposure is the daily ingestion of contraceptive pills,

re fe re ed p a per

w hich only occurs in pre-menopausal women . Results from a 2001 survey reported approximately 27 per cent of Australian women aged 18-49 were taking the contraceptive pill (Yusuf and Sied lecky, 2007). While this figure provides some quantification of contraceptive pill use in Australia and may be ben eficial in modelling concentrations of EE2 entering Aust ralian wastewater treatment plants , as has been d one by Braga et al. (2005), it must be con sidered an underestimate. Only women 18 years and over were surveyed and 86 per cent of 18 to 24 year o lds reported beginning use of t he contraceptive p ill in their teenage years (Yusuf and Sied lecky, 2007).

The most probable source of exposure for males or females not taking t he p ill is intake from d rinki ng water drawn from surface waters receiving wastewater effluent. Although EE2 is detected in sewage treatment effluent at concentrations 10 times lower than 17!3-estradiol (E2 - a natural hormone), EE2 is significantly more p o tent than E2 (Desbrow et al. , 1998) . The intake of EE2 fro m water is, however, much lower t han the prescribed d ose for contraception (Fig. 1). The daily intake levels of EE2 for pre-menopausal women using oral contraceptives range from 20-50 µg/day dependent upon the prescribed pi ll

Table 2. Estimated daily intake (EDI) of contaminants of concern for a 70/kg adult• (µg/day).

Contaminant EE2

HHCB

DEHP

ATRAZINE

NOMA

Exposure Pathway

EDI (µg/d)

Reference

Oral contraceptive

20-50

(Shufelt and Bairey Merz, 2009)

Drinking water (Germany)

0.001

(Kuch and Ballsch miter, 2001)

Recycled water

0.00054

Fish consumption

2.066-8.262

Combined daily exposure - household cleaning products

4.9b

(H ERA, 2004) (Slanina, 2004)

(Slanina, 2004)

Body lotion

rnooc (absorbed dose)

Fragrance cream

17 40c (absorbed dose)

(Slanina, 2004)

Eau de toilette

680c (absorbed dose)

(Slanina, 2004)

Drinking water

0.042

(HERA, 2004)

Recycled water

0.0003

Workplace (general population)

70-28700

(Huber et al., 1996)

Combined exposure (general population)

210-21 OOd

(Latini, 2005, Huber et al. , 1996)

Car temp >60°C

210

(Huber et al. , 1996)

Drinking water

<70

(Huber et al., 1996)

Recycled water

0.4

Diet incl. drinking water (USA)

16.38-59.99 (Acute) 3.22-20.2 (Chronic)

(Rodriguez et al., 2005)

Drinking water (USA)

0.052

(Snyder, 2008)

Recycled water

0.00176

Endogenous processes

22.9

(Fristachi and Rice, 2007)

Beer

0.02

(Fristachi and Rice, 2007)

Drinking water

0.0033

(Fristach i and Rice, 2007)

Recycled water

0.0011

a Assumed water consumption 2Uday;

56 DECEMBER 2010 water

b

Adult 60kg body weight; c based on single application per day; d excludes workplace and medical exposure.

I"\]

chemicals of concern

referee d paper

(Shufelt and Bairey Merz, 2009), whereas the estimated daily intake of EE2 associated with consumption of recycled water is 0.00054µg/day (Fig. 1).

Galaxolide (HHCB)

100 'o' .......

10

5 Ill

Humans are exposed to HHCB via ingestion, inhalation and dermal exposure. The majority of HHCB is excreted (Ford et al., 1999), and ingestion via drinking water, including potable water, has been proposed as a potential exposure route by some authors (HERA, 2004, Rimkus, 1999). The highest exposures to HHCB are associated with consumpt ion of breast milk and fish (Fig. 2). Infants consuming 0. 7L of breast milk with approx 3. 7 per cent w/w fat to milk concentration have an estimated daily HHCB intake of 6.81 µg/kg of body weight (bw)/ day (Slanina, 2004). It is important to note that whilst the concentration of HHCB in fish can be measured precisely, individual daily intakes can vary up to four-fold depending on individual fish consumption patterns.

Estimated daily intakes via dermal contact during t he application of personal care products are even less predictable than those such as ingestion, due to the variability in individual usage patterns of personal care products. While some estimates of daily intakes via the application of cologne and body lotions are provided by Slanina (2004), it has been suggested only a small amount of applied dose is absorbed (Ford et al., 1999). Notable also is the level of combined exposure associated with use of household cleaning prod ucts (HERA, 2004) (Table 2). Estimated daily exposure via recyc led water is negligible in comparison to ot her exposure sou rces (Fig. 2).

.

1

~ ...

0.1

4i Q. .......

2..

·= w N

w

0.01

"C

"' 1ii

E

•,.:; Ill w

ADlw

0.001 0.0001 Recycled

Drinking

OCP

Figure 1. Estimated daily intake of 17•-ethinylestradiol (EE2) via exposure route. Notes: OCP: Oral Contraceptive Pill; ADIW: Acceptable daily intake from water (EPHC/NHMRC/NRMMC, 2008).

:;;-

10000

---~

1000

AOfw

..

QI

~

100

.2.

10

i

1

-~ "'u

0.1

,,:i::

0.01

:i:: QI

Di-2-Ethylhexyl phthalate (DEHP)

1.

0.001

-~ 0.0001

Humans are exposed t o DEHP during the production, use and disposal of plastic products either by ingestion, inhalation or dermal contact (ATSDR, 2002) across their ent ire lifetime, including the intra-uterine period (Latini, 2005). Attempts to quantify exposu re are hindered by the difficulties associated wit h separating exposures (CPSC, 1985) and estimating the amount of DEHP leached from various sources (Warns, 1987).

The ubiquitous dispersal of DEHP in our environment and multiplicity of exposure routes have made calculating exposure levels via individual sources compl icated. Numerous attempts have been made to determine concentrations of DEHP in air, water and food products and the rate of leaching from PVC as predictors of exposure; refer to Huber et al. (1996) for a comprehensive review. However it is important to remember that rarely do t hese exposures occur in isolation. Additionally, dietary exposure varies considerably between countries and according to culture with regard to food types - i.e. high fat or low fat - and food storage techniques. Recent research has calculated combined exposure using urinary metabolites of DEHP (Koo and Lee, 2005, Koch et al. , 2003). Exposure via consumption of recycled water is highly probable as DEHP is introduced into wastewater by both human waste and waste from production plants for PVC products (Warns, 1987).

Atrazine

Medical treat ments are the cause of the highest exposures to DEHP. The most significant chronic exposure, 4-3100 µg/kg bw, occurs in haemodialysis pat ients and the highest acute exposure, 42-140000µg/ kg bw, is seen in infants receiving temporary life support in the instance of cardiac and respiratory fai lure (Tickner et al., 2001 , Huber et al. , 1996). For t he general population combined exposure to DEHP for a 70kg adult is estimated to range between 210-2100mg/day (Huber et al. , 1996). Workplace ai r is the most significant everyday exposure (Fig. 3). Notably t his is not occupational exposure

In the past, occupational exposure experienced by agricultural workers was considered the most significant exposure to atrazine and has been t he predominant focus of epidemiological research (Garcia, 2003). The introduction of regulations regarding protocols and procedures for use and personal protective equipment has seen exposure via this pathway significantly reduced (NRA, 1997). However, it is important to remember t hat t hese regulations have not been uniformly adopted in all countries. The fami lies of workers can also be exposed via contact with pesticide residues on clothes,

"'

e'/:,

.~'lo

;:}, <.,~

4e

~

~,$'

Q

:,_'/:,

,:,_,tf:'

~o"

,,o,;:,

~e o~e

':<:-0

~e

'<;

'/:,e

,._,,,"

Os;

:l,.'I.

o'/S

'b

Figure 2. Estimated daily intake of Galaxolide (HHCB) via exposure route. Notes: ADIW: Acceptable daily intake from water (EPHC/NHMRC/ NRMMC, 2008).

of workers involved in production but the exposure experienced by the general work force associated with DEHP leaching from wal l and floor coverings , furniture and office. The interior of cars when the t emperature has exceeded 60°C provide another significant daily exposure source (Huber et al., 1996). Although medical exposures have been acknowledged as the highest exposure, estimated daily intakes are rarely calculated for this exposure as t reatments such as blood transfusions, drips and temporary life support treatment are often short term ranging from hours to a few days. As with HHCB the level of DEHP in recycled water is insignificant when compared to combined exposure from other sources (Fig. 3).

water DECEMBER 2010 57

chemicals of concern equipment, and shoes brought into the home (Garcia, 2003).

Assuming personal protective eq uipment is used by workers the next most probable exposure routes are ingestion of food sprayed with the herbicide and drinking water drawn from surfaces waters which receive run off.

Atrazine concentrations are not measured in t he Australian Total Food Survey (Food Standards Australia and New Zealand, 2003) and the author believes dietary exposure in Australia is yet to be quantified. This may be due in part to the reduced number of cropping applications of atrazine in Australia as detailed previously. American data suggest that in acute exposure situations dietary intake of atrazine for a 70kg adult can be up to 60 mg/day (Rodriguez et al. , 2005). Limited published data exist on atrazine concentrations in drinking water. The studies that have been published focused on surface waters in agricultural areas in America, Canada and China (Palma et al. , 2008, Donald et al., 2007, Na et al., 2006).

Only one study could be found , on atrazine concentrations in finished drinking waters, wh ich suggested a minimal daily intake associated with drinking water (Snyder, 2008). The estimated daily intake of atrazine from recycled water is substantially lower t han t he ADI calculated from the Australian Guidelines for Water Recycling: Managing Health and Environmental Risks (Phase 2) (EPHC/NHMRC/NRMMC, 2008) (Fig. 4).

N-Nitrosodimethylamine (NOMA) Individuals are exposed to NOMA via ingestion, inhalation and dermal absorption. At the end of the 1980s, tobacco smoke and consumpt ion of food products - in particular beer and cured meats products - were considered the most significant routes of exposure (ASTOR 1989). It is probable that t hese exposures have changed following legislation in many countries to limit smokin g in enclosed areas, thereby reducing involuntary or passive exposure to tobacco smoke. Alterations in brewing techniq ues have also seen the concentrations of NOMA in beer reduced in several countries (Yurchenko and Molder, 2005, Baxter et al. , 2007).

It is now considered that the majority of the estimated 23.1mg/day dose t hat a 70kg adult in the general population would be exposed to results from internal processes within the human body, including metabolism (Fristachi and Rice, 2007).

The level of NOMA prod uced internally is dependent upon the individual's diet and is influenced by t he amount of nitrate present in the foods consumed. High NOMA concentrations have been found in cured meat products such as pepperoni and salami (Jakszyn et al., 2006, Yurchenko and Molder, 2007), and many vegetables including broccoli, spinach and beetroot have been shown to contribute to endogenous production (within the digestive tract) of NOMA (Fristachi and Rice, 2007).

NOMA is a also a by-product of t he drinking water disinfection process, with t he level of NOMA being influenced by the amount of organic matter present and the presence of NOMA precursors. The advanced treatment processes that recycled wat er undergoes prior to entering water retention dams suggest that t he level of organic matter entering the drinking water plant will be lower than in regular water.

Estimates of the NOMA concentration in drinking water and recycled water both sit well below the concentration of NOMA individuals are exposed to endogenously (Fig. 5).

[:st-

refereed paper

_ 1000000 r - - - - - - - - - - - - - - - - - -

I".,

100000

~

10000

1 i

1000

-~

+---------------,-- .j...__ _ _ _ _ ____j

100

c..

:I:

"' C

10

.,

"ti

16

1

"'

0.1

E -~

f/,'t, ()!

~

.:i

;.._,::,4o

/f Q

fl,(,,,._

~

Figure 3. Estimated daily intake of Oi-2-ethylhexyl phthalate (OEHP) via exposure route. Notes: ADIW: Acceptable daily intake from water (EPHC/NHMRC/NRMMC, 2008).

100 , - - - - - - - - - - - - - - - -

'o'

AOlw

§

.,~

..

10

a. ......

2.

i

1

-~ .,

.s ~

0 .1

,,16., 1o

0.01

E -~ w

Recycled

Drinking

Acute diet

Chronic diet

Figure 4. Estimated daily intake of Atrazine via exposure route.

Notes: ADIW: Acceptable daily intake from water (EPHC/NHMRCINRMMC, 2008). 'o' ......

100

...,

10

~.,

a. ......

2.

i

.S <( :::;; C

,,z.,

1 0.1 AOlw

0 .01 0.001

1o 0.0001

-~E w

't,

<>e e,;f.

~

-~'t,

~

·,$'

<:f

~.,

e" ~e

,::-0 f/,

b°''"

r.,,<:'

Figure 5. Estimated daily intake of N-Nitrosodimethylamine (NOMA) via exposure route. Notes: ADIW: Acceptable daily intake from water (EPHC/NHMRC/NRMMC, 2008).

Conclusions

magnitude below the est imat ed daily intake associated with other exposures such as food. Additionally, the predicted intakes for each contaminant were below t he acceptable daily intake outlined in t he Australian Guidelines for Water Recycl ing: Managing Health and Environmental Risks (phase 2) (Tables 1 and 2).

For all five contami nants investigated the estimated daily intake from consumption of recycled water was several orders of

The predicted recycled water concentrations in this study were well correlated with results presented in the Interim Water

58 DECEMBER 2010 water

technical features

refereed paper

Quality Report of the Western Corridor Recycled Water Project (Queensland Water Commission Expert Advisory Panel, 2009) outlining data from t he Bundamba Advanced Water Treatment Plant, Queensland, wh ich processed effluent from four wastewater treatment plants during the period May to December 2008 (autumn to summer). EE2 was undetected at a detection limit of 1ng/ L and at razine was undetected at a detection limit of 1 0ng/L. NOMA was detected once on ly in 60 samples at a concentration of 10ng/ L, and was undetected in the remai nder of samples at a detection limit of 5ng/L. However the detected concentration met the Queensland standards outlined in Schedule 3B of t he 2005 Public Health Regulation (Office of the Queensland Parliamentary Council, 2008).

Acknowledgments This study was supported by fund ing from the Water Quality Research Australia (WQRA) Summer Scholarship Program.

The Authors Jane-Louise Lampard (j.lampard@ griffith.edu.au) is a PhD cand idate at the Smart Water Research Centre at Griffith University. This paper is based on a report to WQRA completed during her WQRA Summer Scholarship under Assoc Prof Heather Chapman and Dr Frederic Leusch.

Dr Anne Roiko is a Senior Lecturer in Health and Environment at t he University of th e Sunshine Coast and co-supervisor for t his research.

chemicals of concern References APVMA 2007. Oxyfluorfen Testing (2006 â&#x20AC;˘ 2007) - Technical Report. In: AUTHORITY, A. P.A. V. M. (ed.}.

APVMA 2008. Atrazine final review report and regulatory decision: the reconsideration of the active constituent, registration of products containing Atrazine and approvals of their associated labels.

ATSDR 1989. N-Nitrosodimethylamine Public Health Statement. Agency for Toxic Substances and Disease Registry.

ATSDR 2002. Toxicological profile for di(2-ethylhexyl)phthalate (DEHP}.

Atlanta, GA.: Agency for Toxic Substances and Disease Registry ATSDR 2003. Toxicological profile for Atrazine. Agency for Toxic Substances and Disease Registry.

BAXTER, E. D., SLAIDING, I. R. & TRAVERS, V. 2007. Current incidence of N-nitrosodimethylamine in beers worldwide. Food Additives and Contaminants, 24, 807-811.

BRAGA, 0., SMYTHE, G. A., SCHAFER, A. I. & FEITZ, A. J. 2005. Steroid estrogens in primary and tertiary wastewater treatment plants. Water Science and Technology, 52, 273-278.

CPSC 1985. Report to the U.S. Consumer Product Safety Commission by the Chronic Hazard Advisory Panel on di(2-ethylhexyl}phthalate.

Washington D.C. CRCWQT 2008. Community view on recycled water: the impact of information.

DAUGHTON , C. G. & TERNES, T. A. 1999. Pharmaceuticals and personal care products in the environment: agents of subtle change?

Environmental Health Perspectives, 107, 907-938.

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Works better under pressure.

That 's w hy he's the perfect Mono employee.

He thrives on pressure, and we have the highest pressure PSS pumps on the market.

He knows great pressure can mean great freedom. Because the more of it you have, the further it' II take you.

chemicals of concern chromat ography w ith mass spectrometric det ection. Journal of Chromatography A, 814, 187-197.

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Seasonality effe cts on pharmaceuticals and ST riazine herbicides in wastewater effluent and surface water from the Canadian side of the Upper Detroit River. Environmental Toxicology & Chemistry, 25, 2356- 2366.

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DORRONSORO, M., LARRANAGA, N ., MARTINEZ, C., NAVARRO, C., QU IROS, J. R., SANCHEZ, M. J., TORMO, M. J. & GONZALEZ, C. A. 2006. Intake and food sources of nitrites and N -nitrosodimethylamine in Spain. Public Health Nutrition, 9, 785-791.

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European Food Research and Technology, 2 12, 247-251 .

techni

I features

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odour management

refereed paper

CORROSION AND ODOUR REDUCTION FOR A RISING MAIN T Hurse, M Stephenson, B Heiberg, J Skene, S White, P Ochre, M Laginestra, F Kashefizadeh, S Palipana Abst ract The management of odour nuisance and corrosion risks in relation to sewage pump stations, gravity sewers and special structures like rising main discharge manholes has received a lot of attention in recent years. This paper concerns the management of corrosion risk inside rising mains and the resulting odour nuisance and corrosion risks along the rising mains. The approach taken is to set out t he major issues briefly, and t hen to provide a case st udy t hat describes how they were addressed strategically. The common rising main (CRM) chosen for the case study serves a community of 38,000 EP, and comprises six pump stations and 24km of pressure main constructed mainly from unduplicated MSCL (m ild-steel cement-lined) and DICL (ducti le-iron cement-lined) pipes.

Introduction Odour generation in sewer networks and corrosion of sewer networks are issues that are oft en related, because hydrogen sulfide (H2 S) is usually the major contributor to sewer odour and is also the substrate converted into sulfuric acid.

In view of t his, measures taken to abate the risk of odour nuisance will usually affect the corrosion risk also - but not always in the same way, as will become clear presently.

Each type of network element (rising main/gravity sewer/pump station/special structure) has its own typical set of causes of odour and corrosion . The prominence of each cause tends to be t ime and location specific. Frequently encountered causes of odour and corrosion are listed in Table 1.

The best opportunity to mitigate the risks of nuisance odour and corrosion occurs when the net work is being planned and designed. However, even with good engineering practice, odour and corrosion problems may still arise subsequently, due to various reasons, e.g. owing to changes in operational and maintenance practices, inappropriate

Table 1. Common Odour and Corrosion Issues in Sewer Networks.

Network Element

Common Causes of Odour

Common Causes of Corrosion

Rising mains

Foul air released from air valves (AVs)

H2S-containing air pockets in cementlined mains

Gravity sewers

Foul air released from vent stacks, and from gaps around MH covers Loss of water-seals due to pressure fluctuation

High H2S concentrations in headspace due to one or more of: • poor ventilation • agitation of sewage • solids accumulation and biofilms Infrequent removal of acid

Special structures (e.g. Foul air released from vent stacks or rising main discharge gaps around inspection covers manholes, emergency Rapid rise of sewage level storage chambers)

High H2S concentrations in headspace due to one or more of: • poor ventilation • agitation of sewage • solids accumulation and biofilms Infrequent removal of acid

Pump stations

High H2S concentrations in headspace due to one or more of: • poor ventilation • agitation of sewage • solids accumulation and biofilms Infrequent removal of acid

Foul air released from vent stacks and from gaps around poorly fitting access covers Fat, Oil & Grease and/or scum accumulation Rapid rise of sewage level Blowing air into wet-well

land development, and changing commu nity expectations about amenity.

The management of odour nuisance and corrosion risk in relation to pump stations, gravity sewers and special st ructures like rising main discharge manholes has received a lot of attent ion in recent years. This paper concerns a less well covered subject, the management of corrosion risk inside rising mains and the resulting odour nuisance and corrosion risks along the rising mains. It is an important subject for operators of networks that feature long rising mains ru nning through undulating terrain, especially if the high points on the sewer are located close to or in residential areas. Below we set out the major issues briefly, and then present a case study to describe what can be done to manage the risk of nuisance odour and corrosion. The case st udy concerns a common rising main (CRM) system in South East Queensland.

A case study of a 24km common rising main.

The Major Issues Gas pockets can develop in rising mains.

Gas pockets are hydraulically undesirable because t hey reduce the cross-sectional area for sewage flow - and thereby increase the resistance to flow. They can also aggravate the effects of a pressure surge. Gas pockets are also undesirable because they promote the corrosion of any cement or ferrous materials with which they are in contact. For t hese reasons, it may be necessary to provide air valves (AVs) at local high points, especially if t he sewage will be in contact with cement or ferrous materials. AVs may also be included to protect pipeline integrity by mitigating pressure su rges, and to facilitate the emptying and the fill ing of t he main.

Air released from rising mains is odorous and is corrosive to cement or ferrous materials outside the pipeline.

If the valve is located in a pit, a means must be provided to allow t his air to escape from the pit. To reduce the risk of causing nuisance to an acceptable level , the gas released from AVs may need further treatment, discharge from a stack, or both of these. A common response to

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odour management odour nuisance is to "turn off" the AV, but this is likely to increase the risk of internal corrosion, to increase the resistance to sewage flow, and possibly to increase the risk of pipeline damage arising from a pressure surge or p ipeline burst. These risks need to be well managed , and a precondition for this is having sufficient and reliable information on which to assess the risks. It should also not be forgotten that air discharge from an AV may contain methane (and possibly ot her volatile organic com pounds also), and that mixtures of air and methane (or mixtures of ai r and volatile organic com pounds VOC) can be explosive.

13

12

11

f

I

NBOIPS

~

.

10

....-··-·;.--.. ....-·· .. .. .. ......

; ............... . . . . . ..../

Common Ri$ing Main (Current 5cen3rlo) +•••••• Commoo Ri,lng Ma;n (Fulure Scenario)

* *

EJ<~llng ARV• ldenllfiod by MBW AAVs lde<lCJlled on [),-awing fo, UncOOOOClod NBOI

Figure 1. Common Rising Main - Current Scenario with Future Duplications and Pump Stations Indicated.

Case Study Background

The CRM in question is operated by Unitywater, serves a community of 38,000 EP, and conveys sewage to the Burpengary sewage treatment plant (STP). The CRM runs underground through land that is generally flat with some gentle undulations. Currently the CRM is connected to six pump stations and comprises 24km of pressure main constructed from unduplicated mainly MSCL and DICL pipes. Aware of the critical importance of the CRM, Unitywater is planning to duplicate parts of it by 2012. By then the CRM will also be connected to eight pump stations and comprise 28km of rising mains (see Figure 1). Currently the CRM is equipped with 15 combination-type AVs, but some of these AVs had been shut off to reduce odour impact in their vicinity. The resulting impacts on corrosion within the CRM (current and upgraded configurations) were not known.

Unitywater wished to be advised of the risk of corrosion to t he current and upgraded CRM and of options for mitigating that risk.

Development of a strategy to reduce corrosion and odour nuisance risks

GHD carried out firstly a preliminary investigation and then works for the development of a corrosion risk mitigation strategy. In essence, the resu lting strategy consisted of the following actions:

62 DECEMBER 2010 water

refereed paper

• Assess alignment drawings and records of AV locations, and inspect all of the AVs;

• Assessing the appropriateness of the existing AVs, and where additional AVs might be appropriate; and

• Find out where gas pockets would tend to arise but for operating AVs;

• Developing chemical dosing options.

• Determine where AVs are actually releasing gas; • Assess the condition of the pipeline at a set of locations representative of the whole main; • Open AVs so as to reduce corrosion risk for t he rising main interior, but consider other risks; • Ventilate AV pits to reduce corrosion risk for the rising main exterior and pit; • Further reduce the corrosion risk and reduce odour nuisance risk by chemical dosing; and • Use a vent stack and/or treatment system to reduce the risk of odou r nuisance further.

The tasks that led to the development of that strategy were:

The main outcomes of these various tasks are reported and discussed below.

Preliminary Investigation

This preliminary investigation included an inspection of all the AV locations, as well as sulfide build-up modelling, and proved to be invaluable. It was conc luded , amongst other t hings: that the sewage in most of the network was sulfidic (and, in some parts, septic); that there had been corrosion of pipework and manhole structures; and that most of the installed AVs might not be operating, these having been tu rned off so as to eliminate odour nuisance. The inspection also revealed that the record of AVs on the GIS was inaccurate, that two AV pits were inaccessible, and that air from one of the AVs smelt of organic solvent.

Air Accumulation Analysis

• Assessing the condition of the pipeline at a set of locations representative of t he whole main;

A question had arisen as to whether the flow of sewage alone would be sufficient to prevent enduring gas pockets from forming within the CRM. A desktop assessment was made of the abi lity of flowing sewage to entrain air. For this purpose the design equations of Escarameia (2007) were used, and it was concluded that only in about 6 km of the CRM (i.e. in about 25 per cent of the CRM) was the sewage flow sufficient to sweep air downstream.

• Reviewing devices for mitigating the odour impact of foul air released from AVs;

Locations along the main were identified where t he downstream flow of any air bubbles would be arrested by a

• Carrying out a preliminary investigation, including site inspections; • Estimating t he ability of sewage flow to sweep ai r from the CRM; • Surveying the H2 S concentration in each AV pit so as to determine whether the AV was open or not;

odour management

refereed paper

steepening downward pipe gradient or by a decrease in sewage velocity attendant upon an increase in the diameter of the main. At such locations, air is expected to coalesce into large pockets, which may remain , or run back upstream against the flow , the outcome depending on pipe diameter, pipe grade, and pumping rate (which, in a CRM, depends on the number of pump stations act ually injecting). Once the sewage flow stops, air wi ll tend to rise to local high points.

The set of predictions made with Escarameia's equations indicated that hydraulic entrainment of air could not prevent the existence of enduring gas pockets in parts of the CRM. The predictions also indicated t hat entrainment of air was considerably more difficult to achieve than the predictions made with the equations of Kalinske and Bliss (1943) would imply.

Survey of H 2 S Concentrations To know whether an AV releases ai r, it is not generally sufficient to confi rm that the isolation valve between the AV and the pipeline is open; and to determine what H2 S concentration may be attained in the normally c losed pit, a one-off measurement is not generally adequate.

Bot h goals can , however, be achieved by placing and leaving Odalogs or the like in the AV pits for at least one day. When t his was done, no H2 S was detected in about half of the AV pits on the CRM. In th ree of the pits in which H2 S was detected , the H2 S concentration exceeded 50 ppm on occasions; and in these three pits the persistence of H2 S revealed by the log indicated inadequate ventilation, and a high likelihood of external corrosion if the pipe coating was damaged.

Condition Assessment The condition of the pipeline metal, t he pipeline coati ng, and the manholes was assessed at selected locations so that Unitywater cou ld effect ively plan and prioritise a broad use, replacement and rehabilitation strat egy for t he risi ng main.

The assessment locations were chosen with a view to the age of the pipeline, t he mat erials from which it was constructed , and the results of the air accumulation analysis and H2 S monitoring in AV pits.

It was decided to assess the pipe-wall condition at 12 of the 15 air valve locations, these: • encompassing a range of pipe materials and diameters;

Figure 2. One of the Inspected AV Pits.

• being readily accessible without excavat ion; • providing sites that have the highest likelihood of internal corrosion (where air is accumulating and the AV is closed); • providing sites that have a high likelihood of external corrosion (where the AV valve is open and the manhole has no ventilation); and • providing sites that are representative of the general pipeline conditions for extrapolation purposes (where the AV is open and operational).

The only relevant environmental condition not covered by assessment of the pipe-work at the AV locations was t hat of pipe-work buried in soil. For this reason two excavat ions were also made at locations where air accumulation in the CRM was predicted.

Measurements of the thickness of the metal part of the pipe wal l were carried out using ultrasonic inspection tec hnology. The fact that the CRM is currently unduplicated and operating made it impracticable to inspect the inside of the pipeline by CCTV. It was found t hat: • the AVs were in fair condition and t hat those tested were fu nctional ; • the manhole structures were in fair condition, though H2 S attack of t he concrete was noted in most cases; • wall thickness readings for the steel pipework were compliant with the requirements of AS 2566; • wall thickness readings for the buried ductile iron pipework were compliant with the req uirements of AS 2566; and

• the external condition of the ductile iron pipe-work within the AV pits ranged from poor to fair (see Figure 2).

Several recommendations were made, two of them being that venting facil ities should be retrofitted at all AV pits where t here was no such facility, and t hat AVs be reopened. These recommendations were made contingent on Unitywater's giving further consideration to factors including : • the type of ventilation to use (natural or forced); • t he potential for causing odour nuisance; • the potential for exacerbating corrosion of the respective pit; and • t he potential for causing pressure fluctuations in t he pit.

The issue of odour nuisance was further examined subsequently.

Review of Odour Mitigation Devices In principle, the odour impact of the foul air discharged from an AV pit can be reduced by improving the dispersion of the foul air in the environment (e.g. by providing a vent stack or by making the vent stack taller), by making t he sewage less odorous, by treating the fou l air prior to its release to the environment so as to make the foul air less odorous, or by a combinat ion of these three methods.

Most AV pits on the CRM were already connected to a vent stack, and it was Unitywater's experience that some of the 7m high vent stacks serving the AV pits did not provide adequate dispersion to prevent odour nuisance. In such situations the odour impact was being abated by passive odour-treatment canisters at the outlet of these stacks.

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refereed paper

This n otwithstanding, a brief review of devices for mitigating the odou r impact

Table 2. Preventative Sulfide Control Technologies.

of foul air released from AVs was requested and undertaken. Reviewed devices included filters mounted at the end of vent stacks, ground-mounted fi lters, an in-g round biofilter, a dry scrubber for manholes, as well as the convent ional drum dry scrubbers. They were all assessed in regard to: capital and operating cost; required services and vehicle access; ease of retrofitting into the existing pit ventilation arrangement; ease of replacement when exhausted; service life; robustness; and resistance to passing the highest antic ipated flowrate of ai r.

Technologies

Advantages

Disadvantages

Oxygen dosing

Relatively simple application Proven technology

Promotes the removal of readily degradable BOD Complex delivery system for effective oxygen transfer Injection does not lead to effective oxygen transfer Cannot be easily relocated Medium/high capital costs Medium operating costs Reaction time is pH dependent and may be slow Need to consider dosing location carefully 02 can accumulate at high points and cause corrosion. Also, risk of explosion is increased Works best under high pressure rising mains Doesn't work well unless flow is semi-continuous Liquid oxygen is hazardous

Magnesium Hydroxide (MHL)

Non-hazardous Increases the alkalinity and reduces the SAR of wastewater Non-corrosive Low/medi um capital cost

Cost is directly proportional to flow treated Single supplier Limited shelf life (3 months) Effectiveness declines as salinity increases Tends to settle to the bottom of PS wet-wells and form a gelatinous mass there Frequent flushing of dosing lines and mixing of storage tank contents is needed to prevent blockages Effect on struvite production at treatment plant is not known

Ferric Chloride (FeCl 3)

Low/medium capital cost Longer shelf life than MHL Handles high sulfide loads Rapid reaction

Hazardous Corrosive Medium operational costs Does not oxidise non-sulfide odorous compounds Consumes alkalinity so alkali addition is often required Dosage increases with sulfide concentration Wi II also react with phosphate Creates a sediment and may have impacts on sludge dewatering and handling at the STP Contains metals other than Fe

Calcium nitrate

Safe handling Suitable for most systems, particularly when dosed prior to sulfide formation

Promotes the removal of readily degradable BOD Increases total-N load, which can be an issue for downstream wastewater treatment plant Stimulates consumption of organic compounds that assist denitrification at the WWTP Potentially high operating costs Complex dosing control In some cases may promote precipitation of CaC03

It should be noted t hat the combination AVs not only release air but may also admit air, and that t he air flowrate may sometimes be large, e.g. during p ipeline fil ling. It was fou nd t hat the suppliers o f most of th e reviewed odour treatment devices were either unable or unwi lling to describe the relationsh ip b etween pressure d rop across the device and the air flowrate passed by the device. Consequently, it is not yet clear how many of these devices have to be arranged in parallel so as to allow t he AVs to function as intended.

With some qual ificatio ns concern ing third party safety, OH&S, back pressure, and filter warm ing due to reaction with substances in the foul air, it was recommended that the brand of vent stac k fi lter preferred by Unitywater be retained, where that had been employed.

Assessment of AV locations Once it had been established that hydraulic entrainment could not eliminate enduri ng gas pockets from the CRM, the meth odology in Section 10.9.3 of Part 1: Planning and Design of the Sewage Pumpin g St ation Code of Australia (WSA 04-2005, WSAA) was em p loyed to determine appropriate locations for AVs to reduce corrosion risk . This section of t he Code states that: "Gas release valves shall be fitted at all high points on the pressure main unless it can be demonstrated that the flow velocity is sufficient to move accumulated gas at the high point downstream to the next high point in the pressure main or point of discharge."

WSAA a lso specifies that automatic combi nation AVs be used as gas release valves for sewerage rising mains.

It was fou nd t hat all the existing com bination AVs were appropriately located to vent air from the CRM, but

64 DECEMBER 2010 water

that combination AVs were requi red at an additional 10 locations. At four other locations AVs would be required for corrosion protection, but for the prediction of hydraulic entrai nment. A conservative approach was taken of recommending that manual AVs be installed in pits at t hese four locations: the AVs to enab le the absence of air pockets to be confirmed, and the pits to facilitate the monitoring of wall t hickness.

Chemical Dosing Options Having reported on means for reducing the risk of corrosion through operat ion of appropriately installed AVs, we developed o ptions for f urther reducing the risk o f corrosion with in the CRM by means o f chemical dosing. Th is options development was preceded by sewage

characterisation at selected points along the CRM, and by application of steadystate models for the daily average total sulfide concentrations in the current CRM and in the upgraded CRM. For t he sewage characterisation, sewage monitoring was undertaken during a 24 hour period in November 2009 at p ump stations and selected scour valves. The characteristics thereby obtained were typical ones for d omestic sewage, with the exception o f the values reported for the single pump station catchment receiving significant amounts of trad e waste.

The sulfide model is based on the methods, equations and advice provided in the Hydrogen Sulphide Control Manual (1989) (HSCM), on recent literature, and GHD experience. Model inputs

odour management

refereed paper

concerning sewage quality (e.g. temperature) were generally based on measured median values, and some adjustments were made to reduce the discrepancy between sulfide concentrations predicted by the model and those measured during sewage characterisation , or to allow for the effects of chemical dosing.

The chemical dosing options were devised with the aim of reducing the concentration of H2S dissolved in t he sewage passing local high points in the CRM by 80 per cent. Four chem icals were considered: oxygen, calcium nitrate, magnesium hydroxide, and ferric chloride. Their general advantages and disadvantages are summarised in Table 2 .

Given that high points are located on most of the six (i n future, eight) branches of the CRM, and given also that it would be easier to set up and maintain a dosing facility at a pump stat ion than elsewhere, t he assessment of the four chemicals was based on t he presumption that dosing units would at least be set up at the pump stations located at the heads of the four longest branches of the CRM (see Figure 1) - additional dosing points along the main would be necessary for ferric ch loride and oxygen, however. The four chemical options were evaluated against several criteria (see Table 3), and a weighted overall score was produced.

The resu lts of the option evaluation are presented in Table 4.

Based on the above multi-criteria assessment, it was concluded that magnesium hydroxide liquid (MHL) was the most appropriate and cost-effective option for meeting the project objective.

It was recommended that further jar testing be undertaken before t he funct ional design so as to determine the effect of MHL dosage on t he pH, the alkalinity, the calci um concentration , and the LSI in parts of t he network downstream of t he four pump stations. It was also recommended that t he effects of proposed MHL dosages on the STP's performance be investigated prior to the functional design.

Conclusions The practice of sh utting off AVs so as to reduce the risk of odour nuisance is likely to increase the risk of internal corrosion in cement-lined mains, and might also increase the flow resistance as well as the risk of pipeline damage if the AV is provided for surge protection and for pipeline filling and emptying. These risks and safety risks need to be well managed .

Table 3. Evaluation Criteria.

Criteria

Comment on Criteria

Effectiveness

Ability to meet the target 80 per cent reduction in dissolved H2S

30

10

Environmental

Whether there are any direct, consequential environmental impacts

5

10

10

10

Weighting

Operability

Worst Possible Best Possible Score Score

Whether the system is easy to operate, and reliable Ease of installation and maintenance OH&S Safety and material handling issues

10

10

10

10

STP and Re-use

5

10

30

10

Cost

Impact on downstream STP and biosolids and effluent re-use plants Net present cost

Table 4. Evaluation Results.

Evaluation Criteria Oxygen

Score (1-10) Calcium nitrate Magnesium hydroxide

Ferric chloride

Effectiveness

4

6

8

Environmental

5

5

5

5

Operability

6

6

4

6

Ease of installation and maintenance

4

5

5

8

STP and Re-use

4

2 0.0 405

8 8 7 6.9 706

7

OH&S Cost

5.0

SCORE

465

One precondition for good management of the risks is sufficient and reliable information with which to assess them.

It wou ld be helpful if t he f lowrate pressure drop relationship of odour treatment devices like passive filters could be defined, and if the effect of passing pollutants other than H2 S throug h t hem could be clarified.

Operators should know the flowrates of gas that potentially need to be passed by the AVs, so that odour treatment devices can be correctly sized and arranged.

The management of corrosion risk would also be made easier if t he pipeline construction details were carefu lly verified, and recorded on fu lly certified drawings.

References Corrosion Risk Reduction in Burpengary Rising Main (2009- 10). GHD Pty Ltd for Moreton Bay Water (now Unitywater).

Escarameia M (2007). Investigating hydraulic removal of air from water pipelines. Water Management 160 (Issue WMI) 25-34.

Hydrogen sulphide control manual - septicity, corrosion and odour control in sewerage systems (1989). Sanders BS and Scott PH (eds.), 2 volumes, Melbourne and Metropolitan Board of Works, Melbourne, Australia.

(Reprints available from Water Services Associat ion of Australia Inc, Melbourne).

Kalinske A A. and Bliss PH (1943) Removal of air from pipe lines by flowing water. Proceedings

6

5 5 4.6 549

of the American Society of Civil Engineers 13(10), 480-482.

Sewage Pumping Station Code of Australia (2005). 2nd edition, Water Services Association of Australia Inc, Melbourne, Australia.

Acknowledgments The authors would like to thank A Schoenmaker, B Castlehouse, B Maule, D Fillmore, B Sheedy, R van Oorschot, C Rydst rom, T Walmsley, A Badini, F Carroll and other Unitywater staff and GHD staff involved in the project.

The Authors Tim Hurse (email timothy.hurse@ GHD.com) is a Senior Engineer at GHD specialising in odour-related aspects of sewerage schemes.

Matt Stephenson, Ben Hoiberg, James Skene, Scott White, Pip Ochre and Mitch Laginestra are al l members of the GHD team .

Flora Kasafizadeh and Sanath Palipama are, respectively, Water & Sewerage Engineer and Principal Design Engineer with Unitywater, which provides water supply and sewerage services to Moreton Bay and Sunshine Coast residential and business customers.

water DECEMBER 2010 65

anaerobic digestion

refereed paper

CO-DIGESTION OF HIGH STRENGTH ORGANIC TRADE WASTE WITH WASTEWATER SLUDGE J Krampe, M Willis, D Richards

7

Abstract The co-digestion of industrial high strength waste streams with the sludge from municipal wastewater treatment plants (WWTP) has present ed the opportunity to maximise efficiency of anaerobic digesters, generate methane for electricity production, re-direct problematic trade waste streams along with reducing the impact of trade waste disposal into sewer networks and WWTP operations. A bench scale trial that involved mixing liquid trade waste w ith municipal wastewater treatment plant sludge, has provided positive results using several t rade waste materials. The experimental results for the co-substrate salty whey show potential energy savings, however negative implications such as increased internal loads have also been discussed. It was found that redirecting two tankers of salty whey per week from the wastewater stream to the sludge stream cou ld reduce the electricity demand from the grid for the WWTP by 425 kWh 01/ day. Other trade waste materials could have an even larger positive effect.

Keywords: anaerobic digestion, co-digestion, trade waste, salty whey

Introduction Anaerobic treatment of industrial wastewater is a common technology.

Major benefits of anaerobic treatment are reduced energy consumption compared to aerobic treatment, biogas production and red uced excess sludge production.

Anaerobic treatment, especially with co-generation, is a significant sustainable option but it is only economical for large volumes of wastewater with high organ ic content. Many industries produce suitable wast e side streams in their processes but in volumes that are in most cases too small to allow an economical implementation of in-house anaerobic treatment and use of the biogas for energy production. The collection and t ransport of suitable streams to larger anaerobic treatment plants with power generation is

66 DECEMBER 2010 water

Industry Co llection of organic waste materials

I

High Loaded Concentrates

Low Loaded Wastewater

r ----------- - ----------- --------- - - - ------------------ --] Mixing/Storage

1+----'

!

I

I

I

I

: --- - - - -:

~

~

~

_____

~~~.?~-), - - - - - - . .

Use _,

I

I ~-----),

Power

WWTP Anoxic/ Aerobic Treatment

Dewatering

---------- ------------------------ ---------------------¡ Effluent Discharge

Dewatered Sl udge

Use

Figure 1. Application of co-digestion on a WWTP (Adapted from Bock and Rott, 2003).

described as co-digestion . Typically co-digestion takes place within anaerobic digesters at a WWTP (Figure 1). The first step for successful implementation of co-digest ion is the separation of different strength waste streams at the targeted industry. The aim is to redirect high organic strength, low volume streams and tanker them separately t o the sludge t reatment process of the wastewater treatment plant. Low strength or high volume st reams from trade waste sites would continue to be discharged into the sewer network and enter the wastewater treatment plant mixed with the municipal wastewater in the sewage stream.

At the WWTP, t he tankered trade wastes are mixed with primary and waste

Bench-scale testing for gas product,on and any mhib1t1on.

activated sludges from the main wastewater treatment process and pumped into the digester. Depending on the quality of the trade wastes this step may follow pre-treatment of the trade wast es such as screening or neutralisation. Easily biodegradable trade wastes discharged into the digesters can show an immediate response in regards to increased gas product ion. In some cases, trade wastes can be dosed during times of peak loading and thus high energy demand. The immediate increase in gas production allows an increased electricity production with combined heat power units which then allows the reduction of energy consumption from the grid and keeps the electricity load based tariff low.

However, t he addit ional flows into t he digesters reduce the retention time which may be a problem for WWTPs that are close to their design load. Alternatively, sometimes improvements in the thickening stages for the wastewater

anaerobic digestion

refereed paper

sludges can provide an opportunity to obtain the required capacity for t he co-digestion in the digesters. The retention time in the digester is the main driver to focus on high organic strengt h, low volume trade wastes.

concn .) to prevent the biogas dissolving into the seal ing liquid.

An additional 4ml methyl orange (0.1 per cent solution) was added as a visual measurement aid.

Gas collection tube

Sealing liquid balancing tube

Typically, the digested sludge will be dewatered with centrifuges. Some trade wastes show an inf luence on the dewatering process either with improved or reduced performance wh ich must be considered. The wast e wi ll, in many cases, have Reaction vessel a significant impact on the supernatant quality. A large portion of the nitrogen and phosphorus introduced into the digester via the trade waste w ill t hen enter the main treatment stream via the supernatant Figure 2. Eudiometer cell. and might result in additional treat ment cost s for nitrificat ion (oxygen demand}, denitrification applications (which is quite often the (external carbon source) and case in Europe). phosphorus precipitation (precipitant).

Chemical composition of trade wastes It is important to c onsider these costs can give a good basis for suitability for right from the beginn ing to ensure extra co-digestion, however it is not feasi ble costs for t reating the supernatant do not to test all t rade wastes for potentially exceed the benefits of the additional inhibiting parameters. Instead biological gas production and electri city test systems which si mulate the generation. conditions in an anaerobic digester can Finally, a proportion of the trade be used to examine trade wastes with waste comprises the stabilised sl udge regards to their potential gas prod uction and it is important that the final use of and any inhibiting effects. the sludge is not compromised in any This paper outlines SA Water's way. approach for an initial assessment of To be suitable for co-digestion , trade wastes. the trade waste needs to fulfil several Materials and Methods requi rements such as high organic content, preferably low nitrogen and The su itability of t rade wastes for coph osphorus content , neutral pH and digestion was tested in an anaerobic should contain no substances that degradat ion trial. The tests were inhibit biological p rocesses or performed in two eudiometers (Sel utec compromise the final biosol id quality.

GmbH, Germany) each consisting of six Typically, a wide range of t rade wastes cells. Each c ell consists of a reaction fulfilling these requirements can be vessel , a gas collection t ube and a obtained from the food and beverage sealing liquid balancing t ube which industries. were connected airtight (Figure 2). The Not all req uirements apply for each reaction vessel was fi lled with a mixture case and the decision whether a t rade of digester sludge and t he trade waste waste is suitable has to be made on to be tested and placed in a water bath which was heated to 37°C to maintain a case by case basis. For example, trade wastes with high nitrogen or mesophilic conditions for the digester phosphorus concentrations would not trial. The contents were mixed using magnetic stirrers. The produced biogas be considered su itable substrates for co-digestion; however if they are displaced a sealing liquid from t he gas already treated in the main stream of collection tube into t he liquid balancing the WWTP t hey could be considered tu be. The gas collection tube has a scale as suitable. Also the nutrient quality t hat allows the recording of t he amount of the biosolids cou ld be compromised of gas produced . The sealing liquid was in cases where t hey are used in prepared as 1000ml distilled H2O, 150 g incinerat ion and not in land based Na2 SO4 and 50ml H2 SO4 (98 per cent

To achieve anaerobic cond itions from the beginning of each trial and allow an exact evaluation of the produced biogas quality, the whole gas system was flushed with nitrogen before each trial.

The anaerobic sl udge was taken from digester 4 of SA Water's Glenelg WWTP. The five digesters are operated with primary sludge and t hickened waste activated sl udge. Typically they are operated at an average temperature of 36°C with a retention t ime of 20 days.

To investigate particular concentrations of trade waste and the subsequent gas generation from co-digestion with sludge, varying volu mes of trade waste were added to each reaction vessel. The first reaction vessel contained the reference digester sludge. The remaining five vessels contained 2, 4, 10, 15 and 30 per cent c oncentration of the trade waste respectively. The higher volumes were chosen to monitor potential inhibition or achieve an overloading of the sludge's biomass. A typical test was conducted over a period of 20 days to ali gn with the retent ion time of the mesoph ilic anaerobic digesters at t he Glenelg WWTP. Before the eudiometer test, t he t rade waste samp les were analysed by t he Australian Water Quality Centre (AWQC) for key physico-chemical properties.

The AWQC uses NATA (National Association of Test ing Authorities) accredited methods and is AS/ NZS ISO 9001 certified for microbiological , biological and chemical analysis.

All samples relat ed to the digester sludge and t he sludge composition before and after the test were performed at the Glenelg WWTP laboratory (AS/ NZS ISO 9001 & 14001 c ertified).

At the end of the test a gas sample was taken from the gas collection t ube.

Gas analysis was performed by Amdel Ltd, an Adelaide based laboratory and technical services provider, accredited to ISO 17025 and certified to ISO 9001.

Figure 3 shows a picture of one of t he two eudiometers and its six cells in the lab of Glenelg WWTP t hat was used in t his t rial.

water DECEMBER 2010 67

anaerobic digestion

•,,

Result Analysis and Discussion Scaling Liquid Tube

As part of t his project 17 initial side st reams, mainly from the food and beverage industries, were analysed in regards to their key chemical parameters. Based on t he results and additional select ion criteria such as availability of the material, volumes, potent ial requirements for pre-treatment and Occupational Health and Safety concerns, a short list of eight trade wastes were selected for a bench scale assessment. These were:

Gas Collection ,,•' Tube Thermostat for water _ ,,•' bath temperature 1m•.--illl..rl!'"'-I maintenance Reaction vessels •-' (containing sludge and substrate mixture)

Magnetic Stirring ~··""' device

,,,, Filled water bath

• Salty whey • Sweet whey • Coolant waste (Ethylene Glycol)

Figure 3. Eudiometer apparatus.

• Chicken blood • Algae • Potato starch • Brewing waste • Cola based alcoholic beverage waste As an example the results for salty whey will be discussed in more det ail in t his paper.

Salty whey is a waste from the dairy industry. The salty whey used for this project originates from t he manufacture of cheddar cheese.

Sweet whey is commonly dewatered to produce whey protein powder or used by pig farmers who incorporate the whey into pig feed, however salty whey cannot be used for these purposes.

Currently, the highly concentrated salty whey is tankered to SA Water's Bolivar WWTP and treated with the main wastewater st ream. This is an ongoing concern, because t he salty whey

Table 1. Analytical results for the salty whey.

Parameter

Salty Whey

TDS (mg/L)

20100 48400 65200 1180 609 3.8 45000

VSS (mg/L)

3810

B0D 5 (mg/L) COD (mg/L) Conductivity (µSi em) N10t (mg/L) P101

(mg/L)

pH

68 DECEMBER 2010 water

increases the salinity of the wastewater whic h is a problem with regards to the salinity of re-use effluent. Treating the salty whey in an anaerobic digester would reduce the salt and organic loads to the wastewater treatment plant significantly, reduce the energy consumpt ion of the WWTP, as well as increase the electricity production at t he plant. By t reating the whey at Glenelg WWTP digesters it is also possible to keep the salinity separated from the mainstream process because t he sludge is t reated in sludge lagoons after digestion. This ensures that most of the salt is retained in t he sludge and not returned with the supernatant.

Salty whey was selected as the initial material to be used in the t rial at the Glenelg WWTP digester.

The analytical resu lts of the salty whey are summarised in Table 1.

The salty whey is produced in liquid form and can easily be pumped and mixed with the WWTP sludge and fed into the digesters.

refereed paper

The salty whey was processed in the eudiometer as outlined above, and the gas production was measured over a period of 22 days.

The cumulative gas production over time is plotted in Figure 4 .

Al l cells show a sign ificant gas production in the first days which then decreases. The lowest cumulative gas production c an be observed for the reference sample without any additional trade waste.

The gas production increases gradually with 2, 4 and 10 per cent trade waste addition. However, the cell with 1 5 per cent trade wast e shows less gas prod uction than the 10 per cent cell and the 30 per cent cell drops below even the 2 per cent cel l.

This behaviour can be explained in conj unction with the alkalinity and volatile fatty acids (VFA) results after digestion shown in Table 2.

Even though t he VSS loading rate for the cel ls with 15 and 30 per cent trade waste addition did not exceed typical values for the operation of anaerobic mesophilic digesters, the VFA are elevated. This can be explained by t he large amount of soluble organics for the salty whey which are not considered in the VSS loading rate.

In the cell with 30 per cent t rade waste t he process was totally inhibited by the low pH valu e. The 15 per cent vessel shows a partial inhibition even though the pH would still be suitable for a complete anaerobic degradation t o methane.

Gerardi (2003) states t hat total volatile fatty acid (TVFA) t o bicarbonate alkalinity (BA) ratios higher than 0.5 can result in stability problems in anaerobic digestion processes and should not

Table 2. Post digestion sludge analyses for the different cells.

Vessel

pH

Alkalinity (mg/L CaC03)

VFA (mg/L)

Reference

7.4 7.4 7.4 7.3 7.0

3112 3191 3137 3146 2787

1.2

0

14 8 8 8 1082 2946

2% 4% 10% 15% 30%

'

anaerobic digestion

refe r eed pape r

exceed a rat io of 1.0. For the 15 per cent loading the TVFA/BA ratio can be calculated as 0.54 and for t he 30 per cent cell as 1.0.

Kroiss (1986) describes significant inhib ition of methane production even with low levels of acetic acid and p ropionic acid in neut ral pH conditions.

Overall, it has to be stated that t ypical VSS loading rates ca nnot be applied fo r co-digestion of highly concentrated organic trade wastes because they are mainly empirical val ues based on primary and secondary slud ge app lications.

Aside from the gas q uantity, the gas quality is important fo r later use in gas engines. The resu lts for the salty whey are summarised in Table 3.

The gas concent rations given in Table 3 are normalised to eliminat e t he effect of the nitrogen used to sparge the eudiometer equipment and thereby create an anaerob ic environment. The reference sample produced a typical b iogas with a relatively high CH4 content which is usual for the Glenelg biogas due to the relatively large amount of p rimary sludge compared to waste activat ed sludge (WAS) t reated in the digesters.

The ce lls with 2, 4 and 10 per cent trade waste addi tion show an improved biog as qualit y with overall higher methane co ntent than the reference sludge wh ich resu lts in a higher calorific val ue of t he biogas.

The cell with 15 per cent trade waste addition produced a typica l biogas whereas the 30 per cent cell produced no methane at all.

Table 3. Methane and Carbon Dioxide concentrations.

Reference sludge

2% 4% 10% 15% 30%

CO2 Mol.%

CH4 Mol.%

31.7 27.6 27.5 25.3 32.1 99.9

68.3 72.4 72.5 74.7 67.8 0.01

Table 4. Average methane/biogas production from salty whey co-digestion (2 to 1Oper cent results).

L of CH 4 produced per kg coo added

L of CH4 produced per kg TS added

318-403 371

2657-3367

Range Average

3100

Overall t he salty whey co-digestion worked wel l between 2 and 10 per cent concentration (Figure 5). A s light decrease is evident at 10 per cent, whic h is likely a result of the bench scale and t he related issues s uch as homogenous sludge diversion, air tig ht sealing prob lems of all tubes and connections etc , as t here is no evidence of biological process issues.

For fu rther evaluat ion the average methane product ion has been calculated for salty whey using the range of 2-10 per cent trade waste addition . On average, 370L of CH4 was produced per kg COD introduced, or 3100L CH 4 per kg of TS added. Wi nter (1993) found a production of 350L of CH 4 produced per kg COD for whey

but it is not clear if sweet or salty whey was used. Also, differences in cheese production at the different dai ry factories , as well as different concentrations of t he whey, have to be t aken into account. Overall, t he different results are comparable and show that the experimental setup was suit ab le for the purpose of preliminary testi ng of potential trad e wastes.

The range and average resu lts for this trial are summarised in Table 4.

With the available q uantity of 165 kUmont h of salty whey, a daily load of 275 kg COD/ day can be red irected fro m t he wastewater st ream into th e digester. The gas production found from the bench scale test translates to a typ ical biogas volume of approximately 150kl biogas per day that can be p roduced from t he salty whey. Assu ming an energy value of the biogas of 6.5 kWh/kl t his would result in 1 MWh/d of produced energy.

Wit h the electrical efficiency of the installed combined heat power (C HP) units of 35 per cent approximately 350 kWh 0 ifday can be produced from this trade waste source.

For t his specific trade waste, it can be assu med that t he nitrogen of the t rade waste woul d be incorporated in the biomass when treated in the aerobic act ivated sludge stage (typically 5 per cent of BOD5).

Therefore, the energy savings can be calculated by simply calcu lating the oxygen demand for the carbon removal. Assu ming an oxygen demand of 1.4 kg 0 2 per kg BOD 5 and an SAE of 2 kg 0 2/ kWh01 t he energy d emand

1000

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900

""

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""

800

0

u

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E .!: C

E

600

..

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- - 2% substrate

-0

- - 4% substrate

500

-+- 10% substrat e

0

a.

0.35

cO

700

0

~

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0.40

0

400

- - 15% substrate

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-+- 30% substrate

300

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ea.

0.25

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Q

0.05

C

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0.20

E

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200

0.30

0.10

-

-

0:

100

0.00 0

0 0

10

15

20

25

4

10

t 15

30

% substra te ,n mixture

Retention time in da ys

Figure 4. Salty whey co-digestion gas production data.

Figure 5. Gas production ratios for salty whey co-digestion.

water

DECEMBER 2010 69

anaerobic digestion

refereed paper

for the aerobic treatment in the mainstream process would be reduced by approximately 75 kWhe1/d.

Overall, the redirection of two t rade wast e tanker loads (44kl total) per week from the wastewater stream into the sludge stream can lead to a reduction of the total electricity demand from the grid of 2 per cent for a 220,000 PE plant. Currently, SA Water is in the stage of ful l scale trials using the salty whey for co-digestion at Glenelg WWTP. Other trade wastes showed similarly promising results and are available in higher organic strength and/or larger volumes. This would result in an even greater positive impact on t he energy balance of the wastewater treatment plants.

In cases where additional sources are added to the WWTP, the extra costs for treatment of supernatant have to be evaluated carefully. Th e business model for the co-digestio n needs to clearly differentiate between the benefits from the carbon and the costs for processing the additional nutrients.

A pot ential business model based on trade waste c harges is shown in Figure 6.

In this model industry wou ld pay for the transport of the t rade waste to t he WWTP. Because the carbon content of the trade waste is of value for the WWTP, the industry is not charged for the BODiCO D load of the t rade waste. On the other hand, there are treatment costs relat ed to the nitrogen and phosphorus load of the trade waste which are charged to the industry. Having the industry pay for t he transport cost s woul d ensure that the processes are optimised and only hi ghly concent rated organic strength trade waste is delivered to the WWTP.

Conclusion For most of t he s elected and tested trade wastes the methodology worked we ll and prod uced useful results.

The overall cons id eration is that each waste stream will have diff erent implications when applied on a larger scale. Nitrogen and phosphorus co ntent, pre-treatment requ irements and long term avail ability vary for each of the trade wastes tested . Th e trade wast es cannot be considered solely upon their CH 4 and potenti al energy benefit. The required

70 DECEMBER 2010 water

Tankering costs drive internal process optimisation Industry isn't charged for organic load

Industry~ charged for N and P load

Share g ain

Share pain

N and P removal in

Energy production in

WWTP

WWTP

Nitrogen and Phosphorus

Carbon

Figure 6. Potential business model for co-digestion.

c on siderations are discussed and presented for the co-digestion of one trade waste in this paper and each potential trade waste material needs similar consideration.

The investigation has provided opportun ities to ascertain the opinions and attitudes of respective waste prod ucing companies towards codigestion and the feedback has been positi ve. From an indu stry point of view, the benefits of disposal via codigestion are numerous, but the most significant is cost saving. Paying for cartage to the c lo sest SA Water WWTP (with digester) and offsetting a portion of the trade waste charges is favourable when compared to t reat ing t he waste stream on site or paying for waste disposal and t reatment by a third party. The long term benefits for producers are also evident, with regards to public perception, and active utilisation of a much more sustainable approach .

SA Water is currently exploring cod igestion in full scale trials to t ake the next step in a regular implementation of co-digestion of high st rength organic trade wast es.

Acknowledgments The investigation cou ld not have been completed without the assistance of the involved industries wh ich were very supportive in identifying suitab le in process streams. The authors also want to acknowledge t he financial support of this project from United Water International and SA Water and the technical support of the team from Glenelg WWTP.

The Authors

Dr Joerg Krampe is Princ ipal Wastewater Treatment Engineer with SA Water and Adjunct Associate Professor at the School of Civil, Environ mental and Mining Engineering, The University of Adelaide. joerg.krampe@sawat er.com.au.

Mason Willis is a Graduate Engineer wit h the South Australian Water Corporation with a BSc in Geography and Geology, and MSc in Environmental Engin eering from Royal Holloway University of London.

Doug Richards is Trade Waste Project Manager with the South Australian Water Corporation.

References Behmel , U., Meyer-Pittroff, R. (1996) Risiken bei der Cofermentation organischer Reststoffe in Biogasanlagen, Korrespondenz Abwasser 12/ 96 Bock, D. , Rott, U. (2003) Co-Fermentation of organic and high coloured concentrate from the textile processing industry , Journal of Environmental Science and Health - Part A, Marcel Dekker, Inc., New York, Vol. A38 (2003). No. 9 Gerardi, M.H. (2003) The microbiology of anaerobic digesters, Hoboken, NJ: John Wiley & Sons, Inc. Kroiss, H. (1986) Anaerobe Abwasserreinigung, Wiener Mitteilungen, Wasser- AbwasserGewaesser, Bd . 62 Winter, B. (1993) Zusatzlicher Energiegewinn durch Mitbehandlung von Molke in kommunalen Faulbehaltern - Ergebnisse eines GroBversuchs, Abfallwirtschaftsjournal, Jg. 5

~

refereed paper

catchment management

_j ..J

..J

C Leigh, M A Burford, D T Roberts, J W Udy Abstract The ability to predict reservoir vulnerability to summer blooms and to det ect t hresholds of change in phytoplankton cell densities in response to environmental factors would provide information critical for decision making, hazard prevention and management.

We used a new method to detect synch ronous change points in densities of phytoplankton taxa along t he gradient of percentage grazing land cover in catchments, based on data collected from 15 reservoirs in subtropical Australia during summer 2009. In addition, we propose a predictive index of vu lnerability t hat is based on simple measures of reservoir and catchment characteristics, including percentage grazing land cover.

Our findings suggest that land use in the catchments of the studied reservoi rs has a strong impact on phytoplankton composition and densities, and hence summer bloom phenomena.

Introduction Toxic cyanobacterial blooms in drinking water reservoirs have been widely documented in Australia and are now reported the world over, particularly during summer mont hs (Padisak 1997; McGregor and Fabbro 2000; Wiedner et al. 2007). To ensure t hat water quality guidelines for ecosystem and human health are met, regular monitoring of reservoirs is often carried out. However, water quality monitoring and the supply of safe drinking water demands considerable human and fiscal resources (Davis and Koop 2006). In addition,

monitoring often begins after reservoirs are built and water quality problems eventuate. Therefore, t he ability to predict the vulnerability of reservoirs to toxic cyanobacterial blooms, along with methods to detect thresholds of change in phytoplankton composition, would provide information critical for decision making, as well as reliable hazard prevention and management.

In order to reliably forecast the likelihood of cyanobacterial blooms, factors that promote poor water quality and conditions favourable to bloom formation need identifying. Climate, combined with the physical characteristics of reservoirs themselves, is a key factor (Jones and Poplawski 1998). In summer, warm temperatures and longer days tend to strengthen thermal stratification, which can then liberate bioavailable nutrients from anoxic sediments (B urford and O'Donohue 2006). In t he t ropics and subtropics, nutrient loads into reservoirs tend to increase in association with summerdominated rainfall; in temperate regions, climate change is predicted to increase nutrient loads and growth of phytoplankton (Matzinger et al. 2007; Paerl and Huisman 2008). Combined with the long water residence t imes typical of water storages, these factors make

Catchment links to blooms: data from 16 reservoirs in subtropical Australia.

summer blooms extremely likely (McGregor and Fabbro 2000).

Another key factor is catchment land use, since reservoir construction and expansion are often coincident with the conversion of forest or savannah to agricultural lands (Blanch 2008; Gucker et al. 2009). Th is can lead to reservoir eutrophication and conditions that promote blooms: 1) by increasing soil erosion and nutrient loads in runoff, wh ich can lead to changes in the ratios of nitrogen and phosphorus; or 2) through a combined effect with other reservoir and catchment attributes, e.g. water storage capacity and catchment size (Arbuckle and Downing 2001 ; Knoll et al. 2003; Davis and Koop 2006; Yang et al. 2008).

Based on these factors, a new index of reservoi r vulnerability to summer blooms of cyanobacteria has been developed (Leigh et al. 2010). The index was shown to correlate significantly and strongly with summer surface water densities of phytoplankton and potentially toxic cyanobacteria, as well as with the proportions of cyanobacteria, within 15 drinking water reservoirs in subtropical, southeast Queensland. The index also showed promise as a decision making tool in planning and managing reservoirs and their catchments with the aim to reduce summer bloom vulnerability. In particular, reduci ng the percentage of grazing land cover via reforestat ion substantially reduced the vulnerability of a plan ned reservoir in comparison with existing reservoirs in the study region.

water DECEMBER 2010

71

E;J

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refereed paper

Therefore, we aimed to determine whether a threshold of grazing land cover existed that equated t o a synchronous increase in cell densities of phytoplankton, including cyanobacteria, in t he st udied reservoirs during the same summer sampl ing period. To do t his, we used a new method that can detect synchronous change points in community structure (TITAN; Baker and King 2010).

We believe these two met hods (the vulnerability index and TITAN) may assist reservoir planners and managers in decision making aimed at red ucing the vulnerability of their reservoirs to bloom events.

Table 1. Physical characteristics of 16 subtropical reservoirs and their catchments.

Location and Methods

NPD

North Pine

Som

Somerset

Wiv

Wivenhoe

Wya

Wyaralong

Sampling locations and phytoplankton analysis We studied 16 reservoirs that supply (or will supply) drinking w ater to t he urban and semi-rural populations of subtropical, southeast Q ueensland (c. 2.8 m illion).

These reservoirs vary in catch ment size and fu ll capacity; however, land use in their catchments is dominated by natural bushland and pastoral activiti es (mainly cattle grazing on unimproved pasture), with smaller proportions of cropping and residential lands (Table 1).

Each reservoir was sampled once bet ween 9 February and 3 March 2009 in the late summer period (referred herein as 'summer 2009'). At least three sites were sampled in each reservoir: near the dam wall; mid-reservoir; and in t he upstream part of each reservoir. We sampled t he deepest point of each site, which was at least 6m (except for the upstream sites of Kurwongbah and Little Nerang, which were 2-4m deep). Four sites were sampled in the large Somerset reservoir and in those with two major arms (Borumba, Hinze, Leslie Harrison and North Pine).

At each site, a 3m depth-integrated sample of surface wat er was collected from which a mixed 250mL subsample was fixed with Lugol's iodine solution (0.6 per cent final c oncentration) for later identification of phytoplankton taxa, including potent ially toxic cyanobacterial species (Anabaena circinalis, Anabaena bergii, Aphanizomenon ovalisporum, Cylindrospermopsis raciborskii and Microcystis aeruginosa), and calcu lation of c ell densities (cells mL-1) . Taxa were identified to species level, where possible, under 400x phase-contrast microscopy; c ells were cou nted using a Sedgewick Rafter counting chamber (Lund et al. 1958; Burford et al. 2007).

72 DECEMBER 2010 water

Code

Reservoir

Bar

Baroon

Bor

Borumba

Cool

Cooloolabin

Ewen

Ewen Maddock

Hin

Hinze

Kur

Kurwongbah

LHD

Leslie Harrison

LNer

Little Nerang

Mac

Macdonald

Man

Manchester

Mar Moog

Maroon Moogerah

Shore (km) SA (km2)

Vol (ML)

Depth (m)

Age (y)

CA (ha)

% Grazing

15.7 12.2

21 46

9.9

30 27 20 40

6530 46900 736

43.0 19.6 6.0

2130 17600 5250

8.5 12.2 38.7 13.2

25.5 44.5

3.9

61 000

3.8

12.8 14.3 67.4 33.4 34.5 10.9 38.3

1.4 2.3 9.3 3.4 4.2 0.6 2.6 2.6

46000 14200

27.3 17.9 29.3 167 237 462 110

3.3 7.7 21.2 39.7 110 1.1

16600 163000 14400 24800 9280 8000 26000 44300

7.4 17.5 4.2 5.9 16.6 3.1 10.0 13.3

83800 215000

10.9 10.1

369000 1150000 103000

9.3 10.5 8.4

25 48 29 93 35 48 33 56 25 na

8890 3600 4960 7260 10500 22700 34900 133000 568000 54590

12.2 42.3 3.3 20.2 36.1 28.5 41.5 46.0 46.9

Shore, shoreline perimeter; SA, reservoir surface area at full supply level (FSL); Vol, water storage capacity at FSL; Depth (mean) = Vol/SA; Age, age to 2009 since the completion of dam construction; na, Wyaralong dam due for completion in 2011; CA, catchment area of each reservoir; % Grazing, percentage of cattle grazing land cover in the catchment area of each reservoir.

TITAN Threshold Indicat or Taxa Analysis (TITAN) is a new method for detecting synchronous changes in t he distribution of taxa along an environment al gradient, e.g. the areal cover of a particular land use in the catch ment upstream of sampling locations (Baker and King 2010). These changes may represent a threshold between different states of ecological condition , e.g. the tippi ng po int at which a phytoplan kton c ommu nity becomes dominated by cyanobacteria, or multiple taxa show a sharp increase (or decrease) in their cel l densities. Briefly, TITAN locates abrupt c hanges in the occurrence freq uency and relative abundance of individual taxa along the defined gradient, quantifies the uncertainty around these change points and estimates their relative synchrony (fu ll details of the method are provided in Baker and King 2010). For th is research, we used the percentage cover of grazing land in the catchments of each reservoir (Table 1) and t he cell densities of phytoplankton taxa identified in the surface water of sites sampled in summer 2009. We ran the analysis with the TITAN package (Baker and King 2010) in R (www.r-project.org/).

Vulnerability Index Several parameters that describe reservoi r and catchment characteristics have been examined for their abil ity to explain variation in reservoi r water q uality (e.g. Forbes et al. 2008). The Vulnerability

Index of Leig h et al. (2010), which ranges from 0 (lowest vulnerability) to 1 (h ighest vu lnerab ility), uses five parameters and is calculated as follows:

VI = (percentage grazing land cover" + reservoir shoreline to surface area ratiobc + reservoir volume at full supply capacity8b + reservoir volume to catchment area ratiobc + age since dam construction8 b) I5 Range standardised so that the highest value = 1 and the lo west = 0

a

b Log transformed to reduce skew c Range standardised so that the highest ratio = 0 and the lowest = 1 Log transformation and range standardisation give each parameter equivalent weighting to create a comparative index of vulnerability among reservoirs (Leigh et al. 2010).

Based on the community t hreshold results of TITAN , we calcu lated the vulnerability of a planned reservoir under different scenarios of grazing land use in comparison to those of the existing 15 reservoirs sampled in summer 2009.

Wyaralong dam (Table 1) is being constructed about 20km northeast of Maroon reservoir and is scheduled for completion by the end of 2011. We fi rst calculated the VI for all 16 reservoirs , using the plan ned dimensions of Wyaralong dam and the cu rrent grazing cover in its catchment (46.9 per cent). We then recalculated t he index using the threshold level of grazing land cover

G

catchment management

refereed paper

estimated by TITAN for Wyaralong but keeping the parameters for the existing reservoirs unchanged. We compared these results to those of t he origi nal study by Leig h et a/. (2010), which used the index to explore the potential effects through t ime of adding or subtracting 10 per cent grazing land cover (via conversion from/to forested land) in Wyaralong's catchment.

One year after construction of Wyaralong dam (2011 +1) 1.0 - Wyara long under current catchment grazing land cover (47%)

0.8 0.6

~ Wyaralong reservoir

0.4

D

Cool LNer e-n Man Hrn

Results Phytoplankton composition and cell densities The phytoplankton community of surface water samples from all reservoirs, in terms of median cell densities, was dominated by cyanobacteria. Borumba had the highest cell density of all reservoi rs (median = 405,000, with an inter-quartile range of 172,000 cells mL路1), followed by Moogerah, Somerset and Wivenhoe (medians > 200,000 cells mL路 1).

Hinze had the lowest cell density (median = 19,900, with an inter-q uartile range of 12,900 cells mL路1). C. raciborskii was the dominant potentially toxic cyanobacterium, except in Maroon reservoir and the upstream site at Hinze reservoir in which A. circina/is dominated.

Five reservoirs had no potentially toxic cyanobacteria identified (Cooloolabin, Macdonald , Ewen Maddock, Leslie Harrison and Little Nerang).

TITAN and community thresholds TITAN identified a peak change point for synchronous increase in cell densities of p hytoplankton taxa at 24.3 per cent grazing land cover. Confidence intervals (representing 5th and 95th quantiles of change points among 500 bootst rap replicates) for this observed th reshold were 19.6 per cent and 36. 1 per cent grazing land cover respectively.

Twenty-five specific taxa bot h met t he TITAN significance criteria (based on 500 bootstrap replicates; see Baker and King 2010 for detail) and showed a positive response (increased cell densities) to the environmental gradient; for these taxa, t he observed change points ranged from 7.2 per cent to 43.0 per cent grazing land cover. C. raciborskii, t he only potentially toxic species to meet significance criteria, exhibited an abrupt increase in cell density at 16.4 per cent grazing land cover (with a boot strap confidence interval of 12.2 per cent to 36.1 per cent).

Index of vulnerability (VI) Based on the vulnerability index calculation for the 16 reservoirs, Wivenhoe reservoir had the highest level

LHO

Mac

Mar

Kur

Bor

Bar

NPO Moog Som

15 existing reservoirs

WN

1.0 -

~

24.3% grazing land cover in Wyaralong catchment 0 ,8

~ Wyaralong reservoir

0.6

D

..!: ~

ii ~

Q)

~

J

0.4

C:

02

~

I

Existing reservoirs with <24.3% grazing land in their catchments

II >24.3% Existing reservoirs \Yith grazing land in

1路1

their catchments

'-1--1-L-'-.L.1......J-J--""-/JL....L...L..L- -L.-L..J....,.-----c_aa.....-...-----.__.a..J Cool LNer Ev.en

Main

Hin

LHO

MK

Mu

Kur

Bor

Sar

-

1.0 . . 0.8

NPO Moog Som WtiJ

16.4% grazing !and cover in Wyaralong catchment

~ Wyaralong reservoir

D Existing reservoirs with

0.6

<16.4% grazing land in their catchments

-

Cool

LNer EMn Wya

Man Hin

LHD

Mac

Mar

Kur

8o!'

Bar

Existing reservoirs with >16.4% grazing land in their catchments

NPO Moog Som W,v

Figure 1. Vulnerability Index for 16 reservoirs in subtropical Queensland, one year since the planned completion of Wyaralong dam wall in 2011, given: (top) the current percentage of grazing land cover in Wyaralong catchment; (middle) the threshold of 24.3 per cent grazing land cover in Wyaralong catchment; (lower) the threshold of 16.4 per cent grazing land cover in Wyaralong catchment. See Table 1 for the key to reservoir coding. Threshold values based on results from TITAN (see text for detail). of vulnerability to summer blooms (VI = 0.88), Wyaralong mid-range vulnerability (VI = 0.55), which was comparative wit h reservoirs like Maroon and Kurwongbah (VI for both = 0.57), and Cooloolabin the lowest (VI = 0.28) (Figure 1). Changi ng the percentage of grazing land cover in Wyaralong catchment to that of the TITAN threshold for abrupt increase in cell densities of multiple phytoplankton taxa, decreased the reservoir's comparat ive VI score to 0.45, the fifth least vulnerable among the 16 reservoi rs (Figure 1). Reducing grazing cover further to 16.4 per cent, the TITAN t hreshold for abrupt increase in C. raciborskii cell density, resulted in a VI score for Wyaralong of 0.42 (t he fourth least vul nerable among the 16 reservoirs; Figure 1).

Discussion The Vulnerability Index of Leigh et al.

(2010) is based on a combination of five parameters (percentage grazing land cover in reservoir catchments, reservoir shoreline to surface area ratio, reservoir vol ume, reservoir volume to catchment

area ratio and reservoir age). It has been demonstrated as an effective index of vulnerability to poor water qual ity and cyanobacterial blooms in summer months for the subtropical reservoirs examined in the present st udy. The index therefore shows potential as a decision making tool for t he management of existing and future reservoirs when aiming to red uce vu lnerability to summer bloom events.

Perhaps the most readily manipulated parameter in the index (in terms of management options at least, particularly for existing reservoirs) may be t hat of land use, as represented by the percentage of catchment grazing land cover. Land use, particularly animal agriculture, has been implicated in t he eutrophication of reservoirs and freshwater systems worldwide (S0ndergaard and Jeppesen 2007). In turn, eutrophication and changes to nitrogen: phosphorus (N:P) ratios are linked with shifts in phytoplankton composition and abundances, including dominance by cyanobacteria (Arbuckle

water DECEMBER 2010 73

catchment management and Downing 2001; Burford et al. 2006; Posselt et al. 2009). As such, we believe t hat a new method of detecting t hresholds of community change along environmental gradients, TITAN (Baker and King 2010) also shows potential as a decision making tool in planning and managing reservoirs for reduced vulnerability to bloom events. The environmental gradient can take many forms, for example, N:P ratios or concentrations of nitrogen or phosphorus in reservoirs , or, as used in this study, cat chment land use cover. Based on phytoplankton data collected in t he summer of 2009 from 15 subtropical reservoirs, TITAN identified a peak change point for synchronous increase in cell densities of phytoplankton taxa at 24.3 per cent grazing land cover (under current land use intensities and management practices), with a confidence interval of 19.6 to 36.1 per cent. Ten out of the 16 reservoirs examined in this study (including the planned Wyaralong reservoir) have at least 19.6 per cent grazing land cover in their catchments.

TITAN estimates change points for each taxon as well as detecting synchronous changes in t he whole community and can t herefore provide insight into thresholds of change in taxa of interest, like cyanobacterial species.

For the studied reservoirs, cyanobact erial blooms tend to be dominated by C. raciborskii. Based on the summer 2009 data, our analysis showed that this species exhibited an abrupt increase in cell density at 16.4 per cent grazing land cover (with confidence interval of 12.2 to 36. 1 per cent). Cooloolabin, Ewen Maddock, Manchester, Leslie Harrison, Little Nerang and Hinze have less than 16.4 per cent grazing land cover in their catchments , and these six reservoirs along with Borumba and Maroon have less than 24.3 per cent. At 28.5 per cent grazing land cover, North Pine would also be included with t his 'under the threshold ' group of reservoirs, if the upper confidence interval of 36.1 per cent was taken as the community threshold at which cell densities (for multiple taxa or C. raciborskii alone) increase rapidly.

We also examined the change in predicted vulnerability of a planned reservoir, Wyaralong, to those of the existing reservoirs used in the threshold analysis. Leigh et al. (2010) demonstrated that under planned dimensions and grazing land cover (46.9 per cent), Wyaralong reservoir would attain mid-range vulnerabil ity among the 16

74 DECEMBER 2010 water

reservoirs to summer blooms just one year after its completion. The reservoir's vulnerability would then increase with time to become similar to reservoirs like North Pine, Somerset and Wivenhoe that often experience summer blooms of cyanobacteria (Burford et al. 2007). At the TITAN threshold of 24.3 per cent grazing land cover, Wyaralong reservoir was predicted to be the fifth least vulnerable to summer blooms one year after its completion, and at 16.4 per cent, the fourth least vulnerable. For either scenario, this represents a substantial change in the predicted outcome for this reservoir. This may equate to fi nancial savings (i n terms of water treatment and monitoring costs) as well as benefits for ecosystem health and the quality of water for human consumption.

For future or existing reservoirs, t hese results cou ld be used to inform planning and management decisions about reservoir location or management options for land use change, such as conversion of grazing land to nat ive forest (e.g. via reg rowth or revegetation), increasing forested land cover withi n agricultu ral landscapes, or change to best management practices such that the same percentage of grazing land cover has a lesser impact on reservoir water quality and phytoplankton dynamics than under current land use practices. Withi n any given percentage of land use cover, however, the spatial arrangement and proximity of the land use relat ive to streams and the downstream reservoir is also likely to affect reservoir water quality (Gergel 2005), and t he vulnerabil ity of any given reservoir to cyanobacterial blooms wi ll not depend on grazing land cover alone. Indeed, it is interesting to note that for the existing reservoi rs in ou r study that had less than the threshold of 24.3 per cent grazing land cover, their vu lnerability index scores were not all lower than t hose that exceeded t he threshold. For example, Macdonald reservoir exceeded the th reshold (has > 24.3 per cent grazing land cover in its catchment) but compared to Maroon reservoir (which has less t han 24.3 per cent grazing land cover) its predicted vulnerability was lower. This emphasises t he need for careful consideration of multiple factors and objectives in the decision making process in the context of environmental management (Ryder et al.

2010). Therefore, we suggest that the results of th reshold analyses, such as those from TITAN, and the Vul nerabi lity Index be taken into consideration along with other results, expert opinions and information on land use intensity and

r e f ereed pape r

spatial arrangement within catchments when used as decision support tools.

Conclusions Thresholds of land use determined by our study were based on water quality data collected from a single summer period in subtropical Austral ia, and thus may be refined upon inclusion of data from future sampling periods. Our results suggest t hat land use in the catchments of the studied reservoi rs has a strong impact on phytoplankton composition and densities, including those of cyanobacteria, and hence summer bloom phenomena.

Alt hough t he methods presented do not provide causal links between blooms and land use, and we stress that land use is only one of many factors that may affect phytoplankton dynamics, t hese methods may assist reservoi r planners and managers wishing t o reduce the vulnerability of their reservoirs to bloom events. Long term datasets on cyanobacteria, including C. raciborskii, that contain measures of cell densities, b iovo lume or even toxic strain s (using molecular methods, Orr et al. 2010) in reservoirs wou ld also help support such findings and decisions.

Acknowledgments This work was supported and f unded by Queensland Bulk Water Supply Authority (Seqwater). We thank rangers and boat drivers and water quality monitori ng staff at Seqwater; Stephen Faggotter and Deb Gale for their assistance with sampling; Queensland Forensic and Scientific Services for phytoplankton identification; Seqcatchments (Brisbane), Monica Poel and Leanne Bowen for catchment boundary and land use spatial data, which was based on Queensland Natural Resou rces and Mines Statewide Landcover and Trees Study data (SLATS 2001; available from http://www.nrw.qld.gov.au/slat s/index.ht ml); and Jo Burton at t he Australian Rivers Inst itute for advice on catchment land use.

The Authors Dr Catherine Leigh (c.leigh@griffith.edu.au) is a Research Fellow and Dr Michele Burford is Associate Professor at the Austral ian Rivers Institute, Griffith University, Brisbane, Queensland .

David Roberts is Senior Scientist (Ecologist) and Dr James Udy is Principal Scientist at the Queensland Bulk Water Supply Authority (Seqwater), Brisbane, Australia.

catchment management

refereed paper

References Arbuckle, K. E., Downing, J.A., 2001. The influence of watershed land use on lake N: Pin a predominantly agricultural landscape.

Limnology and Oceanography, 46: 970-975.

Baker, M.E., King, R.S., 2010. A new method for detecting and interpreting biodiversity and ecological community thresholds. Methods in Ecology and Evolution 1: 25-37.

Blanch, S., 2008. Steps t o a sustainable Northern Australia. Ecological Management & Restoration , 9: 110-1 15.

Burford , M.A., Johnson, S.A., Cook, A.J., Packer, T.V. , Taylor, B .M., Townsley, E.R., 2007.

Correlations between watershed and reservoir characteristics, and algal blooms in subt ropical reservoirs. Water Research, 41 : 41 05-4114.

Burford, M.A., McNeale, K.L., McKenzie-Smith, F.J., 2006. The role of nitrogen in promoting the t oxic cyanophyte Cylindrospermopsis raciborskii in a subtropical water reservoir.

Freshwater Biology, 51: 2143-2153.

Burford, M.A., O' Donohue, M.J., 2006. A comparison of phytoplankton community assemblages in artificially and naturally mixed subtrop ical water reservoirs. Freshwater Biology, 51 : 973-982.

Davis, J.R., Koop, K., 2006. Eutroph ication in Australian rivers, reservoirs and estuaries - a southern hemisphere perspective on t he science and its implications. Hydrobiologia, 559: 23-76.

Gergel, S.E., 2005. Spatial and non- spatial fact ors: when do they affect landscape indicators of watershed loading? Landscape Ecology, 20:

177-189.

Gucker, B., Boechat, I.G., Giani, A., 2009. Impacts of agricultural land use on ecosystem structure

/es&$

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= n d s.com

and whole-stream metabolism of tropical Cerrado streams. Freshwater Biology, 54:

2069-2085.

Jones, G.J. , Poplawski, W., 1998. Understanding and management of cyanobacterial blooms in sub-tropical reservoirs of Queensland, Australia. Water Science and Technology, 37:

161-168.

Knoll, L.B., Vanni, M.J., Renwick, W.H., 2003.

Phytoplankton primary production and photosynthet ic parameters in reservoirs along a gradient of watershed land use. Limnology and Oceanography, 48: 608-617.

Lund, J.W.G ., Kipling, C. , Cren, E.D. , 1958. The inverted microscope method of estimating algal numbers and the statistical basis of estimations by counting. Hydrobiologia, 11 : 143-1 70.

Leigh, C., Burford, M.A., Roberts, D.T., Udy, J.W. , 2010. Predicting the vulnerability of reservoirs to poor water quality and cyanobacterial blooms. Water Research, 44: 4487-4496.

Matzinger, A., Schmid, M., Veljanoska-Sarafiloska, E., Patceva, S., Guseska, D., Wagner, 8. , Muller, B. , Sturm, M ., Wuest, A., 2007.

Eutrophicat ion of ancient Lake Ohrid: global warming amp lifies detrimental effects of increased nutrient inputs. Limnology and Oceanography, 52: 338-353.

McGregor, G.B. , Fabbro, L.D., 2000. Dominance of Cylindrospermopsis raciborskii (Nostocales, Cyanoprokaryota) in Queensland tropical and subtropical reservoirs: implications for monitoring and management. Lakes & Reservoirs: Research and Management, 5: 195-205.

Orr, P.T., Rasmussen, J .P., Burford , M.A. , Eaglesham, G.K., Lennox, S.M., 2010.

Evaluat ion of quantitative real-time PCR to characterise spatial and temporal variations in cyanobacteria, Cylindrospermopsis raciborskii

(Woloszynska) Seenaya et Subba Raju and cylindrospermopsin concentrations in three subtropical Australian reservoirs. Harmful Algae, 9: 243-254.

Paerl, H.W., Huisman, J., 2008. Blooms Like It Hot. Science , 320: 57-58.

Padisak, J. , 1997. Cylindrospermopsis raciborskii (Woloszynska) Seenayya and Subba Raju, an expanding highly adaptive cyanobacterium: worldwide distribution and review of its ecology. Archiv fur Hydrobiologie Supplementbund. Monographic Studies,

107:563-593.

Posselt, A.J., Burford, M.A., Shaw, G. , 2009.

Pulses of phosphate promote dominance of the toxic cyanophyte Cylindrospermopsis raciborskii in a subtropical water reservoir.

Journal of Phycology, 45: 540-546.

Ryder, D.S. , Tomlinson, M. , Gawne, B., Likens, G.E., 2010. Defi ning and using 'best available science' a policy conundrum for the management of aquatic ecosystems. Marine and Freshwater Research, 61 : 821-828.

S0ndergaard, M., Jeppesen, E. , 2007.

Anthropogenic impacts on lake and stream ecosystems, and approaches to restoration.

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Wiedner, C., Rucker, J., Bruggemann, R., Nixdorf, 8 ., 2007. Climate change affects timing and size of populations of an invasive cyanobacterium in temperate regions.

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Yang, X., Anderson, N.J ., Dong, X., Shen, J., 2008.

Surface sediment diatom assemblages and epilimnetic total phosphorus in large, shallow lakes of the Yangtze floodplain: their relationships and implications for assessing long-term eutrophication. Freshwater Biology 53: 1273-1290.

GeoVISIONâ&#x201E;˘ Borehole Camera

water DECEMBER 2010 75

water recycling

THE BALLINA-LENNOX HEAD RECYCLING SCHEME B Douglas Abstract

North Creek Canal it is imperat ive to minimise impacts on the estuary. This is to be achieved by appropriate treatment and release and also implement ation of a significant recycled water scheme.

The recycled water scheme is based on a Recycled Water Use Master Plan that was developed for BSC by GHD. Council adopted t he Master Plan in 2008 with the 80 per cent dry weather recycling target being met by a combination of urban non-potable re-use, irrigation of Council's parks and gardens and also Veget ation Regeneration.

Ballina and Lennox Head are situated on the far north coast of NSW and are growth centres with a current combined population of around 35,000, rising to 50,000 by 2026. The recycling scheme has the potential to red uce potable water consumption by 30 - 40 per cent in new areas and reduce estuary discharges from t he Ballina WWTP by 60 per cent.

This paper shows how an appropriate "fit for purpose" and economic solution was achieved and the investigations and concept work that was done to meet the req uirements of a wide range of stakeholders. The following issues are examined: • Appropriate protection of the estuary and its users • Protecting public health through the use of National Water Quality Management System (NWQMS) Guidelines • Providing an optimised and affordable scheme for the rate payers of Ballina Shire Council (BSC)

Figure 1. Ballina WWTP, North Creek Canal (mid left) and Richmond River (top).

• Embracing new technology and challenges such as carbon (CO2) emissions and rising power costs • Stakeholder involvement The scheme is currently being procured and it is planned to supply recycled water to consumers by 2012.

Introduction In 2006 NSW Water Solutions, within NSW Public Works , won through an open process the tender for the provision of consultancy services for t he ultimate upgrades of West Ballina and Len nox Head Wastewater Treatment Plants (WTP)s and Recycled Water Plant (RWP).

Public Works' Lismore Office was appointed as st rategic project manager for this portion of the work. NSW Water Solutions was engaged to prepare conceptual designs and undertake EIA for t he scheme, including major plant upgrade of the Ballina WWTP, minor

76 DECEMBER 2010 water

upgrade of the Lennox Head WWTP including provision of recycled water plant/s, catchment diversion works, recycled water bulk distribution systems.

Ballina Shire Council (BSC) adopted a consultancy arrangement to ensure t hat the upgrades and concepts developed were coordinat ed and undertaken in an integrated fashion towards provision of an overal l scheme.

Under Council's revised Integrated Urban Water Management Strategy the loading on the Ballina WWTP is set to rise from 3.8MUd (15,000 EP) to 6.3MUd in 2026 (30,000 EP). The Lennox Head WWTP is to have its capacity capped at 25,000 EP which means that the Ballina WWTP will service the majority of the growth in the Bal lina and Lennox Head area. As t he Ballina WWTP currently discharges to the Richmond River via

Navigating through the obstacles.

New growth areas such as Bal lina Heights have already been supplied with a t hird pi pe for supplying non-potable recycled water and all new growth areas will also be provided with a thi rd pipe. Currently, both plants supply recycled water to local amenities such as the Ballina Racecourse, the Ballina Golf Course and some sports fields. This urban open space irrigation is to be expanded t o ot her Council parks and ovals via a combined delivery system.

Concept designs called for the Ballina WWTP to be replaced with a new plant and provision of either a combined or separate RWPs at each of t he two WWTP.

Appropriate Protection of the Estuary and Its Users Determining the appropriat e level of treatment and the way that releases will be handled was an early step that was undertaken in the process. The process involved an examination of current EPA discharge Licence, current releases and past improvements, cu rrent and historical water quality data and a complete ecological assessment of North Creek Canal to help determine what is an appropriate level of t reatment and release philosophy. This information was then used in negotiations with the NSW Department of Cimate Change and Water and used in the EIA for the scheme.

Importantly a local specialist from

water recycling Southern Cross University Centre for Coastal Biogeochemistry was chosen to undertake this study aspect.

The assessment undertaken included water quality (review of exist ing data only), sediment contam inat ion, biogeochemical processes, effluent plume tracing and ecological communities to determine the impact of current release vol umes during summer.

Numerical models were developed t o estimate the impact of the discharge f rom the Ballina plant on water col umn nutrient levels and algal biomass concentrations). An assessment was also made of the likely impact of the proposed reclaimed water volumes and quality on t he ecological health of North Creek Canal and the Richmo nd River Estuary.

The conclusions from t he ecological st udy were as follows : • Current recycled water releases from t he Bal lina WWTP are having a slight to moderate impact on the overall ecological health of North Creek Canal.

Continued augmentation by BSC of the current p lant has resu lted in lowering of impacts over time.

• Increased inflows to the WWTP would result in an increased median nitrogen level in t he canal with the increase being inversely proportional to the percentage re-use achieved.

• A total phosphorus level of 0.3 mg/ L would meet Guideline levels for all scenarios.

• Algal biomass in the canal compared to current conditions under all re-use scenarios would decrease dramatically, however, on ly an 80 per cent re-use in 2026 and an ebb tide release would meet guideline values .

• Overall there should be a significant improvement in water quality and associated ecological health compared to current conditions in North Creek Canal for all t he scenarios modelled, due to t he dramatic decrease in total algal biomass (and total suspended solids).

• An ebb tide release would further decrease impacts in North Creek Canal.

Several assumptions made in the analysis were further tested with additional investigations:

• Winter testi ng in the canal was also undertaken to determine if t he assessment made for summer would also hold under winter conditions. It did. 12 mont hs worth of data has been obtained. Further ongoing testing within the canal and the Richmond River is being conducted to further understand impacts and provide a base line for future monitoring.

• Further assessment was undertaken to identify how much of the algal biomass in North Creek Canal was derived from t he West Ballina WWTP maturation pond and how much was produced in situ. The results showed that t here has been a significant decrease in total chlorophyll-a concentrations in North Creek Canal since t he addition of a Dissolved Air Flotation plant. There would be additional improvements in total ch lorophyl l-a concentrations in North Creek Canal associated with additional improvements in the removal of algal biomass from the treatment ponds (through bypassing the ponds with the proposed WWTP upgrade).

The ecological assessment was ultimately used t o determine t he

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water recycling scheme's sustainability (used in EIA) and as evidence in determining appropriate licence conditions in particular nitrogen, ammonia and phosphorus. This has al lowed the DECC proposed "Accepted Modern Technology" License cond itions to be adopted as it could be proved that these were appropriate and t hus a "fit for purpose" WWTP be provided. Th e study has also provided SSC with a baseline to compare the future operation of the scheme.

and planned schemes was undertaken to gain an appreciation of industry trends. It was found that a variety of methods were employed within Austral ia. Interestingly, wh ilst membrane based systems dominated, a deep bed sand based filtration system is to be installed at Rouse Hill to replace the existing membrane system in the upgraded and extended plant. It was also found that there was a high level of conservatism built into some RWPs, with additional units such as reverse osmosis included in t he treatment process to further lower risks.

Protecting Public Health Protection of public health is a key element of a recycled scheme involving close contact between users and recycled water. SSC had determined that the scheme would provide high quality recycled water for the following uses:

It was determined by analysis of the options that t he fo llowing six barrier treatment process would be adopt ed: • Source control - SSC t rade waste policy and primarily domestic catchment s (Barrier 1)

• Toilet f lushing - new houses to be plumbed with a recycled water supply for toilet flushing;

• Ballina and Lennox Head WTPs including disinfection (Barrier 2)

• Garden watering and other Figure 2. Recycled Water Scheme Bulk Transport outdoor uses such as path System. washing , car washi ng, wall washing and ornamental water the stakeholders to t he project. This features - new houses to be supplied workshop was facilitated by Water with one potable water outside tap and Futures. two recycled water taps.

• Cold water washing machine use SSC is considering t his as a future use for recycled water. This use cou ld add up to 10 per cent re-use.

• Irrigation of urban open spaces including parks, ovals, the golf and race courses.

• Vegetat ion regeneration - to be implemented in the future.

Firefighting would not be undertaken with recycled water as it would have added to the size of the third pipe system but would have provided little re-use.

To determine what prot ection measures were requ ired the Australian Guidelines for Water Recycling: Managing Health and Environmental Risks (Phase 1) 2006 were used. The Guidelines provide a risk assessment framework that is applicable to the recycling of water from stormwater, greywater and treated sewage sources.

The guidelines provide an authoritat ive reference that can be used to support beneficial and sustainable recycl ing. The Guidelines call for a risk-based approach to be used. One of the tasks undertaken was to convene a risk workshop with all

78 DECEMBER 2010 water

The workshop was well attended by a range of st akeholders. Representatives from the users such as the golf and race courses, the scheme operators (Council staff) and the regulatory representatives from DWE, NSW Health and DECC attended . The process was valuable in that this was a good opportunity to inform those attending about the proposed scheme and upcoming works and also to gain different perspectives to address the risks and minimisation strategies. The outputs from the risk workshop were then adopt ed and formed a basis for determining t he quality of recycled water required and strategies to be employed in the planning phase of the works . The workshop was conducted in a day and was considered a success by all participants.

The risk assessment process confirmed that the following treatment requirements would be used for the scheme: • Bacteria - 5.1 log removal • Protozoa - 6.5 log removal • Virus - 6.0 log removal.

An examination of the available treatment technologies used in current

• UF/M F (and RO membranes on ly if required to lower TDS) in RWP (Barrier 3) • UV and c hlorination disinfection in RWP (Barrier 4) • Distribution system re-ch lorination (Barrier 5) • Dist ribution system end user controls (Barrier 6).

This process was chosen as being the most suitable to Ballina, as it would meet the treat ment req uirements t hus ensuring a low risk scheme without being overly conservative or expensive.

Recycled Water Scheme Optimisation Under Counci l's Master Plan the recycled water re-use target is 80 per cent of all dry weat her flows by 2026. This will be achieved through a combination of urban dual reticulation (UDR), urban open space irrigation (UOS) and vegetation regeneration (VR). Ballina is a high rainfall area, mean annual rainfall of 1,731 mm, with wet summers and dry wi nters.

It was decided by SSC early that wet weather storage would not be required and continued estuary release would be adopted during wet weather periods.

The treatment process would treat up to 7xADWF. Releases during large wet weather events would have minimal effect on the receiving wat erways.

UDR re-u se will be achieved at all new developments, up to 7,242 properties, as each will be provided with dual water

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water recycling supply pipelines: a potable pipeline supplying water from the bulk water supplier, Rous Water, and a second pipeline supplying high quality recycled water for non-potable uses such as toilet fl ushi ng, garden watering and also laundry use. It was found that by adding laundry usage t he level of re-use increases by 10 per cent, which is sign ificant. Internal baseline uses are an important re-use component due to the high rainfall experienced between February to June which limits outdoor irrigation uses.

Demands for UDR and UOS were revised from the orig inal Master Plan assumptions. Demand analysis for UDR was undertaken to determine peak day, peak week and peak month demands. It was determined that designing t he RWP for peak month demands rather than peak week demands would save 13 per cent in RWP costs without much reduction in percentage re-use achieved.

Potable top-up would be used if required to meet peak dry and wet weather demands.

Similarly the demands for potable and non -potable water were examined against current demands to determine

RWP and reservoir sizing. The analysis is summarised as follows: RWP sizi ng based on Peak Month Demand (PMD): • Urban Dual Reticulation (UDR) demand is 6.07MUd based on 838L per eq uivalent tenement (ET) per day on 7,242 blocks.

• Urban Open Space (UOS) demand is 3.02MUd which is based on 4.1 mm/ ha.d on 173ha irrigating up to one-third of t he area at one time with an additional allowance for high use customers such as the racecourse and the golf cou rse.

Reservoir sizing based on Peak Day Demand (PDD): • Recorded peak day demand 1,440UET at Ballina Heights, Parklea 1, 100UET, Kellyvi lle 1,600UET and Parklea North 1,700UET, • Total potable and non-potable demands estimated Ballina 1,770UET • Split between pot able and non-potable 885UET : 885UET or 50 per cent : 50 per cent.

Interestingly it was found that the provision of an outdoor potable water tap

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has a big influence on PDD. The outdoor hose used for watering via a sprinkler, at 0.2Us for 30 minutes, can use 400L. BSC has adopted to provide one outside potable water tap so as to allow pools to be topped up or for watering salad vegetables for example. Care needs to be taken in determining demands as many factors wil l influence demands.

Demands for UOS were examined critically and produced significant savings in terms of plant and transport infrastructure. It was determined that irrigation scheduling across BSC's UOS sites would decrease RWP demands by 65 per cent without any loss in percentage re-use. UOS sites wou ld also not be watered during peak usage times to ensure system capacity for UDR which has a higher priority. This optimisation led to a 40 per cent saving in RWP size from t he Master Plan.

Once recycling demands were determined and the RWP sized, then RWP analysis was undertaken. This included comparing provision of a combined RWP at a central location servicing Ballina and Lennox Head demands or separate RWPs at each WWTP. It was determined that once all

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water recycling factors such as the WWTP upgrading, RWP operating costs and dist ri bution system costs were included, that separate RWPs at each WWTP were preferred.

Ballina WWTP Concept Design and Lennox Head RWP The concept design for the Ultimate Upgrade of the Ballina WWTP included three different plant types, namely the Public Works-developed intermittently decanted activated (IDEA) sludge plus an RWP, the continuously aerated activated sl udge (GAS) plus an RWP and a membrane bioreactor (MBA). The RWP for Lennox Head was also developed.

BSC has IDEA based plants at other WWTPs including Lennox Head, Alstonville and Wardell but wanted a range of plant options examined to get the most suitable plant.

NSW Water Solutions developed detailed plant concepts based around IDEA, GAS and MBA options for the provision of the new Ballina plant. Full concept designs were developed for each plant to assess what was the best option for Ballina.

Each WWTP concept design incorporated an elevated inlet works with screening and grit removal equipment, flume and flow diversion, then twin 15,000 EP biological reactors providing full nitrification and denitrification with full biological treatment t o 3xADWF. Partial biological treatment up to 7xADWF was provided with IDEA and CAS options with storm detention provided with the MBA and return of bypassed flows to the plant after the storm passes. Storm detention is proposed to be provided in the top portion of the existing maturation pond wh ich will be bypassed by the new plant in lieu of providing a separate stand alone storm detention pond. A storm detention pond is required to balance wet weather flows as the hydraulic capacity of MBA plants are limited to 3xADWF. This will potentially save considerable costs. The option has been assessed and support from DECC given to the proposal. Chemical alum dosing for TP removal was adopt ed.

Membrane fi ltration either through the addition of stand-alone units or incorporated into the MBA option were adopted. These are t o be followed by UV disinfection system and ch lorination for the recycled water stream. An ebb tide release is to be used for all flows not recycled. It was found that an ebb tide release wou ld enable released water to exit North Creek Canal and indeed exit the Richmond River estuary under most conditions.

Some major constraints are present at the Ballina WWTP. They are ground conditions and land ow nership. Very poor ground conditions were found during geotechnic al investigations, with deep unconsolidated sediments, wh ich means that all structures will need to be supported on piles sunk to the bedrock.

The need to pile all fou ndations lends itself to a more compact footprint WWTP being provided. Limited land is available on the existing WWTP site. The adjacent land owner is reticent to sell part of his land to allow the plant to expand. This also favours a small footprint WWTP within the existing site boundaries.

Reverse osmosis may be required in the Ballina WWTP to lower TDS levels in the recycled water to <600 mg/ L. The incoming TDS is up to 2000 mg/ L but is being lowered currently via Council's 1/ 1 reduction program. Ballina is a low-lying area with a clay pipe reticulation system which is prone to saltwater intrusion.

Depending on the effectiveness of the 1/ 1 reduction program the need for RO will be assessed during detai l design and construction of the WWTP. Provision is to be made in the plant's design to allow RO modules to be supplied in the future.

It is hoped that RO can be avoided as it is an expensive unit process with high operational costs.

Cost and CO2 emission estimates were undertaken for the Ballina WWTP and RWP options.

It was found that the NPV for an MBA based Ballina WWTP and a Lennox Head RWP was the most favourable .

Additional ly the MBA would produce an overall higher quality recycled water for release which was a benefit for no

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additional cost as compared to the IDEA

+ RW P and CAS + RWP options. The cost estimates were subjected to additional analysis to determine if risi ng power costs would have an influence over the relativity of the options. It was found that even with a 60 per cent increase the relativity did not change.

Estimates of CO2 emissions were undertaken based on estimated power costs for the operation of the plants.

These estimates showed that the MBA has a 15 per cent higher power requirement as compared to the IDEA and GAS options plus add-on RWPs. This is because an MBA will treat a higher percentage of flows to a higher treatment level.

Based on the NPV assessments and other factors such as site constraints and achieving a higher rec yc led water quality for release, BSC has decided to adopt an MBA based WWTP for Ballina and a RWP at Lennox Head WWTP.

Stakeholder Involvement Stakeholder involvement is a key requirement for the successful passage on any large infrastructure works, particularly when the resu lting works will impact on rates and enter into the households of a significant portion of the community.

The following stakeholder program was undertaken: â&#x20AC;˘ Community Consultation - BSC has undertaken community consultation throughout the planning phase including a regular comm unity newsletter sent out to all residents detailing news of the scheme and a survey of residents detailing rate rises and their acceptance of the scheme.

Recycled water users were also invited to the Risk Assessment Workshop and provided input. â&#x20AC;˘ Industry Consultation - Two workshops were undertaken wit h a range of membrane suppliers to inform them of the upcoming scheme and to also gain pertinent information regarding industry trends, limitations and preference for procurement strategies.

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water recycling • Regulator Contact - The risk assessment workshop opened communication links with al l the local regulators. These links have been maintained with the regulators. Regular consultation for various aspects of the works has been maintained during this phase of the works, for example in-principle approval has been garnered for release quality parameters from Ballina and the proposal to use t he existing mat uration pond as a SOP.

Conclusions

Acknowledgments

The success of the Concept and EIA phase of the works can be attributed to the following aspects:

The assistance of Council's Rod Dawson and Public Works' Strategic Project Manager, David Williamson and their respective staff during the Concept and EIA process is acknowledged and appreciated.

• Formal Consu ltat ion - As part of the EIA formal consultation with all stakeholders was undertaken. As ongoing consultation has been undertaken the responses received during t he EIA period to t he proposed scheme were largely clarifications. The only objections and the majority of responses from t he community were to the siting of a recycled wat er reservoir at Lennox Head in a local Reserve.

Subsequent modifications including a dramatic reduct ion in volume and using a pumped system, burying the majority of t he reservoir and providing BBQ and toilet facilities have addressed nearly all concerns raised.

The EIA was endorsed by BSC recently.

• Engagement of t he right specialists such as Southern Cross University and Water Futures who are suitably experienced and also wel l known to t he regulators.

This collaborative approach with the commu nity and all t he stakeholders has meant that the scheme has progressed smoothly and to the satisfaction of everyone involved.

• Engagement by BSC of one consultant who undertook all the concepts of the various scheme components. This al lowed a co-ordinated approach of the individual elements of the works and a scheme wide approach.

• Undertaking community and stakeholder consultation throughout t he process, including the industry when new technology may be used.

The membrane suppliers had valuable input to the planning phase of t he works.

• Not limiting options too early. The concept phase of t he works examined a wide range of p lant options. This not only served to clarify and rank options it also demonstrated t hat council was being t horough and looking at all alternatives.

• Testi ng of all assumptions.

The scheme is currently being procured.

Guy Boncardo, Principal of Wastewater Services, and the Wastewater Services team which together helped produce the Concepts and the Geotechnical and Environmental Sect ion who undertook EIA for the scheme is acknowledged and greatly appreciated.

The Author

Brett Douglas is a Project Engineer (Civi l) with the NSW Water Solutions, a group of NSW Public Works, Department of Services Technology and Administrat ion. He has over 10 years experience in the investigation, concept development and design of sewerage infrastructure including collection, transport systems, wastewater treatment systems and recycling schemes. Email brett.douglas@services.nsw.gov.au.

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WATER INFRASTRUCTURE GROUP RECEIVES TWO AWARDS FOR SEW ER REHABILITATION Water Infrastructure Group received a 2010 Australian Concrete Repair Association Award for Excellence for a sewer maintenance hole rehabi litation project for Moreton Bay Regional Council.

water b siness Water Business aims to keep readers alert to business news and new product releases within the water sector. Media releases should be emailed to Lyn ne Bartlett, National Relationship Manager, AWA, at lbartlett@awa.asn.au or Tel (02) 9436 0055.

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The project involved rehabilitation of 75 maintenance holes located across Moreton Bay Regional Council's area of operation.

Brian Mahon, Water Infrastructure Group Manager Construction, said that the 25mm thick coating of calcium aluminate premix is expected to extend the life of the Moreton Bay Regional Council's assets for a minimum of 50 years.

"Water Infrastructure Group's pipeline maintenance division has developed a very advanced technical met hodology and efficient workflow for maintenance hole rehabilitation and I am pleased to see the team's efforts recognised by this award."

Water Infrastructure Group also received a Merit Award for a rehabi litation project in Sydney for two sections of Sydney Water's Northern Suburbs Oc ean Outfall Sewer. The project used a two part epoxy mortar coating syst em that Water Infrastructure Group has refined over a number years to be an extremely efficient, reliable and safe option for sewer rehabil itation.

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WASTEWATER TREATMENT PROCESS OPTIMISATIO N Anders Lynggaard-Jensen, Peter Andreasen, Urban&lndustry, OHi, Aarhus, Denmark; Jakob Kaltoft, Louis Landgren, Aarhus Water, Denmark Modern wastewater treatment p lants have now been automated with SCADA systems and are typically operated using set-points keyed in by operators. Local control loops in PLC ensure that setpoints are achieved - examples include DO-controls and return sludge rate controls. This type of automation has resulted in a tremendous increase in the efficiency of wastewater treatment; however, as documented in t his article it is possible to f urther increase efficiency by taking the automation a step further using automated set-point control for process opt imisation.

Process optimisation involves automat ically keeping processes tuned to operate efficiently during variable conditions, and DHI has together with Aarhus Water (Denmark) developed a methodology that combines general process knowledge with local knowledge of daily operations at specific t reatment plants. The first st ep is identification of

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82 DECEMBER 2010 water