Water Journal April 1993

ISSN 0310-0367

?-AUSTRALIAN WATER &WASTEWATER A.SSOCIATION

Australian Water & Wastewater Association Incorporated ARBN 054 253066

FEDERAL SECRETARIAT Executi ve Di rec tor - Chris Davis Business Manager - Margaret Bates PO Box 388, Artarmon 2064 Telephone (02) 413 1288 Facsi m ile (02) 413 1047

PRESIDENT Barry Sanders, Phone (09) 420 2453

SECRETARYfTREASURER Greg Cawston, Phone (02) 597 0503

Volume 20, No.I, April 1993

CONTENTS 3 My Point of View

Association News 4 News from the Executive 5 Association News 8 IAWQ 9 Industry News Features 11 Watercomp '93 Bob Swinton reports ...

12 The Biological Quality of Water - A Background to Discussions J.R.L. Forsyth

17 Treatment of Sydney's Water Supplies -

An Overview

B.A. Murray and S.J. Roddy BRANCH SECRETARIES Canberra, ACT Alan Wade, D.E.L. P. PO Box 1119, Tuggeranong 2901 Phone (06) 207 2350 New South Wales Michael Polin , GCEC, 39 Regent Street Rail way Square 2000 Phone (02) 699 9922 Victoria John Park, C/- Water Training Cent re, PO Box 409, Werri bee 3030 Phone (03) 741 5411 Queensland Don Mackay, PO Box 41 2, Wes t End 4101 Ph one (07) 840 4844 South Australia Neil Palmer, Cl- State Water Laboratories, E&WS Private Mai l Bag, Salisbury 5108 Phone (08) 381 0268 Western Australia Bill Chapman,

WAWA PO Box 100, Leedervi lle 6007 Phone (09) 420 2462 Tasm an ia Annett e Ferguson, GPO Box 503E, Hobart 7001 Phone (002) 28 2757 Northern Terri tory Lind say Montei th, PO Box 351, Darwi n 0801 Phone (089) 81 5922

EDITORIAL CORRESPONDENCE E.A. (Bob) Swinton, 4 Pleasant View Crescent, Glen Waverley 3150 Offi ce Ph one-Fax (03) 560 4752 Home (03) 560 9306

ADVERTISING Margaret Bates PO Box 388, Artarman 2054 Phone (02) 413 1288; Fax (02) 413 1047

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The Streaming Current Detector in Water Treatment D.R. Dixon, W. Barron, T. W. Healy, M. Pascoe and P.J. Scales 26 The Effect of Water Stabilisation on Copper Corrosion in Geelong M. Muntisov and G. Williams

32 A Planning Scheme for Ballarat's Water Catchments R.J. Ford

34 Technical Note: Paying the Price for Poor Coagulant Selection

.

M. Bourke

Of 35 38 39 40

Interest Water Biennial Index, 1991-1992 Book Review Product Information Conference Calendar

OUR COVER "Australia Pure" enters the market for bottl ed water, with di stribution outl ets already in America, Britain, and Sweden. The source is no mysterious 'radioactive spring', but the myriad of un -polluted streams and natural springs in the Upper Yarra catchment in the Great Dividing Range. The catchment is the home of the majestic Mountain Ash . More importantly, it is protected by government edict so that it is pollutionfree. Australia is renowned as the 'clean continent' with fresh air, wide-open spaces and absence of acid rain. Melbourne Water Corporation has capitali sed on this reputation by Joining forces with an Australian company with wide experience in marketing products in the northern hemisphere. The proposition 1s to export Melbourne's water, in competition with the well -known brands of 'mineral water' which have been sold both in supermarkets and high-class restaurants for years. The background to this development is summarised in t he story on page 9 [Photo courtesy of Melbourne Water]

PUBLICATION Water Is bl-monthly. Nominal distribution times are the third weeks of February, April , Ju ne, August , October, December.

IMPORTANT N OTICE

PRODUCTION EDITOR Jo hn Grainger, Appit a, 191 Royal Parade, Parkville 3052 (03) 347 2377 Fax (03) 348 1206

The Australian Water and Wastewater Association assumes no responsibility for opinions or statements ol facts exp ressed by contributors or advertisers , and editorials do not necessarily represent the oflic ial policy of the organisation.

Display and classified advertisements are Included as an Informational service to readers , and are reviewed by the editor before publication to ensure their relevance to the water environment and to the objectives of the Association .

All mater ial in Water Is copyright and should not be reproduced wholly or in part without the written permission ol the editor.

WATE R Ap ril 1993

1

TECHNOLOGY

THE MICROBIOWGICAL QUALITY OF WATER A background to discussions

by J. R. L. FORSYTH "Men become affected with the stone, and are seized with diseases of the kidneys, strangury, sciatica, and become ruptured, when they drink all sorts of waters, and those from great rivers into which other rivulets run, or from a lake into which many streams of all sorts flow ... " Even before Hippocrates 1 (c. 460-377 BC) propounded these statements which showed that the 'father of medicine', in some sense, comprehended a relation between the state of health of a community and its water supply, it is clear that mankind has valued clean water.

The Minoan palaces of Knossos and Phaestos, built prior to 1300 BC, have the remains of structures to catch and store rainwater and the inlets have settling devices to catch stones and grit before the run-off entered the cisterns. In his historical review, Purchas 2 points to the use of settling reservoirs to improve the appearance of river water in Greece in 250 BC. Ancient Carthage had elaborate systems to allow sedimentation of raw water which were later augmented by the Romans. The works of Roman engineers to supply water, as at Nimes in France, today - still stand as monuments to their skill. This skill was further documented in the writings of Sextus Julius Frastinus with his 'Two Books on the Water Supply of Rome', of 98 AD - cited by Purchas.

Early filtration was by the use of cloth bags - 'Hippocrates sleeves' - or by the use of wicks and siphonage, shown in Egyptian paintings. The origin of sand filters to clarify water is not certain but fountains in the ducal palace in Venice had such a device early in the 9th century. Pliiche, in 1732, apparently observed that a sand filter cleared water faster than sedimentation but that the sand needed to be washed regularly. Sand filters for domestic water was written about, in France, from 1750 and a Mrs Joanna Hemple of Chelsea obtained a patent on a domestic device in 1790.

The reason for these activities was almost certainly aesthetic rather than specifically for health. 3 This is shown by the fact that a crude sand filter was installed in Manchester in 1730 - to supply the calico industry. Paisley, in Scotland, was the first town to get filtered water.

John Gibb installed the filter, in 1804, to supply his factory and the surplus was taken , by cart, to the townsfolk . An attempt to provide filtered water for Glasgow in 1807 failed because of the inadequate design of the preliminary settling pond. It was not until 1827 that an able engineer, John Simpson, from the Chelsea Water Company in London travelled to Scotland and Lancashire to study the filters in operation. 4 His modified design was installed in 1829 to filter the water taken from the Thames and the slow sand filter became known as the 'English filter'.

Urbanisation and industrialisation increased the pressure upon water supplies and upon systems of waste disposal and the years of the 19th century saw the basis of rational water supply and management become established. At first, however, they were also years of high prevalence of disease. By the middle of the century, Britain was affected by major epidemics of cholera, and typhoid was the cause of very substantial endemic morbidity and mortality.

At this time, the notion that these diseases were actually infectious was only just emerging. Not only was the concept of 'contagion' rejected by liberal minded people of the time 5 •6 ·7 - because the corollary was quarantine, viz. with deprivation of liberty for those quarantined - but epidemiological evidence supporting the opposing 'miasma' theory was presented by influential people. 8 Leading articles in the press, in 1848, also attempted to show that the concept of 'contagion' was false. 7 However, incontrovertible evidence of the role of water in the transmission of cholera and typhoid was provided by the work of John Snow9 •10 and William Budd 11 •12 • The brilliantly thorough investigation and analysis, by Snow, of the intervention study unwittingly set up when the Lambeth Water Company moved its

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WATER April 1993

Jocelyn Forsyth is Director of the Microbiological Diagnostic Unit, Department ofMicrobiology, University of Melbourne where he has held this position since 1977. He was Asst. Director from 1968 and during the preceding four years, Lecturer and Senior Lecturer in the Department of Microbiology, Monash University, Victoria.

source of water from heavily polluted stretches of the Thames at Battersea to a much cleaner area at Thames Ditton showed how effectively cholera could be spread in drinking water. At the same time, the relative freedom of the customers of the Chelsea Company, drinking water from a bad source, but which had been filtered, was also demonstrated incidentally. 13 It is interesting to note that the situation in London had been significantly worsened by the apparently sensible move of the Health of Town Commission (1845) to force the cesspools to be abandoned in favour of water-borne sewerage. This meant that the Thames became all the more heavily polluted with raw sewage - with numerous outfalls close to the water intakes. 14 Budd's appreciation that the sewer was merely the continuation of the diseased gut 15 led to his investigation of water as the vehicle of spread of typhoid at Taunton and at Richmond Terrace and his application of what are now cla~ ical epidemiological reasonings to demonstrate his case. 12 The force of these findings obliged Austin Flint, in America, to admit that his epidemiological investigation of an outbreak of typhoid in 1843, which rejected the possibility of waterborne infection despite local opinion, had been faulty. 6 Of course, public opinion was in advance of the savants in London also, as shown by a Punch cartoon of 1849 which echoed the feeling that the water supply spread cholera. 14 The acceptance of the force of these discoveries led to the Metropolitan Water Act of 1852. Although it could not take effect immediately, it prohibited abstraction of water below Teddington weir, obliged the filtration of water taken from rivers, and required service reservoirs in the central London area to be covered. 4 These principles were transformed, gradually, into accepted practice in Europe generally. 16 Nevertheless, the power of the anticontagionists and of the holders of convoluted theories was not dead - and, indeed, lasted until the following century. 17 The cholera epidemic in Hamburg in 1892/ 3, voluminously described by Gaffky 18 and by the famo us Robert Koch 19, was overwhelming evidence of the ability of cholera to be transmitted by the water supply. Here the neighbouring cities of Hamburg and Altona although so conjoined as to have no discreet junction, were perfectly separated by cholera. Both cities abstracted their water from the river Elbe, with Altona, further down, receiving the full impact of Hamburg's sewage. 20 Altona, however, processed the water through settling tanks and slow sand filters and was spared waterborne cholera. Further, Wallichs 21 and Koch 22 analysed the occurrence of typhoid in Altona over decades and linked regular outbreaks to freezing of the surfaces of the filters and to the consequent increased bacterial counts (over 100 per ml) in the filtered water. Koch pointed out, firmly, the need to maintain the filter beds properly and to restrict the rate of flow to maintain adequate efficiency of filtration .

While it has long been clear that both cholera and typhoid can be spread by vehicles other than water, the potential for contaminated water supplies to cause endemic infections to explode dramatically

has been shown, in the past half century, in PrJStina23 and in South Africa 24 for typhoid and cholera, respectively, and even more recently in Peru .25 The discoveries of Snow and Budd had, of course, preceded the discovery of bacteria as a source of disease. Nevertheless, the concepts of some form of proliferating agents as the cause of cholera and typhoid were widespread. In the same issue in which Snow described the Broad Street pump episode, Wolseley26 postulated either a vegetable or animal existence propagating in the same way as yeasts and, a few years later Gairdner 7 lectured that the causation of cholera was by agents which could 'reproduce themselves with great rapidity'.

However, as seen above, the discovery by Koch 27 of the 'comma bacillus' in 1884 did not succeed in convincing everyone - with von Pettenkofer a notable sceptic.

As observations, and the relevant investigations, have continued through this century there has been a continuing increase in the number of aetiological agents which have been shown to give rise to demonstrable outbreaks of waterborne disease.

Among bacteria, shigellas 29 , salmonellas 29 , diarrhoeagenic 30 strains of Escherichia coli3 1•32 , and campylobacters 33 •34, have been added to the agents of enteric fever and cholera. With an improved ability to investigate viral disease, has come the demonstration that the waterborne route can convey hepatitis A 35 and E 36 , gastroenteritis due to rotaviruses 37•38 , and Norwalk type agents 39•40 •41 • The last-named are probably the most common cause of acute gastrointestinal illness associated with polluted water supplies.

It was long suspected that, among protozoa! diseases, amoebiasis 42 could be spread by water but, in recent years, giardiasis43•44 •45 and cryptosporidiosis 46•47 have been shown to be capable of being the agents of waterborne outbreaks in developed countries as well.

The source of all of these agents mentioned is the gut of the infected individual, whether case or carrier, whether human or, as in the case of cryptosporidia, salmonellas, campylobacters, yersinias and, in some situations at least, giardias, another animal.

The need to protect drinking water from contamination with faecal material.

From this it follows that protection of drinking water from faecal material is a basic precaution. At the time at which this association between faecal pollution and disease was recognised, the list of agents which were known to be waterborne was less than at the present time. However, the techniques available for the isolation of such organisms as Salmonella Typhi and Vibrio cholerae from environment samples were quite inadequate 48 • It was clearly sensible to use common members of the gut flora as surrogates 49 •50 and the use of indicator organisms to demonstrate faecal pollution became established 51•52 • At first the choice of indicator organisms was uncertain although an early consensus developed about the use of the coliform organisms. Definition of this heterogeneous group 53 proved difficult and contentious. However, the work of Alexander Houston 54 , Doris Bardsley 55,56 and many others, through the first decades of this century established that the use of Escherichia coli as a marker was not likely to yield false alarms as this organism was virtu·ally certain to have been derived from the gut.

Much of this work was being carried out in England and North America. At that time typhoid was relatively common and served as the major index of the effects of pollution of water supplies although the occurrence of other disease syndromes in the consumers of polluted water was well recognised.

Risk to health should be the major criterion in the establishment of guidelines In the establishment of codes of practice aimed at the prevention of waterborne disease it is clearly desirable to set out criteria, based on the risk to health, which encompass all the elements of a water supply system, collection, storage and distribution, as well as tests used to monitor the quality of the supply.

Ideally, each element of the water supply system should be costed and each linked, not only to the degree to which it contributes to the improvement of laboratory-assessed quality, but to the reduction in the impact of infectious disease. That is, each component of improvement should not only be costed but the degree by which it reduces disease or the risk of disease should be known - and preferably assessed objectively and quantitatively.

This also implies that the efforts required to ~ring a water supply to meet various guidelines should be assessed on these bases.

In this way, not only will the practicability of reaching certain marks of water quality be examined but the relevant community could have the opportunity to assess the economic cost of each degree of improvement against the reduction of risk to health this improvement may bring and to make a choice satisfactory to it.

Attempting to establish criteria based on risks to health In any situation, the chances of waterborne infections occurring in a community depend upon a number of factors: • The concentration of pathogenic, causative, organisms in the water • The per capita intake of water in a potentially infective form (eg. not as a boiled water beverage or food) • The infectious dose of the particular pathogen under the relevant circumstances • The effective immunity of the population - which can vary between absolute, relative or waning, depending upon the pathogen in question.

In 1917 Sir Alexander Houston 54 looked at the concentration of the indicator bacteria in raw river water and that in the supply and compared the mortality of typhoid in major cities of Britain and Europe with that of American cities, pointing out that it was customary, in America, to consider a mortality rate from typhoid of 20 per 100 000 population per year as the 'norm', with Cincinnati having a low rate of 8.8 and Minneapolis a high one of 58.7; while that in London was 3.3 per 105 • This was taken as meaning that the systems of water treatment and delivery in London (and some other cities) had stopped the waterborne transmission of typhoid while other methods of transmission continued. This allegation was, effectively, upheld by Hazen 57 , who set out the typhoid mortality rates of a list of American and European cities. Houston also commented on the apparent sensitivity of the coliform tests of the day in detecting the intrusion of sewage into water.

The infectious dose of Salmonella Typhi, the causative organism of typhoid, has been measured in a number of ways, notably by the experiments in volunteers carried out by Hornick 58 • In these, the dose which caused disease in 50% of volunteers was in the order of 107 bacteria. This high infectious dose is consistent with the experience of Budd in the previous century in which he was able to arrest the spread of typhoid in an institution 15 by means of simple precautions. It would imply that it is relatively difficult to catch typhoid.

• Kehr and Butterfield 59 , however, attempted to establish the relation between the finding of coliforms in water and the presence of Salmonella Typhi. They based their work on analysing the accounts of the numerous waterborne outbreaks of typhoid - for which appropriate data were available - and on systematic studies of enteric bacteria and S. Typhi in rivers which had been carried out in various parts of the world. Their calculations led them to the opinion that the concentration of S. Typhi organisms in the raw water supply could be measured as a function of the number of cases of typhoid in the community in question. Further, they calculated a ratio of Salmonella Typhi to coliforms in water in order to compare the concentration of pathogens in certain outbreaks with the numbers of cases which actually occurred.

From this they calculated that approximately 1.5% of the population can catch typhoid from a single organism - taken in water. This would be consistent with the results of the Croydon typhoid outbreak 60 in which just over 300 cases occurred in a population at risk of between 36 000 and 40 000. Kehr and Butterfield concluded that the coliform test is a useful indicator of hazard from faecal pollution and that even the moderate presence of coliforms indicates danger. Despite the apparent safety factor of the ratio of coliforms to Salmonella Typhi, they cite the Detroit, Michigan, outbreak when a mean coliform count in the water supply of 3 and 10 on two successive days was, in retrospect, the flag for an outbreak of waterborne typhoid.

In the current Australian context, however, indigenous typhoid is rare. That is, the prevalence of the causative organism in the community is exceedingly low. The oyster, associated outbreak of 1978 was a good surrogate as it showed the relative rarity of Salmonella Typhi in urban sewage. Here thousands of people became ill from eating oysters which had been reared in water heavily contaminated by sewage overflowing during a flood in metropolitan Sydney. Hundreds of stools were examined and while the presence of Norwalk-type virus was noted by electron microscopy 61 and by serology of patients, and enterotoxigenic Escherichia co!i62 were WATER April 1993

13

very common, a relatively small number of stools contained salmonellas, but none Salmonella Typhi, and no cases of typhoid occurred.

It is not appropriate to judge the potential threat of waterborne disease by the risk of typhoid alone. Even the epidemics cited by Kehr and Butterfield indicated that in the course of the outbreaks a huge ratio between cases of gastro-enteritis and typhoid was present. Forty-five thousand of the former and eight of the latter was the finding in Detroit.

While the relation between cases of gastroenteritis and of coliforms in water has not been investigated, it is clear that if the presence of small numbers of coliforms can presage waterborne typhoid (given the presence of excretors in relevant circumstances), then the risk from gastroenteritis must be much higher - by several orders of magnitude. Two fur ther factors which indicate the need for a substantial margin of safety in the provision of barriers against infection and in the guideline standards are as follows: • The fact that a sample of water analysed represents only a single point on a probability curve - and that this could be on a tail which under estimates the numbers of indicator bacteria which are actually present.

• The occurrence of enteric pathogens in the presence of few, if any indicators.

The latter may be exemplified by organisms which are relatively chlorine resistant, such as viruses, giardia cysts or cryptosporidium oocysts, or events such as at Riverside, California 63 , when salmonellas appeared to be present in excess of indicators.

These factors, while not providing quantitated health effects criteria, underlie the philosophy of setting codes of practice which put multiple barriers between sewage and drinking water and in setting guidelines which will, within the minor noise of experimental frailty, exclude the presence of faecal organisms.

Difficulties with applying quantitative estimates of risk to the finding of indicators in water supplies The presence of indicators of faecal contamination implies risk to the receiving community, not necessarily disease. This is because of the factors stated earlier. Firstly, it is necessary that the indicators are accompanied by pathogenic microorganisms. The chances of this are determined by the prevalence of the pathogens in the potential sources - people or animals.

Secondly, it is related to the relative level of immunity in the community. It is conceivable that a particular water supply has been repeatedly contaminated and past experience has made the community immune, to a greater or lesser extent, to the effects of the pathogens which have been introduced.

The effects of these are seen in developing countries in which the prevalence of pathogens is high. Among tourists, the drinking of water, or eating unpeeled fruit, by analogy, is frequently followed by overt illness. In these same countries native adults do not show the symptoms to which visitors readily fall prey. This immunity is acquired at a severe cost of morbidity and mortality among children with repeated illness occurring before relative immunity becomes effective. Thus, because of the current lack of accompanying pathogens, a community consuming water with indicators of faecal pollution may show no discernable disease. However, the situation is decidely unstable. Pathogens may be introduced into the polluting faeces from , say, an immigrant to the community6•11 or from a seasonal outbreak of cryptosporidiosis among bovi nes in the catchment.

With small communities the risk of these occurrences may be restricted because of the smaller number of immigrants and the smaller population at risk. In large communities the population at potential risk is much larger - even if the resources to manage water supplies are greater.

Are guidelines for absence of indicators of faecal pollution meaningless because of the occurrence of disease in the absence of indicators?

It is clear that outbreaks can occur in the absence of indicators if disinfection can remove the indicators and leave the pathogens.

This is potentially the situation with the cysts of Giardia sp and oocysts of Cryptosporidium sp.

Chang65 , and Shuval66 following him, have postulated that a significant amount of viral disease in the community may be the result of low level contamination of water with viruses which cause outbreaks of infection. This is helped by the low infectious dose

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WATER April 1993

of viruses and does not come to notice ~cause so many infections are asymptomatic. It would follow that viral indicators need routinely to be sought. Gamble 67 argued that epidemiological analysis does not bear this hypothesis out and that recognised waterborne outbreaks of viral disease are, in fact, associated with the presence of bacterial indicators in water. Furthermore, the polio viruses (mostly derived from live oral vaccines) which are the usual indicators used in viral studies of this kind may not be adequate 68 • The work of Payment 69 , which seemed to show that a section of the communi ty potentially protected from waterborne virus infections by specially treated water experienced less gastroenteritis than controls, might undermine Gamble's position if it can be shown to be of general application rather than confined to a particular community - taking water from a polluted river and providing just conventional treatment, which could , conceivably, be defective. It is notable that specific religious group_s in Holland who reject immunisation have repeatly been shown to be susceptible to poliomyelitis70 , despite the use of water from the polluted Rhine as a water source in that country.

Because the routine testing for potential viral pathogens in water would require the full deployment of modern technology, this situation could well pose the question of opportunity costs to communities in the starkest terms - whether they are prepared to bear the costs of special treatment of water in order to reduce the incidence of gastroenteritis. This would occur when so many communities in the industrialised world have difficulty in meeting much slacker standards. When examining the practical implications of such costs, it is also important to consider that water can be deficient in quantity as well as in quality. Gairdner, in 18617, and Bradley7 1, in 1977, write of the diseases resulting from inadequate water supplies.

In general, however, the occasional failure of conventional indicators to predict disease points out the fact that the prime protection of a community does not lie in tests but in the existence and maintenance of barriers preventing the ingress of faecal material into the water. The tests can only indicate breaches in the integrity of the barriers.

The discovery, in water, of variants of pathogens which are relatively resistant to disinfection 72 •73' and of forms of both indicators and pathogens which cannot be cultured by normal means 74 •75 only reinforces this general principle of primary dependence on multiple barrier~

What risks are presented by organisms free-living in water which are not relevant to the systems for detecting or avoiding faecal pollution?

While the classical waterborne diseases have been shown to be caused by organisms originating in the gut of man or other animals, and hence usually detected by methods aimed at indicating the presence of faecal pollution , many organisms fo und in water are not, or not regularly, associated with the vertebrate gut.

Some of these organisms may cause disease in humans under certain circumstances. The relevance of the presence of these organisms to drinking water criteria needs to be examined. Current knowledge points, in particular, to the capacity for opportunistic infections shown by certain amoebae and bacteria and the potentiality of cyanobacteria to produce toxins.

In recent decades much attention has been paid to the potential for free-living amoebae to cause disease 76 • Naegleria fowleri, the cause of devastating primary amoebic meningoencephalitis, is only a problem in thermally enriched waters 77 and South Australian workers have shown how the threat can be managed appropriately 78 Acanthamoeba species and leptomyxid amoebae 79 are more widely distributed but have caused fewer, and less fulminating, infections. The latter agents have only been incriminated recently.

It is likely that their eradication from water at delivery is impracticable. Control of numbers is desirable.

There is no positive evidence that the drinking of water brings a tangible threat from these amoebae.

Bacteria of the genus Aeromonas are normal inhabitants of fresh water. They are known to cause diseases of fish and amphibia. They have given rise to serious cases of septicaemia in people - often individuals with underlying disease. Aeromonads can occur in large numbers in water, particularly when nutrient rich. Western Australian workers have described an association between gastro-enteritis and childr n, Aeromonas spp. in the stools and seasonally increased numbers of aeromonads in drinking water supplies 80 . Virulence

associated factors have been described in diarrhoea-associated strains81 • Despite all this, volunteer experiments have failed to demonstrate a causative role fo r these organisms82 and typing has shown discordance between strains from patients and strains in water 83 . The position remains unclear.

Other bacterial species, known to be associated with opportunistic infections in hospital patients may be found in drinking water supplies. Klebsiella spp. and Pseudomonas aeruginosa are examples.

It has been inferred that the presence of these bacteria in drinking water, particularly in large numbers, may pose a risk to vulnerable hospital patients and to immunosuppressed persons in the community.

Although there are highly vulnerable patients in some hospitals, some even being managed with extreme precautions including the provision of sterilised food, there is little evidence to suppo rt the notion that these organisms in tap water pose a specific risk of this kind. Wounds and similar sites are treated, if that is needed , with sterile solutions. Where this is not so 84 , infective complications may occur. The relevance of this to drinking water quality is dubious.

Items of food, including salads, frequently contain high counts of similar organisms 85 - higher than those in water. The source of colonisation of patients in hospitals is frequently other patients rather than the environment 86 - with transfer from patient to patient by means of hands. The strains of Klebsiella spp. causing opportunistic infections have been found to have certain 'hospitalassociated' factors including the ability to survive on skin and resistance to killi ng in serum - unlike environmentally derived strains87 ,88 •89 • Klebsiellas, albeit often in small numbers, are found in the gut of most normal individuals. Furthermore, indifferent water in hospital supplies can , at times, be outside the control of watersupply authorities 91• Immuno-suppressed patients in the population at large, including those with AIDS, suffer from a wide range of infections but those associated with Gram-negative rods occurring in water are not the most prominent and it is difficult to incriminate a particular source of these ubiquitous organisms.

Legionella spp. and certain mycobacteria are naturally found in water and can be regarded as ubiquitous environmental flora. While some of the latter have presented particular disinfection problems in hospital situations, the association of both is, primarily, with respiratory tract disease with the infectious dose being delivered by the inhalation of fine, contaminated, particles derived as droplet nuclei from aerosols or dust.

This is not a direct association with the drinking of water. Certainly with Legionella spp, it appears necessary for the bacteria to multiply to significant levels - particularly with thermal enrichment - before episodes of legionellosis occur. The role of free-living amoebae in supporting and protecting the Legionella spp. has become more clear as well 92 . Unusual prevalences of infections with Mycobacterium kansasii have been found in association with the organisms being found in water 93 . It is suspected that inhalation of aerosols may be the significant factor. In both legionellosis and mycobacteriosis, cases occur particularly in people with impaired respiratory defence mechanisms.

The relations of these free-living organisms in drinking water to infections in humans are both indirect and, often, unclear or even dubious. Because they are part of the natural environmental flora they are not going to be eradicated. Their presence needs to be treated with caution and a readiness to take appropriate action when needed, rather than with alarm. Nevertheless, the fact that these associations with disease are present and that epidemiology is primarily a science of numbers and of probabilities, make Koch's insistence on maintaining general quality of supplied water as relevant today as in 1893.

Although Australian observations on the problems caused by cyanobacteria date back a long time 94 , attention has been intensified with the appreciation of eutrophication . This places the responsibility in the court of general catchment monitoring and management95 and indicates, yet again, the essentially holistic nature of water supply, with all components needing due stress.

SUMMARY Provision of pure water and effective disposal of sewage in developed economies have been associated with massive reductions in classically waterborne diseases like typhoid. Intrusion of sewage, or of indications of sewage, into drinking water supplies have frequently been associated with demonstrable outbreaks of disease.

Where there are many routes of transmission 01,2erating in a society, provision of pure water, alone, has not always been shown to be associated with reduction in incidence of suspect waterborne disease 96,97,98 • Because of the intermittency of introduction of pathogens and t he potential dilution of cases among a population of consumers - an unknown proportion of whom may be immune - prediction of outbreaks and attribution of source are highly uncertain.

These factors have made estimates of cost-benefit from specific measures to improve the compliance of water supplies with guidelines very difficult. Also, a saturation effect may occur whereby, beyond a certain level, investments in water supply and disposal have small economic benefits only99 • However, the continued occurrence of major outbreaks associated with the breakdown of the barriers to waterborne disease put in place by suitable management and maintenance of supply systems and the treatment of water supplies indicates the hazards quite clearly.

ACKNOWLEDGEMENTS This article represents an expansion and adaptation of a document prepared during working party considerations of drinking water guidelines. Colleagues suggested that there might be wider interest in the material collected for that purpose - and this is the result.

REFERENCES 1.

Hippocrates. On airs, waters and places. Translated and republished in Medical Classics 3:1938: 19-42.

2. Purchas, D. B. Removal of insoluble particles. Chap. 6 In: Lorch W (Ed.) Handbook of water purification. Chichester: Ellis Horwood, 1987.

3. Frankland, P. F. Water-purification; its biological and chemical basis. Minutes of Proc Inst Civ Eng 1885 / 6; 85:197-219.

4. Skeat, W. 0., ed Manual of British water engineering practice, 4th ed. Vol Ill Water quality and treatment. Cambridge: W. Heffer/ Institution of Water Engineers, 1969.

5. Ackerknecht, E. H. Anticontagionism between 182! and 1867 . Bu// Hist Med 1948; 22:562-93.

6. Evans, A. S. Two errors in enteric epidemiology: The stories of Austin Flint and Max von Pettenkofer. Rev Infect Dis 1885;7: 434-440.

7. Gairdner, W. T. Public health in relation to air and water. Edinburgh: Edmonton and Douglas, 1862.

8. Farr, W. Elevation and cholera mortality in London, 1848-9. In: Vital statistics.

Office of the sanitary institute, London: 1885: 343-347 . Cited by: Langmuir AD. Epidemiology of airborne infect ion. Bacteriol Rev 196l t25:1 73-181.

9. Snow, J. The Cholera near Golden Square, and at Deptford. Medical Times and Gazette 1854 (Oct 7); 9:321-2.

IO. Snow, J. Cholera, and the water supply in the South Districts of London . Br Med J 1857 (Oct 17): 864-5.

II. Budd, W. On intestinal fever : its mode of pro.iogation. Lancet 1856; 2:694-5.

12. Budd, W. Typhoid fever: Its nature, mode of spreading, and prevention. London: Longman Green, 1873.

13. Snow, J. On the mode of communication of cholera. (2nd Edition , much enlarged) .

London: J Churchill, 1855 162 pp. Reprinted In: Snow on cholera. New York: Hafner, 1965 (1936) .

14. Dick inson, H . W. Water supply of Greater London . Leamington Spa: Newcomen Society, 1954.

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16. Ridley, J. E. Experiences in the use of slow sand filt ration, double sand fi ltration and microstraining. Proc Soc Water Treat Exam 1967; 16:170-191.

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30. Lev ine, M. M. Escherichia coli that cau se diarrhea : Enterotox igeni c, enteropathogenic, enteroinvasive, enterohemorrhagic, and enteroadherent. J Infect Dis 1987; 155: 377-389.

31. Swerdlow, D. L. et al. A large waterborne outbreak of antimicrobial resistant E. coli O157:H7 infections. Abstracts of the 1990 ICAAC, Atlanta, Ga. 32. Dev, V.J. , Mai n, M., Gould , I. M., Sharp JCM. Still waters run deep: A possible waterborne outbreak of Escherichia coli 0 157. Communicab le Diseases & E nvironmental Health in Scotland: Weekly Report 1991; 25 (91 / 41): 5-6.

33 . Taylor, D. N., McDermott, K. T. , Little, J. R., Wells, J. G., Blaser, M. J. Campylobacter enteritis from untreated water in the Rocky Mountains. Ann Intern Med 1983; 99:38-40.

WATER Apr il 1993

15

34. Melby, K., Dahl, 0. P., Crisp, L., Penner, J. L. E pidemiology, clinical a nd serological ma nifestations in patients during a waterborne epidem ic due to Campylobacter jejun i. J Infect 1990; 21:309-3 16.

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37. Hopki ns, R. S., Gaspard, G. B. , Williams, F. P., Karlin, R . J., Cukor, G., Blacklow, N. R. A community waterborne gastroenteritis outbreak: Evidence for rotavirus as the agent. Am J Public H ealth 1984; 74:263-265 .

38. Taylor, D. N., McDermott , K. T., Little, J. R., Wells, J. G., Blaser, M . J. Campylobacter enteritis from untreated water in t he Rocky Mountains. Ann In tern Med 1983; 99:3 8-40.

39. C ukor, G., Blacklow, N. R . H u man viral gastroenteritis. Microbial Rev 1984: 48: 157-179 .

40 . Ramia S. Transmission of viral infections by the water ro ute: Implications for developing countries. Rev Inject Dis 1985; 7:180-188.

41. Lawson, H. W., Braun , M. M., Glass, R. l. M. et al. Waterborne outbreak of Norwalk virus gastroenteritis at a southwest US resort: role of geological formations in contamination of well water. Lancet 1991; 337: 1200-1204.

42. Ritchie, L. S. , Davis, C. Parasitological findings and epidemiological aspects of epidemic amoebiasis occu rring in occupa nts of the Mantetsu apartment building.

Tokyo, Japan. Am J Trop Med 1948; 28:803-16.

43. Moore, G. T., Cross, W. M. , McGuire, D. et al. Epidemic gia rdiasis at a ski resort.

N Engl J Med 1969; 281: 402-407.

44. Ramsey, C. N., Marsh J. Giardiasis due to deliberate contamination of water suppl y.

Lancet 1990; 336:880-881.

45. Shaw, P. K ., Brodsky, R . E., Lyman, D. 0. et al. A community wide outbreak of giardiasis with evidence of transmission by a municipal water supply. A nn Int Med 1977; 87:426-432.

46 . Galla her, M. M., Herndon , J. C., Nims, L. J., Sterling, C. R., Grabowski, D. J., Hull, H.P. Cryptosporidiosis and surface water. Am J Public H ealth 1989; 79;39-42.

47. Rose, J. B. O ccurrence and significance of cryptosporidium in water. J AWWA 1988; 53-58 .

48. Koch, R. Ueber ba kterio logishe Forchung. Zentralbl Bakteriol Parasitenk 1890; 8:563. Cited by: Mossel DAA. Microbiology of foods. Utrecht: The U ni versity of Utrecht, 1982.

49. Sc hardi nger, F. Ueber d as Vorkommen Giihrungerregender Spaltpil ze in Trinkwasser und ihre Bedeutung fu r die hygieni sche Beurteilung d esselben. Wien Klin Wochensch 1892; 5:403,431. Cited by: Mossel DAA. Microbiology of foods.

U trecht : The University of Utrecht, 1982.

50. Smith, T. Notes on Bacillus communis a nd re lated forms, together with some suggestions concerning the bacterological examination of d rinking-water. Am J M ed Sci 1985; 110:283-302.

51. Houston, A.C. In: Chalmers AK, chr. Discussion o the varieties and significance of B. coli in water supplies. Br Med J 1912; ii: 704-716.

52 . Lewis, M. J. T he bacterio logical examination o f drink ing water. J Hyg (Comb) 1983; 90: 143-147.

53 . Aust in, B., H ussong, D. , Weiner, R. M ., Colwell , R . R . Numerical taxonomy analysis of bacteria isolated from the completed 'Most Probable Numbers' test for coliform bacilli. J Appl Bacterial 1981; 51: 101-112.

54. Houston, A. C. Rivers as sources of water supply. London: John Bale a nd Da nielsson, 1917.

55. Bard sley, D. A. The distribution and sanita ry significance of B. coli, B. /actis aerogenes a nd intermediate types of coliform baci lli in water, soil, faeces a nd icecream . J Hyg (Com b) 1934; 34: 38-68.

56 . Bardsley, D. A. A comparison of two methods of assessing the number of different types of co li form organisms in wate r. J Hyg (Com b) 1938; 38: 309-324.

57 . Hazen, A. The fi ltration of public water-supplies, 3rd ed. New York: John Wiley, 1903.

58 . Hornick, R . B., Woodward, T. E., Mccrumb, R . F. et al. Study of typ hoid fever in man I. Evaluation of vaccine effectiveness. Trans Ass Am Physns 1966; 79: 361-7.

59 . Kehr, R . W., Butterfield , C . T. No tes on the relation between coliforms and enteric pathogens. Pub/ Hlth Rep (Walsh) 1943; 58: 589-607.

60 . Murphy, H. L. Report on a public local inquiry into an outbreak of typhoid fever a t Croydon in October and November 1937. London: HMSO, 1938.

61. Mu rphy, A. M., Grohmann, G. S., Christopher, P. J., Lopez W. A., Davey, G. R ., M illsom, R. H. An Australia-wide outbreak of gastroenteritis fro m oysters caused

by Norwalk virus. Med J Aust 1979; ii: 329-33.

62 . Luke, R ., Ryan, N . 1978 . Unpub lished fi ndings.

63. Ross, E. C., Campbell , K. W., Ongerth, H . J. Salmon ella typhimurium contamination of Riverside, Calif., suppl y. Amer Water Works Assoc J 1966; 52:

77. Dorsch, M. M., Cameron, A. S., Robinson, It. S. T he epidemio logy and control of primary amoebic meningoencephalitis wil h particular reference to South Aus tra lia . Trans Roy Soc Trop Med Hyg 1983; 77: 372-377.

78. Robinson, B. S., Christy, P. E. Disinfection of water for control of amoebae. Water 1984; II: 21-24.

79 . Gordon, S. M., Steinberg JP, DuPuis MH , Kozarsky PE, Nickerson J F, Visvesvara GS. Culture isolation of Acanthamoeba species and leptomyxid amebas from patients wi th amebic meningoencephalitis, including two patients with A IDS. Clin Infect Dis 1992; 15: 1024-30.

80 . Gracey, M., Burke, V., Robinson, J. Aeromonas-associated gastroenteritis. Lancet 1982; ii: 1304-6.

81. M illership, S. E., Baker, M. R. , Mulla, R. J., Maneck, S. Exterotoxic effects of Aeromonas sobria haemolysin in a rat jejuna! perfusion system identified by specific neutralization wit h a monoclonal antibody. J Gen Microbiol 1992; 138: 261-267.

82. Morgan, D. R ., Johnson, P. C., DuPont, H . L., Satterwhite, T. R., Wood , L. V. Lack of correlation between known virulence properties o f Aeromonas hydrophila a nd enteropathogenicity for huma ns. Infect l mmun 1985; 50: 62-65.

83. Havelaar, A. H ., Schets, F. M., van Silfhout, A., Jansen, W. H. , Wleten, G., van der Koo ij, D. Typing of Aeromonas strains from patients with diarrhoea and from drin king water. J Applied Bacterial 1992; 72: 435-444.

84. Tredget, E. E., Shankowsky, H . A., Joffe, A . M., et al. Epidemiology of infections with Pseudomonas aeruginosa in burn patients: ~he role of hydrotherapy. Clin Inject Dis 1992; 15: 941-9.

85. Sh ooter, R. A., Faiers, M. C., Cooke, E. M ., Braedon , A. L., O 'Farrell , S. M. Isolation of Escherichia coli, Pseudomonas aeruginosa and Klebsiella from food in hospitals, canteens and schools. Lancet 1971; ii: 390-2.

86. Mak i, D. G., Alvarado, C. J., Hassemer, C. A ., Z ilz, M. A., Relation of the inanimate hospital environment to endemic hospital infection. N Engl J Med 1982; 307: 1562-6.

87. Hart, C. A., Gibson, M. F., Buckles, A.M. Variation in skin and environmental su rv ival of hospital gentamicin-resistant enterobacteria. J Hyg (Comb) 1981; 87: 277-285.

88. Cooke, E. M., Edmondson, A. S., Starkey, W. The abilit y of strains of Klebsiella aerogenes to survive o n the hands. J Med Microbial 1981; 14: 443-450.

89. Casewell, M . W. , Desai, N. Surv ival o f multiply- resistant Klebsiella aerogenes and other Gram-negat ive bacilli on fin ger-tips. J H osp Infect 1983; 4: 350-60.

90. Gray, J. D. A. T he significance of Bae/. aerogenes in water. J Hyg (Comb) 1932; 32: 132-141.

91. Comm unicable Diseases Surveillance Centre. Contaminated hospital water supplies.

Br Med J 1979; I : 350.

92. Barbaree, J.M., Fields, B. S., Feeley, J.C., Gorman, G. W., Martin, W. T. Isolation of protozoa from water associated with a legionellosis outbreak and demonstration of intracellular multiplication of Legionella pneumophila . Appl Environ Microbial 1986; 51: 422-424.

93. Kubin, M., Svandova, E., Medek, B., Chobot , S., O lsovsky Z. Mycobacterium kansasii infection in an endemic area of Czechoslovakia. Tubercle 1980; 61: 207-212.

94. Francis, G. Poisonous Australia n la ke. Nature 1878; 18: 11-12.

95 . Health Department Victoria. Blue-green algae in drinking water su pplies.

Melbourne: Health Department Victoria, December 1990.

96. Richardson, N . J., Hayden-Smith, S., Bokkenheuser, V. , Koornhof, H. J. Salmonellae and shigellae in Bantu children consuming dri nking water of improved quality. Sth Afr Med J. 1968; 42: 46-49.

97. Tompkins, A. M., Drasar, B. S., Bradley, A. K., .Willia mson , W. A. Water supply and health and nutritio n in No rthern Nigeria. Trans Roy Soc Trap Med Hyg 1978; 72: 239-243 .

98. Walker, A. R . P., Walker, B. F. Pure water and infections in Africa . Lancet 1978; ii: 639 .

99. Shuval, H. I., Tilden, R. L., Perry, B.J L , Grosse, R. N. E ffect of investments in water supply a nd sanitation on health status: a threshold-saturation theory. Bull Wld Hlth Org 1981; 59: 243-248 .

165-174.

64. Cravioto, A, Reyes, R . E., Ortega, R ., Fernandez, G., Hernandez, R. , Lopez, D. Prospective study of diarrhoeal disease in a cohort of ru ra l Mexican children: Incidence and isolated pathogens during the first two years of life. Epidemiol Infect 1988; IOI: 123-134.

65. Chang, S. L. Waterborne viral infections and their prevention. Bull WHO 1968; 38: 401-414.

66. Shu val, H. l. Water needs and uses: the increasing burden of enteroviruses on water quality. In: Berg G, Bodily HL, Leonette EH, Melnick JL, Metcalf TG. Viruses in water. Washi ngton DC: APHA, 1976: 12-25 .

67. Gamble, D. R. Viruses in dr inking water. Lancet 1979; i: 425-8.

68. Katzenelson, E., Kedmi, S. Unsuitability of polioviruses as indicators of viro logical quality of wa ter. Appl Environ Microbial 1979; 37: 343 -344.

69. Payment, P. , Richardson, L., Siemiat yc ki, J., Dewar, R., Edwardes, M., Franco, E. A randomi zed trial to evaluate the risk of gastrointestinal disease due to consum ption of drinki ng water meeting current microbiological standard s. Am J Public Health 1991; 81: 703-708.

70. Centres for Disease Control. Poliomyelitis - Netherlands, 1992. MMWR 1992; 41: 775-778.

71. Bradley, D. J. H ealth aspects of water supplies in tropical countries. In : Feachem R, McGarry M, Mara D, eds. Water, wastes and health in hot climates. Londo n: John Wiley, 1977: 12-13.

72 . White, P. B. The rugose varia nt of vibrios. J Pathol Bacterial 1938; 46: 1-6 .

73. Rice, E.W., Johnson CJ, Clark RM et al. Chlorine and survival of "ru gose" Vibrio cholerae. Lancet 1992; 340: 340.

74. Xu, H. S., Roberts, N., Singleton , F. L., Attwell , R . W., G rimes, D. J. , Colwell , R . R. Survival and viability of noncultural Escherichia coli and Vibrio cholerae in the estaurine and marine environment. Microb Ecol 1982; 8: 313-323.

75. Roszak, D. B., Grimes, D. J., Colwell , R.R. Viable but nonrecoverable stage of Salmonella enteritidis in aquatic systems. Can J Microbial 1984; 30: 334-338.

76. Ma, P., Visvesvara, G. S., Martinez, A . J. , T heodore, F. H., Daggert, P. M., Sawyer, T. K. Naegleria a nd Acanthamoeba infections: review. Rev Inject Dis 1990; 12: 490-513 .

16

WATER April 1993

Continued from page 11 exciting potentials for the future, using computer technologies to enable us to do things we have never thought of before, or never been able to do, and it will be realised as business and technology strategies are integrated. However, she sounded a note of caution .

I.T. can be a positive force for change, but unless it serves or reinforces the business objectives of the organisation it may become just another under-utilised capital investment, incurring interest charges in years to come.

Other keynote speakers were Dr Michael Abbott, Professor of Informatics at the International Institute for Hydraulic and Environmental Engineering, in Delft, who spoke on the Impact of Knowledge Revolution in the Water Industries; Mr Darryl Davies, Director of the Hydrologic Engineering Centre, US Army Corps of Engineers, who outlined their philosophy on software development, and how he sees the typical engineering office of the near future; Dr Kurt Fedra, from the International Institute for Applied Systems Analysis, who spoke on Integrated Information Systems for Water Resources Management.

This was a very useful conference and the recordings should be of considerable value both to engineers and managers. A more detailed report should be printed in a future issue of this journal.

TECHNOLOGY

TREATMENT FOR SYDNEY'S WATER SUPPLIES An Overview of Pilot and Prototype Plant Studies

by B. A. MURRAY and S. J. RODDY SUMMARY The Sydney Water Board has embarked on a Drinking Water Quality Improvement Program to supply consumers with water meeting the 1987 NH&MRC/AWRC Drinking Water Quality Guidelines. As part of this program four major water treatment plants are to be constructed and pilot and prototype plant studies were undertaken to develop processes to meet these objectives. The major processes studied in the pilot studies included two stage, direct and contact fi ltration, with normal water, turbid and coloured water and cold water. Both natural and artificial turbid, coloured and cold waters were studied. A range of filter media evaluated including filter coal, sand and various dual media of varying sizes and depths. The addition of lime and carbon dioxide for corrosion control was studied. Various primary coagulants were evaluated with the aim of achieving greater run times at high filtration rates. The use of pre-coagulation chlorination and pre-coagulation ozonation to improve filtration performance was also evaluated as was the use of potassium permanganate to remove manganese. The effects of raw water and process parameters on aluminium speciation through the plant was also studied and pathogen removal was investigated.

Monitoring devices such as a streaming current detector, a particle coun ter and on-line aluminium analysers were tested and used to evaluate coagulation and filter performance. This work enabled the conceptual design of each of the WTWs, enhanced further design details and helped resolve other operational issues. The work was carried out by the Water Board, in conj unction with a number of consultants and contractors.

INTRODUCTION In 1989, the Water Board decided to proceed with the construction of water treatment works (WTW) at Prospect Reservoir (Prospect), Woronora Dam (Woronora), Broughtons Pass (Macarthur) and Avon Dam (Illawarra) for the following reasons: • A progressive increase in the quality required for potable water

by Drinking Water Quality Guidelines in Australia, in line with overseas trends; • Gradually decreasing raw water quality; • Increasing problems in the Board's water distribution system due to unfiltered water carrying organic matter into the system.

Further, in accordance with State Government policy, the four WTW will be constructed by the private sector under a Build , Own and Operate (BOO) scheme. This scheme will require private organisations to finance, build, own and then operate these plants for 25 years. The Board will continue to manage the total water supply system with the treatment plants as an element of that system.

P lanned for completion by 1996, Prospect WTW will be the largest direct fi ltration water treatment plant to be built in a single stage of development in the world. The plant will have a capacity of 3000 ML/ day, with provision to increase to 4200 ML/d, and will serve a population of about 2.7 million people or 80% of the Board's customers. Macarthur, Illawarra and Woronora WTWs will have capacities of 265, 235 and 200 ML/d, respectively.

Pilot plant testing was deemed to be a necessary part of the concept development. A pilot plant testing program was developed and pilot plants were erected at each location and operated for periods of up to 2 years, approximately in parallel. A larger scale prototype plant was built at Prospect Reservoir in 1991/92 with testing commencing in July, 1992. Testing on the pilot and prototype plants at Prospect continues.

Pilot plants were erected at Brough tons Pass, Woronora Dam and Upper Avon Dam. A new pilot plant was constructed at Warragamba Dam for Prospect WTW. The Prospect pilot plant was located at Warragamba Dam, initially, to enable testing of water from various depths in the dam but was later relocated to a site beside Prospect

Bruce Murray is a director of the consulting and techno logy firm - City Water Technology Pty Ltd. He is a chemical engineer with 11 years' engin eerin g experience including almost 10 years in water and wastewater treatment. The company's main interests lie in research and technology development in the fields of water and wastewater treatment.

Steve Roddy is the Senior Design Engineer for the Water Board's Water Treatment Group. He has worked in the fields of water and wastewater treatment for 18 years.

Reservoir, adjacent to the Prospect prototype plant. The two plants share faci lities and some instrumentation. Both of these plants will be located near the proposed Prospect \\:TW. They will be used to verify design parameters in future testing and will continue to be used as training and research tools once the final plant is constructed.

All pilot plants and the prototype plant were similar in design in that each contained the main process components for contact and direct filtration - pre-coagulation oxidation , coagulation, flocculation and filtration. The Prospect and Macarthur pilot plants also provided two stage filtration. A flow diagram for the Prospect pilot plant is given in Figure 1. A photograph of the Prospect pilot and prototype plant complex is given in Figure 2.

The 3 processes examined in each of the studies may be defined as follows: • Contact Filtration . This process comprises the dispersion of chemicals (coagulation) followed directly by filtration.

• Direct Filtration. In this process coagulation is followed by flocculation, in which gentle mixing is used to aggregate small particles, and filtration.

• Two stage Filtration. In this process coagulation is followed by two consecutive filtration steps. The first stage filter contains a coarser media bed and provides flocculation as well as filtration .

Further, as part of the research and development commitment a study was initiated to identify the bio-available aluminium species in drinking water for trials at the Prospect Prototype Plant. The aim of the study was to examine the effects of raw water and process parameters on aluminium speciation through the plant. Several related studies were run concurrently with this work. A streaming current detector was investigated and used to evaluate coagulation efficiency; a particle counter and two on-line aluminium analysers were tested and used to evaluate filter performance; mixing studies were undertaken; and pathogen removal was investigated.

RESEARCH OBJECTIVES The objective of the pilot plant research projects was to provide information on the processes capable of treating water, from the various sources - Warragamba Dam, the Upper Canal and Prospect Reservoir, Broughtons Pass (which is fed by a number of dams), WATER April 1993

17

Fig. 1 -

Fig. 2 -

Prospect pilot plant flow diagram

Prospect pilot and prototype plants

Woronora Dam , Upper Avon Dam - to a standard in excess of the current National Health and Medical Research Council/ Australian Water Resources Council (NHMRC/AWRC) guidelines for drinking water quality. Each pilot plant incorporated sufficient operational flexibility to allow the direct comparison and fine tuning of alternative treatment processes.

Operation of the pilot plants enabled the most suitable process to be determined, based on: • Achievement of all water quality objectives; • Cost effectiveness in establishing and operating the main plant; • Process flexibility to enable the plant to deal with differing raw water conditions. Filter run times of about 24 hours with good quality raw water and at least 8 hours with poor quality raw water were targeted; • Environmental factors such as the quantity of residuals to be disposed of.

The pilot plant studies provided valuable information for the design of each plant after fine tuning of the selected process.

Process performance monitoring equipment was also to be examined with the aim of simplifying the operation of the plant and increasing the reliability of the operation.

A submersibl~ pump was installed just upstream of a weir at Broughtons Pass to supply the Macarthur pilot plant.

Due to the limitations of the raw water supply, it was sometimes necessary to create artificial conditions which would model some of the worst raw water that the full scale plant may encounter. Artificial modifications to the raw water quality were made by injection into the raw water supply line between the header tank and pilot plant chemical dosing systems. Turbidity, colour JRAlt/ 4 (organics) and manganese were the artificial contaminants spiked in order to reduce the TRAINS quality of the raw water for testing.

Artificial ttU"bidity was produced by dosing a suspension of fine particulate matter drawn from the bottom of the appropriate dam or from fine clays obtained nearby. This particulate matter was produced by settling out grit and heavy particulates from the mud or clay. The suspension of fine, organic and inorganic particles was then dosed at a controlled rate into the raw water.

Artificial colour and organic acids were prepared by taking humus, leaves and bark of the vegetation most common in the catchment area and leaving them to soak in water for about one week. The strained, concentrated solution was dosed into the raw water.

Manganese chloride solution was dosed to provide artificial, dissolved manganese.

These procedures were found to closely simulate the results obtained with naturally occurring poor quality water in each dam although difficulties were encountered in variations in the particle size distribution and suspended solids concentration of each batch.

In the Prospect prototype plant tests were conducted with three different types of raw water - low, medium and high turbidity and colour raw water. Comparisons of results for the three different raw waters under optimised alum based coagulation are given in Figure 3.

The results show that run times (and UFRV*) are significantly reduced when the raw water quality deteriorates, as expected. Filter ripening times and filtered water quality were found to be best with the best quality raw water.

Industrial chillers were also used to artificially cool the raw water but this process was not found to give results consistent with those achieved with naturally cold water. Cold water was generally obtained in the cooler months and/ or from lower levels in the dams.

PROCESS COMPARISON After early broad process and coagulant evaluation the most economic and best performing processes were narrowed down to

35

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:, 0

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RAW WATER SUPPLIES Raw water from Warragamba Dam and Woronora Dam was pumped to the respective pilot plants from pontoon mounted centrifugal pumps. For the Illawarra pilot plant raw water was obtained from a tapping in the rising main adjacent to the existing pump station in the dam off-take tower. For the Prospect pilot and prototype plants raw water was taken from a tapping on one of the Warragamba pipelines just prior to discharge into Prospect Reservoir.

18

WATER April 1993

1 NTU, 15 HU 10 NTU, 35 HU 25 NTU, 50 HU Raw Water Quality

Fig. 3 - Effect of raw watertype on filter performance • UFRV - units m3/ m2 o r m - is the volu me of wate r that passes thro ugh a filter per u nit a rea of filter. It is equivalent to filtra1ion rate (m / h) • filter run time (h).

direct and contact filtration. Two stage filtration was also found to give satisfactory results but was not considered to be economic for these waters.

Detailed comparison testing between direct and contact filtration was then carried out with natural raw water, including turbidity events, and artificially produced waters which had, separately, high turbidity and colours, high manganese and low temperature. The effect of filtration rates was considered in these studies.

Results led to the selection of contact filtration of various configurations for each of the concept designs. While direct filtration was found to give similar or, in some cases, better results than contact filtration the additional cost of mechanical flocculation was not found to be justifiable.

polymer addition was required under cold watey conditions, whilst a lag time of 100 to 200 seconds between cationic and nonionic polymer addition was required under the same conditions to achieve maximum throughput.

The type of mixing and the mixing energy at the point of addition of the various chemicals was also studied to gauge the effect of the amount and type of mixing versus chemical usage and filter run time.

High energy, short contact time, flash mixing provided either by mechanical or pumped injection mixers were found to give the best results for low alum dose coagulation. Rapid mixing or flash mixing was found to be satisfactory for cationic polymer mixing while lower energy mixing was found to be preferable for mixing the nonionic polymer used as filter aid.

COAGULANTS

PRE-COAGULATION OXIDATION

During the course of the testing a number of coagulants were studied leading to the selection of alum with cationic polymer. A nonionic polymer filter aid was also found to play an essential role in maximising filter performance. The high rates of filtration selected, particularly for Prospect (25 m/ h), would not have been practicable without the use of cationic polymer with alum. Filter run times at this rate were around 16 hours with alum alone and up to 30 hours with alum in combination with cationic polymer with good quality raw water.

In consideration of possible links between aluminium and Alzheimer's Disease a number of iron salts were also extensively tested as coagulants - ferric chloride, ferric sulfate and hydroxy lated ferric sulfate, with and without cationic polymer and filter aid.

Whilst these were effective, filter run times were reduced compared to those of alum/ cationic polymer, by up to 50%. Aluminium levels were reduced from around 30- 50 Âľg / L to between 10-30 Âľg / L, although iron and manganese concentrations increased.

Hydroxylated ferric sulfate (HFS) was tested on Warragamba Dam water only and was found to be the most successful of the ferric salts. It was found that, with warmer surface waters of good quality, HFS generally compared well in performance to alum in terms of both treated water quality and filter run times. However, with cooler waters and with poorer quality raw water the performance of HFS dropped away but was still superior to the other iron salts tested.

The effect of temperature was significant enough to indicate that longer flocculation time and / or greater mixing energy may assist.

Less filter aid was required with alum coagulation.

Aluminium speciation studies showed that organically bound aluminium was removed in the treatment process but that inorganic aluminium concentrations increased when alum was used as the primary coagulant. Aluminium levels were found to be reducible, even when alum was used as the coagulant, by controlling the pH of coagulation. The optimum coagulation pH in terms of aluminium minimisation was found to be in the range of 6 to 6.5 as shown in Figure 4.

Studies were conducted using ozone and chl6rine as oxidants in addition to runs with no pre-oxidation. Figure 5 compares the performance of the two oxidants with that of no pre-oxidation.

Ozone improved Unit Filter Run Volumes (UFRVs) for all sources by up to 200%. This was due in part to the oxidation of organics and in part to the micro flocculation ability of ozone, both of which allow reductions in the coagulant dose. Ozone was particularly effective for good quality Warragamba water, where the dissolved organic carbon is relatively high - a dose of at around 5 mg/ L, filter UFRVs of up to 1200 m 3/ m 2 . However, it did not always produce water of a satisfactory quality when the raw water quality deteriorated and was found to be uneconomic for any of the plants proposed.

Chlorine was also effective in improving filter UFRVs for Warragamba water and, due to its high benefit to cost ratio, was selected as the process of choice in the concept design for Prospect WTW. Filter UFRVs of up to 670 m 3/ m 2 were achieved with chlorine on good quality Warragamba water and up to 280 m 3/ m 2 on 40 Nephelometric turbidity units (NTU), 40 True colour units (TCU) water.

LAG TIMES AND MIXING TYPES Lag times - the detention time between the addition of the primary coagulant and the secondary coagulant and the detention time between the addition of the secondary coagulant and filter aid - were both studied in some detail. Lag times were found to be of significant importance in a ll source waters, particularly at lower temperatures. A lag of at least 20 seconds between alum and cationic

700

------

FILTER MEDIA A range of dual and monomedia were examined. These included monomedia crushed sand of 2.0 mm effective size (E.S.) 2.0-2.4 m deep; monomedia filter coal 1.4, 1. 7, 2.0 and 2.2 mm E.S. at depths ranging between 1.7 and 2.9 m; and dual media 1.7, 2.0, 2.2, 2.5 mm E.S. coal at various depths, over a 1,0-300 mm deep sand layer with E.S. ranging from 0.65 mm to 1.0 mm . At Prospect media depths of up to 3.0 m were tested due to the possibility of a change to granular activated carbon, in the future, and an empty bed contact time requirement of at least 7.5 minutes.

In general, as shown in Figure 6 the coarser dual media performed best, providing a 30% increase in UFRV compared with 2.0 mm sand and filter coal. Dual media also provided slightly better filtered water quality and it was generally easier to optimise chemical dosages.

A coal with a lower uniformity coefficient of 1.28 gave around 10% better filtered water production than a coal with the more standard uniformity coefficient of 1.4.

UFRV (m3/m2) Raw Water Turbidity and Colour

------,-

0

600

1,400 1,200

40 NTU, 40 TCU

l!ZJ 20

NTU, 40 TCU ~ 3 NTU, 30 TCU

'-re~~------------;;~~~~~~~~~;-'

1,000 .

800 600 400 200

No Pre-oxidant

5 Fig. 4 -

The effect of

5 .5

6 pH

pH on filtered

6.5

7

7 .5

water aluminium concentration

Pre-chlorine

Pre-ozone

_____________

18 m/ h 25 m /h 2.9 m deep, 1.7 mm filter coal

Fig. 5 -

35 m/h

__,

Pre-coagulation oxidation

WATER April 1993

19

Filter media with a pre-coat of mang~nese dioxide was tested on the Illawarra plant and, using a pre-chlorine dose of 2 to 3 mg/ L, manganese levels of below 5 J.lg/ L were easily achieved. A level of less than 20 J.lg/ L was achieved with a chlorine dose of only 0.5 mg/ L. Ozone was tested unsuccessfully on all sources, being found to be either ineffective or 'too effective' at oxidising manganese. In some cases ozone was so effective at oxidising the manganese that permanganate was formed which passed through the filters. More work would be required with ozone dose and pH optimisation before conclusive results are obtained.

UFRV (m3/ m2)

500 400

DISINFECTION BY-PRODUCTS

O 2 .5DM32 .2DM21 .7DM12.0S2 .42 .2A2.91 .7A2.91 .7A2.01 .4A1 .7 Filter Coal Dual Media Sand

Fig. 6 -

Filter media comparison

BUFFERING FOR CORROSION CONTROL AND CARBON DIOXIDE

LIME

The southern dams supplying Sydney's water are all characterised by low alkalinity and low hardness and, without further treatment, are very corrosive to copper pipes and fittings as well as cement linings in pipes. The most appropriate method of corrosion inhibition is alkalinity buffering using lime and carbon dioxide. The effects of these chemicals on the process were _studied in the pilot plants and also in the laboratory.

Both the quicklime and slaked lime available in NSW were found to contain a number of contaminants - including insoluble compounds (which lead to turbidity increases in the dosed water), aluminium, manganese and iron. For this reason it would be an advantage if the bulk of the lime required were to be dosed prior to filtration.

The use of lime and carbon dioxide for corrosion control when dosed prior to coagulation was examined and found to be economically viable at Macarthur, whilst at Woronora differing results were obtained. At Illawarra, pre-coagulation buffering was also found to be cost effective. The increase in coagulant dose required for these plants was approximately 4%, whilst turbidity and aluminium elevations in the filtered water were substantially reduced.

For Prospect, since the raw water alkalinity is higher, post-filtration lime dosing only (without carbon dioxide dosing) was found to be sufficient to provide satisfactorily buffered water with only a slight but acceptable increase in turbidity and aluminium in the filtered water. A corrosion cell was set up in the Prospect pilot plant to study the effects of post-filtration chemical dosing on the corrosion of copper and brass. Results indicated a close correlation between Langelier Index and corrosion rate - as measured by corrosion current. Also, it was found that an alkalinity of at least 50 mg/ L as calcium carbonate should be maintained in the treated water to minimise corrosion.

MANGANESE REMOVAL Manganese occurs to varying degrees in each of Sydney's water supply dams; the most problematic in terms of customer complaints being at Illawarra. The water quality objective for manganese, set at the outset of the projects, was 20 J.Lg/ L. To consistently obtain such low levels required considerable testing and fine tuning in the pilot plants.

Testing carried out included the use of various oxidants such as ozone, potassium permanganate and chlorine at various doses and at various pHs. Testing was carried out at each pilot plant and in the laboratory.

Potassium permanganate was found to be very effective in oxidising manganese but the dose was critical and careful optimisation was required. A pH of around 8.5 was also found to be necessary, requiring the use of an alkali to raise the pH prior to permanganate addition. Acid dosing was then required to bring the pH back down to satisfactory levels for colour removal in the coagulation stage. Removal of manganese to levels below 20 J.lg/ L was achievable, with some difficulty, but levels below 10 J.lg/ L were not achieved at any of the pilot plants with potassium permanganate.

20

WATER Apr il 1993

The anticipation of ever tightening water quality guidelines, especially for disinfection by-products (DBPs) required that attention be given to these in the pilot plant studies especially with precoagulation chlorination being proposed in addition to postfiltration disinfection by chloramination, in some plants.

Trihalomethane (THM) levels were not found to be excessive less than 100 J.lg/ L - at any of the pilot plants under normal operating conditions. Even for the Prospect plants with prechlorination, THMs only exceeded 100 J.lg / L under adverse conditions and averaged 50 J.lg/ L. The total THM concentration was principally comprised of chloroform and, to a lesser extent, bromodichloromethane. THM concentrations were found to increase with increasing pH, chlorine residual, chlorine contact time and raw water colour.

The formation kinetics of some haloacetic acids, haloacetonitriles and haloketones were also examined at the Prospect prototype plant.

Haloacetonitriles and haloketones were only detected at low levels, less than 7 J.lg/ L even under adverse conditions. The concentrations of dichloroacetic acid and trichloroacetic acid were found to be more significant, approaching the levels of THMs recorded. For these DBPs, it was found that at higher pHs the rate of formation and the rate of decomposition were higher leading to significant changes in concentration with pH. Chlorine residual and raw water colour did not have as significant an effect as with THMs.

PERFORMANCE MO~ITORING A particle counter was installed in the Prospect pilot plant and later in the prototype plant, mainly to assess the efficiency of the fi lters in removing particles of the size of Cryptosporidium and Giardia cysts. The particle coun~ r was found to be a useful tool in evaluating process performance. The removal efficiency of the filters for particles in the size range 2 to 350 microns was found to be of the order of 99%.

A streaming current detector was used in the Prospect prototype plant and was found to be useful in assessing coagulation performance and minimising primary (alum) and secondary coagulant (cationic polymer) doses.

On-line aluminium analysers .were found to be useful for indicating trends in aluminium concentrations in the filtered water. In laboratory studies the accuracy of results was found to be high in terms of the acid extractable aluminium fraction measured and the repeatability of results was also found to be very good.

PATHOGENS Limited testing with spikes of high concentrations of Cryptosporidium showed that high removal efficiencies (99.99%) were achieved by the coagulation and filtration process and that stopping and restarting the filters did not result in the release of any of the Cryptosporidium trapped in the filters. However, further testing is required over a range of Cryptosporidium doses before any conclusions may be drawn from these results.

CONCLUSIONS The pilot testing program conducted on the four source waters for the four proposed water treatment plants was sufficiently thorough to allow concept designs to be developed with confidence.

Contact filtration with high filtration rates as well as relatively coarse filter media was selected for all plants - in particular the proposed rate for Prospect WTW proposed was 25 m/ h. The filtration rates selected for the other plants ranged from 15 to 18 m/ h.

Pre-coagulation dosing of lime and carbon dioxide was found to be beneficial and practicable and was included in the concept designs for the Illawarra, Macarthur and Woronora WTWs. continued on page 38

TECHNOLOGY

THE STREAMING CURRENT DETECTOR IN WATER TREATMENT

by D. R. DIXON, W. BARRON, T. W. HEALY, M. PASCOE and P. J. SCALES ABSTRACT The use of streaming current detectors (SCD) as a method of controlling coagulant dosing in water treatment plants has been reviewed in a project funded by the Urban Water Research Association of Australia (UWRAA) and jointly carried out by the CSIRO Division of Chemicals and Polymers, the Advanced Mineral Products Research Centre at the University of Melbourne and the Brisbane City Council. It involved theoretical and practical studies that included laboratory tests, pilot plant trials and full scale plant operation.

A laboratory examination of several electrolytes and standard suspensions showed excellent correlation between data obtained from SCD measurements and from conventional electrokinetic techniques, namely electrophoretic mobility and streaming potential and led to the development of an improved theory of SCD measurement.

An SCD was used in extensive pilot plant trials at the North Pine Water Treatment Works in Brisbane. SCD signals responded to changes in coagulant dose and pH for alum, ferric chloride, polyaluminium chloride and two cationic polyelectrolytes. Full scale trials at Westbank Water Treatment Plant, Brisbane, confirmed these data as raw water characteristics varied during several rainfall events.

The Westbank Water Treatment Plant at Mt Crosby was the site of a full-scale plant investigation of the SCDs capacity to control alum dose. Plant parameters including alum dose, pH, raw water turbidity, conductivity and colour and SCD response were monitored. Several high turbidity and high colour events occurred during an unusually wet summer period providing an opportunity to study the proficiency of the instrument over a wide range of conditions.

Finally, the SCD was used to control alum dose on the full scale plant for a short period. It is concluded that an SCD has the capability of controlling coagulation processes, provided plant operators have sufficient working knowledge of the instrument.

Practical recommendations are made to both the manufacturers of the instruments and to operators.

INTRODUCTION Most modern water treatment plants use a coagulation stage to ach ieve clarification. Coagulants such as aluminium sulfate (alum) or ferric chloride are added and the pH adj usted to promote the formation of metal hydroxide floes which in turn result in the removal of unwanted colour bodies and turbidity particles. Unfortunately, inefficient method s of determining the optimal coagulant concentration often result in overdosing, which increases operating expenses not only because of higher than necessary chemical costs, but also because of increased sludge handling and disposal costs.

Incorrect coagulant dosing can lead to an increased residual of dissolved coagulant in the filtered water and possible precipitation within the distribution system .

Although the SCD was invented by Gerdes (1966), it has only recently been considered as an alternative to the traditional jar test method of determining optimal coagulant dose (Dentel 1988) . The aim of the present work was to examine the mechanism of operation of SCDs with a view to understanding its capability and capacity in controlling coagulant dosage in water treatment processes.

JAR TESTING Oft quoted criticisms of jar testing include (i) Changes in raw water conditions can occur more rapidly than the jar test can be performed. Or in other words, the most useful time to do jar tests is when the raw water is changing rapidly, precisely when an operator can least afford the time to do jar tests.

Dr. David Dixon is a Senior Principal Research Scientist with the CS/RO Watertek program in the Division of Chemicals and Polymers. He has a PhD from Melbourne University, in colloid and surface chemistry, and over twenty years's experience in the fields of water, wastewater and industrial effluents.

Wendy Barron is a Chemist in the Environment and Wastewater Laboratory in the Government Chemical Laboratories in Brisbane. She graduated in Applied Chemistry from the University of Central Queensland in 1989. For the duration of this project she worked at the University of Melbourne and with the Brisbane City Council.

Thomas Healy is Director of the Advanced Mineral Products Centre and Professor of Physical Chemistry at the University of Melbourne. His research interests include colloid and surface chem istry, aque ous interfaces, interfacial spectroscopy, ultrasmall co lloidal particles, stability of colloidal dispersions and the chemistry of mineral processing.

Mark Pascoe is Chemist-in-Charge, Water, Treatment, with Brisbane City Council, where he has worked for 20 years. He now manages the operation of the Brisbane Water Treatment Plants. He has postgraduate qualifications in environmental engineering and is interested in most areas of water management.

Peter Scales graduated BSc(Hons) and Ph.D from Melbourne University in 1981 and 1988 respectively. He then worked in the coal industry in colloid chemistry related areas and in the UK with JC/ Corporate Colloid Science Group. He is now managing Advanced Mineral Products Research Centre and working on a range of research topics in surface chemistry.

T his paper is a short ve rsion of th e fin al report to U WR AA , No. 44, {Barron, 1992) which co mains the complete se1 of experimental data and a more detailed interpretati on. Papers concent rati ng on the more fundamental aspects of strea mi ng cu rrent measure men ts are still to be writte n. A fu n her paper is contained in the Proceedings of the AW\VA 15th Federal Convent ion.

WATER April 1993

21

(ii) The alum added to the raw water is a fairly crude mixture of bauxite and sulfuric acid that contains a variable percentage of solids and impurities. Therefore, the exact concentration of aluminium sulfate is variable. · (iii) The jar test is performed in a stagnant flow situation whereas the full plant operates at a high flow rate.

THE STREAMING CURRENT DETECTOR In the water treatment process, aluminium or iron salts are added to raw water under carefully controlled pH conditions to coagulate particles dispersed in the water phase. The coagulation process is driven by particle destabilization which is usually achieved by inorganic coagulants via either of the following mechanisms: adsorption of coagulant to produce charge neutralisation or enmeshment in a precipitate (ie. 'sweep coagulation'), and if polyelectrolytes are used, via inter-particle bridging.

Electrokinetic phenomena are convenient for following the progress of coagulation processes. They present a clear link between the change in surface charge of particles and their coagulation behaviour (Healy 1990). Towards this end, the direct signal from an SCD has been extracted and compared with results from the classical electrokinetic techniques of particle electrophoresis and flatplate streaming potential.

An SCD is an on-line instrument capable of measuring continuously the charge on particle surfaces as coagulation proceeds.

As with all electrokinetic techniques, the magnitude of the streaming current is related to the zeta potential of a colloid or surface. Zeta potential is a difficult quantity to measure in an on-line situation as it normally requires high precision instrumentation.

The functional component of the SCD is shown in Figure 1. The creation of a streaming current is dependent upon a pressure drop

Motor

between the ends of a capillary. In an SC:D, a capillary is formed between a piston and a cylinder. The oscillation of the piston produces a sinusoidal fluid flow and consequently an oscillating pressure drop between the ends of the capillary. Electrodes at either end of the capillary detect the ionic flux caused by the fluid flow (nominally termed the streaming current) and after eleccronic processing, the result of the ionic flux is an output to an LED display.

Figure 2 shows a typical application of the SCD in a water treatment plant. The water is sampled at a point downstream of coagulant addition. The operator, or electronic controller, compares the streaming current to an optimum value which has been previously determin ed, and alters the coagulant dosage accordingly (Dentel 1989). Successful practical application of the SCD is dependent on the regularity with which the optimum value must be redetermined.

COMPARISON OF AVAILABLE

Table 1 -

Features of the three SCD instruments used in this study

~sample out Electrode

Cylinder

Piston material Bore material Piston frequency Electrode material Flow regimes• Sensiti vity Ultrasonic cleaner

Floerger (C DC)

Millon Roy (CCC)

Chemtrac

Teflon polypropylene 5 Hz silver _ in 7 out adjustable ra nge 1- 10 optional

Delrin Delrin 5 Hz stainless steel q, in 7 out adjustable gain l x,2x,5x,10x,20x opt ional

Feature

-

RANDS OF SCD

Three different SCDs were used at different stages of the project.

Other brands were available, but the opportunity to use these did not arise. The laboratory experiments and some fieldwork were performed using a 'Milton Roy' Generation 1 Coagulant Control Centre (CCC) . A 'Chemtrac' Streaming Current Monitor (SCM) was used for pilot plant experiments. A 'Floerger' Coagulant Dosage Controller (CDC) was also used for comparison. The SCM and CCC were available for the full study whereas the CDC was available for only a short time.

Each instrument has a range or gain setting by which the output sensitivity may be adjusted. For all experimental work reported, the CCC unit was set on a range setting of 1 and the SCM unit set on a gain of 5X. Table I lists the differences between the main features of the three SCD models. The effects of the differences of these features will be discussed in a later section. The ultrasonic cleaner was found to be of no assistance in the cleaning of the surfaces and was disconnected.

It should be noted that the absolute magnitude of the SCD output as a function of pH is dependent upon both the gain factors employed in the electronics, and the surface charge density of the materials of construction. It should also be stated that the units of the SCD output are arbitrary, since the exa,ct relationship between the output and classical electrokinetics has not yet been developed.

Response as a function of electrolyte concentration Figure 3 shows the SCD response as a fu nction of pH in 10-4, 10-3 and 10-2 moles dm-3 KC! solutions for one of the three SCDs.

(SCM)

Teflon Teflon 8 Hz stainless steel q, in q, out not adjustable ni l

• The sy mbol s a re intended to des ignate whether the sa mples a re in trodu ced by gravit y feed or pump1 and th e rela tive position s of the inlets and outlets to the ce ll .

10 4

• Fig. 1 -

Schematic diagram of the sensor of the SCD meas urement cell

10 M KC! a 10-3 M -2 10 M

5

• [1'J

Raw

Flocc ulation

wa ter

basins

0 Settling basi ns

u

I I

I

I

::

-10

Recorde r

Fig. 2 - Typical placement of an SCD in a process sequence for watertreatment

22

WATER April 1993

• C

High/Low alarm

I f-----~---,

-----Coagulant feed control

•

•c•

Coag ulan t reed

'-------

•

•

-5

I

+II

.

~

u u

••

C

a

•• -15

3

4

5

6

7

8

•a • 9

.

10

Fig. 3 - SCD response as a function of pH for different concentrations of KCI using the CCC

The results are in accordance with the Gouy-Chapman electric double layer prediction that zeta potential, defined as the potential at the shear plane, (t), and hence streaming current, is dependent . on the ionic composition and concentration (James 1972). The diffuse double layer is predicted to be compressed as salt concentration increases causing f to decrease in magnitude (Grahame 1947). The trends observed for the CCC unit and the SCM unit are very similar, becoming less negative with increasing electrolyte concentration. However, the CDC unit's response is observed to be positive and becomes less positive with increasing concentration of electrolyte. This suggests that the electronic arrangement is out of phase compared to the other two instruments.

Our recommendations for an 'ideal' SCD would include:• Constructing both piston and cylinder from the same material, preferably a plastic which does not become irreversibly coated with organic materials and co lour-causing substances.

• Piston and cylinder materials with a net surface charge that does not change significantly across the pH range in which the instrument is employed.

• A compact instrument whose position can be easily changed enabling its use in other areas eg. sludge thickening.

• Easy disassembly for cleaning.

• Detachable electrodes to allow for rigorous cleaning procedures.

• A flow through system with inlet at the top and outlet at the bottom of the sensor.

• A calibration standard supplied with the instrument to enable assessment of state of cleanliness.

variation in SCD response, divalent electrolytes,£ave a lower response due to their enhanced ability to compress the electrical double layer.

Silica and alumina were used as model colloids. The SCD response was consistent with electrophoretic mobilities and streaming potentials in the presence of these colloids. The SCD response for several clays also showed the predicted negative surface charge.

JAR TESTS

SCD AND OTHER TECHNIQUES

Standard jar tests were performed using raw water from North Pine Water Treatment Plant. Each 2 litre sample was adjusted to a pH of 6.5. Alum was added before flash mixing for 1 minute at 160 rpm and flocculating for 20 minutes at 30 rpm. After 30 minutes settling, 40 mL samples were filtered for turbidity measurement and the remainder were then pumped through the CCC unit.

A pilot plant experiment (described later) was then performed in which the same concentrations of alum were dosed to raw water and the pH adjusted to 6.5. The CCC unit's reading was recorded and a sample filtered for turbidity measurement. The CCC unit's response and the measured turbidities for both jar tests and pilot plant trials are shown in Figure 4. Although the respunses do not coincide, the magnitude of the change across the range of alum dose concentrations (from - 6 to - 4 for the jar tests and from - 4 to - 2 for the pilot plant trials) is similar. The difference between the jar test and pilot plant values may be attributed to a number of factors including the presence of residuals from previous experiments in the pilot plant and associated pipelines, time of contact between sample and CCC unit surfaces, and the stagnant flow of the jar test as opposed to the high flow rate of the pilot plant.

The SCD response in the presence of various electrolytes and model colloids was compared with other electrokinetic techniques.

Streaming potentials of Teflon, polypropylene and a combination of the two plastics were measured in a conventional apparatus to confirm the SCD prediction that the plastics possess a nett negative surface charge. Whereas monovalent electrolytes showed little

PILOT PLANT The pilot plant installed at North Pine Water Treatment Plant consisted of a flash mix tank, three flocculation tanks and a filtration unit. The latter was not utilised in this study. Raw water was pumped to the pilot plant at a rate of 20 000 litres/ hour. The coagulants and 2

l

X

Q

l.2

0.8

E~

~ ti:

0.8

~

I

•

0.4

I

0

I

I

-4

u

¢

1t -6

• •

• •

• •

•

I

• •

• 2

3

4

-4 ~

•• <>

u (/)

-8

jar test pilot plant

I -10

5

0

6

I

••

X

2

3

~

•• <>

X

X

4

5

<>

6

Alum Dose (mg/I)

Alum Dose (mg/I) CCC response and filtered turbidity data for jar test and pilot plant experiments as a function of alum dose

I

-2

-6

•

X

i

0

I

•

-10

Fig. 4 -

•I

I

I

-8

0

X

0.4

•

-2

u u

•• •

"O

I

~ ti:

1.2

~ :,

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:,

E~

pH 6.0 pH6.4 pH 7.0 pH 7.4

~

.2 "O

'o ii ...

"O

X

s E-

sE-

•• <>

1. 6

1.6

6-

'

X

Fig. 5 -

SCM response and filtered turbidity for the dosing of alum to the pilot plant for a range of pH conditions

WATER April 1993

23

water were pumped into a common line before being added to the raw water in the flash mix tank. A siphon from the first flocculation tank supplied the SCD with a continuous sam ple. .

Table 2 shows SCD response for the case where the water was sampled from either the flash mix or one of the three flocculation tanks. Samples were taken at the SCD outlet. The pH was recorded continuously at the SCD outlet. Sulphuric acid and potassium hydroxide were added directly to th e fl ash mix tank to adj ust the pH. The data shows minimal variation as a function of post coagulation residence time.

Tab le 2 - SCD response and pilot plant tank residence times for sa mples, taken from different flocculation tanks when dosed with 6 mg/ L alum.

SCD Response

Tank

Fl ash mi x Floc l Floc2 Floc3

-

6. 10 6.24 6.38 6.46

Residence Tim e (secs)

5 100 120 170

Raw water co nditions: Turbidit y 4.0 NT U; Colour 8.0 PCU; pH 7.65 .

T he CCC unit and the SCM unit were installed side by side on the pilot plant with separate siphons, both taking water from the first flo cculation tank . The pH was adjusted with acid to pH 6.0, t hen alkali was added to the fl as h mi x tank to slowly increase the pH to 7.4. The responses of both SCDs were similar and a representative graph as a function of alum dose is shown in F igure 5, together with the meas ured turbidities. The SCM unit gave a wider separation in response to pH than the CCC unit. The data indicates that an alum dose of about 4 mg/ I was suffi cient to reduce the turbidity to an acceptable level if the pH was kept at or below 7.0.

This corresponded to an optimal output of about - 5 for the CCC unit and - 6.5 for the SCM unit.

Similar results were obtained when either ferric chloride or polyaluminium chloride were used as coagulants in place of alum .

The SCD also performed satisfactorily with cationic polyelectrolytes the response varying in accordance with their nominated charge density. Conversely the use of non-ionic flocculants evoked a poor response, as might have been expected. Sampling from various positions along the pilot plant showed that the residence time of sampling after flocculation was relatively unimportant to the SCD output. This suggests the coagulation process is very fast once the coagulant and raw water come into contact in the flash mix tank.

The results achieved using the SCD on the pilot plant and the raw water from North Pine Dam indicate that the SCD would function well in a full scale water treatment plant, provided the plant was not dosing with a nonionic or low charged polyelectrolyte.

FULL-SCALE WATER TREATMENT PLANT SCD monitoring, Westbank Water Treatment Plant The CCC unit was installed at Westbank Water Treatment P lant and the output signal was connected to the plant's computer based control system via a local programmable logic controller (PLC).

Other parameters influencing the coagulation process were also recorded, these being alum dose, pH, raw water turbidity, colour and conductivity. The plant's computerised data acquisition system averaged readings collected each 5 seconds every 30 minutes for all parameters except colour and conductivity. T hese were taken from ¡operator measurements made approximately once every eight hou rs when raw water conditions were constant and more frequently when the raw water was changing. A complete record of this data for a period of 4000 hours is shown in the fin al UWRAA report (Barron , 1992).

Westbank d¡raws its raw water directly from the Brisbane River which has many tributaries in its catchment area. The raw water may change rapidly after storm activity. A n extremely wet summer allowed us the luxury of monitoring the plant's operations during a number of high turbidity events. The CCC unit was used in a monitoring mode only and was not controlling alum dose. The data collected until the flood of 12 February, 1992 suggest that an optimum CCC unit value of approximately -3.8 would have controlled the alum dosage successfully. It was apparent that savings on alum usage could have been made had this fi gure been employed.

It is also evident from the data that overdosing of alum occurred to ensure that the output turbidity was kept at a desirable level. This is concluded from the variations in th e signal from the optimum value. It should also be noted that control of pH was carried out using sodium hydroxide. This occurred when the alum dose required for effective treatment was such that the coagulation pH was below

24

WATER April 1993

6.5 . At other times, the pH was determined only by the alum dose (and raw water characteristics) and range<! between 6.5 and 8.0. The flood resulted in an increase in the amount of colour in the raw water and a consequent increase in alum dose. The CCC unit signal became positive for the first time and from this point the signal was extremely erratic and remained positive on average even once the colour and turbidity levels decreased. Although we have no complete explanation for this phenomena, it is believed that organic substances and colourcausing components may have coated the surfaces of the piston and cylinder rendering the instrument ineffectual. Eventually this situation was rectified by soaki ng the sensor surfaces in a concentrated caustic solution. The output signal then began to react in the expected manner, albeit, with a high noise level.

Under normal water treatment plant operating conditions, the CCC needed to be inspected every couple of days. Special care was requi red for raw waters with a high soJids loading. Inspection involved removing all parts of the measurement sensor and flushing out debris. F low through the sensor was also monitored to ensure that sample lines did not become clogged . The sensor of the CCC unit could be inspected in less than five minutes and did not require the use of any tools. When raw water conditions changed appreciably, particularly when the colour or organic content increased, the sensor surfaces were cleaned by soaking in a concentrated alkaline detergent.

A less rigorous cleanin g procedure was used for the SCM unit sensor due to a higher fluid flow through the system but it still required inspection weekly. However, it was not as easy to remove a ll water exposed surfaces. The piston was very easily removed but to access the surrounding components required some tools and time (approximately 15-20 minutes). The sample line used with the SCM unit had a wider internal diameter which decreased the frequency of clogging but did need to be checked regularly. The sensor surfaces of the SCM unit are constructed from Delrin. This materia l did not foul and lose its sensitivity as easily as the Teflon and polypropylene surfaces of the CCC unit.

Alum dose A manual adjustment of alum flow was made to observe the response of th e CCC unit in a full plant trial. Output signal , pH and actual alum flow were recorded and are shown in Figure 6. As the alum flow increased, the pH decreased 'and the CCC unit signal increased. As the alum flow decreased, the pH increased and the signa l decreased The change in signal occurred approximately 5-10 minutes after the change in a lum flow was instigated .

Using SCD to control the alum dose in a plant The alum dose being supplied to one of the two flocculation basins at the Westbank water treatment plant was controlled using the SCD. A n a lgorithm, consisting of a double Proportional Integral Derivative loop, was written for this purpose (Beyers 1992). The alum flow was given a setpoint which was determined by operator knowledge of optimal conditions. The a lum flow setpoint was controlled by the SCD which was given a setpoint determined by previous monitoring of the plant. Every ten minutes, the difference between the SCD setpoint an d SCD actual was compared by computer. If the error between the two numbers was above a predetermined valu e, the alum flo w setpoint was changed automatically by a predetermined amo unt. The changes were made - 1.5

9.0

-2.0

6.45

c

Cl

-2.5

u

~

8.5

3'

Cl)

:c

0

,;::

C.

E :::, .; -3.0

6.35 8.0

-3.5

time(min)

Fig. 6 -

Alum flow, pH and SCD response as a function of time when alum flow was adjusted manuall y

at ten minute intervals as it took 10-15 minutes for any change in alum flow to affect the SCD output. The time interval used was adjustable and was dependent on the positioning of the SCD sample . line in the flocculation basin .

The alum flow was controlled using this algorithm for one day.

The raw water conditions did not change appreciably during this period. The trial proved successful although savings in alum usage were estimated to be minimal during such a period of little change.

During a further trial, a freak event occurred when raw water conductivity increased from 330 Âľmhos to 600 Âľmhos over a short time. The SCD reading decreased in accordance with this conductivity change due to compression of the electrical double layer.

The change in SCD reading did not represent a need to decrease alum flow.

This is one of the pitfalls of SCD operation that had not been programmed to the algorithm . In the absence of such an algorithm, the event would normally set off the low alum flow alarm and the operator would switch back to manual operation until the event had passed or a new SCD setpoint was determined. Conductivity increases at the Westbank water treatment plant are usually well anticipated after rainfall events but not on this particular occasion.

Although incomplete, the data collected from all sources suggests that, with an adequate working knowledge of the SCD and factors affecting output from the instrument, it has the capacity to provide all the claimed benefits.

CONCLUSIONS (a) Comparison with other electrokinetic techniques Excellent correlation was observed between SCD response, streaming potential and electrophoretic mobility measurements on the same systems. The predicted true streaming current and the output from the SCD electrodes showed similar trends but no absolute correlation was found. This result is considered to be fortuitous for SCD manufacturers. The theoretical basis of SCD measurement is not well understood but significant progress has been made. (b) Laboratory Trials The jar tests performed with the Milton Roy CCC unit gave a similar response to that achieved by the same instrument on the pilot plant. The magnitude of the signals in each case differed . This was attributed to a number of factors and once again exemplifies the difficulties in relating jar test results to a full scale operation.

However, the magnitude of the change in the signal when alum dose was increased was similar for both jar test and pilot plant. Under normal operating conditions with stable raw water quality, the introduction of an SCD would obviate the need for jar testing, provided good correlations with plant operating efficiency had been established. (c) Pilot Plant trials Excellent results (Barron, 1992) were obtained for a range of coagulants and polyelectrolytes with the SCD installed on the pilot plant. There was a significant change in signal with corresponding change in dose except in the case of nonionic polyelectrolytes. With cationic polyelectrolytes, the SCD signal changed in proportion to the charge density of the polyelectrolyte. (d) Plant Performance Limited data was collected from full plant trials with the SCD controlling alum dose. This was attributed to difficulties in preparing an algorithm capable of performing the task for the particular setup. These trials are ongoing. The short period for which the plant alum dose was controlled by the SCD was considered successful.

The plant was monitored by the SCD for some months to identify problems likely to be encountered.

The major problems identified were: 1. Large increases in colour and/ or organic matter in raw water may cause coating of SCD sensor surfaces, increasing the demand for rigorous cleaning procedures.

2. Changes in conductivity of the raw water causes a change in SCD signal that does not necessarily require a change in the coagulant dose.

3. As with the case of conductivity, changes in pH will affect the SCD signal, although not significantly in the pH range 6.0-7 .5.

These factors imply that a sudden large change in raw water conditions may not be dealt with successfully by an SCD unless a sufficiently detailed algorithm had been previously devised. However, even without complex algorithms, substantial savings in alum could be made by controlling alum flow with an SCD after.the turbidity,

conductivity and/ or colour from a major rain~ll event have peaked and begun to subside. During this time, a plant is normally overdosed due to difficulties in predicting the rate of decrease of the turbidity. (e) Overall recommendations On balance, we would recommend the use of SCDs in water treatment plants as a cost effective way of reducing coagulant dosage, and the resultant on-going costs associated with overdosing. We would nonetheless suggest that the following points be noted.

A regular cleaning and checking of sample lines be undertaken to prevent clogging and blockages.

The sensor surfaces be soaked in concentrated alkaline cleaning solution if they have been exposed to highly coloured or high organic content water.

Manual control be invoked under conditions where raw water conditions change rapid ly over a short time period.

Operators should be aware that the SCD signal also responds to changes in pH and conductivity.

We would also like to see the instrument modified to make the electrodes removable. A further suggestion is that the plastics which constitute the piston and cylinder be both removable and easily and cheaply replaceable (ie modular change-over units).

ACKNOWLEDGMENTS The financial assistance of the Urban Water Research Association of Australia is gratefully acknowledged.

The authors would like to thank the Australian Research Council for funding and the Brisbane City Council for the provision of research facilities for this project. The technical assistance of Mrs B. Bornstein of the University of Melbourne, the theoretical input from Professor L. R. White, Department of Mathematics, University of Melbourne and the on-going communication with Dr Steve Dentel of the University of Delaware were much appreciated.

REFERENCES Barron , W., Healy, T. W., Scales, P. J., Murray, 8. S., Di xon, D. R. , and Pascoe, M ., UWRAA Report 1992.

Beyers, G. (1992) Alum dose control via SCD algorithm Westbank Water Treatment Plant, Mt Crosby, Bri sbane. , Dentel, S. K., Gossett, J. M. (1988) JAWWA April 187-198 Dentel, S. K. , Kingery, K. M. (1989) JAWWA 8:85-94 G erdes, W. F., (1966), 12th Natl. Analysis Instrument Sym, Houston, Texas, May 1966.

Grahame, D. C. , (1947), Chemical Reviews, 41 :441 H ealy, T. W. , Metcalfe, I. M., (1990), J Chem. S..oc. Faraday Disc. , 90:335- 344 James, R. 0. , Healy, T. W. (1972) J Colloid ana Interface Sci., 40:53-64

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AVAILABLE Water Journal is pleased to announce that AWWA's Federal Office has been appointed to manage its advertising sales and accounts.

Enquiries should be directed to: Margaret Bates Australian Water and Wastewater Association PO Box 388, Artarmon NSW 2604 Telephone (02) 413 1288 Fax (02) 413 1047

WATER Apr il 1993

25

TECHNOLOGY

THE EFFECT OF WATER STABILISATION ON COPPER CORROSION IN GEEWNG

by M. MUNTISOV and G. WILLIAMS SUMMARY Data on copper corrosion in Geelong has been analysed following the introduction of water treatment and partial water stabilisation.

Copper corrosion in water services, as measured by the copper concentration in sewage at Geelong's sewage treatment plant has reduced by 60% which corresponds to a reduction in the copper corrosion rate of 30 g/ water service/ annum. The significant red uction in copper corrosion has occurred even though the treated water has a slightly negative Langelier Index. This suggests that the absolute bicarbonate concentration may be an important factor in corrosion control at least in the concentration ranges considered in this paper. The reduced copper corrosion cou ld achieve savings approaching $1 million/ annum for Geelong residents. Potential impacts of water stabilisation on sewage treatment and disposal have been identified and include reduced heavy metal concentrations in effluents and sludge, and changed phosphorus loads due to altered detergent/ washing powder usage patterns.

INTRODUCTION The Geelong & District Water Board is responsible for the supply of water to the city of Geelong, Victoria, serving a population of 196 000. The Board operates two main water sources. The major source is from the Barwon River catchment which rises in the Otway Ranges. The other source originates in the Moorabool River system.

The Board also has a groundwater source which is used only when demand necessitates.

The water of the Barwon system, which supplies approximately 750Jo of Geelong's water requirements, is relatively soft and low in mineral content when compared with the Board's other sources but suffers in varying degrees from turbidity caused by suspended clay particles. The water is aggressive to concrete and corrosive to metals.

A summary of historic water quality at Wurdee Boluc Reservoir, which is the final Barwon Headworks storage prior to the Geelong distribution system is given in Table I. Table 1 - Wurdee Boluc Reservoir Average Water Quality 1981 TO 1991 C haraclersitic

pH True co lour Turbidity Hardness Total Alkalinity Iro n Calcium Manganese Ch loride Sulfate Langelier Index

(Hazen units) (NTU) (mg/ L CaC03) (mg/ L Ca C03) (mg/ L) (mg/ L) (mg/ L) (mg/ L) (mg/ L) (approx)

Average

Maximum

Minimum

7.2 23 18 30 23 1.5 4.8 0.02 35 5. 1 -2.4

8.2 60 82 60 38 8.8 11.0 0.45 57 21 -0.8

5.7 5 3 24 7 0.3 0.6 0.00 27 0.4 -5

As part of the Board's water quality program, a 260 ML/ d contact filtration plant using pressure filters was constructed at Wurdee Boluc Reservoir in 1991. Details of the plant are provided by Muntisov, Williams & Crockett (1993).

A feature of the new plant was provision of lime and carbon dioxide dosing to stabilise the filtered water. By stabilisation is meant chemical treatment to adjust water to a desired non-corrosive state.

CORROSION INDICATORS pH A range of guidelines have been suggested for pH in order to minimise corrosion. AWWA (1976) suggests a pH value in the range of 6.8 to ¡1.3 for a well conditioned water, and avoidance of the range

26

WATER April 1993

Michael Muntisov is a Senior Water Treatment Engineer at Gutteridge Haskin & Davey's Melbourne office. He was the design manager for the Wurdee Boluc Water Treatment Plant project.

Gwyn Williams is Engineering Manager, Special Projects, at Geelong and District Water Board. He was project manager for the Wurdee Boluc Water Treatment Plant project and is currently managing the design of the upgrade of the Black Rock Sewage Treatment Plant.

8.0 to 8.5 because of the low buffer capacity in this range. Holm et al (1982) suggest a pH range of 8 to 8.5 to minimise pitting of copper in hot water systems.

Moss & Potter (1984) found that' to passivate copper surfaces in cold potable water, the pH value needs to be raised to 8.3 (for TDS < 520 mg/L) to counteract the activating effects of dissolved sulfate and chloride. When no sulfate is present the protective pH value fell to 7 .3 .

By contrast Gilbert and Wildsmith (1982) report evidence of copper pitting in cold water with a pH of 8.4. More recently work by the Hunter Water Corporation has led to its adoption of a guideline value for treated water of7.6 to 8.0 (Nicholas, 1987). ;rhe suggested upper limit is imposed to restrict the formation of dezincification product (meringue) which can block fittings at pH >8.5.

Barwon water has an average pH of 7 .2 but is known to be corrosive to metals and aggressive to concrete. The above evidence suggests that although useful as a rough guide, pH alone is not a sufficient indicator of the corrosion potential of water.

Langelier Index and Carbonate Chemistry Although there are at least 12 corrosion indices identified in the literature (Naylor and Nicholas, 1991) the Langelier Saturation Index (LI) remains the best known . It is defined as follows: LI = pH-pHs where pH is the measured pH of the water, and pHs is the theoretical pH which would result if the water is brought into equilibrium with respect to calcium carbonate saturation, given the alkalinity and calcium concentration of the actual water.

A negative LI indicates a water which will have a tendency to dissolve calcium carbonate and is thus likely to be aggressive to cementitious materials. A positive LI indicates a water which is supersaturated with respect to soluble calcium carbonate and will tend to precipitate a layer of calcium carbonate on conduits carrying the water. This layer can provide a form of protection against corrosion for all types of conduit materials, although the morphology of calcium carbonate precipitation is difficult to control.

One suggested objective is to stabilise a water so that it has a LI of zero to slightly positive, the target positive LI value being

determined by a desirable CaCO 3 precipitation potential with suggested ranges being 4-10 mg/ L (AWWA, 1976) and 4 mg/ L (Lowenthal et al, 1986). To minimise chemical costs and prevent scaling in hot water systems, a slightly negative LI has been suggested as a more practical guideline for Australian and New Zealand waters (Nicholas, 1993, Stevenson, 1983). Experimental evidence suggests that despite the negative LI there is sufficient bicarbonate ion to stabilise a passivating copper tube surface oxide film (Naylor & Nicholas, 1991).

Another suggested objective related to the carbonate chemistry of the water is to achieve calcium and alkalinity values of 40 mg/ L (AWWA, 1976) or 50 mg/ L as CaCO 3 (Lowenthal et al, 1986) in order to enhance passivation and minimise corrosion. For calcium, this equates to a minimum concentration range between 16 mg/ L and 20 mg/ L as Ca. The average LI of the Barwon system raw water is approximately -2.4 as shown in Table 1 with a maximum value of -0.8 and a minimum of about -5. It should be remembered that LI is measured in logarithmic units, so that each unit change in LI represents a tenfold change in relative ion concentration.

The Barwon system raw water is relatively low in alkalinity and calcium, compared to desirable levels with average values of 23 mg/ L and 11 mg/ L respectively (as CaCO 3).

By these measures, it is confirmed that Barwon raw water is aggressive to cement lining and concrete, and corrosive to metallic conduit materials.

Chlorides and Sulfates It is well understood that under certain conditions chloride and sulfate ions can stimulate the rate of corrosion and inhibit passivation of metal surfaces. It is thought that the presence of chloride and sulfates prevents or disrupts the formation of sound passivating layers on metal. A significant amount of work has been carried out on this subject in Australia particularly with copper corrosion (eg.

Moss & Potter, 1984, Nicholas, 1990). It is generally agreed that the relative concentrations of chloride, sulfate and bicarbonate can provide an indication of corrosion and pitting potential for copper.

One guideline suggested for stabilised water is to limit the ratio (CJ-+ SO/Valkalinity ~n milliequivalents• to less than or equal to 0.2 if possible, to prevent corrosion of ferrous metals (Lowenthal et al, 1986).

Other suggested guidelines include maintaining the ratio of chloride to alkalinity at 0.33 or less to minimise dezincification of brass fittings (Stevenson, 1983) and the ratio of sulfate to bicarbonate of 1 or less to minimise pitting of copper in hot water systems (Mattson and Fredriksson, 1968). The latter ratio appears to be high given pitting failures recorded in waters complying with this value (eg. Sato et al, 1982), and a ratio not exceeding 0.2 is more in line with Mattson and Fredriksson's own data.

The average chloride and sulfate ion concentrations in Barwon system raw water are moderate, 37 mg/ Land 5 mg/ L respectively.

The relatively low alkalinity results in average ratios of er- + SO/to alkalinity of approximately 2.4, chloride to alkalinity of 1.5, and sulfate to bicarbonate of 0.4. By these measures the raw water is expected to be corrosive to metals including copper.

Cost of Corrosion By the various corrosion indicators discussed above, the Barwon system raw water is corrosive to metals and aggressive to cement and concrete. This is confirmed by actual experience in the Geelong distribution system .

Of particular concern in the Geelong region has been corrosion of copper hot water cylinders and services. Copper hot water cylinders are now rarely installed and glass-lined cylinders are most common. However, these lined cylinders are reputed to have had a short life of 7 to 8 years in Geelong compared to a normal life expectancy of 10 to 15 years in most Australian capital cities. The average annual cost to Geelong residents of this shortened life expectancy in hot water services was estimated to be $1.1 million pa (GDWB, 1988).

In city buildings, 'green water' has been a problem at the start of the working week, particularly in the cold water supply. As a result refrigerated water drinking fountains have had to be removed.

Some dezincification has been experienced. Indeed, brass manufacturers developing dezincification-resistant alloys have used Geelong water for testing their products. (Bitcon,1982). Current plumbing regulations in Geelong require that new brass components be made from dezincification-resistant alloys.

Inspection of concrete surfaces exposed to water indicated signs of attack although no comprehensive survey o?cost data is available.

OPTIONS FOR STABILISATION Evaluation In the design of the Wurdee Boluc Water Treatment Plant, a total of eight chemical dosing options were considered including: • conventional alum and polyelectrolyte dosing with lime for pH control • ferric sulfate in lieu of alum as the primary coagulant • cationic polyelectrolyte as a fu ll or partial alum replacement • full or partial stabilisation with CO 2 and lime for the above options.

It is worth noting that provision of coagulation-based water treatment and chlorine disinfection has several effects which can make treated water more corrosive. Firstly coagulation treatment using alum or ferric sulfate increases the sulfate concentration making the water potentially more aggressive to copper. Secondly, it lowers the pH and alkalinity of the water usually requiring some form of post-alkali addition. Finally, because the colour organics present in the raw water can inhibit corrosion (Lowenthal et al, 1986), removal of colour by water treatment can therefore increase the corrosivity of the water. In addition, chlorination slightly increases chloride levels and free chlorine residuals are also implicated in increased corrosion activity.

From the dosing options a short-list of the three most economical options were further developed. These were based on conventional alum and polyelectrolyte dosing and varied only in the degree of stabilisation provided after fi ltration. The different degrees of stabilisation considered were: 1. lime addition only to a target pH of around 8.3.

2. partial stabilisation: lime and CO 2 addition to achieve an LI of approximately -0.3 and a pH of approximately 8.3.

3 . fu ll stabilisation: lime and CO 2 addition to achieve an LI of 0 and a pH of approximately 8.3.

Carbon dioxide addition is necessary to stabilise this soft water. pH limits constrain the quantity of lime alone that can be added to stabilise soft water. By using carbon dioxide to lower the water pH while at the same time maintaining its alkalinity, sufficient lime can to be added to achieve the degree of stabilisation required .

Table 2 summarises the predicted chemical changes in the raw water fo llowing the three treatment options and provides estimated • chemical costs (GHD, 1988).

Table 2 Para meter

True Colour Tu rbidity pH

(Haze n) (NTU)

A lka li nit y TDS Sod ium Magnesium Ca lcium C hloride Sulfate Bicarbonate Hard ness

(mg/ L Ca C O 3) (mg/ L) (mg/ L) (mg/ L) (mg/ L) (mg/ L) (mg/ L) (mg/ L) (mg/ L CaCO 3

Indicators La ngelier Index er /A lka li nit y s o / 1Hco 3er + s o /-/A lkali nity Chemical Doses A lum Polye lectro lyte Lime Carbon dioxide

Predicted water chemistry Raw Wate r

Opt ion 1

Option 2

Average

Li me Onl y

Partial

Full

Sta bilisati on

Sta bilisati o n

8.3

3 1 8.6

3 I 8.5

27 108 27 4 II 37 12

45 129 27 4 18 37 12

57 144 27 4 22 37 12

44

60

72

-0 .8 1.4

-0 .3 0. 8

0 0.6

2.4

1.4

1.1

17 0. 15 8

17 0. 15 20 14

17 0 .15 29 25

$250 000 $6.25

$470 000 $ 11.75

$650 000 $16.25

23 18 7 .2 24 95 27 4 6 37 5 15 32

-2.3 1. 5 0.3 2 .4

(mg/ L) (mg/ L) (mg/ L) (mg/ L)

Chemical Cost (1988 dollars) $p.a . (40 000 ML p.a.) $/ ML

Option3

WATER Ap ril 1993

27

Table 2 shows that without carbon dioxide addition (Option I) the treated water alkalinity is only slightly higher than the raw water condition and still below the guideline value of 40 mg/ L. The Langelier Index is reduced from -2:3 to -0.8 due to the increase in calcium, but the calcium concentration remains below the guideline values. The ratio of sulfate to bicarbonate would increase due to the use of alum as the primary coagulant which significantly increases the sulfate concentration of the water.

Option 2 (partial stabilisation) provides for a reduction in LI to -0.3, a reduced ratio of chloride and sulfate to bicarbonate and alkalinity, and an alkalinity complying with the guideline value of 40 mg/ L. The minimum guideline value for calcium is also achieved.

The estimated cost to achieve this additional degree of stabilisation is nearly twice the cost of the lime-only option. This equates to an additional estimated annual cost of $220 000 pa or an extra $5.50/ ML (0.55c/ kL). This should be considered in the context of the overall operating cost of water treatment which for Geelong is about $25/ ML including partial stabilisation.

Option 3 (full stabilisation) achieves a LI of zero, alkalinity and calcium of over 40 mg/ L (as CaCO 3) and lower ratios in relation to chlorides and sulfates. On the negative side, the predicted water hardness would be more than twice the raw water value. Scaling of hot water systems and noticeable effects on industrial boilers could be expected, as well as generally increased detergen t use. The estimated annual cost to go to fu ll stabilisation is more than two and half times greater than the lime-only option . The additional estimated annual cost is $400 000 p.a. or an extra $10/ ML (lc/ kL).

Selected Option In the design of the Wurdee Boluc Water Treatment Plant the partial stabilisation option (Option 2) was selected as a first stage in providing improved corrosion protection for the Geelong distribution system. The additional chemical costs associated with partial stabilisation were justified against cost of corrosion previously experienced in Geelong, estimated to be more than $1.1 million.

Partial stabilisation also has the advantage of minimising the increase in water hardness and hence minimising scaling and increased soap and possibly detergent use, while still providing a significant degree of corrosion protection.

Facilities for achieving partial stabilisation of the treated water were provided at the Wurdee Boluc Water Treatment Plant. These facilities included: • a 60 tonne lime silo, day bins and feeders • a 25 tonne liquid carbon dioxide storage vessel • carbon dioxide feeder and dissolving system in a dedicated feeder room.

These systems were designed to permit future upgrading to full water stabilisation, if necessary.

15 mg/ Land 9 mg/ L respectively. This is about 70% of the predicted dose and explains, to a degree, the lower average LI of -0.7 actually achieved compared to the -0.3 value used in Table 2.

Effect on Copper Corrosion

Reduced Corrosion. The changed water quality and reduced corrosiveness has had a marked impact o·n copper corrosion in ~··-

9

~\t f·5 vfi~·~~ , ·-Pre Trealm8rlt Plaril

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Aug-87

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May-90 DATE

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.-----------,.=-----,------~

1c

EFFECT OF STABILISATION Effect on Water Quality Figures la, lb, le show the actual impact on water quality in the Geelong system following commissioning of the water treatment plant. This data is taken from Pettavel Basin which is the first service reservoir receiving water from Wurdee Boluc. Water in this basin has been chloraminated. The water quality in this basin is representative of the water in Geelong's distribution system.

What is evident from these graphs is that the water pH has increased from an average value of approximately 7 .2 prior to plant commissioning to a pH generally in the range 8 to 8.5. The low pH recorded in late 1992 was due to the need to take the lime system off-line for repairs.

The graph of Langelier Index reveals an increase in the index from a range of -1.5 to -2.5 prior to commissioning to a range of O to -1 afterwards. Again the low readings in late 1992 were due to lime system repairs.

The graph of the ratio of chlorides and sulfates to alkalinity shows little change in trend since commissioning. This is due to higherthan-expected alum doses initially required due to the poor raw water quality, particularly colour, experienced in Wurdee Boluc Reservoir since completion of the Reservoir enlargement works in 1991. The peak in this ratio between late 1989 and mid 1990 was due to an increase in chloride levels and a decrease in alkalinity in the raw water which are attributed to the reservoir enlargement works being carried out at that time.

Table 3 shows the average water quality of the raw and stabilised water since plant commissioning. The average doses of lime and carbon dioxide applied in the 12 months since commissioning were

28

WATER April 1993

Pre Treatment Plant

0

'-----------~--~-L---~---__J

Mar-86

Aug-87

Dec-88

May-90 DATE

Sep-91

Jan-93

Jun-94

0.4

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u 0

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.

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Dec-88

May-90 DATE

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Jan-93

Jun-94

Fig. 1 - Water quality (a, b, c) and sewage (d) parameters before and after water stabilisation in November 1991

Table 3 -

Average water quality since 1991 Raw

C haracteri stic

Treated , Stabili sed and

(Wurdee Boluc .Reservo ir)

Disinfected

(Pellavel Basin )

pH True Colour Turbidity Total hardness Total Alkalini ty Iron Calcium Manganese Ch loride Su lfate Langelier Index

(Hazen units) (NTU) (m g/ L CaC0 3) (mg/ L CaC03) (mg/ L) (mg/ L) (mg/ L) (m g/ L) (m g/ L) (approx)

7. 2 59 16 32 24

8.3

1.3 53 33 0.2 14 0.01 34 17 -0.7

1.3 4. 8 0.02 37 4.2 -2.3

Geelong. A broad measure of this improvement is demonstrated in Figure ld which shows the concentration of copper in sewage entering the Black Rock sewage milliscreening plant which receives all of Geelong's sewage.

The mean copper concentration in sewage reaching Black Rock has. reduced from 0.19 mg/ L (std dev 0.042 mg/ L) prior to commissioning of Wurdee Boluc Water Treatment Plant, to 0.07 mg/ L (std dev 0.024 mg/ L) since June 1992. This corresponds to a 60% reduction in copper concentration. The data suggests that the copper concentration is continuing to fall and is yet to reach an equilibrium level. This result leads to the hypothesis that the passivation of copper services due to increased calcium and alkalinity is a slow process particularly when partial stabilisation is practiced.

This reduction in copper concentration corresponds to a reduction in mean copper discharge of 6.6 kg / day which equates to approximately 30 g/ service/ year if the difference is attributed entirely to reduced copper corrosion.

Other Sources of Copper Reduction. A review of raw water copper levels in Wurdee Boluc Reservoir showed that the average copper concentration was between 0.01 and 0.02 mg/ L. Even if this is totally removed in the treatment plant coagulation process, it does not account for the average change of0.12 mg/ Lin copper concentration measured at Black Rock.

Finally, no relevant trade waste dischargers were found to have closed down since the Wurdee Boluc plant was commissioned.

Indeed, the pre-stabilisation concentration of copper is comparable with background domestic sewage levels measured in other untreated soft water supplies in Australia (AWRC, 1992) and in domestic sewage previously measured in Geelong.

Other Metals. Using a similar approach described previously for copper, the impact on other metals susceptible to corrosion was also evaluated. Measurements of lead and cadmium at Black Rock showed no evident change following implementation of water stabilisation. However, trends are apparent for lower iron and zinc.

In the case of iron any reduction might be attributed to the removal of iron by water treatment as is evident in Table 3. Zinc shows a consistently lower trend since 1986, possibly due to ongoing replacement of galvanised fittings and the use of dezincificationresistant alloys, as well as reduced trade waste discharges. At this stage there is no evidence of any effect due to water stabilisation.

Costs of Stabilisation The costs of providing water stabilisation must be viewed in comparison with the cost of providing conventional pH correction after water treatment.

In these terms, the actual additional capital cost to implement partial water stabilisation of the 260 ML/ d Wurdee Boluc water treatment plant was of the order of $130 000 to provide for larger lime equipment and a carbon dioxide facility.

The actual additional operating cost of partial stabilisation is made up as follows: Additional lime usage $35 000 est.

Carbon dioxide usage $40 000 Lease of CO 2 vessel $12 000 Additional power $18 000 est.

Additional maintenance $5 000 est.

TOTAL $110 000 pa @ 23 100 ML p.a.

(12/ 91 to 11/92) OR $ 4.76 / ML (0.48 c/ kL)

This additional cost of $110 000 p.a. compares with the estimated cost of corrosion to the Board and the community of in excess of $1.1 million p.a. prior to implementing water stabilisation. The data presented in this paper confirms that the cost of corrosion will be significantly reduced due to water stabilisation, and savings approaching perhaps $1 million p.a. could be achieved in hot water systems alone.

DISCUSSION There has clearly been a significant reduction in copper corrosion in the Geelong water supply system since the implementation of partial water stabilisation. The majority of this reduction may have occurred in hot water system components, given the short life of hot water systems generally experienced in Geelong prior to the implementation of water stabilisation. An alternative dominant mechanism could be a reduction i,.1 pitting of cold water copper piping due to stabilisation of the copper oxide protective film (Nicholas, 1993).

Similar reductions in copper corrosion were recorded when water stabilisation was implemented in the City of Fort Collins, Colorado, USA (Kuchenrither et al, 1992). In that case the level of copper in the drinking water reduced from an aver~ e of 0.047 mg / L to 0.012 mg/ L after stabilisation. A significant resultant impact at Fort Collins was the reduced copper concentration in the city's digested sewage sludge. It was reduced from an average of 1140 mg copper/ dry kg to an average of 850 mg/ kg after water stabilisation. This reduction in copper loading increased the site life of the city's sludge disposal site by 25%.

Similar benefits could apply in Australia where copper or other heavy metals in sewage sludge may limit its beneficial use or increase allowable land application rates of sludge.

Water stabilisation could also have other influences on sewage treatment. First, the increase in water pH cou ld be translated into a higher sewage pH. This can increase the fraction of total ammonia that is un-ionized . (Kuchenrither et al, 1992). However the practical impact of this on nitrification or ammonia removal at the waste water plant is likely to be minor.

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pH (a) and Total Phosphorus (b) in sewage at Black Rock Sewage Treatment Plant before and after water stabili sation in November 1991

WATER Ap ril 1993

29

We're going In to

B.A.T. for AUSTRALIA

the Best Available Technologies are:

TROJAN -

u.v. EFFLUENT

DISINFECTION

PI CA -

ACTIVATED CARBON

ODOUR CONTROL CHEMICAL SCRUBBING TOWERS WITH LEADING EFFICIENCY LANPAC MEDIA BIOLOGICAL ACTIVATED CARBON FOR WATER TREATMENT AND CHLORINE USAGE REDUCTION

LANPAC -

MEDIA FOR TRICKLING FILTERS

AND BIOLOGICAL TOWERS SEWER STORMWATER OVERFLOW SYSTEMS SLUDGE LEVEL AND SUSPENDED SOLIDS MONITORING

Secondly, the increased hardness of ~tabilised water can affect soap, detergent and washing powder use and hence the amount of total phosphorus in the sewage. This could also have an influence on waste water treatment plant design and operation.

Figure 2a, 2b show the sewage pH and total phosphorus measured at Black Rock before and after partial water stabilisation. There has been no noticeable change in sewage pH but total phosphorus to Black Rock has reduced slightly since water stabilisation was introduced. The reason for any reduction in total phosphorus is difficult to identify, although it could be related to the cleaner water following treatment and consumer perceptions that less washing powder may be required. In any case, this data raises some interesting implications for waste water treatment and disposal arising from water treatment and stabilisation.

In summary, the wastewater issues of heavy metal concentration in effluent and sludge, nitrification reqajrements and phosphorus loads can all be influenced to some degree by water stabilisation.

This indicates that wastewater issues can be important considerations when assessing the costs and benefits of water stabilisation and should be taken into account where appropriate.

SUMMARY AND CONCLUSIONS The raw water of the Barwon system supplying the City of Geelong is naturally aggressive to cement and concrete and corrosive to metals including copper. Three options for water stabilisation of Barwon water were evaluated, and a partial stabilisation system was adopted.

Partial stabilisation was implemented in 1991, as part of the new 260 ML/ d Wurdee Boluc Water Treatment plant which treats Barwon Water. The capital cost of partial stabilisation compared to conventional pH correction was of the order of $130,000 and the actual additional operating cost has been $4.76 / ML (0.48 c/kL.) Since the implementation of partial stabilisation, copper corrosion in the Geelong water supply system has reduced significantly. The copper concentration in sewage at Geelong's sewage treatment plant has reduced by 60% and a continuing reducing trend is apparent.

The measured reduction in copper concentration corresponds to 30 g/ water service/ annum .

This significant reduction in copper corrosion achieved by partial stabilisation confirms that an increased bicarbonate concentration and a slightly negative Langelier Index can provide substantial improvements in corrosion protection.

Additionally, the reduction in c'opper corrosion has been achieved despite relatively unchanged ratios of chloride and sulfates to alkalinity and bicarbonate. This may suggest that the absolute bicarbonate concentration is more important than its ratio to chlorides or sulfates, in the concentration range considered in this case.

The reduced copper corrosion could achieve savings to Geelong residents of up to $1 million p.a. which alone justifies the implementation of water stabilisation.

• Potential impacts of water stabilisation on sewage treatment and disposal have been identified and these include: • reduced heavy metal concentration in sewage sludge and effluent • possible increased sewage pH • change in total phosphorus due to changed detergent/ washing powder usage patterns.

These factors should be considered, if appropriate, when economic evaluations of water stabilisation are carried out.

ACKNOWLEDGMENTS

NO POL

FINE BUBBLE AIR & OXYGEN DIFFUSERS

CENTROX

OXYGEN AND AIR INJECTION SYSTEMS

PROCESS AND POLLUTION CONTROL P/L 49 NOBLE STREET WILSTON OLD AUSTRALIA TELEPHONE 07 356 3098 FAX 07 356 3096

The authors wish to acknowledge the reviews and comments on early draft sections of this paper by Mr David Nicholas (Hunter Water), Mr Ian Lowther (Geelong and District Water Board) and Mr Jonathan Crockett (GHD).

REFERENCES Australian Water Resources Council (1992) Draft Guidelines for Sewerage SystemsAcceptance of Trade Wastes (Industrial Wastes).

American Water Works Association (1976) Corrosion Control By Deposition of CaCO 3 Films, A Handbook of Practical Application and Instruction. Denver, Colorado.

Bitcon, J. C. (1982) The Development of Forgeable Dezincification Resistant Brasses in Australia, Proceedings of the International Symposium on Corrosion of Copper and Copper Alloys in Building, Tokyo.

Geelong and District Water Board (1988) Wurdee Boluc Water Treatment Plant Stage 1, Proj ect Justification Report.

Gilbert , P. T. and Wildsmith, G. (1982) Avoidance of Pitting Failures of Copper Water Tubing, Proceedings of The International Symposium on Corrosion of Copper and Copper Alloys in Building, Tokyo.

cominued on page 33

30

WATER April 1993

MANAGEMENT A PLANNING SCHEME FOR BALLARAT'S WATER CATCHMENTS

by R. J. FORD THE BALLARAT WATER SUPPLY The Ballarat Water Board draws water from a network of surface reservoirs built between 1862 and 1952 located north-east of the City on the southern slopes of the Great Dividing Range.

The catchments for these reservoirs comprises approximately 10 000 hectares of red volcanic soil and is almost wholly within the shire of Bungaree. The Board has management of only 2875 hectare s, principally in the immediate vicinity of its reservoirs and channels. The balance is privately owned land used for agriculture.

In 1968, when additional water was required for Ballarat and Geelong, the State Government created a new authority, the West Moorabool Water Board, to construct and operate the Lal Lal Reservoir. This reservoir is located on the West Moorabool River about 26 km south-east of Ballarat and is downstream of three of Ballarat's oldest reservoirs.

Water is purchased in bulk by the Ballarat Water Board and the Geelong and District Water Board from the West Moorabool Water Board to augment their own resources.

The catchment of the Lal Lal Reservoir is almost exclusively private land, 1200 hectares of which lies within the Shire of Bungaree and 19 000 hectares in the Shire of Buninyong.

The catchment areas also contain approximately 2000 separate allotments which were created last century. Many farms comprise a number of separate saleable titles permitting farmland to be fragmented without the usual approvals that would be required for a subdivision.

The Municipal Planning Schemes of the Shires of Bungaree and Buninyong generally permitted a house to be erected on each allotment if Council was prepared to grant a permit. Councillors came under intense pressure from landowners to allow a house.

To protect its catchment the West Mo?rabool Water Board had appealed agamst some 35 decisions of Council to grant permits for houses. The Appeals Tribunal, in approximately 750/o of cases, supported the Board.

PLANNING SOWTIONS The two Water Boards requested the two Shires to amend the Planning Schemes to designate the Boards as formal Referral Authorities for those permit applications that may impact on water quality. This would have required the Shire to, in effect, obtain the Board's approval although landowners or developers would have the right to appeal. The Shires advised they were opposed to such a proposal but the Shire of Bungaree suggested that it would be prepared to consider modifying its Planning Scheme to include specific conditions for

Bob Ford is the Engineer-in-Chief of the Ballarat and West Moorabool Water Boards. He graduated B.Eng. (Hons), B.Sc. and Dip. Bus. Admin.

He worked initially for GHD in Sydney, then as their Supervising Engineer in Canberra. In 1977 he became Deputy Engineer at Ballarat, and took over the Chiefs position in 1985. He is an active and vocal member of the AWWA Victorian Branch.

development, to satisfy the Board's concerns.

The Boards agreed that this would be a better alternative if suitable conditions could be agreed upon. Only a few house sites on marginal land \VOuld then need to be referred. All other houses could be permitted "as of right", subject to meeting predetermined conditions. This would create certainty.for the Shire, the Board and the community.

THE INVESTIGATION A working party comprises representatives of: the Water Boards, the Shire of

THE PROBLEM Following completion of the Ballarat to Melbourne Freeway, which passes through the Lal Lal Catchment, the Shire of Buninyong began to experience a growth in rural/residential and hobby farm development. The area comprises rich red and grey basaltic soils with a high reliable rainfall. Water harvested from the catchment is generally of excellent quality only requiring disinfection. Farming practices in the catchments are generally broad acre potato growing, grazing and some cropping.

The heavy clay soil is relatively stable and resistant to erosion and because of the high rainfall, generally well covered by grass or crops. The topography is gently undulating and the large number of farm dams within the catchment act as silt traps.

Both the Ballarat Water Board and the West Moorabool Water Board were concerned that a change in land use from broad acre farming to rural/residential or hobby farming would be detrimental to the catchment. It was also of concern to other authorities and the Shire of Bungaree that the rich soils of the area could be lost to productive agriculture by such development.

32

WATER April 1993

''t':r....,..I GR,

BALLARAT

BALLAN

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-

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2

3

4

5

!--ii

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Bungaree, the Shire's Planning Consultants, the Department of Agriculture, and the Department of Conservation and Environment was established.

A plan of the study area is shown in Figure 1.

The land ownership pattern s were mapped and all allotments identified. This indicated that within that portion of the Shire of Bungaree containing a water catchment there were 577 separate allotments comprising 334 tenements. (A tenement being a lot or group of adjoining lots under one ownership) .

The Department of Conservation and Environment updated earlier mapping of the Shire to identify areas considered not suitable for rural residential development by virtue of inappropriate soil conditions.

The Water Boards provided plans of all reservoirs, channels and streams and indicate their desired set-backs for houses, septic tanks and absorption fields. This ranged from 100 m to 300 m depending upon land slope and pollution risk. Tables showing the number of lots and tenements in various size ranges were prepared and the affect of a number of options analysed. The whole process from initial meetings to exhibiting the final scheme took two years to complete.

THE NEW PLANNING SCHEME The Shire's Planning Consultant prepared an Issues Paper which was made available for public comment and a final planning document for Council.

Beside the issue of protection of water quality the other major issue to arise was the "rights" of individual landowners. Many landowners confused their right to continue agriculture (which is protected under the Planning Act) and their "rights" to do what they wish with their freehold land . This included a desire to subdivide their land or to sell off individual titles for their 'superannuation'.

It was agreed the right to build a house should exist (even if in a limited form) but that the total number of additional houses would need to be controlled to protect both the catchment and the rich agricultural land of this area.

Control options included: (i) Minimum lot sizes for a house. (ii) Tenement controls. (iii) Density controls. (iv) Some form of discretionary approach (requiring every new house to have a permit).

The study concluded that the most equitable form of control was a form of tenement control which acknowledges that every discrete rural holding has the right to one house. (Rural holdings were identified

and a map prepared to form part of the scheme).

The final scheme, as approved by the Minister, includes a control on houses that requires a minimum allotment size of 40 ha for each house. However, where lots are less than 40 ha one house only may be constructed on the whole tenement, irrespective of the number of titles owned.

It was originally proposed to define a tenement as adjoining titles in one ownership as at the date of publication of the Issues Paper. However, a subsequent check with the Titles Office indicated very little activity in transferring Titles during the public consultation phase which may have indicated attempts to circumvent the proposed controls. Hence, to avoid possible complaints of alleged back-dating (which would not have been strictly true), tenements were defined as one contiguous holding as at the aproved date of the Scheme. Tenement maps have been prepared and are part of the formal Planning Scheme maps.

Stream protection zones based on the Board's set back criteria and special protection zones areas for areas of poor soil absorption have been defined on the Scheme maps and development is not permitted in these areas. There are approximately 30 tenements which cannot be built on because of these restrictions. Because of the limited number, a transferable right will be created to permit a second house on another tenement provided that tenement is greater than 30 ha. Major effluent producing activities such as feed lots, piggeries, caravan parks are prohibited within the catchment.

Septic tanks will require a permit. This is to permit a design check by the Shire staff and to require a legal Agreement under Section 173 of the Victorian Planning and Environment Act. This Agreement, which has become a standard requirement in the catchment areas, requires that the owner arrange for the septic tank and absorption field to be inspected annually by a qualified Environmental Health Officer at his cost and arrange for the septic tank to be pumped out at three yearly intervals. A copy of the Health Officer's report will be forwarded to Council and the relevant Water Board. To ensure all future purchasers of the property are aware of their obligation to maintain their septic tank this agreement is registered on the title of the property, as provided for under Section 181 of the Planning and Environment Act. The Shire, the Water Board and the owner are all party to the Agreement. Agreements are recorded on a computer data base and reminder notices sent to owners who fail to arrange inspections or regular pumping out.

The total number of houses that could

M. MUNTISOV and G. WILLIAMS conlinued from page 30 Gutteridge Haskins & Davey Pty Ltd (I 988) Wurdee Boluc Water Treatment Plant Design Review Report.

Holm, R. Sunderg, Rand Mattson, E (1982) Corrosion of Copper Pipes in Fresh watersSwedish Experiences, Proceedings of the International Symposium on Corrosion of Copperand Copper Alloys in Building, Tokyo.

Kuchenrither, R. D. , Elmund, G.K., and Houck, C.P. (1992) Sludge quality benefits realised from drinking water stabilisation, Water Environmental Research, Vol 64, No. 2 pp 150-153.

Lowenthal, R. E., Wiechers, H. N. S., and Marais G.V.R . (1986) Softening and Stabi lisation of Municipal Waters, Water Research Commission, Pretoria, South Africa.

Mattson , E. and Fredriksson, A. M. (1968) Pitting Corrosion in Copper Tubes - Cause of Corrosion and Counter Measures, British Corrosion Journal , Vol. 3, September.

Moss, G. and Potter, E. C. (1984) CSIRO Investigations into the Interactions Between Cold Potable Water and Copper Tubes, Report 1534R, CSIRO, Nth Ryde NSW.

theoretically be bui!, on existing allotments within that portion of the Shire of Bungaree that lies within a domestic Water Supply Catchment, under the original planning controls without further subdivision, was 1022. Under this Scheme the maximum is 464. No new allotments of less than 40 ha are permitted. (Excisions for family members actively engaged in farming for a house are permitted subject to certain conditions. Rearrangement of lots is also permitted provided the total number of lots is unchanged).

The overall potential density of housing is one house per 28 ha. Although this is less than the Board's desirable maximum density of one house per 40 ha, this was considered acceptable as no houses could be built in designated areas close to streams, reservoirs, channels or swamps.

RESULTS TO DATE During the exhibition stage only one landowner group expressed concern.

The Minister of Planning has congratulated the Shire on the positive steps they have taken to upgrade the Scheme and given his formal approval.

In October, 1992, in response to submissions from a number of water authorities, the Minister amended all Planning Schemes in Victoria to require formal referral of planning permit applications for development in domestic water supply catchments to the relevant Water Supply Authority.

Because the Shire of Bungaree had, in conjunction with tlte Water Authority, introduced specific planning controls to protect the catchment, the Minister granted this Shire an exemption from this requirement. â&#x20AC;˘ The Scheme only effects the rural areas of the Shire and a further study is about to commence for two small township areas in the catchment.

The results achieved by the co-operation between the relevant Department, the Shire and the Water Boards is an example of the results that can be obtained from all parties openly expressing their concerns and being prepared to listen to each other. The protection of water catchments depend upon more co-operation of this type.

REFERENCES Water Supply Catchments and Aquifer Intake areas, Interim Planning Guide. (Department of Planning and Environment, Victoria, June 1987) .

Septic Tank Code of Practice, 1990. (Department of Water Resources, Victoria).

Land Management Study for Water Supply Catchments within the Shire of Bungaree. (Meldrum Burrows October 1990).

Planning and Environment Act, 1987.

Shire of Bungaree Planning Scheme Ordinance, Rural (Water Catchment) Zone. (Shire of Bungaree).

Muntisov, M., Williams, G. and Crockett, J (1993) Design of a 260 ML/d Pressure Filtration Plant, AWWA 15th Federal Convention, Gold Coast, Queensland.

Naylor R., and Nicholas D. (1991) The effectiveness of corrosion indices in predicting performance of brass/copper galvanic couples in potable waters. Proceedings Australasian Corrosion Association Conference 21, Sydney, NSW. Nicholas, D. (1987) Corrosion <;:ontrol in Hunter Waters : Effects of Calcium Bicarbonate. Hunter District Water Board Internal Report.

Nicholas, D. (1990) Effects of Potable Water Chemistry on the Corrosion of Copper and Copper Alloys . Proceedings Australasian Corrosion Association Conference 30, Auckland, New Zealand .

Nicholas, D. (1993) Personal Communication Sato, S. et al (1982) Case Studies on the Pitting Corrosion Failures of Copper Tubes in Hot Water, Proceedings of The International Symposium on Corrosion of Copper and Copper Alloys in Building, Tokyo.

Stevenson, C.D. (198 3?) Corrosion Aspects of New Zealand Water Supplies. Source unknown.

WATER April 1993

33

TECHNICAL NOTE

Paying the price for poor coagulant selection?

by Michael Bourke, Senior Project Engineer, ICI Watercare INTRODUCTION Selection of the best coagulant for a water treatment process is not simply a matter of buying the cheapest product available.

Coagulation pH, sludge disposal, mixing conditions, temperature and the particular water characteristics all have a bearing on which coagulant is most suitable for an application .

In Australia alum has traditionally been the first choice for coagulation due to availability, as it is produced in most states in either powder or liquid grades. Alum performance characteristics are also well understood in Australian water treatment plants.

Alternative coagulants such as ferric chloride and polyaluminium chloride (PAC) have been used in isolated cases where alum has not been able to achieve the treated water quality objectives. NHMRC approved polyelectrolytes (poly DADMACS' ) are also used at a few water treatment plants where water characteristics are suitable for this type of coagulant.

In recent times tighter potable water requirements and higher consumer expectations have meant that in many cases, colour and turbidity removal followed by disinfection is no longer enough to meet the latest treatment objectives. Iron and manganese removal or artificial hardening for corrosion protection may need to be incorporated into the existing treatment process. THM or residual aluminium levels may also be of concern along with the disposal of water treatment sludges.

In many cases the increasing demands on water treatment facilities will make it necessary to re-evaluate the current coagulation conditions so that all treated water objectives can be achieved.

Alternative coagulants such as ferric chloride, polyaluminium chloride and poly DADMACs all have different properties which may be utilised to overcome operational or water quality problems that are encountered using alum .

COAGULATION AT ELEVATED pH . Coagulation at an elevated pH may be desirable in the following c1rcumstances:a) If it is necessary to remove iron and/or manganese by oxidation with chlorine or potassium permanganate. These reactions are most effective at a pH of 7.5 - 8.0. b) If disinfection by chloramination is practiced. The optimum pH for chloramination is around 8.0, where the potential for odorous chloramine compound formation is minimised. c) If, in soft waters, stabilisation of treated water with lime and CO 2 is required to minimise corrosion of the reticulation system. d) If, due to the acidic nature of alum or iron salts, post treatment pH correction with lime may be necessary to prevent downstream corrosion of the reticulation system.

The optimum pH range for coagulation with alum is 5.5-7.0.

Outside this range the performance of alum deteriorates rapidly.

When alum is dissolved in water it reacts to form a number of hydrolysis species. During coagulation, negatively charged organics and particulates are adsorbed onto the positive hydrolysis species or enmeshed in a hydroxide precipitate. The hydrolysis species formed are pH dependent, and at high pH anionic (negative) species are formed, reducing the effectiveness of the coagulant and resulting in high aluminium residuals in the treated water. Where lime is used for post treatment pH correction such as in cases b), c) and d), it is generally desirable to dose the lime after sedimentation, but prior to filtration, so that the treated water turbidity will not be increased.

Undissolved lime and impurities in the lime will then be prevented from entering the treated water supply. A problem with this practice is that alum floe carries over to the filters and can resolubilise at elevated pH, thus causing the treated water aluminium limit to be exceeded.

Ferric salts such as ferric chloride do not form anionic hydrolysis species until much higher pH and are, therefore, effective over a wider range of conditions than alum. Of course, aluminium residuals are not an issue where iron salts are used.

'Poly (Dimethyl Diallyl Ammonium Chloride)

34

WATER April 1993

PAC is another coagulant that performs well over a wide pH range.

Because PAC consists of pre-hydrolysed aluminium species, its effectiveness is less sensitive than alum to pH variations. At elevated pH, coagulation with PAC therefore results in lower aluminium residuals than alum .

Polyelectrolytes work well on waters with medium to high turbidities and low dissolved colour, where the polymer molecules can bridge between suspended particles to form larger, settleable aggregates. Where a water source contains high levels of colloidal colour (i_e high true colour), poly DADMACs are not very effective.

Inorgamc coagulants on the other hand, will form insoluble hydrolysis species which allow removal of colloidal particles by enmeshment in the precipitate.

SLUDGE DISPOSAL Disposal options for water treatment sludges can also influence coagulant selection. Where aluminium or iron based coagulants are us_ed, sludges contain hi~h levels of aluminium or iron respectively.

Disposal routes may be limited by the composition of these sludges.

The_cost of sludge disposal, or the capacity of sludge handling eqmpment, may also be a concern.

Sludge volumes are reduced when using PAC due to the formation of a denser floe compared to the fluffy, porous floe formed with alum. Poly DADMACs are only suitable for coagulation of a limited range of raw waters, but for suitable waters the doses required are a fraction of those for inorganic coagulants such as alum or ferric chloride, and the sludge volumes are similarly reduced.

HYDRAULIC OVERLOADING/FLOC CARRYOVER Poor sedimentation in clarifiers may result in overloaded filters which will then require more frequent backwashing and may increase the incidence of turbidity breakthrough. Iron and aluminium have different r~act!on kinetics, with iron hydrolysing much more rapidly.

The resultmg iron floe forms muqb faster and is heavier than alum floe. This property can reduce floe carryover problems and allow debottlenecking of hydraulically overloaded water treatment plants.

TOTAL DISSOLVED SOLIDS LEVELS Where a water treatment plant supplies process water for industrial applications, it may be preferable to minimise TDS levels in the treate? water. Downstream cost savings can then be achieved by re~u_cmg further ~retreatment requirements. PAC is only slightly ac1d1c compared with other inorganic coagulants, and therefore little or no pH correction is required, i.e. less dissolved salts are added to the treated water. The lowest TDS levels are achieved where poly DADMACs can be used.

LOW TEMPERATURE COAGULATION The effectiveness of alum is reduced at coagulation temperatures lowe_r than a?ou~ 10 °C where the reaction rate is slowed considerably.

Ferne chlonde 1s more effective than alum at lower temperatures due to faster reaction kinetics, while the performance of PAC is less dependent on temperature due to preformed hydrolysis species. These properties obviously have greater significance in cooler climates.

CONCLUSIONS Increasing demands on water treatment facilities have meant that past coa_g ulation practices may no longer be satisfactory to meet the reqmrements of the consumer, the regulatory authority and the plai:it operator. Whil~ al~m may still be the cheapest coagulant available, when cons1denng alternatives additional costs such as ?efraying capital expenditure, sludge disposal, operability 1mpro~ements, reduced chemical usage, and meeting water quality obJect1ves must also be taken into account. It may be that the cheapest coagulant does not necessarily offer the most cost effective treatment method overall.

REFERENCES Johnson, P. N. and Amirtharajah, A., 'Ferric Chloride and Alum as Single and Dual Coagulants', 1993 Journal AWWA, May, pp 232-239.

WATER BIENNIAL INDEX FROM 1991-1992 This index has been abstracted from the computer database prepared and continually up-dated by P R & J L Williams, Queensland University of Technology. These files index all papers presented to AWWA Federal Conventions and Summer Schools.

Their program AWWASEEK enables rapid searching to be

performed. The disks are IBM compatible, and are available for purchase from the Queensland Branch Secretary.

Note that in the following simplified index some titles have been precised to highlight the keywords, and the papers have been arbitrarily sorted into nine subject areas.

ENVIRONMENT

WATER INDUSTRY AND MANAGEMENT The British Water Industry John Court Feb 1991 Zero Discharge from Chemical Plants E A Swinton Feb 1991 A New Strategic Management Scheme for S.W.B. A G Wright & M S Stamp Apr 1991 Melbourne Board of Works Centenary W J Dulfer & EA Swinton June 1991 Water Demand Management in Melbourne ¡ HP Duncan June 1991 Customer Service - The Board's Experience D Patterson June 1991 Developer Financing of Water, Sewerage & Drainage R Miller & J Meeske Aug 1991 Telemetry Project for Gosford/ Wyong G Burton Oct 1991 Water Industry Training: National Perspective N Whyte & B Davis Feb 1992 Multi-skilling at the Hunter Water Board: W Scholz & S Weatherstone Feb 1992 Award Restructuring in W.A .W.A. D Knight & PG Lutz Feb 1992 Safety Aspects in a Highly Aerated WWTP J Charlton & J Foreman Feb 1992 Safety and Operator Training J Park Feb 1992 AWWA Position Papers, Ocean Disposal, Drinking Water Quality, Waste Minimisation . S.A.R.P. June 1992 National Water Quality Strategy B Sheedy Dec 1992 The Industry Commission Report (July 1992) J Henshall Dec 1992

The Werribee Treatment Complex: Environmental Perspective.

A J Bremner & AW Chiffings New Wastewater Irrigation Guidelines in Vlctoria S Davis Observations on Water Pollution from a Train S Davis Rapid Detection of Sewage Contamination in Natural Waters.

SC Apte & GE Batley Trace Element Speciation in the Natural Environment B N Noller Survey of Sydney's Coastal Environment P Nichols, R Leeming & G Crosswell Long-term Sublethal Effects of Trace Metals W Maher, S Baldwin, M Deeker & S Apte Murray Basin Hydrogeological Map Series W R Evans River Murray Salinity Mitigation Schemes in South Australia.

R J Newman Salinity and Groundwater Control - Shepparton region.

W Trewhella , Groundwater Pumping - an Effective Means of Salinity Control.

J Nolan A Groundwater Blue-Green Algae Relationship?

T J Verhoeven Peert Coastal Groundwater Schemes D Hopkins Groundwater Flow near Shallow Lakes LR Townley & JV Turner The Great Artesian Basin: A Need to Conserve JR Hillier

June 1991 Aug 1991 June 1992

Aug 1992 Aug 1992 Aug 1992 Aug 1992 Dec 1992

Dec 1992

Dec 1992

Dec 1992 Dec 1992 Dec 1992 Dec 1992 Dec 1992

WATER SUPPLY AND TREATMENT WATER RESOURCES A lice Springs - The Mereenie Sandstone Aq uifer June P B Jolly, G W Prowse & D N Chin Infrastructure Management in Queensland's Non-metropolitan Water Sector.

Aug A Hughes Instrumentation Development for Lake Mixing Investigations.

Oct J Imberger Intelligent Interface: Remote Sensing N Goldie, I Johns & I Durham Oct Focus on Some North Queensland Water Quality Issues.

A Moss & J Bennett Dec Water Quality in Lake Tinaroo, N.Qld. Dec J Littlemore, M MacKinnon & G Sadler Candowie Reservoir- Blue-Green Algal Bloom Apr IM Bartlett & I McNish Manganese Speciation in Surface Waters B Chiswell, D Dixon, G Hamilton, L Sly & T White Aug Sulfur Compounds Causing Odour in Water J E Wajon & P D Wilmot Monitoring of Algal Problems in Victoria W van Dok, B T Hart & R Royle

1991

1991

1991 1991 1991 1991 1992 1992

Aug 1992 Aug 1992

Commissioning Procedures for New Water Pipelines L S Burn & T J Richards Electrochemical Coagulation Filtration Process LO Kolarik, CT Chin, L F David, MB Roberts Fouling in Membrane Desalination: W.A. Perspective.

R Robinson & G E Ho Automation of Chemical Metering Pumps PT Barlow The Principles of Flowmeter Selection R A Furness A New-technology Water Meter DJ Lomas Tighter Chlorination System Control D Little & S Bienak Ecologically Sustainable Water Clarification at the Clear Water Lagoon, Mt.Isa. T J Wrigley, P D Farrell & D J Griffiths Cross-flow Micro-filtration with In-line Flocculation .

S Vigneswaran & S Boonathon

Feb 1991 Apr 1991 Aug 1991 Oct 1991 Oct 1991 Oct 1991 Oct 1991

Dec 1991 Feb 1992

Water Supply Peaking Factors: Effect of Demand management.

M Clewett & L Applegren Dec 1991 Appropriate Control Method for Chlorine Disinfection.

D W Braden Oct 1992 WATER April 1993

35

WATER QUALITY Microbiological Quality of Drinking Water ... the Major Urban Systems.

K Power & L Nagy

Feb 1991

SEWERAGE SYSTEMS AND WASTEWATER TREATMENT Effluent re-use: Shoalhaven Heads Project D P Wilkins & J M Anderson Modified Dissolved Air Flotation by Simple Retrofit: North Head STP. P Thomas, M Laginestra, P Rearson Application of Deep Bed Filtration to Wastewater Treatment.

S Vigneswaran Estimation of Asset Lives.

R Vass On-site Wastewater Disposal in a Small Community.

PM Geary & R van de Graaf Measurement of Turbidity in Wastewater Treatment G Schrank & J Lane Solids Measurements Improve Performance of Wastewater Treatment Plants.

S Valheim Four:beam Turbidimeter for Low NTU Wastes K King Clean Water Oxygenation and Mixing Tests J Charlton, K Barr & S Low Design of Nitrogen Removal Plant with Sequencing Batch Reactor Capability.

J Charlton Ultraviolet Disinfection in Municipal WWTP A MacDougall Measured Infiltration Rates/Savings in Design A M Norrish & C R Weeks Erosion Control by Macrophyte Planting D Hutchison & J Locke Odour Minimisation at Werribee T Gulovsen, D Hutchison, J Russell, P Scott Update on Odour Control in Geelong's Wastewater System.

G J Sewards & D S Barkley Odour Problems from North Head STP. M Laginestra Odour Control by Wet Scrubbers at North Head.

A MacDougall Odour Control Strategies at Bolivar STP. M F Kennedy, P M Thomas & K P Yerrell

Apr 1991 Apr 1991 June 1991 Aug 1991 Aug 1991 Oct 1991 Oct 1991 Oct 1991 Dec 1991 Dec 1991 Feb 1992 Apr 1992 Apr 1992 June 1992 June 1992 June 1992 June 1992 June 1992

INDUSTRIAL WASTES Wastewater Management for intensive rural industries.

K H Bowmer, P Laut, E A Swinton Emerging Technologies for treatment of Industrial Wastewaters.

R J Eldridge

36

WATER April 1993

Feb 1991 April 1992

Removal of Heavy Metals from Efflue_pt Streams by the Guardsman ACF Process.

B Copper Membrane-based Solutions to Plating Waste R G Macoun Metal Recovery using Magnetite. D R Dixon Coke Ovens By-Products Wastewater Treatment Plant at Port Kembla.

D Paris & A Jell The UASB Process.

T Lawson Recovery of Dissolved Metals from Dilute Effluents.

C Hertle Recovery of Mercury from Industrial Wastewaters N S C Becker & R J Eldridge

April 1992 April 1992 Aug 1992

Oct 1992 Oct 1992 Oct 1992 Oct 1992

TECHNICAL NOTES Energy Requirements for PVC and D.I. Pipe Milliscreening in aquaculture use of disc filters Blockage of Piggery effluent pipes a Magnetohydrodynamic solution Wastewater Disinfection by UV A Worker-Friendly Personnel System The Urraween Inground Reservoir Project Wagga Effluent Plantation Project Valve Actuation Solves many Needs Olfactory Studies Relating to Odour Emissions Odour Control - Some Queensland Notes Effective Sulfide Deodorization Location of Underground Assets by Acoustics

June 1991 Feb 1991 Feb June June June Aug Oct June June June Aug

1991 1991 1991 1991 1991 1991 1992 1992 1992 1992

BATEA and Secondary Treatment, Hardwood Mills Feb Water Quality Strategy, NSW Apr 14th Biennial Convention Apr Working with Lobby Groups Apr Queensland Workshop - Dirty Water Discharges Aug Corporatisation, Melbourne â&#x20AC;¢ Aug NSW Regional Conference Aug Asset Management - Maroochy Regional Conference Dec AWRC Water Technology Committee Dec Asian Water Qua!, 91 Feb Environmental Water Allocation, Armidale Workshop. Feb Hazardous & Solid Waste Convention, 92 Apr Blue-Green Algae, Melbourne Seminar Apr Wastewater Reduction & Recycling, Geelong Aug AWWA Seminars N.T. & W.A. Oct Sewage into 2000, Amsterdam Oct Stockholm Festival to Water Oct Cement Kilns in Waste Management Oct ANZECC W.Q. Guidelines Forum Dec Community Consultation, Queensland Dec

1991 1991 1991 1991 1991 1991 1991 1991 1991 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992

CONFERENCES, SEMINARS

BOOK REVIEWS HANDBOOK OF CHWRINATION AND ALTERNATIVE DISINFECTANTS Third Edition by Geo Clifford White Pub. Van Nostrand Reinhold. Available through Thomas Nelson Australia, South Melbourne: 308 pp. A$259.95

The 1992 third edition of George Clifford White's handbook on everything to do with disinfection is not only an extra 190Jo thicker, but contains additional information on chlorination of drinking water, ozone, ultra violet radiation; peroxone and dechlorination , and treatment of industrial wastes. In particular, risk management issues such as chlorine leak control and general health and safety are a focus of this edition.

It is well worth acquiring, even if you have the second edition, if your interest is in the history, design or operation of disinfection systems.

Usable methods to define chlorine leak rates from ruptured pressurised tanks and the design of caustic soda based scrubber systems to treat the chlorine released are included. The basis for evaluation is the Uniform Fire Code (revised 1990).

Wallace & Tiernan chlorination systems are added to the others discussed (e.g.

Capital and Fischer & Porter). The principles of operation and reliability/suitability issues are presented for chlorine residual and chlorine dioxide control systems.

Some additional information on microbes which cause waterborne disease (myco -

bacteria, Giardia and Cryptosporidium) and on effective disinfection (e.g. 'ct' factor) is included. Problems associated with use of chloramination as a primary disinfectant are discussed more fully including nitrification in reservoirs with floating covers (California experience). Disinfection processes using chlorine/chloramine/ ozone in various combinations are discussed in more detail and TOC removal technologies (to control THM's) are outlined.

A section on Marine biofouling and control (e.g. zebra mussels) is included along with a brief discussion of the treatment processes to produce drinking water from treated sewage effluent.

The phenomena of "Bacteria Regrowth" has become a major section, but remains relatively general.

Discussion of chlorine dioxide byproducts, regulations, impacts on dialysis patients and processes for removal of chlorite iron has been added.

Solubility and transfer efficiencies as well as residual control and exhaust gas monitoring for ozone are covered in detail.

Some new installations in Canada and elsewhere are summarised. Disinfection byproducts and assimilable organic carbon issues (e.g., stim ulation of bacteria regrowth) are assessed. A number of new wastewater systems are reviewed. A new separate chapter on ozone system design looks at latest technologies, mixing of gas in water, contractor basin layout, off-gas destruction and automatic control systems.

The new Los Angeles plan is discussed.

The role of Peroxone and ozone in reduction of colour, taste and odour and volatile organic compounds is summarised.

The wastewater disinfection section now includes a short discussion on the deleterious effects of organic nitrogen and the impacts of changes in effluent composition due to new denitrification requirements for waste water treatment plants.

In the design section, modern leak detectors, corrosion resistant direct feed chlorinators and redox control of chlorinators (used in cyanide destruction) are new items of interest.

Aeration and UV processes are added to the list of possible dechlorinating/ dechloraminating agents.

In the new separate chapter on UV radiation, discussion of photo reactivation, short circuiting of flow problems and cleaning requirements are included. Design and operational requirements based on a review of 36 facilities in Canada and the USA are presented.

The appendices contain useful additional data on leak neutralisation, chlorine gas density and chlorine solubility in water.

Significant omissions in this edition are field data on reliability of actual disinfection systems versus costs and up-to-date costs generally. (Many are still 1970's costs). A review of recent waterborne disease outbreaks and relationship to lack of appropriate disinfection is also missing.

M. Chapman

â&#x20AC;˘

B. A. MURRAY and S. J. RODDY Continued from page 20

Manganese was found to be removable to the objective levels after oxidation with potassium permanganate and also with prechlorination and pre-coated filter media.

Ozonation was not found to be economic at any of the proposed plants.

Pre-chlorination was found to improve filter performance where dissolved organics were high in the raw water and was the preferred process for Prospect WTW. Alum with cationic polymers were recommended as primary and secondary coagulants for each of the contact filtration plants.

However, if, in the future, alum is found to be directly implicated as a causal agent for Alzheimer's disease then further investigation should be made into hydroxy lated ferric su lfate or other coagulants with cationic polymers.

Disinfection by-products were found to be within current guidelines even with pre-coagulation chlorination. However further consideration will need to be given to likely future trends in DBP guidelines.

ACKNOWLEDGMENTS The contributions of Keith Craig and Rod Naylor of the Hunter Water Corporation are gratefully acknowledged. The Water Board would like to thank all the consultants and contractors who contributed to this work.

38

WATER April 1993

REFERENCES This paper is a summary of the Sydney Water Board's recent pilot and prototype plant research. More detailed information on the work is to be found in five papers in the Proceedings of the AWWA 15th Biennial Convention, April 1993, and a number of reports to the Water Board.

NAYLOR, R., CRA IG, K., RODDY, S., MURRAY, B. Pilot Plant Studies of Filtration Processes for Sydney Water Suppli es, AWWA convention, 1993.

MURRAY, B., RODDY, S. Pre-Coagu latio n Oxidation and High Rate Co ntact F iltration, AWWA conference,1993.

NAYLOR, R., CRAIG, K., MURRAY, B., NICHOLSON, C. The Use of A lum Versus Ferric Salts with Cationic Polymer in Contact Filtration Studies, AWWA conference, 1993.

ENTWISLE, T., MURRAY, B. Particle Removal in Contact Filtration , AWWA conference, 1993 .

NAYLOR, R., NICHOLAS, D., RODDY, S., MURRAY, B. Optimisation of Calcium Carbonate Buffering for Corrosion Control in Potable Water, AWWA conference, 1993.

WATER BOARD, AWT SCIENCE & ENVIRONMENT (1992) The Study of Disinfection By- Products Formation Including Trihalomethanes, Haloacetic Acids and Haloacetonitriles of Prospect Prototype WTW. PROSPECT WATER GROUP (1992). Prospect Water Treatment Work s: Concept Design Report, Volumes 1,2,3.

GUTTERIDGE, HASKINS & DAVEY / CH2M HILL (1992) Avon Water Q uality Project: Concept Design Report, Volumes 1,2,3.

CAMP, SCOTT & FURPHY (1992) Macarthur Water Quality Project: Concept Design Report, Volumes 1,2,3.

SINCLA IR KN IGHT & PARTNE RS/ JM MONTGOMERY (1992) Woronora Water Quality Project: Concept Design Report HUNTER WATERTECH (1992). Avon, Macarthur and Woronora Water Quality Projects: Pilot Plant Studies Repons for Water Board , Sydney.