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WATER certain customers, such as industrial users with boilers.

Key Information Requirement s In making decisions regarding stabilisation and buffering, it is important to obtain the key in fo rmation that allows the situation to be analysed. T his information includes: • Asset life in formati on including failure frequency, and particularly informatio n where the asset life is limited through attack o n cement linings of pipework, and asset repair and replacement costs. • The chemical compositio n of the water and its variation, toge th er w ith pH variation, through the reticulation system. • The presence of inhibito rs, such as organi cs and phosphate. • The desired system service objectives, including maximum pH fo r any customer (or pe rce ntage of c ustom e rs), and maximum number of supply interruptions.

Concluding Remarks It ca n be appreciated fr o m this discussio n that determining the optimum stabili ty and buffering conditi ons for potable water supply systems is not always a simple matter. It is important to distinguish the different requ irements for stability and buffering, and w hat eac h is achiev ing. H igh quality, soft unfiltered suppli es as occur in Australia can be some of the most challenging for determining w here th e optimum operating conditions lie. Because these waters will often have relatively high orga ni c co ntent, they may not be particularly aggressive to co ncrete and cement Linings, and from an asset life perspective it may not be necessary to operate th e

supply with a positi ve CCPP and the substantial chemical add itions that this would require. However, such waters can have a low buffer capacity, and in o rder to avoid a percentage of the customers experiencing high pH conditions, the controlling requireme nt fo r chemical addition may be the need to avoid the most extre me pH co nditions rather than asset li fe. The key to optimal o peration of water supply syste ms is a good understandin g of the fundamental wate r chenustry, actual operating conditio ns, maintenance requ irements and asset life, and custo mer service requirements.

References Degremont ( 1991) Water Treatment J-/ml{/book, Sixth Edition 1: 36 1 Lavoiser Publishing, Paris Langelier WF (1936) "The analytical control of anti-corrosion water cream,ent",J A WWA 28: 1500 Sontheimer H , Ko lle W, Snoeyink VL (1981) "The siderite model of the fonnation of corrosion resistant scales".JA WWA 73: 572 Stumm W and Morgan JJ ( 1981) Aquatic Chemistry, Second Edition, John W iley &Sons, New York Su ess E (1970) " In terac ti o n o f organic com po unds with calc ium carbo n ate" Ceod1i111(1 et Cosmoschimira Acta 34: 158 - 168. van Langerak, A (1998) Thesis "Control of [{l/ci11111 rnrbo11ate precipitation i11 mwerobic ret1ctors", Wagcningen University, N etherlands

The Authors Bob Turney, now a retired consulta nt specialisin g in minin g and mi neral ex tra cti o n problems, was Mana ging D irector of Boby Water Treatment Pty Ltd. Dr Peter Nadebaum, a chemical engin ee r, is th e Nati o nal M anager, Environmental Management, for Egis Consulting Australia.

BOOK REVIEW E.A.Laws: Aquatic Pollution. An Introductory Text. Third Edition. ISBN 0-471-34875-9 RRP $205.80 plus po s ta ge $ 11 . Availabl e f rom bookshop@a 1va .as11 .a11. Teleplto11e +61 2 9413 1288 Fax +61 2 9413 1047 This is a comprehensive introductory text presenting a systematic study of pollution in oceans, lakes, streams and underground aquifers: so warns the back-side of this detailed hardcover editi on. The first chapter starts with fundamentals - an excellent approach given that most engineers and many pure scientists la c k the ecological and ecosystem approach which so often informs modern environmental writings. Food webs, ecosystem stability and photosynthesis give way to an expla-

nation of trophic levels w hich eases the reader gen tly into a first example of aquatic pollution, the very natural event - eutrophication. From here, Laws moves to non point sou rce pollution, sewage pollution, pathogens in natural rivers and toxicology, all points amply illustrated by case studies. It is clear that the reader is being led through the spectrum of natural to human forms of water pollution to industrial and what could only be termed intentional tampering with the quality of the water through events such as thern1al power production, radioactive c ooling and m i ne wash i n g. Gro u ndwater poll u t io n a nd acid deposition are also dealt with. Not cheap but worth the money.

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Water Journal March 2001  

Water Journal March 2001