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AUSTRALIAN WATER &WASTEWATER ASSOCIATION

Volume 20, No 6 December 1993

Editor Bob Swinton

Editorial Correspondence 4 Pleasant View Crescent Glen Waverley Vic 3150 Tel/Fax (03) 560 4752

Advertising Sales & Administration Margaret Bates Tel(02) 413 1288 Fax (02)4131047 A\Y/ WA Federal Office Level 2, 44 Hampden Road, Arrarmon PO Box 388, Arrarmon NSW 2064

Editorial Board F R Bishop, Chairman MR Chapman, M Muntisov, P Nadebaum P Draayers, JD Parker, A J Priestley GA Holder, B Lade, W J Dulfer

Branch Correspondents ACT - Alan Wade Tel (06) 207 2350 Fax (06) 207 6084 New South Wales - Mitchell Langinesrra Tel (02) 412 9974 Fax (02) 412 9876 Northern Territory- Mike Burgess Tel (089) 82 7111 Fax (089) 82 7430 Queensland - Lyndsay Chapple Tel (07) 835 0222 Fax (07) 832 6335 Sou th Australia - Phil Thomas Tel (08) 259 0244 Fax (08) 259 0228 Tasmania - Jim Stephens Tel (002) 31 0656 Fax (002) 34 7334 Victoria - Mike Munrisov Tel (03) 600 1100 Fax (03) 600 1300 Western Australia - Tony Hendry Tel (09)497 1344 Fax (09) 497 1281

WATER (ISSN 0310-0367) is published six rimes per year February, April, June, August, October, December by

Australian Water & Wastewater Inc. ARBN 054 25 3 066 PO Box 388, Artarmon NSW 2064

CONTENTS MY POINT OF VIEW Build-Own-Operate-Transfer

3

The Hon Alan Stockdale

ASSOCIATION NEWS President's Message From the Executive Director

4

From the Branches

5

2

FEATURES Aluminium in Drinking Water - A Current Perspective

Mary Drikas

16

,.

Behaviour of Aluminium Species During Water Treatment

M J McCormick, J G Hughes, P Zhang, M Brymner Guidelines for Use of Biosolids -The Queensland Scene

20 23

PD Beavers Effluent Disposal Using Sand Exfiltration

G J Cashin Polyethylene Water Services

27 31

GCLong Yan Yean Water Treatment Plant-The Client's Perspective of BOO contract

35

B G Mcllree, MR Chapman, GP Joyce, EA Swinton

Federal President Richard Marks

Executive Director Chris Davis Australia Water & Wastewater Association assumes no responsibility for opinions or statements of facts expressed by contributors or advertisers and editorials do nor necessarily represent the official policy of rhe 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 co the objectives of rhe Association. All material in Water is copyright and should nor be reproduced wholly or in parr wirhour the written permission of rhe Editor.

Subscriptions \\1/ater is sent co all members of rhe A\Y/W A as one of the privileges of membership. Nonmembers can obtain \Ylater on subscription at an annual subscription rare of S30, rhis includes cosr of surface mail postage.

REPORTS Regional Conferences BOOT Projects: Effective Planning and Implementation

8 39

EA Swinton Disinfection 93, Queensland

41

Phil Wi lliams

DEPARTMENTS Books International Affiliates

22

Industry News

43

Letters to the Editor

13 4

Meetings

4

Products

26

Cover photography Bill van Aken, CSIRO


TECHNOLOGY

ALUMINIUM IN DRINKING WATER A CURRENT PERSPECTIVE Mary Drikas * Summary Aluminium is one of che mosc abundant elements in che earth's cruse and is an essential component of many minerals. Aluminium is also used in many industrial and domestic applications in various forms. Alumini um sales, principally aluminium sulphate, are also used widely as coagulants in water creacmenc. While most aluminium added co water is removed with the coagulated material as waste sludge , a small amount remains dissolved in the filtered water. Residual aluminium levels above 0.2 mg/L have been shown co result in pose-flocculation causing a number of water quality and supply problems for water auchoricies. Aluminium has for some time been implicated in the occurrence of dialysis dementia in individuals requiring renal dialysis. Recently, however, che intake of aluminium has also been implicated in che aetiology of several neurological diseases, such as Alzheimer 's disease, pre-senile dementia and ochers. Aluminium in potable water has been identified as a potential source of exposure. This review discusses the current knowledge of che health aspeccs of aluminium in drinking water, the current guideline levels established by various health organisations and highlights areas requiring further research. The use of aluminium sales in water creacmenc is ouclined and aluminium levels in created and uncreated water supplies are discussed.

Occurrence Aluminium is one of che most abundant elements in che earth's cruse and is found in chemical combination in a wide variety of forms. It is che major component of a large number of minerals such as clay, feldspar, mica, sillimanice etc. Industrially important minerals such as poccer's clay, china clay and Fuller's earth are also aluminium silicates. Bauxite, an aluminium oxide, is the principal mineral from which elemental aluminium is obtained. Aluminium metal is used principally for overhead high tension line, for fabrication of plane for use in che chemical, food, dairy and pharmaceutical industries, in building and 16

for archiceccural purposes, co manufacture cooking utensils and soft drink cans and in che form of powder for che manufacture of aluminium paints. Aluminium in the form of foil is used for packaging of foodstuffs , sweets, cigarecces ecc while crumpled foil is also used for heat insulation. Aluminiumbase light alloys are also of particular importance in all branches of engineering conscruccion , where the use of anodising results in extremely resistant and accraccive finishes. Less obvious are che al uminium compounds chat are found in produces such as foods, medical preparations, cosmetics and roochpasces.

Use in Water Treatment Aluminium sales, principally aluminium sulphate (alum), have been used for the clarification of water for at lease a hundred years. Aluminium sulphate was first mentioned as a coagulant by Pliny in about 77 AD. Particles of fairly large dimensions can be removed by sand filtration but finely divided and colloidal impurities need co be brought together by coagulation co form larger seccleable particles, either by chemical inceraccions or physica l entrapment. When an aluminium sale is added co water ic becomes discribuced inco various soluble and insoluble species depending on che mineral content and che pH of the water. These species chen chemically react with colloids in suspension. Minimum solubility of che aluminium ion is achieved ac pH 6.6 in distilled water. However solubility wil l vary in natural waters depending on che chemical characceriscics of che wacer. The effect of pH on che solubility of the alum floe is critical and minimal aluminium residuals can only be obtained by flocculation ac optimum pH values. Although ocher coagulants including iron sales and more recencly synchecic polyeleccrolyces are available, aluminium sulphate still remains one of the most widely used primary coagulants because of its ease of use and low cost. Alum is used in all water creacmenc planes in South Australia. The creacmenc of water co improve the physical characceriscics of che water supply also provides an associated and important improve-

ment in the efficiency of disinfection and minimisation of disinfection by-produces, thereby enhancing the safety of che public water supply. While most aluminium is removed with che coagulated material as waste sludge, a small amount remains dissolved in che filtered water and ic is imporcanc chat ics concencracion is kept low co avoid posc-flocculacion of insoluble aluminium hydroxide in che distribution system. Concencracions above 0.2 mg/L have been shown co result in poscflocculacion causing a number of water quality and supply problems for water authorities. For example, elevated aluminium residuals may increase turbidity, interfere wich disinfection and , by deposition, reduce che hydraulic capacity of che discribucion system. In several studies, high intake of aluminium has been suggested as a causative agent in several neurological diseases, such as Alzheimer's disease, pre-senile dementia and ochers. Recencly, che presence of high aluminium residual concentrations in potable water has been linked wi ch these diseases.

Existing Criteria Scace, national and international organisations and agencies have established limits for coca! aluminium in drinking water. Except for the European Economic Community (EEC) which has regulated the concentration of aluminium, the limits sec co dace have been guidelines. All of che guidelines have been established for aesthetic reasons associated with posc-flocculacion - none are health related. The 1987 National Health and Medical Research Counci l/ Auscralian Water Resources Council (NHMRC / AWRC) Guidelines, 1984 World Health Organisation (WHO) Guidelines (Sayre, 1988) and che maximum admissible concentration level of the EEC Drinking Water Quality (Carney, 1991) are all 0.2 mg/L, pased on aesthetic considerations. The US Environmental Proceccion Agency (EPA) under che Safe Drinking Water Ace has sec a secondary maximum concaminanc level of 0.05 - 0.2 mg/L for alu*Mary Drikas, Australian Centre for Water Quality Research. WATER DECEMBER 1993


minium to prevent posr-precipirarion of aluminium and discolouration of drinking water in distribution systems (Pontius, 1992). The EEC has also recommended a guide level of 0.05 mg/L in addition ro irs maximum admissible concentration, although Eureau, rhe Union of National Associations of Water Suppliers from countries within the European Community and Economic Free Trade Association, has proposed rhar this guideline level be om itted and rhar aluminium be designated a health parameter (Eureau, 1992). The WHO and HMRC/AWRC gu idelines are also currently being reviewed although draft documents produced to dare rend to suggest rhar there will be no change from rhe current aluminium guidelines. The Eng in ee rin g and Water Supply Department in South Australia has estab li shed operating guidelines with which all water treatment plants must comply. This includes a guideline for total aluminium in treated water of nor more than 0.20 mg/L. The correct use of aluminium sulphate, or other aluminium salts , as a primary coagulant in water rrearment results in aluminium levels in the treated water below rhe guideline value of 0.20 mg/L, averaging of rhe order of 0.10 mg/L. Ir is technically possible to operate water treatment plants using aluminium sulphate to produce water with less th an 0.10 mg/L aluminium provided optimum conditions are employed, particularly pH control. Ir should also be noted rhar the use of alternative coagulants such as polyelecrrolyres can also result in an aluminium residual associated wirh colloidal clay if less than optimal conditions are urilised and turbidity levels are nor minimised. Elevated levels of aluminium are sometimes present in unfiltered water supplies and can exceed the cr iter ion of 0. 2mg/L se t in th e national drinking water guidelines. Ir is not clear how avail able this aluminium may be ro the human body as it is probably present as colloidal clay silicates. Ingestion of aluminium can occur from a variety of sources; average (adult) levels suggested by the Water Research Centre, United Kingdom , are: air 20µg/day, water 290 µg /day and 7000µg /day in food. The value for food does nor include the inadvertent ingestion of aluminium caused by the use of aluminium saucepans with acidic food, nor any possible contribution from aluminium soft drink cans. Considering rhe significant difference in intake there needs ro be some study to determine the relative contriburion and effect of aluminium ingested from these vanous sources.

Health Effects Despite the ingestion by most adults of between l-20mg of aluminium a day only 15 µg /day is absorbed from the gastrointestinal tract, leading to a median plasma level of 7 µg /L (range 1. 5-15 µg/L) (Potocnik, 1990 and Alfrey, 1986). The remainder is accounted for by excretion in faeces. WATER DECE MBER 1993

Factors which affect rhe absorption of aluminium by rhe gasrroinresrinal tract are poorly understood but physico-chemical conditions such as the solubility of aluminium complexes and rhe gastric pH appear important. There is some evidence rhar individuals suffering from chronic renal insufficiency absorb aluminium more readily than normal individuals (Knoll er al, 1984). Aluminium once absorbed appears to bind to serum proteins, in particular the plasma protein rransferrin, also responsible for transporting iron. Absorbed aluminium appears to be eliminated from the body by rhe kidneys (Alfrey, 1986). Individuals with some renal insufficiency rend to accumulate aluminium as a consequence of their inability to excrete ir through the kidneys (Alfrey er al, 1980). In healthy adults the total bod y store of aluminium is approximately 35 mg, mostly in bone, and remains largely constant with age (Alfrey, 1986). Indi vidua ls whose rena l function is severely compromised and who require renal dialysis can suffer severe health problems from rhe presence of aluminium in dialysis fluids. The main risk to dialysis patients from hi gh aluminium levels is dementia. Th e mechanis m of neurotoxicity in dialysis dementia has nor been determined. In dialysis, blood from the patient passes through a machine which acts as an artificial kidney. Waste materials in the blood pass across a semipermeable membrane into the dialysis fluid kept separate from the blood which returns to the body. Aluminium toxicity can occur from rwo sources. Firstly, high concentrations of a contaminant, such as aluminium , in rhe dialysis fluid may transfer directly across rhe semipermeable membrane to the blood. Ir should also be nored rhar aluminium is nor unique in this effect. As there is direct transfer to rhe blood from the dial ysis fluid, high levels of other chemicals in rhe dialysis fluid are also potentially harmful. Secondly, patients on dialysis have ro rake medicines co ntaining alumin ium ; dialysis may fail to remove rhe resulting high aluminium concentrations from the bloodstream if a higher freque ncy of dialysis rrearment (wi th aluminium-free dialysis warer) is nor used (Knoll er al, 1984). The EEC recommends rhar the diluting water for dialysis nor exceed 0.03 mg/Land the fluid used for dialysis nor exceed O. lmg/L. The established practice to remove contaminants from water used to prepare dialysis fluids is to use a rwosrage treatment process consisting of reverse osmosis and granular activated carbon. Aluminium has also been implicated in the aetiology of rwo severe neurodegenerarive diseases, amyotrophic lateral sclerosis (ALS) and parkinsonism dementia (PD), which have a very high incidence amongst the Chamorro people of Guam and also in rwo other areas of rhe Pacific, Western New Guinea and rhe Kii peninsula of Japan . Both ALS and PD are characterised by the loss of motor neurone function and rhe presence of neurofibrillary

tangles in rhe braj.n (Garruro er al, 1990). A possible cause is rhar the soils and drinking water are low in calcium and magnesium bur very high in alum inium and iron . This , assisted by a basic metabolic defect, may result in increased absorption of aluminium , causing deposition in neurones in the brain (Garruto and Yase, 1986). Support for rhis hypo th es is is giv en by th e appreciab le decrease in the incidence of these rwo diseases as each of rhe affected areas have become westernised wirh associate d changes in dietary habits and local water supply, and much less dependence on locally grown foodstuff (Garruto er al, 1990). Recently an association has also been estab lish ed be twee n aluminium and Alzheimer 's disease. However the role of aluminium as a causative factor in rhe development of Alzheimer's disease is still an area of debate. In January 1989 Martyn et al published the resul rs of a survey designed to determine whether a geographical relationship existed between Alzheimer's disease and aluminium in drinking water. The risk of Alzheimer's disease was found to be 1.5 rimes higher in districts where rhe mean aluminium concentration exceeded 0.11 mg/L rhan in districts where concentrations were less rhan 0.01 mg/L. However the authors also suggested caution in interpretation as, with all epidemiological surveys, unknown confounding variables may well have been operating. The paper also faced criticism in rhe succeeding edition of rhe journal when doubts were expressed in letters to the editor as ro the f;_pide miolog ical valid ity of rhe study. Birchall and Chappell (1989) have proposed that rhe observed effect was due to rhe silicic acid content of water which was found ro significantly alter the availability of dietary alu minium ar alkaline intes tinal pH. They proposed rhar the waters which contained high aluminium were low in silicic aci d, allo wing hi g h ava il ability of aluminium, while rhe ingestion of aluminium was probab ly fai rl y constant within the population. Further research into rhe mechanism for accumu lation of aluminium in th e brain (Farrar et al, 1990) has shown rhar people with Alzheimer's disease and Down 's Syndrome have a defective form of the protein rransferrin. This protein normally binds aluminium in the blood and prevents ir from entering rhe brain. In people with this defect, less aluminium is bound and hence more is available to enter rhe brain and may result in rhe neurotoxic changes seen in Alzheimer's disease. The exac t nature of the functional defect of rransferrin remains unclear although there are some links with a particular gene on chromos ome 21 (Go re1ick and Bozzo la , 1991). Further studies to elucidate rhe mechanism continue to be undertaken which may lead to future preventative and therapeutic possibilities. Recently Landsberg er al (1992) fai led to derecr any increase in levels of aluminium in 17


neuritic plaque cores caken from unstained brain tissue of clinically characterised cases of Alzheimer's disease. They have ·suggested char previous evidence of aluminium in these cores may have been caused by contaminacion of the tissue by aluminosilicates present in most reagents used for analysis of stained tissue and have questioned the evidence relating aluminium co Alzheimer's disease. Good et al (1992) have subsequently refuted this • possibility in further work using laser microprobe mass analysis confi rming the presence of aluminium in neurofibrillary cangle formation in Alzheimer's disease. Although there are some similarities between dialysis dementia, ALS/PD on Guam and Alzheimer's disease, there are also significant differences which case doubt on th e suggestions char aluminium has a primary causal role in all three diseases. Although the link between aluminium and Alzheimer's disease appears co be better undersrood, the level and form of aluminium which results in problems for people with the defective transferrin has nor yet been determined. Also the level of aluminium available co complex co transferrin is highly dependent on a number of facrors, particularly the pH and the anions available in solution such as silicates, phosphates and citrates with which the aluminium can complex. Complexes that are not digested or adsorbed will remove the aluminium from the body with the faecal matter while aluminium che laces or aluminium ion released during digestion will be more likely co be carried across the intestinal lining. It is clear char the issue of aluminium availability in the body is complex and influenced by the nature of the aluminium compound, the pattern of aluminium ingestion and the composition of the diet. Whether, and co what extent, aluminium is involved in neurological disorders is still a matter of conjecture. Research studies are being directed at determining the bioavailabilicy of aluminium from food and water as well as studying its neurotoxicicy. Given the apparent higher level of exposure to almnini11m in food versm wate1; a reg11lation of aluminimn in water may not have a significant impact on health protection 11nless the issue of bioavailability is clarified.

Aluminium in Untreated Waters Natural waters contain suspended matter which varies widely in origin, concentration and size. An important contriburion is from land-based sources such as clays and silts. As discussed earlier, aluminium is an essential component of these clays and its concentration will be directly related co the amount of clay present. The availability of this parciculace aluminium co the body is unknown and hence the need for health concerns of aluminium complexed with clay silicates is also not clear. Some waters, particularly those sourced from the River Murray, have exceedi ngly 18

high aluminium. These alum inium concentrations are due co the high levels of colloidal particulate matter that is manifested in extremely high turbidity levels in the river at most times of the year. Aluminium determined after filtration through a 0.45 µm membrane is by definition called soluble, however it has been shown (Van Benschoten and Edzwald, 1990 and Emmett and Kennedy, 198 7) that filtration through smaller pore size membrane filters will result in lower aluminium levels. Thus it is fairly certain that even the "soluble" aluminium contains a significant proportion of colloidal particulate matter. The aluminium concentrations i n untreated waters in Souch Australia during the period January 1992 - June 1993 are summarised in Table l. Most waters are from surface reservoirs, apart from those listed as the River Murray. The Anstey Hill Water Treatment Plant (WTP) can be sourced either from the River Murray via the Mannum Adelaide pipeline or from Millbrook Reservoir which is also often supp lemented from the River Murray. The data listed in Table 1 for the Anstey Hill WTP is from the River Murray. On the average all but one of the waters exceed the 0.2 mg/L aluminium guideline set by the HMRC for coral aluminium. In fact · in all waters except two the aluminium concentration is higher than 1 mg/L for 90 % of the rime. However all sources contain considerably less soluble aluminium some below 0.2 mg/1. As the results show some of these aluminium concentrations can be exceed ingly high, it is of the utmost urgency co determine any possible health implications co enable remedial measures co be introduced. The determination of the form of aluminium is critical for health reasons ie; whether it is present as uncomplexed aluminium ions, unteactive colloidal clay or complexed aluminium species. This will also impact significantly on che operation of water treatment plants. For example, if uncomplexed alu minium ions are shown co be the only aluminium species available for uptake by the human metabolism then only 'free ' alu minium wi ll need to be maintained at low levels and complexed aluminium arising from

turbidity breakthrough will nor be an issue.

Aluminium in Treated Waters A number of the sources listed in Table 1 now undergo full treatment with lower resultant aluminium concentrations generally; this is particularly obvious for che systems supplied from the River Murray. All plants practise conventional water treatment consisting of flocculation, sedimentation and rapid filtration. The primary coagulant used is alum although the Morgan WTP uses a polyelectrolyce at certain times of the year when che water quality is suitable. Aluminium sulphate is acidic and results in a decrease in pH which must be corrected prior co entering the distribution system co prevent corrosion of pipework. All water treatment plants practise pH correction using lime. As lime contains considerable grit and forms a suspension of active alkali , addition after filtration would result in a turbidity increase in the treated water. Lime is therefore dosed in the settled water duce. This results in an increase in pH which causes solubilisation of alum floe. The higher the pH the higher the amount of aluminium resolubilised from the alum floe. Chlorine is used for disinfection at all plants except Morgan which utilises chloraminacion co ensure a disinfectant residual at the end of the long pipelines which it supplies. The pH is corrern:d co 8.4 for optimum chloramine formation and scabilicy which results in signifi cant resolubilisation of alum floe and consequently high aluminium residuals. Invescig ftions are currencly underway co determine the most economic method of dosing alkali after the filters at all plants. This has increased in importance since che Engineering and Water Supply Department has decided co provide water at pH levels of 7.5 co 8.0 co minimise pipeline corrosion. Ac pH levels above 7.5 in the serried water the aluminium concentration is very likely co be above 0.2 mg/L. Morgan WTP has addressed this problem by the use of alternative coagulants such as polyeleccrolyces and more recencly by the use of caustic soda for pH correction pose fi ltration when the primary coagulant is alum . The aluminium concentrations in water

Table 1: Al11111inimn in Untreated Waters in 5011th Amtraiia, January 1992-June 1993 Source

Total Alum inium (mg/L)

Soluble Alumi nium (mg/L)

Max

Min

Ave

90,f

Ave

Hope Valley WTP - Inlet to Plant

1.4 1

Anstey Hill WTP - Mannum No I P/Srn

5.49 1.85 0.205

0.1 32 0.584 0.0 18

0.635 2.63 0.44 7 0.146

1.27 4.9 1.64

0.187 0.232 0.2 14 0.062

Barossa WTP - B/C Tap* Li ttle Para WTP - B/C Tap Happy Valley WTP - Inlet to Plant Mvnon2a Reservoir - B/C Tao River Murray Morgan Murray Bridge No. l P/Srn Swan Reach

1.34 0.597 10.l 5.25 10. l

0.093 0.217 0.088

0.8 17 0.258

0 195 1.22 0.544

0.681 0.609 0.676

3.2 1 2.25 309

6.5 1 5.04 5.94

I

0223 0. 11 9 0.325 0.230 0.3 12

*B/C Tap - Tap located on inlet to plant (idemi fied as before chlorination for hisrorical reasons)

WATER DECEMBER 1993


from water treatment planes and distribution systems during the period J anuary 1992 June 1993 are summarised in Table 2. Composi te samples (24 hour) are take n thre e rim es a wee k from che outlet of eac h water creacmenc plane . The location is se lec ted afte r all stages of treatment in cl uding disinfection but prior to any storages. Thi s enables direct assessment of plane performance. Mon itoring at che cuscomer tap (by grab sampling) was introduced in August 1987 co give better information on the quality of the water received by the cuscomer, in compliance with guidelines issued by the NHMRC. All water creacmenc planes except Morgan are sacisfaccorily meeting che 0.20 mg/L operating guideline for at lease 90% of the rime. Compliance with the guideline does nor occur 100% of the rime mainly due co the occasional operational difficulty although data over the years indicate chat compliance has improved significantly since an increased emphasis on the importance of aluminium monicoring has been applied and with che introduction of improved sampling and analytical techniques. The average results obtained at the customer taps in eac h sys tem are ge ne rally similar co chose obtained directly after creacmenc at the plane. Mose systems tend co modulate the highs and lows experienced at the plane resulting in lower maximum levels and higher minimum levels at che cuscomer tap as might be expected. This also results in cuscomer caps generally having a higher 90 percentile than chat at the plane although chis is still below the 0. 2 mg/L guideline level. The Morgan system cannot be monicored usin g customer tap locations to refl ec t changes in created water through the system as ocher water sources from uncreated reservoirs can be used co supplement the supply as required. Locations on che main pipeline are Table 2: Alumini11m in Treated Waters in South Australia,Janttary 1992-]ttne 1993 Supply Hope Valley WTP After Treatmenc Customer Taps Barossa WTP After Treatment Customer Taos Anstey Hill WTP After Treatment Customer Taos Happy Valley WTP After Treatment Customer Taos Little Para WTP After Trearmenc Customer Taps Morgan WTP After Treatment Morgan NC Tap* Morgan-Whyalla Pipeline (Hanson Flowmeter)

Total Aluminium (mg/L) Max Min Ave 90% 0.263 0.199

0.032 0.070

0 103 0. 127

0 165 0.188

0.683 0.221

0.029 0.060

0.1 37 0 130

0 192 0.200

0.783 0.167

0056 0 059

0.1 32 O.l 13

0. 190 0.154

0.245 0233

0.044 0.039

0109 0. 116

0.154 0.167

0.275 0.159

0.027 0.060

0.087 0. 123

0. 124 0.158

0.563 0.455

0.008 0.015

0. 167 0.112

0.349 0276

0. 167 0.238 0.04 1 0096 * A/C Tap - Tap located on pipeli ne after treatment and chloramination

WATER DECEMBER 1993

used fo r chis purpose. There is a significant reduction in th e aluminium levels in che Morgan system as reflected by the results at Morgan A/C Tap and at Hanson Flowmecer on the Morgan-Whyalla pipeline, indicating chat pose flocculation is occurring in chis particular pipeline.

Conclusions

Di sease: Ep idem iology and Etiology of Amyotrophic Lateral Sclerosis ?rid Parkinson ism -dem encia in the Western Pacifi c, Environmen tal Geochemistry and Health, 12, 137-151 Good P F, Perl D P, Bierer L Mand Schmied ler J (1992), Selective Accumulation of Aluminium and Iron in the Neutofibrillary Tangles of Alzheimer's Disease: a Laser Microprobe (LAMMA) Study, Ann. Netl1'ol. , 3 l, 3, 286292 Gorelick P B and Bozzola F G (1991), Alzheimer's Disease: Clues to the Cause, Postgradua.te Medici,,,, 89 , 4, 231240 Knoll 0 , Kellinghaus H, Bertram H P, Zumkley H and Graefe U (1984), Gastrointestinal Absorption of Aluminium in Chronic Renal Insufficiency, Co1Ztrib11tions to Nephrology, 38, 24-31 Landsberg J P, McDonald Band Watt F (1992), Absence of Alumi ni um in Neuritic Plaque Cores in Alzheimer's DisettJe, Nat11re, 360, 65-68 Martyn C N, Barker DJ P, Osmond C, Harris EC, Edwardson J A and Lacey R F (l 989), Geographical Relacion Between Alzheimer's Disease and Aluminium in Drinking Water, Lamet, i, 59-62 Pontius F W (1992), A Current Look at the Federal Drinking Water Regulations,] A\\1/\VA, 84, 3, 36-50 Potocnik F (1990), Aluminium and Alzheimer's Disease in Perspective, GeriatRx, 2, 2, 14-18 Sayre IM (1988), International Standards for Drinking Water, J A \\1/\VA, 80, l, 53 -60 Van Benschoten J E and Edzwald J K (1990), Measuring Aluminium During Water Treatment: Methodology and Application ,] A\\1/\VA, 82, 5, 71-78 Water Resea rch Centre/Medical Research Counci l Study (1988), Aluminium in Drinking Water and Heal th , Personal Communication from Wessex Water Authority

Under certain circumstances aluminium is coxic co humans. In most cases chis appears tQ be related to expos ure to elevated aluminium levels and a reduced ability co eliminate aluminium from the body. Research into the mec han ism fo r accumulation of al uminium in the brain needs co be undertaken. The exact nature of the functional defect of the protein cransferrin and ics role in chis mechanism needs co be elucidated, leading co future preventative and therapeutic possibilities which may negate the health effect of aluminium. Aluminium has also been implicated in the aetiology of Alzheimer's disease and an epidemiological study correlated the risk of Alzheimer's disease with aluminium in drinking water. Although chis study was strongly criticised, the importance of aluminium in drinking wate r in relation to Al zheimer's disease requires further evaluation. The relative bioavailabilicy of aluminium in created Authors Mary Drikas has been the Senior Chemist, and uncrea ted drinking water needs co be determined, cogecher with the extent of con- Water Treatment Unit, in the A11stralian Centre tribution from sources ocher than water eg: for Water Quality R'esearch since its inception in food. Answers co these questions need co be 1987. She has been employed by the Engineering determined co enable meaningful and relevant and Water Supply Department since 1976 with guidelines to be established for the water ten years exj!erience in water treatment studies. She has a B Sc (Hons) from Adelaide University and industry in the future. Water quality guidelines are currently a Post Graduate Dip in Analytical Chemistry being reviewed by a number of national/ from the University of South Australia. internatio nal bodies. These rev iews will include aluminium. It appears unlikely chat the current aluminium guidelines wi ll be reduced or altered from aesthetic co health related guidelines.

References Alfrey AC (1986), Aluminium Metabolism, Kidney International, 29, 18, 8-1 l Alfrey A C, Hegg A and Craswell P ( l 980), Metabolism and Toxicity of Aluminium in Renal Failure, American Joumal of Clinical Nutrition, 33, 1509-1516 Birchall] D and Chappell J S (1989), Aluminium, Water Chemistry and Alzheimer's Disease, Lancet, April 19, 953 Carney M (1991 ), European Drin king Water Standards, ] AWWA, 83, 6, 48-55 Emmett WE and Kennedy R (1987), Soluble Aluminium Levels in Treated Water, Internal Report, State Water Laboratory , Adelaide Eureau (1992), Drink ing Wate r Directive 80/77 8/EC Eureau's Views on Ptoposals fo r Mod ificat ion, J Water SRT-Aqua, 41, 2, 101-108 Farrar G, Al rmann P, Welch S, Wychrij 0 , Ghose B, Lejeune J, Corbett J , Prasher V and Blair J A (1990), Defective Gallium-Transferrin Binding in Alzheimer Disease and Down Synd rome: Possible Mechanism fo r Accumularion of Aluminium in Brain, Lancet, 335, 747 -750 Garruto R M and Yase Y (1986), Neurodegenerative Disorders of the Western Pacific: the Search for Mechanisms of Pathogenes is , Trends in Neurosciences, 9, 368-374 ,Garruto R M, Yanagihara R and Gajdusek D C (1990), Mod els of Env ironmenta lly In duced Neuro logical

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19


TECHNOLOGY

BEHAVIOR OF ALUMINIUM SPECIES DURING WATER TREATMENT M] McCormick,] G Hughes\ P Zhang, M Brymner

·"'

Abstract

fluoridated drinking water in the Morning- and Driscoll, 1984). The total monomeric Water from the Bunyip river and Tarago ton Peninsula water supply. These levels were fraction was determined using extraction by reservoir is used as part of the water supply above the WHO guideline (0.20mg/L). The the chelating agent 8-hydroxyquinoline. A for rhe Mornington Peninsula. This water is Mornington Peninsula currently receives 20mL aliquot of the rest water was transferred highly coloured and requires relatively high most of its water from Cardinia reservoir, to a separatory funnel. Five drops of phenol doses of alum if colour is to be removed by supplemented from the Bunyip and Tarago red indicator and 4 mL of 5% 8-hydroxyfiltration. The addition of alum , however, can river catchm en ts. The Bunyip Main Race quinoline were added. Ammonia solution (10 lead to high levels of residual aluminium . conveys water to the Tynong water treatment molar concentration) was then added dropThis can produce post-treatment flocculation, plant from the Bunyip and Tarago catch- wise rill rhe solution turned red. Immediately leading to 'dirty water' complaints. High ments. The untreated water has a high level after this 5 mL of pH 8.3 NH3 /NH4Cl concentrations of aluminium in drinking of colour and, at rimes , turbidity, and is fluo- buffer and 15 ml of MIBK were added. The water may also lead to human health prob- ridated at Tonimbuk (Table 1). The treatment aq ueous phase was then separated and lems, bur this is only a hypothesis at present configuration is 11m1s11al in that fluoridation is analysed for aluminium using the method (Ashton and Laura, 1989) (Drikas, this issue). carried out before the alum coagulation/ sedimenta- discussed above. Monomeric aluminium was A study was undertaken to determine the tion/ filtration process used in the Tynong water calculated by rhe difference between total behavior of both aluminium present in treatment plant. reactive alumi nium and nonextracrable alunatural water and aluminium added during mmmm. water treatment processes. An important aim Materials and Method The monomeric inorganic or labile (cationSamples. Water samples were collected exchangeable) aluminium fraction was deterwas to obtain a set of operating parameters to minimise aluminium concentrations in the from the Bunyip main race and rhe Tarago mined by ; assing a water sample through a channel leading into the main race. Batches filtered waters. The two parameters found to have the of 40 litres were collected and stored in poly- Table 1 Typical Data for the Unfluoridated greatest effect on residual aluminium levels ethylene carboys. pH, alkalinity, colour and Water S11pply were alkalinity and fluoride concentrations. turbidity were measured immediately after 6.1-6.8 pH Fluoride, in particular, when present at about the water samples arrived at the laboratory. 5-12 alkal inity (mg CaC03/L) colour (Pt-Co units) 45-65 0.9 mg/L was found to cause greatly elevated Jar rests were carried our to determine the turbidity (NTU) 3-8 levels of residual aluminium in filtered water. optimum alkalinity for stable alum floe fortotal reactive A1 (mg/LOO) 009-0 2 Speciarion studies were carried out on both mation. Fluoride was measured by Ion ChroFluoride (mg/L) <.l the raw and treated water. The results show ma rog raph y usin g a Dione x 2010i Ion that the alumin ium is largely organically Chromatograph. Table 2 The Resid11al Al11mini11m Levels at Aluminium Detennination. To deterbound before treatment but is mostly in Varying Alkalinities an inorganic form after alum coagulatio n mine low levels of aluminium , care must be 8 20 30 40 50 60 70 80 and filtration. Most of the increased alu - taken to avoid contamination . Laboratory Alkalinity minium in the presence of fluoride seems to glassware is a major source of such contami- (mg CaCoJL) Alum Dose 20 35 50 65 80 95 100 115 be bound as so luble cationic fluoro and nation. Polythene containers were used ro (mg. L) store samples and standards. All containers pH after hydroxy complexes. 5.6 6.5 6.6 6.8 69 7.0 7.2 7 3 were soaked in 10% AnalR grade nitric acid flocculation Introduction 200 8 9 16 4 7 19 24 for at least 24 hours prior to use, and then Residual Al Aluminium salts are widely used as coag- rinsed with distilled water. Aluminium (µg/L) ulants in the water treatment industry. Coag- analyses were performed by Graphite Furnace ulation by alum then filtration is effective for Atomic Absorption Spectrometry (GF-AAS), Table 3 Resid11al Alimzinium Levels of removing turbidity and colour from natural using the Perkin Elmer Zeeman 5100 GF- Water Containing 0.8 mg!L Fluoride waters. However, the use of aluminium coag- AAS with an AS-60 auro sampler. 1% Alkalinity 8 20 30 40 50 60 70 ulants, particularly alum , may result in ele- Mg(NO3)1 was used as modifier. Samples (mg CaCoJL) 25 35 50 70 80 90 100 vated concentrations of aluminium in treated were filtered through a 0.4 5µ.m membrane Alum Dose (mg.L) waters (Driscoll and Letterman , 1988). filter and acidified to 1%(v/v) using AnalR pH after 5.6 6 5 6.6 6.7 6.9 7.0 7.4 The present study, jointly sponsored by grade HNO3 prior to analysis. Following rhe flocculation the Mornington Peninsula and District terminology of Driscoll (1984) this is referred Residual Al 1103 224 74 69 48 35 35 (µg/L) Water Board (now part of Melbourne Water) to as the total reactive al,mzinimn. and the Urban Water Research Association of Separation of specific aluminium fractions Australia, was initiated after observations of can be achieved by using various pretreatment *Jeff Hughes, Applied Chemistry Departelevated levels of aluminium in previously steps (see Van Benschoren and Edzwald, 1990 ment, RMIT Univers it y. 20

WATER DECEMBER 1993


i

-

J!111. J i

. ! Trpt" Of WatcrTcstcd

j

~

E-

!

Al~

Figure 1 Speciation of Al D11ring Alum

Treatment strong acid cation-exchange column. Amberlice IR-120 resin in che sod ium form was used . The co lumn was pre-was hed wich 0.00 1M NaCl. The eluenc was collected and analysed for aluminium as previously. The difference between chis fraction (the organi cally bound aluminium) and the coca! reactive aluminium is che monomeric inorganic aluminium.

Results and Discussion Characteristics of the Natural Water. The natural unfluorid aced water

can contain quite high levels of coca! reactive aluminium (Table 1). Effect of Alkalinity on the Residual Aluminium After Alum Treatment.

entering the Tynong creacmenc plane is about 0.9 mg/1 and chis drops co about 0. 7 mg/1 in che fi nal _fi ltered water from the plane. The effect of fluoride in che water is a markedly higher level of residual aluminium compared co unfluoridaced water receivi ng che same creacmenc (Table 3). The elevated levels of residual aluminium in the presence of fluoride have previously been noted by Sung and Rezania (1985) and Driscoll and Letterman (1988). The levels of residual alumi nium in the treated water from jar tescs drop markedly over che range 20-30 mg CaCOi/1 of alkalinity. Thus the unwa nted effec t on res idual alum inium of flu oridati on can be red uced by a small increase in alkalinity. However much more alum is needed, creat ing higher slud ge production. Also, residual aluminium levels were scill 3 co 10 times chat for unfluoridated wacer. Changes in Speciation of Aluminium during Alum Treatment. In

the present study aluminium was separated inco a coca! monomeric (oxine excraccable) frac tion and a polymeric or colloidal fraction. The monomeric frac tion was furt her speciaced using cation exchange inco a labile fraction (species such as Alfr, AlF·· , Al(OH)2· and Al(OH ).. ) and a non-labil e fract ion (alumina-organic complexes). Neutral species such as AlF3 would also be included in che laccer frac tion (Driscoll , 1984). Ac che pH levels of both che treated and uncreated water (in che absence of fluoride) of 6-7 ch e prin ci pal ca ti oni c spec ies is

Al(OH )2· . In che prese nce of fl uoride, ac about lmg/1, 'llF" is che pri ncipal species of fl uoroaluminace (Piecer, 1985). The pH is critical, as above pH 7, ac chis level of fluoride, only hydroxy species exisc. The calculated distribution of aluminium species is shown in Figure 2. Calculations are based on data from Piecer (1984). Jc should be noced chat over much of chis pH range che princi pal species of aluminium present in solution is Al(OH)i(aq). The speciacion studies show chat for the natural water, boch in che prese nce and absence of fluoride, che aluminium is predominantly in cfie non-labile form (Figure 1). The raw water, collec ted pri or co fluoride creacmenc, was created wich alum using che jar cesc technique. The residual aluminium is now mos tly in che monomeri c inorgani c form. With fluoride present the coca! residual aluminium increased mark edl y and ch e increase is mainly present as cationic species (as shown by che cation exchange studies). Jc thus seems chat che increase in soluble aluminium is due co the formation of species such as Alf° ·. Figure 2 shows che calculated distribution of aluminium complexes as a fun ction of pH. The calculacions show chat below pH 6.3 ca ti oni c flu oro species predominate, although che pH of the water samples after fl oe fo rmati on and filt ra ti on is usuall y slightly above chis range (6.3 co 6.8). Calculations used co pr,oduce Fjgure 2 give the percentage of each species of aluminium only. However, using che percentage of free alu-

Effective flocculati on by alum treatment is based upon che formation of a stable floe of coagulated colloidal material. The fl oe consists of coag ul ated suspe nd ed soli ds and humic substances cogecher with hydrolysis ... produces of alum. The reactions of alum with alkalini cy in water can be represented by the fo ll ow ing eq uati on: Al2(S O4)i.1 4H2O + 6HCOi2Al(OH)i + 3SO4= + 6CO2 + 14H2O 'Alum ' 'Alkalinity' On the basis of chis scoichiomecry, 1mg/1 of alum would decrease the natural alkalinity +--= 0 of the water by lmg/1 (as CaCO3). Alum is 5.5 6.5 6 7 dosed ac the inlet co the creacmenc plane ac a pH concencracion of 20mg/L and che alkalinity is adjusted co obtain optimum fl oe formation. ---o-- AIOH2+ - - + - AIOH3 -<>-- AIOH4The natural water has a low alkalinity (Table 1) and chis causes poor floe fo rmation and - XAIF2+ --ts-- AIF + + -<>-- A IF3 undesirable colour retention. A study of the effect of alkalinity on residual aluminium , Figure 2 Distrib11tion of Fluoro and Hydroxy Aluminium Complexes at lppm F after alum creacmenc (Table 2), for unfluoridaced water shows that low alkalini cy causes high levels of aluminium in che created water 160 - - - - noF (due co poor floe formation). However, high 140 alkalinity requires increased dosage of alum ---0-- + lppm F co achieve a stable floe and chi s produces 120 more sludge during creacmenc. 100 The alkalinity shown in Table 2 is che c( 80 coca! alkalinity in the water sample prior co ..QQ. Q. 60 additi on of alum. Th e alum dose is the minimum dosage necessary to ach ieve a 40 stable fl oe . The residual aluminium is che 20 measured aluminium in che water, after for0 mation and seeding of the floe and filtering.

=

-

Effect of Fluoride on Residual Aluminium After Alum Treatment.

The level of free fluoride in the raw water WATER DECEMBER 1993

5

6

7

7.5

8

pH

Figure 3 Total Reactive Afzmzinittrn 21


minium from these calculations and the solubi li cy constant for Al(OH)3 (10-33.5, Marcell and Smith, 1989) che coc;il concentration of soluble aluminium can be calculated. Figure 3 shows the pH dependence of coral aluminium (with no F, and lmg/L). Boch curves show a minimum in the pH range 6-8, bur the curve with fluoride present is much more dependent on pH. This supports the earlier observation char the residual aluminium can be reduced by increasing alkalinity.

Conclusions The results of chis study show char levels of residual aluminium in drinking water are strongly affected by both the initial alkalinity and levels of fluoride. The latter, in particular, can cause greatly elevated levels of aluminium ro levels well above chat specified as desirable in HMRC/AWRC(l987) and WHO(1984) guidelines for good, aesthetic water quality. The increased soluble aluminium is present mainly as cationic inorganic species. The solubilising effect of fluoride can somewhat be reduced by increasing the alkalinity bur chis means higher levels of alum are needed co achieve a stable floe, producing more alum sludge for disposal.

References Ashton] F, Laura RS (1989) Search, Vol. 20, 180. Dri scoll CT (1984) , llltern. J. Environ. Anal. Chem., Vol. 16, 227 Driscoll C T, Letterman R D (1988) J. E11vil'o11. Eng., Vol. 114, 21. Marcell A E, Smith RM (1989 'Critical Stability Constants' , Plenum Press, New York Pitter P (1985) \Vat,,. Res., Vol. 19,281 Sung W, Rezania S, Environment Technology Lettel's , Vol.6, 11 Van BenschotenJ E, EdzwaldJ E 0 990)A\f/\f/A May, 71

Authors Ma,lcolm McCormick is a Senior Lecturer in the Department of Applied Chemistry, RMIT His research interest is in environmental analytical chemistry and includes heavy metal speciation, the fate of toxicants during sewage treatment and the meamrement of toxicity ming the Microtox test. Jeff Hughes is a Lecturer in the Department of Applied Chemistry, RMIT He teaches in the areas of physical and environmental chemistry and has research interests in the areas of water treatment, toxic waste disposal and chemometrics. Mark Brymner is a Senior Analytical Chemist with Melbourne Watet: He has previously worked as an Analytical Chemist with the Latrobe Valley Water and Sewage Board and an Environmental Chetnist with the Alb11ry-Wodonga Development Corporation. His main research interests are in inorganic analysis of waters, wastewaters and sediments. Zhang Pei has just completed a Masters thesis in the Department of Applied Chetnistry, RMIT and is mrrently working in the Organic Chemistry section of the State Chemistry Laboratories.

22

BOOKS Bioaccumulation Proceedings of the Workshop, Sydney, 1991. ISB N 0 7305 2611 9. 330 pages. Publisher, The Sydney Water Board and the Australian Marine Sciences Association Inc. Available from Dr A Miskiewicz, Environment Management Unit, Water Board, PO Box A53, Sydney South NSW 2000. Cost $75 This excellent record _of the three-day workshop contains 32 full papers and eight abstracts of posters and oral presentations. Key-note speakers from UK and USA joined with presenters from all scares of Australia. A considerable proportion of the Workshop related co the effects of the Sydney ocean discharges, providing a database for future moni coring, bur ocher data ranged from the Torres Strait co Tasmania. A feature was the critical analysis of analytical techniques. The book is well-rounded by a 14-page review of bioaccumulacion of trace contaminants in aquatic environments by Dr DJH Phillips, of Acer Environmental, UK, accompanied by well over 100 references. This in itself would justify purchase of the book, but the results of many research projects around Australia make the book a required reference for anyone involved in the field who was not chemself a delegate co che Workshop. EA Swinton

Design of Flood Storage Reservoirs

Editors: M J Hall, Professor of Hydrology, Delft. D L Hockin, Flood Defence Consultant. D B Ellis, Professor Middlesex University, (CIRIA) London and Butterworth Heinemann. First Published 1993. ISBN O 7506 1057 3. 180 pages in 8 chapters. Available from Butterworth-Heinemann, PO Box 34$, North Ryde NSW 211. Cost: $155 This book contains practical guidance and recommended methods for runoff estimations from urbanising areas, the design and operation of flood storage reservoirs and guidance on water quality issues. Ir is based on and supersedes CIRIA's Technical Nore T 100 'Guide co the design of storage ponds for flood control in partly urbanised areas' (1980) after the addition of sections on water quality and considerable review by practitioners. Procedures are focused on the English practice and legislacion. Five chapters (70 pages) deal wi th the need for flood control basins, planning and design procedures and hydrologic methods for flood estimation and flood routing using graphical, simplified and complete procedures for wee, dry , onscream and offstream reservoirs. A chapter on water quality gives 70 pages of performance dara and analysis procedures for pollut nc routing under steady and Marine Disposal Systems varying flow conditions and provides practiEditor: Garber. Pergamon Press. ISB N cal and cheorecical guidance for predicting both the conditions within the reservoir and 0080421865. Cost:£ 50 This W.S.T. £i:9 is devoted co the pro- in downstream waterways. In chis regard ic is ceed ings of an IAWPRC Conference held a valuable reference. in Lisbon, 20-22 November, 1991. Some 31 A comprehensive compendium of design papers are presented under six copies; envi- formulas , parameters and functional design ronmental impact studies, submarine outfall is given in the 60 pages of chapter 7. Wee design and constructi on, and cultural legal and dry basins are covered, as are hydrologic, and social issues. As these headings indicate, hydraulic, environmental and recreational the conference was nor focussed sole!y on considerations. Outler arrangements novel ro the technical consideration of outfall design, the Australian scene are described with pracbur brought our thoughtful contributions tical examples. on issues such as: the appropriateness of enviChapter 8 describes in 6 pages fundamenronmental standards by which co gauge tal operational considerations for che reseroutfa ll performance (Lu dwi g et al), the voirs and associated pollution control framing of monitoring programs by which measures. Appendices deal with UK scacuongoing outfall performance can be measured cory requirements and generic requirements (Gardner). for water spores. · Papers of interest co che reviewer include The publication should provide a valuable char of Kaye & Haddad, looking at natural compendium for planning, design and operafluorescence in effluent-seawater mixtures as tion for Australian applications covering a a tracer of outfall fields - the ocher natural comprehens ive range of issues for flood tracer coproscanol, is cursorily dismissed in control reservoirs (retarding basins/detention chis paper. The paper of Bell et al, examining basins/compensating basins) in the urban che interaction of proposed sewerage outfalls context. The book's value is in its completeon che west and ease side of the mouth of ness and practical approach co design, operaWellington Harbour, New Zealand, is also a tion and water quality even through a large very comprehensive accounting of che various pare contains hydrologic and flood routing factors influencing faecal coliform concentra- procedures which have liccle correspondence cions in receiving waters. with current Australian practice. David Mitchell Tim] Pollock WATER DECEMBER 1993


MANAGEMENT

GUIDELINES FOR USE OF BIOSOLIDS - THE QUEENSLAND SCENE PD Beavers* Summary The Queensland Department of Primary Industries-Water Resources is developing guidelines for the beneficial use of biosolids. These guidelines will assist local Authorities with selecting the most practicable and cost effective beneficial use option. This paper discusses some of the more relevant aspects of the Guidelines and presents some maximum contaminant concentrations that will be permitted for the adopted three tiered biosolids classification system. Current biosolids projects being undertaken by local Authorities and the Department of Primary Industries are discussed.

Introduction One of the challenging issues confronting local Authorities in Queensland and other Australian States is the disposal of the solid residue - sludge - from the treatment of domestic wastewater. To most Australians, sewage sludge creates an image of an unwelcome evil ooze. This image must be dispelled if sewage sludge is to be promot ed as a resource. The wastewater industry is trying to respond to this poor impression of sludge with bmer communication skills. The industry, particularly in the USA, has recommended a new name for sludge, "Biosolids".

"Biosolids" - processed wastewater solids that can be managed safely to 11tilise beneficially their nutrient, soil conditioning, energy or other value. In this paper will be used the term "bioso lids" for the processed material and the term "sludge" will refer to material collected in treatment plants before it is processed. The term includes products which contain a percentage of biosolids. The beneficial use of biosolids is gaining momentum throughout local Authorities in Queensland. Over the pas t few years, the Department of Primary Industries has encouraged the beneficial use of biosolids where practicable and safe to do so. The definition of "safe" in thi s co ntext was ap tly defined by Sparkes (1993) as " where risks to human health, anim al health, che environment and quality of agricultural produces are within acceptable levels. " To assist local Authorities with selecting WATER DECEMBER 1993

the most practicable and cosc effective beneficial use option, guidelines are being developed by the Department of Prim ary Industries (referred co herein as DPI Guidelines). The DPI Guidelines will indicate current philosophy and what is considered co be sound practice ac this time. Ir is anticipated chat che DPI Guidelines will be completed and circulated in early 1994. This paper summarises che current biosolids invescigacions and beneficial use projects that are being undertaken in Queensland and discusses some of the more relevant aspeccs of che DPI Guidelines.

Current Biosolids Use Table 1 compares biosolids production in Queensland and ew South Wales. Queensland does not produce the same volumes of biosolids as New South Wales. In 1989 a survey of biosolids disposal practices in Queensland was carried out and the results of chis survey showed char 60% of local Authorities scockpiled all their biosolids on dedicated land, 30 % landfill ed the biosolids and che remaining 10% used some of the biosolids beneficially. Out of 134 local Authorities only 3 scared that 100% of che biosolids production was beneficially used. Attitudes have changed. A large number of local Authorities are now implementi ng small pilot schemes which include composting of biosolids co produce a produce suitable for their requirements. Logan City Council has contracted BioRecycle Pry led co process a percentage of che biosolids production into a soil product which wi ll be suitable for marketing as a fertiliser and soi l conditioner. Negotiations are scill in progress for Logan City Council to make available 10 connes/day (d ry solids) of biosolids Q. Evans, pers. comm. Nov 1993) for incorporation into marginal quality agricu ltu ral land on che southern edge of che Darling Downs. New Hope Corporation limited, Jeebropilly Coal Mine, near Ipswich, used biosolids for open cue mine rehabilicacion. The dewatered cake was applied ac che rate of 50 dry tonnes/ha over an area of approximately 10 ha and incorporated co depth of 75 mm immediately after spreading. The

'

exposed barter was then seeded wich mixture of pioneer rhodes, couch and winn rye grasses (Bio-recycle, 1993). This pile scheme has been so successful chat forth, areas are co be rehabilitated with biosolids. The Brisbane Cicy Council commissiont che DPI co "study the effects of sewai; sludge application co forests and soils of d Beerburrum Forestry District, and co ma! recommendations on che suicabi licy of d future long term app li cation of sewai; sludge". The results of chis study should f published in 1994. In addition , che Brisbar City Council have used biosolids, after a ageing period of cwo years, as a subsoil f< land rehabilicacion at creacmenc planes, refa rips and Government outlets such as the co1 scruction of the international airport. A couple of local Authorities are invest ga ting the use of biosolids on sugar car lands. The DPI will be involved in these pi!, studies when chey gee underway. Ac presen the DPI is initiating several research projec with Griffith University but the final decai of these projects are nor available. The resul of all the pi lot studies wi ll be collared ar used co either sec guidelines or validate cl guidelines char are in use at present.

Guideline Development In 1990, Draft "Guidelines for Dispos or Use of Sewage Sludge on land" were pr pared by che then Wacer Resources Commi sion. They were initiated ac che request several local Authorities which had raist concerns about che li ab ility in the use biosolids in public parks and recreation areas, by give-away co the general public ar in the production of composting material The Draft Guidelines were a first attempt formalising local practices which have devt oped over a number of years. Since the production of the Draft Guid lines knowledge of biosolids app li catic co land has increased considerably. Tl USEPA Pare 503' Regulations for the "U and Disposal of Sewage Sludge " ha, been promulgated; the NSW Agricultu "Guidelines for che Use of Sewage Sludi on Agriculrnral land" have been revised ar

* P D Beavers, Water Resources.


in 1990 the Agricultural and Resource Management Co un cil of Au stra li a and New Zealand (A RMCA NZ), embarked on the preparation of Nationa l Gu{de lin es for Sludge Management. The DPI Guidelines, which will be a revision of rhe previous Guidelines will serve as an interim document until the publication of the arional Guidelines. After rhe arional Guid elines are pub lished DPI-Warer Resources will review the DPI Guidelines to ensure they fir within the National framework.

Aim and Objectives of the Guidelines The objectives of the DPI Guidelines are ro: • Encourage beneficial use of biosolids; • Encourage deve lopment of sustainable and cost effective biosolids management strategies by Local Authorities; • Ser cri reria ro define and classify various classes of biosolids and prod ucrs of biosolids in relation to contamination and utilisation; • Ensure adequate controls are ser ro protect the environment, public health, animal health, agricultural land and agricultural products; • Estab li sh procedures for monitorin g, reporting, record 0 keeping and auditing. Importantly th e DPI Guide lines wi ll promote biosolids as a resource which can be used beneficially where it is safe and economically practicable. This requires assessment of the levels of risks and balancing them against setting conditions on Local Authorities and users which are nor too onerous. The Local Authorities must also aim ro reduce the level of contaminants in biosolids. This can be achieved in part through trade waste control programs and by encouraging the use of environmentally friendly pesticides.

Beneficial Use and Disposal Options To achieve the best use of biosolids and ro ensure adeq uate environmental and public health protection, the prime consideration when developing a biosolids management program is to select the preferred beneficial options or a disposal routes . The options may be broadly classified as follows: • Unrestricted use/sale of sludge or sludge product; • Agricultural land application; • Non-agricultural land application; • Secure landfill; • Stockpile on dedicated land; • Thermal processing. Thermal based processes use hear ro drive off water and desroy volatile organics. There is a variety of these processes including incineration, oil from sludge, aqueous-phase oxidation and the Carver-Greenfield process. They require large capital and operating expenditure and are not being considered at present in Queensland. 24

The optimum strategy for implementing any of the beneficial use or disposal options comprises: • Sustai nability; • Cost-effectiveness; • A least environmental risk approach; • Operational securiry; • Sufficient security to accommod ate reasonable future changes in legislation and accepted operational practice.

Classification Quee nsland proposes to adopt a three ti ered biosolids classification sys tem. The classification system is based on the measured levels of heavy metals and chlorinated organic compounds in rhe biosolids. Through a sampling and resting program, biosolids can be classi fied into one of the three classes. A range of allowable beneficial uses or disposal methods will be permitted for each class. The three classes are: • Class A: includes biosolids whi ch are suitable for unrestricted sale to the public and can be used as a soil or as soil supplement for domestic, horticultural and agricultural applications. • Class B: includes biosolids which have levels of heavy metals, chlorinated organic compounds or pathogens which exceed the Class A limits given in Tables 2 and 3 and are suitable fo r application to land subject to sire management practices rhar wi ll be defined in the DPI Guidelines. • Class C: includes any biosolids in which th e co nr aminanr s exceed th e Class B limits given in Tables 2 and 3. Biosolids which have not been sampled and tested are classified as Class C and should remain under rhe control of the Local authority. Each beneficial use or disposal method will have requirements for the reduction of pathogens and vecrors. Queensland proposes to include, for heavy metals , maximum concentrations in rh e topsoil and maximum cumulative loading rares for biosolids application ro agricultural land based on those given by Ross (1991).

Heavy Metals The presence of heavy metals in biosolids is a major constraint to their use on land. Unlike pathogens which have a finite life, heavy metals persist in the environment. When calc ulating safe loading rares for biosolids ro land , rhe target is that the soil should nor be degraded beyond acceptable limits. Thar is, sustainability of the application sire should nor be prejudiced in the imm edi ate or long term . A conserva tive approach ro setting maximum concentrations of heavy me tals in Class A been has been taken ro ensure sustainability of the application sire particular! y because biosolids could be marketed for use in the home garden. Facrors taken inro account when setting ma ximum he avy mera l concentrations included ph yrorox icir y of planes, back ground levels of heavy metals in soils and

the available information on the potential risk ro public h alth from heavy metals such as cadmium and lead. Queensland proposes to adopt rhe maximum heavy metal concentrations given in Table 2 for Class A and B biosolids. In the absence of suitable data pertaining ro Queensland it has been decided ro adopt rhe Ceiling Concentration Limits contained in the USEPA Parr 503 Regulation for rhe "Use or Disposal of Sewage Sludge". Pilot Projects being initiated by the DPI wi ll be used ro confirm that rhe maximum concentrations for Class Bare relevant to Queensland.

Chlorinated Organic Compounds A range of roxic chlorinated organic compo unds is found in biosolids. These comTable 1 - Comparison of Biosolids Production in Queensland and New South Wales NSW * Qld Tonnes Tonnes Locality dry solids/day dry solids/day Malabar 63 Bond i 9 Brisb. Ci ty Council North Head 10 45 4; Sub Total 82 Cronulla, Warriewoocl Inland Plants 23 Blue Mountains Plants 2 Illawarra Plants 8 Total Sydney 120 , Water Board

Locality

Newcastle,

Hunter Rural NSW

100

Gold Coast Rural Qld

10 78 133

m • Information provided by the Sydney Water Board

Table 2 - Maximum Concentrations for Heavy

Metals in Biosolids When Applied to!.And Constituent Arsenic

Cadm ium Chromium Copper Lead Mercury Mol ybdenum 1ickel Selenium Zinc

Class A mg/kg (dry solids)

Class B mg/kg (dry solids)

20.0 2.0 200 140 150 1.5

75 0 85, 3000 4300 840 57 75 420 100 7500

60 300

Table 3 - Limits for Selected Chlorinated Organic Compounds in Biosolids Constituent

Class A mg/kg (dry sol ids)

Class B mg/kg (dry solids)

DDT/DDD/DDE 0.5 50 (Total Isomers) 2.0 *Aldrin 0 05 *Dieldrin 2.0 0.05 Chlordane (Total Isomer) 2.0 0.05 Heptachlor and heptachlor epoxide 0.05 2.0 Hexachlorobenzene (HCB) 2.0 0.05 Lindane (gamma HCH) 005 2.0 Polychlorinated biphenyls (PCB's) 0. 3 30 * Dieldrin is formed from aldrin by metabolic oxidation in animals or by chemical oxidation in soil

WATER DECEMBER 1993


pounds include organochlorine pesticides, PCB's, chlorinated hydrocarbons, as well as chlorinated aromatic compounds. The origin of these compounds is unclear but sources appear co be through infiltration, illegal disposal co a sewer, dumping of old chemicals co the sewers by householders and possibly through our diets. During the sewage treatment processes the organic subsrances accumulate in the primary and secondary sludges. The chlorinated organic compounds are characterised by one or more of the following: • Resistance to conventional aerobic and anaerobic biological treatment and persistence in sludge; • Low water solubility and minmum mobility in soil; • Persistence in soil due to resistance co microbial degradation; • Fat solubility and ability to accumulate in fat tissues; • Known to be carcinogenic and mucinogenic. Australian Agricultural Authorities have considerable experience in the study of excessive organochlorine pesticide residues in grazing animals. Derailed risk assessment of the hazards of applying sewage biosolids containing pesticides have been made by Ross (1992). Use of chis data has been made in setting maximum concentrations for organochlorine pesticides and PCB's given in Table 3. Levels of dieldrin of 0.05 mg/kg (dry solids) and above in the biosolids/soil mixture may produce maximum residue violations in cattle. Where biosolids are applied to land on which livestock may graze after application, the coral DDT/DDD/DDE concentration in the soil/biosolids mixture must not exceed 0.5 mg/kg (dry solids) and 0.02 mg/kg (dry solids) for any ocher organochlorine pesticide. The same is currently applicable in New South Wales (Ross, 1991).

reseed for compliance with the following pathogen levels; • the densi cy of Salmonella sp bacteria in the biosolids shall be less than 3 MPN per four grams of coral solids (dry weight basis); • the density of enceric viruses in the biosolids shall be less than one Plaqueforming Unit per four grams of coral solids (dry weight basis); • the density of viable helminch ova in the biosolids shall be less than one per four grams of coral solids (dry weight basis).

Class B These sludges require a lesser degree of pathogen reduction as rheir end use is co be controlled and therefore considered co be less susceptible co the spread of disease. A sludge can be classified as Class B provided it has been created by one of the processes given in Table 4. The practice in Queensland has been to srockpile biosolids for a minimum 12 months before application co land. The origin of the time period is uncertain. The Department of Health, at the request of the then Water Resources Commission reseed sludges from several different planes over a twelve month period to determine among other parameters rhe pathogen reduction. The results showed a 4 log reduction in E Coli per gram of coral solids (dry basis) over rhe twelve month period. Salmonella sp was dececred at each plane when sampled one month after scockpiling bur was not detected in samples taken after six months. Protozoan cysts and helminth ova were nor derecred in any samples over rhe 12 month period. The results of chis study are inconclusive and biosolids srockpiled for twelve months cannot be classified as Class A.

Table 4 - Processes to Achieve Class B Pathogen

Reduction Process Descriprion Aerobic Digesrion Agirarion of rhe sludge under aerobic conditions fo r residence ri mes between 60 days ar 15°( ro 40 days ar 20°( with volarile solids reducrion of 38% in aero bic conditions. Air Drying Sludge drained on beds for a minimum of 3 monrhs wirh maximum deprh of 225 mm . Absence of air, with residence rimes from Anaerobic Digesrion 60 days ar I 5°C re 15 days at 35°C achieving 38% volarile solids reducrion. Composring Using windrow, static pile or in-vessel merhods,sludge remperature mainrained ar minimum 40°( fo r 5 days wirh 4 hours ar a remperarure in excess of 55°C. Lime Srabilisation Addition of lime to maintain a pH of 12 fo r two hours. Other Methods Other methods or operating condirions may be acceptable if pathogen and vector am acrion of rhe wasre are reduced re the exrenr of rhe above methods.

Table 5 - Nutrient Content of Biosolids from

Oxley Creek Sewage Treatment Plant (1 14190 22/6190) mg/kg dry weight Parameter Mean Calcium 20,300 Potassium 1,570 Magnesium 3,760 Sodium 958 Total itrogen 35,800 Ammonia/Nitrogen 3,890 Total Phosphorus 16,500

Srd. Dev. 7,440 309 690 22 1 2,000 303 200

Range 9,300 - 32,500 700-2 ,120 1,640 - 4,650 60 1 - 1.390 33,600 - 38,900 3.330 - 4,560 16,000- 16,800

present as NH !° . Biological cm1sformacions of the nitrogen occur in the soil. The race of mineralisation or immobilisation will depend on the soil and its inherent organic matter and nitrogen levels, the climate, biosolids characteristics and the degree of incorporation in the soil (Sommers and Giordano, 1984). The two forms of nitrogen in biosolids chat are available co crops are ammonium ion, which under Queensland conditions is rapidly converted to nitrate by soil microbes, and nitrate Vector Attraction itself. Nitrate is readily soluble in water and Vectors such as rodents, flies and mos- does not absorb onto soil particles in nonPathogen Reduction quitoes play an important role in rhe spread acid soils and will be leached out of the soil. Requirements of disease . The control of these vectors in Crops in rapid growth need a plentiful The degree co which pathogens muse be biosolids is cri ti ca l to rhe provision of supply of nitrate , but once the grow ing reduced in biosolids is very dependent on the adequate public health protection. Vecror period ceases the dem and for the nitrate final use or disposal route. The pathogen attraction and odour production are influ- ceases. Rain or irrigation water may cause the reductio n requirements are based on the enced by che organic content of the biosolids nitrate to be leached through the soil co the USEPA Part 503 Regulation (1992) and are and can be controlled by the processes listed groundwater or washed into a surface water. in Table 4. briefly outlined as follows: The leachate trials associated with biosolids application to forest areas at Beerburrum Nutrients Class A (Queensland), have found chat 25 % of the Biosolids contain significant proportions applied nitrogen will be leached within 4 - 5 • The temperature of the biosolids is raised co 53°C for five days, 55°C for three days of nitrogen , phosphorus and organic matter weeks after application (G. Barry, pers. or 70°C for one hour dried to at least (See Table 5), sufficient ro supply a large comm., Oct 1993). When to apply the 75% solids and the density of faecal col- pore ion of the ni crogen and phosphorus sludge, so chat the ·greatest benefit ro the iform in the biosolids shall be less than requirements for most crops. crop is achieved , is a difficult question. A itrogen occurs in biosolids as organic crop growing in a fertile soil will probably 1000 Mose Probable Number (MP ) per gra m of total solids (dry basis) or the nitrogen (org N), and the inorganic forms of manage quite well unti1 seems shoot up, then density of Salmonella sp bacteria in the ammonium (NHi·) and nitrate ions (NO,-). ir needs its main application of fertiliser. biosolids be less than 3 MPN per four The concentrations of org N, NH ,· , and However, at this time applying the biosolids NO ,- in biosolids are affected by the treat- is ex tremely difficult without ca usin g grams of total solids (dry basis). • Alternatively, if the above time/tempera- ment and handling processes. Unless aerobic damage co the crop. Application before ture relationships are not obtained then conditions have prevailed during creacmenc planting is a logical solution, bm then there ch e sludge or sludge produce may be process, over 90% of the inorganic N will be is the risk of the nitrate being washed out WATER DECEMBER 1993

25


through rain or irrigation. To reduce chis risk, biosolids application should be limited to a race where the available nitrogen in the biosolids meets the requirements of the crop to be grown (Chaney,1993).

PRODUCTS Sulzer SMF Mixer

The Sulzer SMF mixer was specially Conclusions developed for mixing product streams conThe DPI Guidelines wi ll be subj ect co taining solids. Fluids such as sludges, suspenchange. When the National Guidelines are sions with fibres or flakes or free flowing released , the DPI Guidelines will probably bulk materials (granules powders) can be require revision to fit in within the national mixed efficiently. The open mixer design framework . guarantees reliable operation without the Th ere are still many unknowns with danger of clogging. biosolids/soil assim ilation. Multidisciplinary The dewarering of sludges of communal research teams wi ll bridge the knowledge waste water installations, paper mills or gap in the biosolids /soi l ass imilation. chemical plants is usually carried our continHowever, further field studies are required on uously. The new Sulzer Polypropylene SMF the behaviour of nitrogen in the biosolids and mixer dis tribu tes flocculation chem icals the biosolids/soil mixture. In Queensland , (polymers) intensively but gently into the research projects have been set up through sludge scream in front of decanter cenLocal Authorities and the Department of trifuges , moving belt or chamber fi lter Primary Industries. The results of these propresses, resulting in polymer savings, shortjects will assist in serring guidelines for using ened fi ltration times or enhanced dewacering. biosolids on land. It is available in stainless steel or polypropySo chat the high standard of public health lene. Information: Sulzer Australia Tel experienced in Queensland is not jeopardised (02) 476 2355 . and the environment will not be damaged for future generations, a conservative but responsible approac h co biosolids use has been ITT Marlow Solids Handling adopted in the DPI Guidelines. Pumps The Trash Hog II range of self-priming so lid s handling pumps is now availab le References Addiscott AP, Whitmore AP , and Poulson D S, (1991 ) in Australia through ITT Flygt Limited. "Farming, Ferti lisers and the Nitrate Problem. " CAB Featuring a nonclog impeller, removable International wearplace , simpl e clean-out cover and Bio-Recycle Pty Ltd (l 993). "Rehabilicarion Jeebropilly Open adjustable bearing carrier, the pumps are Cut , Trial Area. " Unpublished Report to 1ew Hope ideal for rugged duty in sludge and industrial Corporation Chaney R L (1993) "Risks Associated with the Use of Sewage process systems. The dynamically balanced, Sludge in Agriculture." in Proceed ings of AW\Y/ A l 5th semi-open nonclog impeller comes with Fedecal Convention , Gold Coast, Queensland. either two or three extra heavy curved_vanes, Ross A D, Law rie R A, \Y/hatmuff M S, Keneally J P, and depending on pump size. The eye of the Awad , AS (1 99l) "Guidelines for the Use of Sewage impeller features smoothly rounded leading Sludge on Agricultural Land " S\Y/ Agriculture Ross A D, Lawrie R A, \Y/hatmuff M S and Keneall y J P edges, which are designed to maximise effi(1992) , Estab li shing Guidelines fo r Appl ica ti on of ciency. Pump-out vanes on the rear of the Sewage Sludges Containing Organochlorine Pesticides to back shroud reduce axial thrust, seal chamber Agricultural Land. "In : Proc. ationa l Workshop on pressure and the accum ulaci on of so lid s Organochlorine Residues : Strateg ies for Management and Research in Australian Agriculture. " Aust.Govt. Publishbehind the impeller. This also provides for ing Service, Canberra extended seal, bearing and shaft life. Made Sommers L E, and Giordano P M (l 984) "Use of Nitrogen either of cast iron or 316 stain less, the from Agricul tural , lndusrrial and Municipal \Y/astes ." removable wearplace provides protection to In: Hauck, R.D. et.al.(ed) Nitrogen in Crop Producthe pump casing from abrasive wear. Easy to tion. American Society of Agronomy, Mad ison, \Y/is. pp. 207-220. remove, the lightweight 150 mm clean-out Spa rkes J (199 3) "Th e NS\Y/ EPA 's Slud ge Regulation cover exposes the eye of the impeller for the Program." In: Reg ulating Sewage Sludge, A\Y/W A removal of debri s. The cover also provides Seminar, Sydney easy access co check impeller-to-wearplace USEP A (1992) "US Sewage Sludge Regulations, Part 503 Standards for the Use or Disposal of Sewage Sludge. " clearance . An adjustable bearing carrier in the pump permi ts infinite external adjustment of im peller- to-wearplace clearance, Author which results in optimum operating efficienPeter Beavers is an Executive Engineer with cies. Fine adjustments of clearance are easy to the Queensland Department of Pri111a1y Industries- do. The Trash Hog II range is available in Water Resources. He has 15 years experience in the size from 760 mm to 305 mm , with capacitreatment and disposal of wastewater and sewage ties of up to 378 1/sec. Full service and spare sludge and is mrrently responsible for preparing pares are available through ITT Flygt. Infor-

g1tidelines for beneficial use of bioso/ids and s1tpervising associated biosolids research ptojects.

26

Micro-Check Mace Instruments is now extending the range of rests available for the Micro-Check, hand- held , portable water quality analyser. Users can now purchase kits for most trace metals and pollutants includ ing cadmi um , copper, cyanide, lead, mercury, phosphates, phenols and chlorines. The Micro-Check is a fast , on-the-spot, way to measure all water quality parameters accurately. Information: Philip Crosby, Mace Co Pty Ltd Tel (02) 638 5166.

Pollution Trapper A pollution control machine char will prevent contaminated water pouring into harbours and rivers has been demonstrated in Sydney. It aims to trap 100 per cent of waste water run-off from operations such as truck and car washing, yard -hosing, and liq uid spills. Called Portaboom it is an American invention which will be released all over Australia. Porcaboom consists of a flexible semicircular suction cube - the boom - which is attached to a powerful vacuum unit. The boom is laid on the ground and acts as a dam to trap the run-off from hard surface washing and hosing operations and sucks it away co a holding tank or to i waste water treatment plant. Portaboom operates as well on rough surfaces as it does on smooch concrete. The boom com~ in sections measuring 1.5 metres, so it can be lengthened or shortened accordi ng to the job. Information: John Brookfield (Viking) Tel (02) 602 3666.

New Liquid Coagulant Nalco Australia has released details of a new cationic coagulant, Nalco 223, described as a highly charged , high molecular weight so luti on polymer deve loped for use as a primary coagulant in mineral processing and effluent treatment. Nalco 223 offers an effective alternative to powder coagulants since it provides dust-free handling, avoids powder spillage and eliminates the hazards of fine dust particles causing irritation to operators' eyes. Used ei ther alone or in conju nct ion with a Nalco anionic flocculant, Nalco 223 can be used to improve the water quality of recycled plant water, to reduce solids loading and to improve water clarity. Nalco claims th at in typical cases, coagulant operating coses can be decreased by 10-20%. In some cases anionic demand can also be decreased. Info:mation: Michael Groesz, Nalco Australia Pty Ltd Tel (02) 316 3000 Fax (02) 666 5292.

mation: Bill Murdoch, ITT Flygt Limited Tel (02) 7647 1855 Fax (02) 648 4701.

WATER DECEMBER 1993


TECHNOLOGY

EFFLUENT DISPOSAL USING SAND EXFILTRATION GJ Cashin* Abstract This paper contains an overview of the various sand exfilrracion methods of effluent disposal. The factors effecting sire selection are discussed, and operational problems that have occurred with ex isting sys tems described. Design guidelines for exfilcration systems are also given. It is fou nd that, wherever possible, pond exfi ltracion systems be constructed because of their simplicity and ease of operation. Where trench or injection bore systems are con structed, effluent filtration and chlorination should be provided co prevent clogging and bac terial growth. These latter types of systems should preferably be installed with continuous, rather than incermiccencly decanted, rreatmenc planes.

Introduction The disposal of created sewage effluent by sand exfilcration involves the discharging of effluent into a sand dune system , where the effluent then filters through the unsaturated sand layers until it enters the und erlying groundwater. This form of effluent disposal is very si milar co direct groundwater recharge, however the passage of the effluent through the sand results in a high quality effluent reaching the groundwater. Sand exfi lrracion systems have also been called "dune disposal" or "rapid infiltration" systems, wi th che latter cerm being common in the USA. Effluent disposal using various methods of sand exfi ltracion is becoming increasing ly common in NSW coastal areas. This system of disposal is suited co areas with well developed coas tal dune sys tems and favo urable ground water conditions , and is a form of effl uent disposal favoured by the SW Environment Protection Authority (EPA). With the rig ht sire conditions sand exfi ltraci on provides a practical and often inexpensive form of effluent disposal, however che driving fo rces for a number of exfilcrarion systems appear co be community opposition co ocean outfalls and the exceptionally high effluent standards being required by the EPA for disposal co surface waters.

Types of Exfiltration Systems There are three com mon types of sani:I WATER DECEMBER 1993

exfilcrarion sys tems, these being pond and biological growth on the trench walls systems, trench systems and injec tion bore and floor. Filtering of the effluent alone has systems. All systems are based on the same been found co be of licde use in solving this principle, wi th the choice of system for a par- problem, and both fi ltering and chl orine ticular site generally governed by the existing dosing are req uired for the trench co work site constraints. sacisfaccorily. Injection Bore Systems. Inj ection Pond Systems. Pond systems are the most simple and effective type of exfi ltration bore systems are generally used where there system. They consist of a number of shallow are one or more permeable sand layers underponds with a sand floor. Final effluent from lying material of lower permeability or layers the treatment plant is discharged into the of indurated sand . Vertical drains are conponds , from which it percolates down structed from the surface through co the perthrough the underlying sands. meab le layers, allowing the effl uent co be The ponds essentially act like slow sand injected into these layers. To dace two inj ection bore systems have filte rs . After a period of operation che cop sand layer becomes clogged with both che been conscrucced in NSW. These systems are suspended solids retained in the effluent , and located at Tuross Head SIP on the south biological growth , and it is necessary co rake coast, and at Bonny Hills SIP on the mid the pond our of service and scarify the cop of north coast. Both of these systems are in fac e the sand bed. For chis reason it is usual co conjunctive pond/injection systems. Injection alternate the effl uent disposa l betwee n a bore systems were constructed at these si res number of ponds. Alternating between ponds becaustof impermeable sand layers or regular also helps co mai ntain the natural balance of clay bands through an otherwise permeable strata. Derails of the Tuross Head exfi lcracion soil bacteria in the sand beds (PWD, 1989). Trench Systems. Tren ch systems system are shown on Figures l(a) and 1(6). Inj ec tion bore sys tems su ffe r from the involve che const ruction of long trenches, generally perpendicular co the direc tion of same cloggi ng problems as trench systems, groundwater flow. Effluent is fed into the and the effluent entering these systems needs trenches, which are fi lled with graded sand co be fi ltered and chlorinated. With conjuncand gravel, and seeps our through the trench tive pond/injection bore systems filtering is floor. Trench systems produce a much flatter not required because of the filtering action of groundwater mound than pond systems, and the pond floor. Choice of Exfiltration System. The for chis reason trench systems have been used in locations where a pond system would place choice of exfi lcracion system for a particular coo great a load on che groundwater system sire will depend upon the local groundwater and lea d ro permanent abov e-gro und co ndition s and sit e constraints. Where ponding of effluent. Trench systems have also a choice of exfi ltration system is available been used in locations where there is only a for a particular sire, a pond system is prenarrow dune system, such as at Sussex Inlet ferred because of the simplicity and ease of on the south coast, where a pond sys tem maintenance. would have resulted in coo much disturbance Site Selection Requirements and desrruccion of the fragile dune system. The successful operation of a sand exfilcraThe land requirements , cost and complexity of a crench system are normally increased cion system is very much sire dependent, with significa ncly over the requirements for a pond a number of factors requiring consideration . system. With trench systems in che frontal The most signifi cant factor affecting site dun e syste m, part icular ca re needs co be selection is the permeability of the underlying given co the possibility of significant beach sands, however ocher factors such as grounderosion from storm ac tivi cy. Th e bi gges t water hydrology, water table depth, scab iiity problem, however, ch ar has occurred with of th e dune sys tem, proximity of sur face trench systems is the blinding of the trench waters and che likely effects on dune vegecaitself. This blinding has occurred due co suspended solids and algae in the final effluent, *G J Cashin, Sinclair Knight . 27


on

I() u,1.1.1orT ORUI PIP($ PER U T $ P4 t (Oâ&#x20AC;˘T !,OOC(NUU,

Figure 1 (a) Exfiltration System General Arrangement Tuross Head STP

300 1 Cl FI G.600 J0HH VALVE /

300 1 01 PIPE

cess of sand exfilrration creates a recharging effect on the existing groundwater table, and a groundwater mound is established under rhe exfiltration area. The shape and extent of this mound is governed by the efflu ent flowrate, sand permeability, and depth of the origin al gro und water table. Other facto rs co ntrolling rhe shape of the groundwater mound are the loca tion of imperm eabl e boundaries, such as rock outcrops, and rhe location of (essentially) constant head boundaries, such as the ocean. Where there is a deep groundwater table the shape of rh e grou nd water mound is usually nor signifi cant. In many cases, howeve r, the topography around rhe sand dunes is undulating, ofte n with drainage channels or lagoons nearby. In rhese cases the shape of the groundwater mound created is particularly important, as there can be considerable difficulty in keeping rhe water table below rhe ground surface in the vicinity of rhe exfilrration area. The shape of rhe ground water mound likely to result from an exfilrrarion system can be esrimared by finite difference modelling. For modelling to produce reasonable estimates of water table rises, it is necessary to have existing groundwater levels against which the model can be calibrated. Improved res ults can be obtained if rainfall is also recorded . For this reason ir is important that boreholes drilled in rhe vicinity of rhe proposed exfilrrarion ar1;a are monirored for wa ter rable dep th for a reasona bl e time period before modelling is commenced. Stability of the Dune System.

Much of rhe c'basrline of NSW is receding, wi rh some areas experiencing average recession rares of up ro 2 m per year (PWD , 1989). This, together with the fragile nature of dune systems, has strong implications for rhe selection of a sire suitable for sand dune exfiltration. Na tural dun e sys tems are inh ere ntl y unstable. Frontal dunes form part of the beach and are drawn down in exceptional srorms and rebuilt in settled weather. Removal of the frontal dunes by the sea will expose rhe secondary dunes to rhe wind, and rhe process of wind erosion will commence unless that area SECT ION is very well vegetated or artificially stabilised. Figure 1 (b) Exfiltration System Details Tuross Head STP Only a small area of rhe dune needs to be exposed for the erosion process ro begin. Sires suitable for sand exfilrrarion should rion must also be considered. These facrors are ference models used in rhe design of exfilrrabe generally well vegetated, and should be discussed below. rion systems shows rhar permeability is a Soil Conditions. The flow rare of efflu- hi ghl y sensitive parameter, whil e orher , located in rh e secondary dune sys tem to ent away from rhe exfi lrrarion area and into fac tors such as sand thickness and distance guard against beach erosion. A number of sires in NSW are located well back from rhe rhe groundwater system is given by Darcy's from the shoreline are less sensitive. Law, and therefore rhe lower rhe soil permeTypical permeabilities of sands can vary actual dune sys rem, ar distances of up to 1 ability, rhe greater rhe area of ponds or rhe over two orders of magnitude, and iris there- km , thereby eliminating rhe risk posed by greater rhe length of trench rhar is required fore important that actual permeabilities for a beach erosion. Proximity of Surface Waters. The for th e exfi lr ra rion area. Permea biliti es, particular sire are obtained from site samproxi mity of surface waters to a potential however are rarely homogeneous throughout pling prior to making a sire selec tion. For a sand dune system, and horizontal perme- preliminary sire assessment , typical dunal exfilrrarion area can be important due to rhe abilities are usually greater than vertical per- sand permeabilities of 10 ro 15 m/d can be potential for the transfer of pathogenic bactemeabilities due to relatively thin bur often used in rh e abse nce of site spec ifi c data ria and viruses. This is particularly important if rhere is only a shorr flow path from the relatively imperm eable silt laye rs (Mackie (PWD, 1989) Marrin, 1984). An analysis of the finite difGroundwater Hydrology. The pro- exfilrrarion area to the ocean, or to a coastal TOP 000 OF SANO BED TO BE SCARIF IED BUT NOT CLOSER THAN 000 NEAR AHY STRUCTURE

SA NO BE D LEVEL

8E O ROCK LEVEL

28

WATER DECEMBER 1993


lagoon used for public bathing. Viruses have been found to move both horizontally and vertically through soil, with viruses detected at distances of up to 410 m from an effluent source (Californian Department of Health Services, 1990), while bacteria have been found to survive for extended periods in moist or saturated sands, with minimal die-off (Parker and Mee, 1982). Because viruses have lower decay rates than bacteria, they present the biggest potential public health risks in waters receiving effluent from an exfiltration system. Viruses can be adsorbed to soil particles, however once adsorbed they can also desorb, which may occur after rainfall. This can result in transient spikes of relatively high virus concentrations in the groundwater. Lefler and Kott (1974) carried out a study on the behaviour of enteric viruses in sand dunes. This study found that only bivalent cations (Ca 2â&#x20AC;˘ and Mg 2¡ ) when they exist in effective concentrations in the tap water and effluent are responsible for virus retention in sand. Rainwater, with very low ion concentrations, will flush viruses out of the sand, and thus produce the transient virus spikes. Therefore, it can be concluded that the unsaturated soi l zone cannot be relied on to be an effective barrier against the movement of pathogens. For the majority of exfiltration systems this should not be a concern, however for systems close to bathing waters the effl uent may need to be disin fected. Chlorinating the effluent prior to it entering a trench or injection bore system to prevent biological growth would also serve the dual purpose of disinfecting the effluent. Effects on Vegetation. As stated above, sand dune sys tems are fragi le, and instability in the dune system can occur easily and rapidly. Dunes are particularly susceptible to wind erosion if there is a loss of vegetation, which can occur from either construction activities or from an alteration ro the natural soil water balance. Alteration of the soil water balance can occur after the commissioning of an effluent exfiltration system, therefore particular care needs ro be taken when siting and designing the system. Of particular concern ro dune vegetation is the raising of the dune water table. A wide ly fluctuating water table within a plants root zone is likely ro result in plant death (Clements, 1992) and can lead to dune instability, while raising the water table at or above the ground surface will restrict surface vegetation ro hydrophytes (swamp or aquatic plants). Hydrophytes are specifically adapted ro water logged soils, and any lowering of the water table for extended periods could eliminate them , which can also lead ro dune instability (PWD, 1989). A shallow water table can also lead ro plant biochemical problems. An exfiltration system can also alter the moisture availability in the soil profile. Significant changes in moisture conten t are likely to lead to a change in dune vegetation as the natural vegetation , used ro a scanty WATER DECEMBER 1993

water supply, is replaced by different species. This should not be a problem provided that the more sui.table plant species can rapidly colonise the area, however if there is an insufficient supply of plant material or species more suited ro the altered conditions, deterioration of the natural dune vegetation can lead to dune instability. As a guide, the effects on dune vegetation can be minimised provided that the resulting water table after the installation of the exfiltration system is at a depth greater than 1. 5 m (PWD, 1989).

Operation of Sand Exfiltration Systems As stated above, sand exfiltration systems act as slow sand filters. Slow sand filtration is a combined biological and filtration process, and the efficiency of the system as far as solids removal is concerned is primarily a function of the algal growths on the filter surface (Metcalf and Eddy, 1979). Other bacteria, worms and larvae also add to the filtration that occurs (Barnes et al, 1981). For pond exfiltration systems, operation of the pond is the same as that of a slow sand filter, in that the pond is periodically taken out of surface and the surface scarified (or removed in the case of a slow sand filter) ro regain permeability once head losses have become excess ive. For trench and bore systems, scarifying of the clogged sand layer is not possible, thus the presence of the biological growth can lead to complete blocking of the system unless preventative action is taken. The exfiltration process also produces the bonus of removing significant quantities of nitrogen and phosphorous. Although effluents are usually well denitrified in extended aeration plants, denitrification can also occur in the upper soi l layers. Alternati ng the hydraulic loading also allows aerobic bacteria ro become active in organic matter decomposition, which helps to break up the clogging laye r, and allow s nitrification co occur (Metcalf and Eddy, 1979). Resting periods of between five and 20 days are required for this process to occur. The primary mechanism of phosphorous removal is by adsorption and chem ical precipitation. Soil systems have a finite capacity to remove phosphorus, however for many sites this capaci ty can be quire large (Metcalf and Eddy, 1979). Period ically replacing the sand bed will renew the capaci ty of the system ro remove phosphorus, however with most exfiltration systems nutrient removal is not a maior concern. Operational Problems With Trench And Injection Bore Exfiltration Systems. There are currently rwo

trench exfiltration systems operating in NSW, one at Hastings Point and one at Sussex Inlet. Both of these systems have experienced clogging problems due to blinding of the fi lter layer with biological growths. Examination of the trench system at Hastings Point SIP has shown that although bac-

teria levels in the effluent entering the trench were quite low, bacteria and micro-organism levels in the trench walls themselves were quite high. It was also observed that the organisms were secreting substances, either as metabolic by-products or for other reasons, which were acting as a cement to hold the sand particles rogether and form an impermeable barrier (PWD, 1987). Similar clogging and cementing problems have been observed in leachate collection drains in sanitary landfills (Ramke, 1989). Adding to the problem of clogging due to biological grow th , physical clogging has occurred due to the presence of algal cells and suspended solids, however the physical clogging mechanism is of secondary importance ro that caused by biological growth. The clogging of these types of systems is ro be expected, given that the systems behave similarly to slow sand filters , as discussed above. Not taking this into account has proved ro be expensive for both of these plants, as the exfiltration trench needed to be exhumed and reconstructed. Following remedial works at both plants, the problem of biological clogging has been contro lled by dosing the effluent with sodium hypochlorite upstream of the trench. The problem of algal build up in the trench walls is still a potential problem, but is less so at the Sussex Inlet plant, where fi lters have been installed. Clogging problems have also occurred with the injection bore system constructed at Tuross Head . The Tuross Head system was designed and constructed before the trench system at 1-Iastings Point, however the clogging problems that are occurring at Tuross Head have only recently come to light. This is because the plant is underloaded , and because of the operational flexibility designed into the plant. Analysis of the moniroring data from the plant has shown that the bores have become clogged, with the entire effluent load being exfi ltrated through the upper sand layers. This has resulted in a perched water table, and will result in the permanent aboveground ponding of effluent at design loads if remedial works are not carried out. Similar problems have also occurred with a rece ntl y co mmissioned inj ection bore system at Bonny Hills. The Bonny Hills system consists of rwo ponds with a thin base of fine sand, overlaying an impermeable sand layer. Bores have been constructed through the impermeable sand layer into the more permeable sand below in a similar manner to rh e system at Tuross Head, however the system at Tuross Head has six ponds. The Bonny Hills system was constructed without filtration or chlorination, and failure of the system has also occurred (Clements, 1992, pers comm).

Design of Sand Exfiltration Systems General. Sand exfi ltration systems are 29


relatively simple co construct and operate. From the material presented above, however, it is clear that there can be significant operational problems if sufficient attention is not paid co detail at the design stage. The facrors that need ro be considered in the design of sand exfilrrarion systems are discussed below, and design recommendations are made. Site Data. Sire investigations should be commenced prior co a final decision being made on the type of disposal system co be adopted . This is because, no matter how attractive a sire appears co be for exfilrrarion, it is the actual permeabilities and groundwater characteristics that will govern whether or not a site is suitable. As well as soil sampling and testing, the site investigation should include the installation of a number of groundwater moniroring wells , spaced throughout the general area likely to be affected by the exfiltration system. The water levels in these wells should be measured over a number of weeks prior co undertaking any numerical modelling or preliminary design , and rainfall should also be recorded to aid in model calibration. Depending on the location of the sire, it may be necessary to install a rain gauge. For all sites, numerical modelling should be carried out to estimate the response of the groundwater system, and to see if there are likely to be problems with surfacing of the water table. The accuracy of this modelling in predicting the actual effect of the exfiltration system on the groundwater table will depend on the quality of the data collected, and the length of time that groundwater monitoring has been carried our. The ideal sire for an exfiltration system should: • have high permeability coarse grained sands; • have a minimum depth to the water table of 2m; • have a minimum sand depth of 2m to 3m below the water table; • be well vegetated; • be located in the hind (secondary) dune system , or even further back from the dunes if feasible; • be at least 500 m (and preferably further) from any surface recreational or srock feeding waters; and • not discharge into a fresh water aquifer used for potable water supply. It will be difficult to find sites satisfying all of these criteria, and the suitability of a site for an exfiltration system in these cases will depend upon the individual site circumstances. Type of Exfiltration System. Pond exfilrration systems should be installed wherever circumstances permit. These systems are easier and cheaper to operate than trench or injection bore systems, as the effluent does not need co be chlorinated to prevent biological growth, and they are also far more rugged and less affected by events such as solids carry over from the treatment plant itself. Trench 30

and injection bore systems should only be considered when a pond system would not be able to keep the water table below the ground surface, or would result in excessive destruction of dune vegetation, leading to the consequent destabilisation and erosion of the dune system. Hydraulic Loading. The exfiltration system should be designed to cope with the peak hydraulic load passing through the treatment plant. This will obviate the need for balance ponds upstream of the exfilrration system , and should largely eliminate clogging of the system caused by a build up of algae in the balance ponds. Peak seasonal loadings can be accommodated by providing additional or modular units, which can be brought on line when necessary. Sufficient units should be provided so that the peak hydraulic load can be passed through with one or more units off line. The number of units required will depend upon the actual design, however the units should be rotated to allow for the scarifying of the bed in the case of pond systems, and to allow for an aerobic cycle (20 to 30 days) to destroy the build up of bacterial and vegetable matter deposited during the exfiltration cycle. In the unlikely event that disinfection is required prior to exfi lrration , it cannot be achieved by maturation or detention ponds, since this which would result in algal growth and consequently cause the same problems as balance ponds. Specific Requirements for Trench and Injection Bore Systems. To elimi-

full hydraulic loac!,.from the treatment plant.

Conclusions Effluent disposal using sand exfiltration methods can often provide an economic and environmentally acceptable method of effluent disposal for small coastal communities. It is imperative, however, that detailed site investigations and numerical modelling of the proposed exfiltration system be undertaken before a firm decision is made on the method of effluent disposal to be adopted. Several existing sand exfilrration systems have been constructed in NSW on marginal sites. These systems were primari ly constructed because of the difficulties, both environmentally and economic, in constructing an ocean outfall. Effluent disposal by sand exfi ltration shou ld always be considered along with other disposal options, such as effluent reuse and artificial wetlands, however they should not be considered as fall back options in lieu of ocean outfalls. The effectiveness of an exfiltration system is very sensitive co site conditions, and in some circumstances an ocean outfall will provide the best, and perhaps only, viable form of effluent disposal. Despite this, it is likely that more exfilrration systems will be constructed on marginal sites because of the strong community and political opposition co ocean outfalls, unless public perceptions about ocean outfalls can be radically changed.

References · Barnes D, Bli ss P J , Gould B \YI, Vallenti ne H R, (198 1) 'Water and Wastewater Engineering Systems' , Pi tman Clements A all(! Associates (1992) draft comments on 'Fern Bay active transg ressive dune stabilisation programme and use of sewage treatment products', Pu blic Works Department of NSW Ca li fo rnian Department of Health Serv ices (1990) 'Background information on proposed criteria for groundwater recharge with reclaimed municipal wastewater' LeAer E and Kott Y (1974) Enteric virus behaviour in sand dunes, !Sl'ae/} 011.-nal o/Tech110/ogy. Vol. 12. Mack ie Martin and Associates Pty Ltd (l 984) Appraisal of Dune Seepage Capacity, Hastings Poi nt Sewerage Scheme, Public Works Department Metcalf and Eddy Inc (1 979) 'Wastewater Eng ineering: Treatment, Disposal, Reuse', second edition, McGraw Hill Parker W F and Mee BJ ( 1982) Survival of Salmonella Adelaide and Faecal Coliforms in Coarse Sands of the Swan Coastal Plai n, Western Austral ia, Applied and E111•iro11111mtal /l lin-obiology Public Works Department of NSW (1987) Bogangar, Hastings Point, Pottsv ille Sewerage, Hasti ngs Point Sewage Treatment Works Dune Disposal System Mod ifications, Construction Report, Report No. Lil 35 Publ ic Works Depart ment of NS\XI (l 989) Effiue nt Disposal Manual (draft), PWD Report No 90/003 Ramke H G (l 989) Leachate Collection Syste ms, in Chri stensen T H, Cossu R, Stegmann R, 'Sani tary Landfill ing: Process Technology and Environmental Impact', Academic Press London

nate clogging problems in trench and injection bore systems caused by biological growth it is necessary to chlorinate the effluent before it enters the exfiltration system. By designing the system to cope with the full hydraulic load, as discussed above, the problem of clogging by algae or other vegetation will be largely eliminated. There is still the potential, however, for the system to clog due to the build up of suspended solids carried over in the effluent from the treatment plant. To minimise this risk and extend the life of the system, the effluent should be filtered upsrream of the exfiltration area. For intermittently decanted treatment plants, balance ponds would be necessary to even out the load on the fi lters, as these types of plants produce a high batch hydraulic loading during the decant phase. If balance tanks are to be constructed , they should be sized just large enough co balance the flow over one operating cycle, that is, the pond should empty just before the next decant cycle commences. Ponds that incorporate a permanent water srorage should definitely not be constructed, in order to prevent algal Author I growth and the consequent likelihood of Greg Cashin is a Senior Engineer with Sinclogging. clair Knight, based in the Sydney office. He holds Balance ponds can be eliminated if contin- Bachelor of Engineering and Master of Engineeruously operated plants are constructed with ing Science Degrees from the University of New trench and injection bore systems, rather than South Wales. His career to date has involved the intermittently decanted plants. The exfiltra- investigation, design, construction and operation of tion system can then be sized to accept the water supply, sewerage and solid wastefacilities. 1

WATER DECEMBER 1993


TECHNOLOGY

POLYETHYLENE WATER SERVICES G C Long* Summary This paper describes studies carri ed out by the Sydney Water Board into rhe characteristics of polyethylene service pipework from rhe main co the meter.

Background

the Water Board co investigate the properties of a new main co meter arrangement , with the intent of implementing into the Board in 1994. A second issue arose as a result of the dual water supply system to be constructed for Rouse Hill. With ponible and recycled water supplied co every house and wirh rhe limirarions in space in new narrower subdivision roads, it was important co reduce the amount of pipework within the road reserve. Therefore a single service pipe co rwo houses which split at the boundary was included in the mvest1ganons.

For mosr of chis century rhe Water Board and most other water supply authorities, have adopted a pipework arrangement for main co merer pipework using copper pipe and jumper valves. (See Figure 1). This arrangement has generally proved co be satisfactory except for: (a) The dissimilar merals of copper for service pipe and cast iron for rhe main Investigations causing a corrosion problem at the point The properti es of rh e pipework ro be of connection. The ex tent of chis investigated were head loss versus flow and problem increased with rhe introduction warerhammer. The Water Boards Hydraulics' of Ductile Iron pipes for the mains. Laboratory at Manly was engaged co carry our (b) The metalli c pipework accentuating these investigations. ie: warer hammer noises inside rhe house (a) Comparison of the hydraulic characteris(in some situations). tics of rhe existing copper service and (c) Some waters reacting with the copper different arrangements of medium which corrodes and causes staining in density polyethylene services. All rests the house. were carried our ro determine rhe coral (d) The jumper valves at rhe mainrap and head loss from a point on rhe main merer rap being ineffectual over th e upstream of the connection point co a long term as backflow preventers. point on rhe house service downstream (e) Relatively high cost of maintenance of of rhe merer. the maintap and meterrap. (b) Comparison of the waterhammer characWith the introduction into Australia of teristics of a copper service and a single medi um density polyethylene pipe and and dual medium density polyethylene fittings and its use by other Authorities it service. was considered co be the appropriate time for In order to carry our these rests a number of main co merer services were constructed Table 1: Fitting flowrates for varied mains and attached co a simulated house containing pressures all rhe normal water using appliances. As FLOWRATES 111s well as the warerhammer effect it was also ITEM 15m 4-0m 60m 60m 100m SHOWER1

0.25

0.46

0.53

0.64

0.79

SHOWER 2 (water saving)

0.10

0.12

0.11

0.1 2

0.11

BASIN

0.24

0.42

0.53

0.60

0.70

GARDEN TAP

0.36

0.66

0.80

0.97

1.14

Table 2: Coverage of two types of garden sprin-

possible to rest the head/flow characteristic of each appliance. Hydraulic Characteristics of Ser vices. A single and dual copper service wa

assembled as shown in Figures 2 and : (Water Board, 1992). The single 20 nomina diameter service arrangement is identical re present Board practice. The dual 25 nomina diameter service arrangement equates co hov rhe Board would follow its existing practice if constructing a dual service. Both arrangements were rested for 2 m length and 17 rr length for simulation of the main in the samc footpath as the property served and of th( main on the opposite side of the road. A new arrangement was assembled for 2( nominal diameter medium density polyethylene as shown in Figure 4. The layout wai used co rest both single and dual serv-ices. A 25 nominal chameter dual service was alsc tested (see Figure 5). Ar rhe rime of the rest a dual check valvf was DQt available. Therefore additional headloss was included for a TITA dual check valve, the figures being taken from headloss rests carried our by TITA in accordance with AS 2845 -1-1991. The headloss co a single house through a dual service is dependent on rhe flow rate char is go in g ro th e second house. The minimum flow through rhe common section of pipe would be the flow co one house only. The maximum possible flow would be twice the flow ro one house . The probable maximum flow has been estimated at 1.46 times the flow co one house. This factor was taken from the diversity factors defined in AS 3500 Table 3.2 . These three scenarios are included on each of the graphs of results for

Table 3: Appliance filling times FIWNGTIMES min 1:,m

I "" CISTERN

1

4.00

2.50

1.75

1.50

1.00

FUUFLUSH

6.00

4.50

2.25

2.25

1.50

WASHING MACHINE

klers

4um

HALF FLUSH

FIU

CYCLE

12.00

7.00

6.00

5.50

6.00

65.00

55.00

SO.OJ

SO.OJ

SO.OJ

(16mln wash)

""~

15m

spray leng1h

(m)

spray width

(m)

FLOWRATE

(Vs)

2.40

N

4-0m 5.20

60m 5.80

60m 7.32

100m

7.63

Table 4: Effects of flow to both homes with a

dual service

2. 10

3.70

4.30

4.58

4.58

0,1

0.2 1

0.27

0.33

0.37

15m

15m

spray radius

(m)

FLOWRATE

(Vs)

7.00

""0.1

WATER DECEMBER 1993

4-0m

60m

60m

(Vs)

4-0m

60m

60m

100m

0.25

0.46

0.53

0.65

0.79

FLOW TO SHOWER WITH W/M FIWNGNEXT DOOR

0.22

0.40

0.52

0.60

0.74

FLOW TO SHOWER WITH W/M & SPRINKLER NEXT DOOR

0.21

0.41

0.52

0.60

0.69

FLOW TO SHOWER

IMPACT SPRINKLER 100m

12.3>

11 .9J

14.30

17. 10

0.22

0.30

0.35

0:40

TO HOUSE

Figure 1 Typical Water Service lnstat!ation

* Graeme Long, Sydney Water Board 31


TAPPING F"OR PRESSURE MEASUREMENT 20mm DIA. PSM WATER METER STRAIGHT METER CONNECTOR ~ 20mm DIA 90 deg METER C O C K ~

'"Ol-w ~~

20mm01A

"'>

:--.._ """-2omm DIA Cu PIPE 18 GAUGE \--,.,_- - - 90

\

de3

BENO AS SUPPLIED

~:6~m~IN~::

PIPE

20mm ~ MILNES" MAI NTAP WITH TAPPlNG COLLAR

TAPPING FOR PRESSURE MEASUREMENT

Figure 2 DN20 Single Copper Service

dual services. Results of che rests are shown in Figures 6 co 12. From Figure 6 it is clear rhac there is less head loss through the proposed 17.5m long polyethylene service over the flow range of 0. 3 to 1.0 1/Sec which is the normal flow range for a house service. This is due to the better hydraulic characteristics of the ball valves and the polyethylene pipe. There is virtually no difference in the head loss for the 2.5m long services as the savings of the polyethylene pipe and ball valves are marched by rhe head loss through the dual check valve. Figures 7 and 8 show char the polyethylene dual service using all 20 diameter pipework will have eq uivalent hydraulic characteristics to the present single 20 diameter copper service. Figures 9 and 10 show the hydraulic advantage if a 25 nominal polyethylene diameter common pipe is used. Figures 11 and 12 show the hydraulic charncrerisrics of a 25 diameter dual copper service.

Advantages of Proposed Polyethylene Service. .

Figure 3 DN25 Dual Copper Service

TAPPING FOR

PRESSURE MEASUREMENT 20mm DIA. PSM

WATER METER ~gmd°:'g D~~LL VALVE 20mm DIA

"'[!~

Cu P ~ 18 I GAU:~ PE

!

() 1-~~

-----

,oo

05fl1

i'::i

PRESSURE MEASUREMENT N020 MOPE cl. 16 N020 BALL VALVE

TAPPING FOR PRESSURE MEASURE MENT

Figure 4 DN20 Dual MDPE Service

Figure 5 ND25 Dual MDPE Service

32

• Head loss is less for a single long service. This is particularly important in areas where the mains pressure is low. • A dual service can be installed using all single size pipework at no performance loss. • Backflow prevention is positive and can be maintained by replacement of rhe check valve at the rime of merer replacement. • less cost to maintai n a single service because of less maintenance of main tap and merer tap. The Water Board may proceed to delete the ball valve at the main if clamping of medium density polyethylene pipe for isolation purposes is considered satisfactory. A dual service has significant capital cost savings and lower mamrenance costs.

Water Hammer Characteristics Both the present and proposed single services were rested for warerhammer effects in the house. Ar varying mains pressure a pressure transducer was used co measure the pressure spike at the merer when various appliances were turned on and off in the house. The pressure spike was also measured at the merer of the second house ro measure the extent of water hammer transfer from one house to irs neighbour. Qualitative rests on the different services were also car ried our for noise and flow surging due ro water hammer. Various appliances were rested ro determine which was the most cri rical. Closure of che solenoid valve on the washing machine was found co cause the greatest problem. The results of the pressure measurements a.re shown in Figure 13. Ir can be seen that there was a significant reduction in pressure

surge using the p~lyerhylene system with mains pressure up ro 70m. This accounts for 90% of rhe Water Board's supply. Ar mains pressure over 70m the reduction in surge was less pronounced. The surge transferred co the adjoining house of the dual service was at levels of 20m or less. However the problem with a dual service is nor how small the surge is, it is the cusromer expectation that there will be no effect on supply because of usage by a neighbour. Although the surge resting showed there was some effect on the adjoining house, the question arises as ro whether it can be felt by the human senses. • Qualitative rests were carried our for noise. The results are shown in Figure 14. Ir was obvious that for a single service the proposed arrangement had very little water hammer prob lems whereas th e exi sting arrangement did have a problem with mains pressures over 40m. There was no discernible effect co rhe adjoining house using rhe proposed arrangement. Qualitative rests were also used for flow surges. There were minor flow surges for the sing le services when household appliances were turned on and off suddenly bur there was no discernible flow surging in the adjoining house. In order co confirm the qualitative results the Water Board carried our a field rest in conjunction with Wyong Shire Council. Dual services, using conventional materials , have been used in NSW rnuntry cowns for over 20 years. Wyong has had problems with waterhammer between the adjoining houses and has been proJressively replacing rhe dual services with single services. Co-operation between the two authorities saw an existing copper dual service in Budgewoi which had generated num erous complaints from the owners, replaced with a new polyethylene dual service in the Water Board's proposed arrangement. The owners had no problems at all with the new service. Advantages of Proposed Service. (a) Provides a significant reduction in water hammer noise in cusromers house. (b) Allows a dual service ro be used with no discernible water hammer effects between rhe adjoining properries.

Appl iance Performance Household appliances were rested for flow race and fi lling rimes at varying mains pressure. Results are shown in Tables 1 to 4. Derai ls of rhe appliances used are in Water Board (1993). However performance of the water supply cannot necessarily be quantified. Ir is mainly a qualitative measure by the cuscomer of the pressure and flow availab le through che various devices in his house, particularly the 1 shower and raps. Results in Table 1 show char a water saving shower has virtually no change in flow rare with a change in mains pressure and there was no perc eived change in performance. However, the normal shower rose had a significant change in flow rare over the WATER DECEMBER 1993


HEAD LOSS VS FLOW CHARACTERISTIC S

HEAD LOSS VS FLOW CHARACTERISTICS

HEAD LOSS VS FLOW CHARACTERISTICS

Head Loss (metres)

Head Loss (metres)

Head Loss (metres)

100

100 /

,,, ,,,, ,,,

/

I J /I

100 ,0

'/ II

I/,

I,¼

I, I I /

V

I,

11 111 , 11 11

10

Ill

I$

8~

10

I,

10 I/

/;

J ::;

,, 7

I/ I/

I/

/

I/ Copper 17.5 m long MOPE 17.5 m long MOPE 2. 5 m long Copper 2.5 m long

1 2 3 4

/

1'1

~

Description

Curve

/ [/

Cu rve

/ I/

Description

1,,-0 ~

2.0 x flow MOPE servlce

1 2

1.46 x flow MOPE service 1.0 x flow MOPE service Standard copper service

3 4

2

3 4

~

Description

2.0 x flow MOPE service 1.46 x !low MOPE service 1.0 x flow MOPE service Standard copper service

1

r7

I

7

I

7

0.1 0.1

10 Flow Rate (litres/sec)

0 ,1 0.1

10 Flow Rate (litres/sec)

Figure 7 Comparison of Single DN20 Copper Service and DN20 Dual MDPE Service, 17.5 metres long

Figure 6 DN20 Main to Meter Service

HEAD LOSS VS FLOW CHARACTERI STICS

0.1 0.1

HEAD LOSS VS FLOW CHARACTERI STICS

Head Loss (metres)

Head Loss (metres)

,,,

KN

///

g

f1// I ,'I

Ill

Ill

V 1 11

10

//' 10

/

/.

/ (/

//~

"

///

/II

~

IJ

10

100

,,

///

/

10

Figure 8 Comparison of Single DN20 Copper Service and DN20 Dual MDPE Service, 2.5 metres long

100

100

1 Flow Rate (litre/sec)

HEAD LOSS VS FLOW CHARACTE RI STICS

Head Loss (metres)

A

Curve

~

/4

~

Curve 1

ON20 single Cu service

2 3

2 .0 x flow MOPE service

1.46 x flow MOPE service 1.0 x flow MOPE service

4

Curve Description

V".'. ~

Description

,

7}

1 2 3

2 .0 x flow MOPE service 1.46 x flow MOPE service 1.0 x flow MOPE se rvice

4

DN20 single Cu service

1 VI

:tW

/

1 2

1

I

0.1 0,1

Cu,ve

10

,,

0.1 0.1

10 Flow Rate (litres/sec)

Flow Rate (litres/sec)

Figure 9 DN25 Dual MDPE Service &

Figure 10 DN25 Dual MDPE Service &

DN20 Copper SingleService, 17,5 metres long

DN20 Copper SingleSeroice, 2.5 metres long

HEAD LO SS VS FLOW CHARACTERISTICS Head Loss (metres)

3

~

0Hcrlptlon 2.0 x flow ON25 Cu Hrvlc::• 1.48 x flow ON25 Cu Hrvlc::• 1.0 x flow DN25 Cu Hrvlc::•

0.1 0.1

10

1 Flow Rate (litres/sec)

Figure 11 DN25 Dual Copper Service,

17.5 metres long

wate r hamm er spike (m)

160 - - - - - - - - - - - --

-

Key: O• no sound , t • very sli ght, 2=notlceable, 3- loud , 4• dlstu rbl ng

100

Noise factor

140 .. II,

Ill

5

120 ·

ff

w 10 ~

/4

/4 'fl

A

Curve

1 2 3

Description

2.0 x flow DN25 Cu Hrvlce 1.-46 x fl ow ON25 Cu Hrvlc. 1.0 x now DN25 Cu Hrvice

,.,,,, .,

W'

30

40

50

60

70

80

90

100

mains pressure (m)

0.1 0.1

- Sing le Cu service 1 Flow Rate (l itres/sec)

Figure 12 DN25 Dual Copper Service, 2, 5 metres long WATER DECEMBER 1993

10

+ MOPE dual service

"*" pressu re at 2nd house

Figure 13 Water Hammer at Varying Mains

Mains Pressure (metre s)

~ Single copper service

!l!l! Dual MOPE service

Figure 14 Severity of Waterhammer Noise

Pressures 33


Water and Wastewater Analysis

Trace Element Analysis

range of mains pressure and was not considered co be satisfaccory with pressures less than 15 metres. Different types of garden sprinklers were tested as described in Table 2. Performance of the sprinklers was considered co be satisfactory at mai ns pressure grea ter than 25 metres. A mains pressure of 15 metres was not satisfactory. The Board's video "A New Standard of Water Service" gives a better idea of these tests. Table 4 shows that the use of appliances in a house with a dual service does not significantly effect performance of the supply in the adjoining house.

Contaminated Sites

Conclusions

Pesticides & Organic Residues

Microbiology

Occupational Hygiene

Routine Quality Control .

There are significant advantages in using medium density polyethylene pipes with ball valves and a dual check valve for the main to meter pipework. • The inert material means no corrosion problems either internally or externally. • The use of ball valves will provide a saving in maintenance costs. • The system provides improved head loss characteristics which is particularly beneficial in low head areas of th e water supply system. • The polyethylene pipe and ball valves reduce water hammer effects to insignificant levels. • With the reduct ion in water hamm er problem it becqmes feasible co install a dual service to adjoining properties. Cost savings in terms of capital and maintenance are significant. • Back flow prevention is more positive and susrainable over time. Three main conclusions resulted from the testing of household appliances: • The satisfactory performance of the watersaving shower rose at all mains pressures. • The unsatisfactory performance of the garden sprinklers and garden hoses at mains pressure less than 25 metres. • egligible performance effects due to the use of appliances in the adjoining house when using a polyethylene dual service.

AGAL We Specialise In

Australian Goverment Analytical Laboratories 51 -65 Clarke Street SOUTH MELBOURN E 3205 Phone : 03 685 1777 Fax : 03 685 1788 Melbourne Water Approved

NATA Registered

Quality And Service At The Right Price

HYDRAULICS WORKING WITH TH E

ENVIRONMENT The 1994 Cooference on Hydraulics in Ovil Engineering UNIVERSITY OF QUEENSLAND, BRISBANE 15-17 FEBRUARY 1994

~ANCOLD

The

Institution of Engineers,

'I)

Australia

References Water Board 0992). Water Serv ice Connection - Hydraul ic Characteristics, in: arch Western Region Water Business - October 1992 Water Board (1993). Medium Densiry Polyethylene Water Service Connections - Wacerhammer and Flow rare Perfo rmance Tests, in : 1orth Wes tern Region May 1993 Report No t WR-001

Author Graeme Long is a practicing engineer in the Water Board's North Western Region with over 20 years experience in investigation, design and constmction ofpublic authority,water supply systems.

To receive a copy of the program & registration form, contact Elizabeth Hutchinson Convention Manager AE Conventions P/L

Ph 06 270 6520 Fax 06 273 2918 PO Box E181 Queen Victoria Terrace ACT 2600

34

WATER DECEMBER 1993


MANAGEMENT

YAN YEAN WATER TREATMENT PLANT THE-CLIENT~S PERSPECTIVE OF A BOO CONTRACT BG Mcllree, MR Chapman, GP Joyce, EA Swinton * Summary

suburbs via the transfer pipelines and supply BOO project existed. A core ream was assembled compri si ng reservoi rs shown schematically in Figure 1. This paper outlines the processes through which the Build Own Operate contract for five engineers (B Md lree , M Chapman, G During lace winter/spring, Yan Yean reservoir th e Yan Yea n water treatment plant was Joyce, P Horvarch, 1 Grove), their expertise is topped up by about 25 % of cleaner water developed over a period of 18 months. As cove red pro jec t manage ment , trea tm ent transferred from Silvan Reservoir to Yan Yean chis was the first major project in this field, processes, operat ions, des ign/constructi on by the link pipeline. Yan Yea n is then bro ught in se rvice much had to be learned, on all sides, and ic is and commercial considerations. Whenever hoped char the lessons can be applied generi- appropriate, the ream brought in consultants during summer, and supplies peak demands call y to futur e projec ts, both within and for con tractual, legal and fi nancial matters, in che north-west suburbs, including some plus advice in public consulcacion, industrial 100,000 households and a significant indusoutside the water industry. relations, due diligence and insurance. trial zone. Introduction The ream was responsible for all major Ir is a shallow reservoir, built over disperA number of BOO (Build, Own, Operate) aspects of the deal, including shortlisting of sive soils. In the period after a large drawand BOOT (Build, Own, Operate & Trans- bidders, technical and commercial evalua- down, wave action across the shallow areas fer) projects are being commissioned in the tion, contract development, negotiation and during refilling causes a rise in tu rbidity water industry, as well as in ocher fi eld s obtaining approvals both within Melbourne (Figure 2). NHMRC/AWRC (1987) Guidewhich in Australia have traditionally been Water Corporation and fro m Government lines for Drinking Water cannot be met in the province of government or semi-govern- Departments. respect of turbidity, colour and iron following ment authorities. A major activity throughout was 'devel- the peak demand period. When turbi dity The Yan Yean Water Treatment Project opment of che rules ' between government exceeds 8-10 NTU the chlorination process (WTP) which was contracted by Melbourne and industry as well as in-house. Changes co becomes ineffective and the microbiological Water Corpora tion in February 1993 to a legislation, evaluation methods and approval and THM guidelines at rimes cannot be mer. consortium operating as the special purpose processes were found to be necessary. Several company, Yan Yean Water Pty ltd , is the 'mythical' commercial and legal risks had to first major BOO proj ect to go into the con- be dispelled, mainly in the negotiations with struction phase, with a NPV of $27M. It is a financial institutions. true BOO project as there is no plan to transThe result was an innovative and complex fe r ow nershi p bac k to Melbourne Wa ter arrangement which defines long- term relaunless default occurs. Ac termination, after tionships between several parries. The lessons 27 years, either the contract will be extended learned, on all sides, can be applied generior che plane demolished. cally to many future BOO and BOOT pro(Perhaps the only wry humour allowed in jec ts, both within and outside the water the negotiations was char the dace of termina- industry. tion was sec as 02. 02.20.20) Figure 1. Melbourne Water Headworks System The consortium partners are Norch West The Need for the Project Turbidity Yan Yean was Melbourne's fi rst water (FTU) Water Australia Pry led and Transfield Pry led . No separate fin ancier is curre ntly in storage (prev ious supp li es hav ing bee n 30 , - - - - - - - - -- -- - - - - - , place, and funds are being supplied directly obtained by diversion weirs) . Ir was commisby the consortium. However, the terms of che sioned in 185 7 during the height of the gold 2 5 1 - - - - - - -- -- -- - -----< contract allow a separa te fin ancier to be rush. More significantly, in 1885 ic became the fi rst reservoir ro receive water from uninincluded into che consortium at a lacer dace. The advantages of BOO/T, from the per- habited catchments. These were in the forests spec tive of the concraccor, have been dis- on the northern slopes of the Great Dividing Range, the water being diverted by a system cussed by Dooley, 1993. Within Melbourne Water, in 1990, a final of weirs and aqueducts. This source still conevaluation of social, technical, environmental, tributes about 75% of the reservoir water. Ir eco nomi c, po lit ica l and industry iss ues is discoloured by natural organics leached (STEEPI),as discussed lacer, led co a decision from forest leaf li ccer. / O•c Over the following ce ntury the water to install a 15 5 Ml/d capacity water creacI l•;"'"'°'°"''w; I menc plane at the outlet of the Yan Yean resources of the protected catchments in the reservoir. A comprehensive pilot plane study huge forests of the eastern mountains were Figure 2. Yan Yean Reservoir Turbidity: Seawas undertaken (Chapman et al, 1993) and a progressively developed, culminating in the sonal and Drawdown Effects benchmark cost for the plane was defined. completion of the Thompson dam in 1985 . * This paper was prepared by the Edi tor Ac the same time, evaluation of fundi pg This water is substantially cleaner, and is options revealed char an opportunity fo r a suppli ed to both the eas tern and western from notes and discussions with the authors.

...

Jul

Aug

Sep

Oct

Nov

1

WATER DECEMBER 1993

Jan

Feb

Mu

No,mal Op11 11ionP1rlod

A.pr

May

.I

35


The supply area contains 13 of the top 100 industrial water users, some of whom have co operate on-site pretreatme[)t planes. In some years , customer complaints about 'dirty water' and taste and odour have risen from about 20-30 per month co 300-500 per month after the Yan Yean supply is brought in. Domestic water filters have, within five years, already captured some 12 % of this domestic market. Generally, they are considered co be a less effective and a more costly option for the community than treatment of the bulk supply. In fact, if not properly maintained they can create a health hazard by providing a growth medium for bacteria. The option of abandoning the reservoir was considered, but finally rejected in favour of treatment for the following reasons: • Its strategic location within the rapidly developing Plenty Corridor. • Ir is the only source of supply not transferred from the eastern catchments, and it could reduce peak day transfers from the Silvan Reservoir, thereby delaying major augmentation of the cross-city transfer pipelines. • All service reservoirs in the supply area had recently been covered co eliminate recontamination. • Since there were low algal and microbiological risks in its raw water, a treatment plant would be relatively inexpensive, and existing chlorinarors could be retained. • Its use would reduce use of the expensive treatment of rhe more polluted Lower Yarra water in the Winneke treatment plant. • It would demonstrate Melbourne Water's commitment co equal water quality for all rare-payers. • Ir had rhe potential to be an innovative and cost-effective method of achieving these goals. • A storage with a capac it y of between 1600-1300 ML would need to be constructed to manage peak hour demand variations.

Why a BOO Project?

lined by the project ream.

During 1991 , Melbourne Water was assessing rhe options for financing a number of projects, and rook notice of trends overseas cowards service contracting and BOO/T projects. The decision to rake the Yan Yean WTP through the BOO process was based on a number of facrors: • Ir was a small well-defined project on which co rest the viability of the BOO/T process. • There was a 'no more borrowings' policy imposed by the Government for an indefinite rime whereas the need was fairly urgent. • Corporarisarion of Melbourne Water was likely co require a 'level of service' contract and the BOO performance contract arrangement could be used as a model. • There would be genuine transfer of traditional public sector risks to the private sector. • There was a need to develop the rules between Treasury, industry and internal players. • The experience would be useful for proposed contracting-our of maintenance services, and proposed internal service agreements (eg between Planning and Operations Departments). • It could lead to expansion of rhe Corporation's activities into other areas of Victoria, Australia and overseas in partnership with private sector players. • The experience and intellecrual knowledge would stand in good stead for the future , and would show leadership in rhe Australian Water Industry, both in technology and contractual experience. • Involvement of other partners, some with overseas experience, would provide benchmarking and competi tion for other segments of the Corporation's activities.

Expressions of Interest. In rhe first six weeks an Expression of Interest document was drafted , and advertised. This defined the project dimensions, and, more importantly, the cri reria for evaluation of bids. In parallel a draft contract document and supporting information to renderers was being developed. Shortlisting. During the rwo months following the advertisement , a total of 13 companies and consortia replied, and these were narrowed down to three, on the basis of: advice from many of rhe bidders that they would prefer a rapid selection process to no more than four preferred renderers; known capability in design and construction of water treatment plants; operational experience and commitment to R & D; commitment to the Australian water industry; use of local resources; potential for sharing of technology; experience with environmental and social issues; appreciation of rhe BOO process; financial strength and commitment; understanding and acceptance of transfer of risk. An independent audit of Melbourne Water's evaluation process was carried our by Price Waterhouse to ensure fairness . Approvals. Before moving to the next stage in which the shortlisted consortia had to prepare derailed submissions, approval had to be obtained from Melbourne Water's Executive Committee and irs Board. Following this, rhe agreement of rhe Minister and Cabinet had to be ob,rained, along with Treasury opinions on whether the project would be outside Loan Council Requirements.

The Contract Development Program A timetable, spanning one year, was our-

Objective : A plant process that will work for the stated conditions Summary of Proposals: Benchmark Issue Adequate . - • -.Inadequate • High sustained flow • Start/stop and varying flow • Design raw water qual spec. • Demands greater than design spec. • Raw Water Quality variation beyond design spec. • Treated water quality guarantee • Undesirable chemicals

A C

> > > >

B A B B

> > > >

C C B

> >

B B A

> > >

C A

B

Effect on treated water & costs Pilot plant tested, stable perform. Excess capacity, no bottleneck process Turbidity/colour Algae Risk of process failure, degree of backup and control THM's from pre-chlorination

>

B B

A A A

==

> >

• Marketability elsewhere

B

>

C

>

C C A

A

>

C

B • • • • • •

Balanced solution In series and/or in parallel "State of art", compact, modular, R&D value, motivated consortium

== Balanced reliable solution given known factors Ability to handle unforseen likely conditions Allowance for future Pilot plant tested Demand variation accommoda1ed Marketable product in future joint ventures

Figure 3. Adequacy of Water Treatment Method

36

Excess capacity, low failure risk

C

>

Comment

C

• Tailored solution • Flexibility for future

Overall Rating:

Selection of the Preferred Bidder.

Ar this stage derails of all the pilot plane work, the minimum consumption and peak day hydraulic requirements and the assumptions inferred, rhe water quality history for the raw water and details of the treated water quality objectives were made available to the three short-listed consortia. Likely variations in annual demands, raking into account climatic conditions and three development see-

1995

2020

Figure 4. Annual Charges to Melbourne Water WATER DECEMBER 1993


narios for rhe zone, were provided, based on the WASP computer simulation model (Kuczera er al, 1988) Ir was noted char water production would nor be continuous. The plant would be brought on-line usually for 5 ro 7 months each year, commencing in Ocrober or ovember. Several srarr-ups and shut-downs could occur in any year, and the plant design had to cope with chis requirement. Two consortia hired the existing pilot plant facility ro evaluate their particular treatment processes. In the following 12 weeks they prepared derailed submissions, covering process, desi gn, construction , operation as we! I as commercial structure and financial packages. The process of final selection was swift, again in accordance with the natural desire of the renderers. However, whilst one preferred renderer was soon nominated , rhe ocher two were 'kept alive' so that if negotiations fai led, their bids could be re-considered with minimal delay. This was possib le be ca use there were only small margins between all three. The criteria on which this selection was based were: Basic: Conformity with the conditions of rendering. Technical: Adequacy of rhe treatment method; Adequacy and derail in design and project delivery processes. Financial: Risk profi le definition; Contractual srrucrure; Commercial arrangements and tariff structure. Whilst rhe Melbourne Water ream which assessed the bids remained the same, external auditors for legal, commercial and technical processes were used as required. Examples of Assessment Procedure. Some of the key aims were to ensure

that: the plant would deliver the specified quantities and quality; the plant would work we ll for the whole contract period, ie economy in construction would nor jeopardise operations and maintenance; monitoring was capable of ensuring agreed performance targets and that QA plan requirements were achieved; in event of default, the penalties would encourage rapid corrective action; both short-term and long-term contractual and commercial structures could survive the uncertainties of rhe 27 year period. An example of the technical analysis procedure is outlined in Figure 3, based on the information supplied and subsequent discussions. A benchmarking process was employed ro define the relative adequacy of the treatment processes, and all issues were scored and weighted for significance. In these respects, Tenderers 'A' and 'B' were found to superior ro Tenderer 'C'. Examples of the financial analysis are given in Figures 4a and 4 6. The tariffs were based on (a) avai labi li ry of rhe plant, i.e. the fixed charges, and (6) usage charges per megalirre produced. Tora! actual cosrs as annual charges for rhe most likely scenarios of water usage , inflation, CPI and insurance escalation rares for the life of the plant are shown. Ar a particular discount rare WATER DECEMBER 1993

these cash flows will reduce to the same et Present Value. However, the approach adopted by Tenderer '2' of full disclosure of all charges, identifying the fixed charges for loans and the esrimares for operations and maintenance, together with his policy of reducing financial exposure in later years to any blow-our in indices, was preferred. An important issue for the renderers was whether Melbourne Water would guarantee a minimum usage for rhe plant each year. The unusual scheduling of the plant for only peak loads raises the theoretical possibility that in a wet year very little water could be demanded. The actual historical range of consumption has been between 9500 ro 27000 Ml per year. Simulations suggested that future ranges would be 10000 to 25000 Ml, averaging 175 00 Ml, per year. Those consortia who did nor require any minimum usage guarantee were preferred. An illustration of the extent of rhe risks to be allocated and incorporated into rhe contract document is given in Figure 5. One renderer did nor accept the risk allocation preferred.

Risk

Melbourne Water

Processor

Shared

• E1Cisting Dosing Plant ~ration & maintenance

=~t~o/ity

• Industrial project specific non-project • Environment approvals leg!slation changes compliance

• Com~;~ ~~1efJ~'::ct post ~gn of contract 0

PhyslctJJ~ conditions Patent ground conditions surveys authorities possession

• OesigS.,ysical process • Construction sutx:ontractOf performance materials availability program completion • Commissioning

• Operations • Financial lmerestrates

~tir1lcrn::H~.

cnstruction cost Increase operating cost Wease initial taxation assumptions 1axation legislation changes • Aawwater treatment

~~~~~

changes • Changes 10 treated waler standards • Demand lor treated water • Force majeure

Figure 5. Risk Allocation

Community Issues and Liabilities.

Ar this stage, with the proposed plants fairly well defined, it became important to ensure that there would be local community acceptance, and that there were no unresolved archaeological, planning-related or possible sire contamination issues. Specialist extern~! consultancies were brought in to advise before finalisation of the selection.

The Negotiation Process Following selection of the preferred consortium, the derails of the final contract were worked our by intense discussion. The game plan involved three parties, each with their own agenda. The Public Sector Client had these key objectives: • Genuine transfer of risk • Capital cos t outside Global Borrowing limits (off-balance books) • Service ar competitive price • Penalty arrangements which apply progressively rather than rhe 'sudden death' of default , and which affec ted all tariff charges. • Clarity in the technical derail • A practical QA plan • No guarantee by the Government The Sponsors (consortium) had ocher objectives, to: • Take on only the risks they could manage easily • Maximise return on equity invested • Minimise recourse in case of default • Off-the-balance books • Minimise commitments ro client and financier • Ensure that the client would remain viable The Financier's key objectives were to: • Eliminate risks not manageable by either parry

Figure 6. Typical Commercial Stmcttwe

• Maximise return on loan • Minimise risk of non-repayment of the loan • Obtain maximum recourse from sponsors and/o.r the client • Maximise opportunities to recover service agreement • In case the operator defaults • Obtain pre-agreed arrangements to cover reduction in the client's trading capacity, or any assignment of the contract (eg resulting from a change in the corporate structure of Melbourne Water by Government. Obviously some of these objectives were in opposition and this created an environment which at rimes required delicate positioning and brinkmanship. This was especially so when the Stare Treasury and the Commonwealth Taxation Office joined in the game. However, on the whole it resulted in a very creative environment leading to a robust and finely tuned set of documents.

The Contract Documents The principles of the base contract between client and the Special Purpose Company, Yan Yean Water Pry. ltd . were similar ro the usual contracts, expressing performance, interfaces,I safeguards, bonuses, penalties and implementation. The commercial structure which resulted is summarised in Figure 6. Features worth noting are that in add ition co the central service agreement the client has defined two other major arrangements: the Security Deed and the Sponsors' Deed. The Security Deed defines 37


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the relationship with the Financier in che event char_ic becomes a separate parry. Of pamcular importance are the criteria used co define the screngch of Melbourne Water's trading capacity and what happens if it falls below pre-determined criteria. The Sponsors' Deed defines the relationship with the parent companies behind th e Special Purpose Company. Of particular importance are che processes regard ing arrangeme nts in th e event of default during both conscruccion and operation. Under these agreements, in the event of non-performance and default by the operacor Melbourne Water is nor liable co any financier. The coral number of documents cabled ac the signing function on February 25 ch.1993 was twelve, of which six related co clientsponsor and client-financier, and the ocher six were between the consortium partners.

widely in areJ S where clear interfaces exist, eg public seccor/privace sector, as above, or between Planning and Operanons departments.

Conclusions

The BOO contract for the relatively small Yan Yean water treatment plane is che first example in the Australian Water Industry co be put into effect. Ir was a contract of about $27M as PV. Ir required a degree of forecasting and planning beyond char normally employed by a government enterprise, where traditionally risks have been carried 'inhouse', co be accepted and corrected in the future as che need arose. When a contractor cakes on these risks in a competitive environment, at a stipulated tariff, over a period of 25 years or so, it is essential for all parries co forecast correctly, right from the start. From the above description of che process and an estimate of che number of persons involved on_all sides, it can be seen that formulating Lessons Learned The image held in many places is char a chis first contract was a fairly expensive exerBOO/T scheme is merely an easy solution co cise. However, rhe lessons learned by Melbgovernment capital funding. The above dis- ourne Water, and the procedures evolved can cussion shows chis co be a myth. The reality be applied generi cally co a wide range of is an innovative and complex arrangement BOO/T systems, so char in the future they which defines a long-term rela tion ship can be considered for smaller projects. between several parries. Important lessons Acknowledgements were learned: The authors represent all the members • True life-cycle cost ca n be quantifi ed, of th e Melbourne Wa ter Proj ec t Team: although there is no doubt char chis could Brian Mdlree, Mic,hael Chapman, Graham have been done in-house by Melbourne J oyce, Peter Horvath and Lorraine Grove. Water had the necessity been there. We acknow ledge the help and advice • The efficiencies and gains are real, due co from our assistants and the various consulcompetition. The capital cost was lower canes empmyed, and the professional relabeca use of innovat ive design and fast tionships with our renderers , successful and delivery, bur the operaror 's interes ts unsuccessful. ensured conservative design and best construction. The Team • Construction management is simple for Brian Mdlree is currently Manager, BusiMelbourne Water: there is only one sire ness Services and Development Division, and supervisor and one equivalent supervising has a background of over 30 years in che conengineer. srruction and project management area. • Complex operations and interfaces should Mike Chapman, a chemical engineer, is be modelled before scare-up co ensure currently Manager, Water Quality, in che smooch assessments of monthly payments Planning Services Division. and a workable Q/A plan. Graham Joyce, a civil engineer, is in the • Banks and governments find it difficult co Proiecc Management Group of Business quantify and prioritize risks in the water Services and Development Division. industry. P_ecer Horvath, a mechanical enginee r, To achieve best results: was in the Engineering Design Group at the • The common objectives of all the partners commencement of the project. He now works muse be defined right at the scare. in the Business Services and Developm ent • Due diligence muse be exercised on legal Division. risks and the role of che lawyers . There _ Lorraine Grove, a civil engineer, worked were significant differences in under- in che commercial area of Melbourne Water's standing of the legal issues between che Treasury, and now works for Macquarie various law firms employed. Corporate Finance Led. • The approvals process needs co be simplified. References I In the event, we found char: Chapman MR , Collins G, Johnst0n N, Nadebaum P (1993) • The values of the public and private secror 'The role of pilot trials in selecting a cost-effective water treatment process'. Proc. AWWA 15th. Federal Convenoperacors were basically similar. tion, April. Vol.4: 11 30-1136. • The process maximises the benefits of an Dooley G J (l 993) 'To BOOT or nor t0 BOOT \Valer, 20, (5) integrated techni cal/legal/commercial Kuczera G, et al (1988) 'General Wacer Supply Sysrem Simuream working as an entity co 'do che deal' lanon Model' }11/ \Vat Res P/a.1111i11g & Mn11age111eut 11 4 (4) ' • The principles of the concracc can be used WATER DECEMBER 1993


SEMINAR

BOOT PROJECTS: EFFECTIVE PLANNING AND IMPLEMENTATION Report by Bob Swinton Introduction A seminar was organised by rhe Victorian Branch on September 21 , responding to rhe inreresr aroused by rhe near-completion of rhe Yan Yean water treatment plant, and the signing of rhe contracrs for rhe Prospect and Macarthur (and Illawarra) plants in Sydney. An audience of over 100, wirh strong contingents from rhe business sides of industry illustrared rhe deg ree of ineerest. Speakers discussed the BOOT process from their differe nt viewpoints.

Government The Treas urer of the Scare of Vicrori a spoke on rhe approval of Government in rhe process, and his paper has been summarised and published in chis issue as the guest edi torial, My Point of View.

The Owner Yan Yean Water Pry Lrd is a consortium of orth Wes r Warer Australia Pry Ltd (a subs idiary of orrh Wes r Water Internacional) and Transfield Construction Pry Ltd. Graham Dooley, Managing Director of rhe former company, discussed the advantages of BOOT in rhe October issue of Warer, and ar rhe seminar, he presented these arguments. (David Iverach, representing Transfield , concluded the seminar).

The Customer: Melbourne Water In chis issue a derailed paper by Mdlree et al describes rhe processes by which rhe Yan Yean contract was brought to fru ition, and chis was ourlined co rhe seminar by Graham Joyce, one of rhe Melbourne Warer ream.

The Sydney Scene David Man zi, now Manager Utilities, W reg ion of the Wa ter Boa rd , was Manager of the Drinking Water Program, and involved with the BOOT con tracts for their rhree plants. He agreed with the experi ence of the Melbourne ream, but srressed char though Syd ney has rake n rather longer co fi nalise their contracts, they cover 94 % of the city's suppli es, whereas Yan Yean is a relati vely minor component of rhe Melbourne system. The Prospect plant was contracted ro SW Water Services Pry Led (a consortium of Lend Lease Corporat ion, P&O Australia and Lyonnaise des Eaux Dumez) only the day before rhe se minar, the Macarthur plant to orrh Wesr Warer/Transfield a week prior. The Illawarra project had been delayed fo r WATER DECEMBER 1993

further community consultation. He sees the pri me advantage of BOOT as rhe focus on long-rerm planning. Th eir financia l arrange ments show some 15 % savings, and they have benefirred from international technology. Th roughout the negoriarions, rhey preserved a non- adversarial philosophy, but the relatio nships wirh rhe fin anciers entailed many hours of debate, and rheir demands for QA were pe rhaps more derailed rhan engineers would have required . However, rhey did succeed in specify ing outputs rather than methods. Allocation of risks is a vital component, and he advised chat risk management principles could equally be appli ed to the processes of contract building. The inherited cul tures of rhe va rio us part ies had to be modifi ed. Within the Board , th ere was a certain inertia, due co rheir own skills and politics. The contraccors tended from habit to revert co 'cost plus', and financiers and governm ent were bas ically suspicious. All this will be easier in subsequent contracts , and experience helps, bur nore thar every project will be unique.

The Rural Water Corporation J ane Grieg explored the possibili ties of BOO/I in the rural sce ne, and sa id ch ar rhe diffuse srructure and rather small projects made it unlikely co be applied. The really big potential was in rhe Murray-Darling system bur ir seemed vi rtually imposs ible co conceive of rhree States and the Commonwealth agreeing simul taneously on approvals.Within Viccoria, privatised Irrigation Districts might become clients in the future, and the four proposed irrigation channels might be a suitable size.

The Financier David Howell of atWest Bank gave the viewpoint of th e, much mali gned, banks on infras rructure fin ancing. In mosr cases, certainly wi th warer supply, there is one cuscomer only, which breaks a fund amental rule of bank ing. (Contrast the situati on when a domestic mortgagee defaults). Financing is prim aril y by debt , with enough eq uity 'co keep them honesr'. The big questions co the banks were: how long was the project co run , who 'owned' it, what happens on termination, or if the company fails) The attitude of the Loan Council was a serious issue. The cash-flow may be guaran teed by the community, bur if rhe government changes, and/or the operating company

fa ils, what then? Banks do nor operate ware1 trea tm ent plants. Yer th e proj ec ts mad ( sense, and were simil ar co the funding ol public hospitals. 'Force Majeure' (eg major srorm damage, or a general strike) might stop rhe operati on, yet the interest coses would continue. Thert seemed to be three solutions: (a) the Government to continue co pay the 'avail ability' tariff even though the plant is not 'available'; (b) rhe operator continues co pay up to a capped amount ; (c) som e insurance cover might be arranged . In th e eve nt of un sa ri sfac rory performance, the cusromer would exact penalties, but eventually there could be a rerminarion. Ir would seem then char the bank would have co arrange a temporary workfo rce until they could recruit an alternative contractor. This is not rhe scenario a bank would enjoy!

The Taxm~n An other fi nancial aspect was explored by Simon Hatcher, who organi sed the tax package for the Yan Yean render. The degree of corripetirion was such that every financial advantage had co be explored, and company, sales and scamp taxes had robe optimised. In the case of BOO/I projects, the Tax Officers were learning at rhe same rime as rhe consortia, and becoming increasingly sophisticated . Their main concern was the allocation of risk. Governments, per se, do nor pay tax. Private enterprises rake risks,and their tax packages reflect chis. The current situation is char the interest paid by companies is a deduction from income, so char in effect, th e Commonwea lth is parti all y fundin g BOO/I infrasrrucrure proj ects. Sales tax and stamp duty arguments were almost the opposite of the income rax criteria, so there was a delicate balance. However, he worked closely wirh the Tax Office right from the start, and was open and consistent. However, the gold en rule was neve r co ass um e a ruling until it was in wrmng.

The Project Manager John Moody, of CMP S&F, ha s been involved in the Yat'l Yean contrac ts from render preparation through co the constructi on. While the represe ntati ves of North West Water and Transfield prepared the bid, J ohn manage d the des ign and tec hni cal input. During the pre-contract phase CMPS & F continued co provide technical support, and once derailed des ign and construction 39


commenced, John ac ted for the Owner as Proj ect Manager. Figure 1 is a simplified matrix of rhe organisation. Th e three phases demanded different skills. In the three month tender phase the challenge was co merge che skills and business philosophies of the major partners. Boch were powerful organisations, used co getting their own way. However, fi nally their aims and skills were matched co provide a workable, reliable and presumably profitable bid. In the second phase, fi nancial and legal considerations dominated. The third phase was a welcome relief, being the more traditional cask of delivering the completed plane on time, co budget and co quality. His ceam had rhe cask of moniroring design and construction, liaison wi th the cusromer, checking and certification of all subco ntrac ts . Throughout all chis, effective QA was fundamental on the pares of all parties. The ro les change in each phase, but having been through ic all , he had no doubt chat there were real benefits in involving and committing so many parties. The Yan Yean project, for 150 ML/d, rook 19 months, the Macarthur project, for 260 ML/d, some 24 months co reach signing point. This involved a very shore and hectic program of design , but ic has led co substantially less expensive facilities which still meet the objectives. In future, better co-ord ination of the various approvals from government, environment and public consulcacion would be of prime benefit.

The Investor

Dr. David Iverach, Executive General Manager, Transfield Projects, concluded che presencacion of papers by outlining what he saw as the real benefi cs of the BOO/T process for public infrastructure. Transfield is coowner of the Yan Yean and Macarthur planes, and also owns ocher public infrastructure proj ec cs in Australia, notabl y the Syd ney Harbour Tunnel. Transfield Construction has che turnkey contracts for Yan Yean an d Macarthur. Dav id said chat he ag reed rocally with Alan Scockdale's assessments. While initial financial benefits were attractive, the more significant benefirs were the long- term performance and lower cosrs resulting from the more disciplined planning and contractual accouncablicies required for the 20-30 year terms. However, he warned chat because of the extra effort and cos es involved in BOO/T negociacions all parties should make sure chat any project was really required and economically justifiable. He believed char some Government agencies had proposed non-viable projects in the past, and so it was important for potential investors co do their own due diligence prior co expressing inreresr. Transfield themselves had declined from bidding for some projects advertised within Ausrralia. He had come co respect and value rhe role of rhe Banks in financing BOO/Ts. Transfield only earned dividends after debt was serviced, so if the banks were concerned about some aspect, chis deserved their own consideration. The Operator Ic was important co select bank(s) chat had Ian Petty, Operations Manager, North people who understood infrastructure and rhe West Water, for the Yan Yean plane, outlined relationships involved. Although their 'what his input co the contract process. Obviously, if' questions seemed tedious and pedantic , after the capital expenditure of construction, they had thrown up situations which had binding estimates have co be made for fitting been missed by the ocher parties, including out, srocking and maintenance and manage- the government agency concerned. ment systems, before production can comDavid emphasised char rhe two main difmence. Fixed coses continue even when no ferences between BOO/T and ocher forms of water is bei ng produced, and then are added contract were, first, the requirement co lockthe variable coses of coagulant, power, dis- in the lifetime cost up-front, and second , the posal of residuals, and labour, including presence of effective sanctions for under-permonitoring and analyses. formance. His own personal experience as a Since a 27 year li fe was demanded there planner in a Government agency made him muse be recognition of che need for replace- aware rhac officers were usually sensitive co ments and refurbishment of equipment and rhe need co minimise lifetime cosr, but were sensible provision for the future. Some provi- generally not obligated, or able, co enter sion has co be made for coses consequent on long-term contrac tually binding commi tinterruption of service, and the coses involved ments co operation and maintenance. In in the scare-up and shut-downs required by BOO/T projects, design, construction , operathe cusromer, and allowances for off-spec tion and maintenance conrracrs and prices are q uali cy.For 'unforeseen circu mstances ', a committed simultaneously at the scare of the simple 'contingency percentage' could not be project. Government Agencies also found ir used, in view of che closeness of competition, difficult co impose penalties on themselves if so chat allowances had co be made in each their estimates were wrong or performance seg ment of che estimate. Th e escalation under-par. In the Yan Yean and Macarthur clause was vital, and its principles had co be conrracrs, payments are reduced for underclearly seated and agreed. The coral degree of performance in such a way char rhe conrracrisk in all chis had co be incorporated inco the rors lose less money by fi xing the problem profit margin demanded by the consortium . than by leering ir continue. Obviously, these estimates were as important David said he had never seen a Governas, and perhaps more difficult co forecast than men r or Government Age ncy, ho wever the construction cost. well -run, successfully si mulate chis profit

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incentive for rh~long term. In summ ary, the BOO/T approac h ensured char all issues important co Government, investor, banker, constructor and operator were thrashed out prior co signing of the contract. This greatly increased the probabilicy chat the project would be, and would be seen co be, successful. While such a process was very demanding on all parties, all chose who had participated in a BOO/T project, without exception, vigorously endorsed the approach. He beli eved chat chis had been very evident at the seminar.

Questions What are the lower limits for size of B00/T projects? Dooley: current contracts are $20M plus, but a limit of $10M was feasible. In cwo or three year's time, as experience was gained, a figure of $5M might be considered. (2) What happens if a Water Authority increases its requirements beyond the scope of the contract? Manzi: The Sydney Water Board have said they will nor sec up another plane in competition, but if necessary would develop recycling co fill the gap. lverach: The majority of the tariff is for 'availability', not for operation. If forecasting cannot be done with cercainry for a 25 year period, then negotiate for a shorter term. (3) What happens at the end of the contract? ' Iverach: The Yan Yean contract does not extend beyond the stipulated period. Since che land ~n which the planes are built belongs co rhe auchori cy, then automatically they will assume ownership, and the contract stipulates "make safe, remove materials, etc". Whether the conrracr will be extended is something co be decided by the next generation. (4) Was there a need for independent guarantors? Howell: The banks are banking on rhe cash-flow from the governments, not from rhe contractor. If there were no government guarantee, banks would nor be involved. (5) Can the contract be transferred? Dooley: Certainly, if rhe contractor fails. However, chis is a remote possibility. North West Water, and most of the ocher contractors, are world-wide companies, with hundreds of planes in various forms of conrracr. Their core business is water and wastewater creacmenc, and they are in ir for the long haul. The contract does allow transfer by mutual three-pare agreement as well . Finally, David Howell reseated a basic truth. In most of such conrracrs, there are five parries, and they muse rrusr each other. If any one of them is suspicious, rhe matrix wi ll never work. For exarr'iple, rhe contracts for the Loy Yang Power Station fill 3000 pages of typescript, and even then, all parties had co realise chat there still could be an unforeseen factor. If chat eventuates, nobody muse hold a grudge. (1)

WATER DECEMBER 1993


SEMINAR

DISINFECTION 93, QUEENSLAND Report by Philip Williams This Symposium was held at Griffith University, Brisbane 'on September 28 and 29, 1993. Jc was organised through the Waste Management Research Unit which is pare of che School of Environmental Engineering. The organising committee of Philip Wi lliams , Hans van Leeuwen, Peter Neeve and Sunil Herac brought together a wide range of expert speakers - from research centres, local government, pollution control auchoricies, equipment/technology suppliers and academia. The aim of the Symposium was to focus debate on the contentious issues regarding both water and was cewacer disinfection as well as to examine the various technologies available. Approximately 70 delegates from all avenues of the wacer/wascewacer industry attended. The Symposium was opened by the Vice Chancellor of Griffith University, Professor Roy Webb, who emphasised the university's pioneering role in environmental education. The keynote address was delivered by Dr Ian Lambert, Director, Standards and Industry Guidelines, Commonwealth EPA. The presentation covered a number of areas including the need to use ecologically sustainable development as the guiding principle in the management of our water resources, the role of the Commonwealth Environmental Protection Agency (CEPA) and the National Water Quality management Strategy. He emphasised che need for a national approach to limiting the levels of all constituents of concern in disinfected effluents. The first technical sessions on potable water disinfection followed.

Dr Scott Cameron,Communicable Disease Control Unit of che South Australian Health Commission, urged chat chose involved with the design and operation of water supplies view any population chat consumes water from a common supply as an ecosystem. The should cake into account che agents of infection chat may threaten the water supply. Then it should be possible to design che collection, treatment and distribution system so chat the risk of water or transmission of infectious agents is minimised. Dr Bill Razzell, Director of Brisbane City Counc ils Scientific Services Branch stood in for Mark Pascoe, also of BCC, who was originally to have made the presentation. The experiences of BCC with chloraminacion of its long distribution system were outlined. WATER DECEMBER 1993

le found chat free chlorination was sometimes required to counter the effects of ammoniaoxidising bacteria in che system which were causing the deterioration of the residual combined chlorine and subsequent regrowth of coliform bacteria. Paul Sherman, Scientific Officer with DPI - Water Resources gave an overview of disinfection practices and bacteriological quality of urban water supplies in Queensland. Ninecyeighc percent of the Queensland population is supplied with reticulated water, disinfected by chlorination or chloraminacion in accordance with Queensland Government policy. The major problem in Queensland is chat sufficient sampling of the drinking water is not carried ouc. Currently only about 11 % of the towns and cities (supplying about 57% of the urban population) can confidently claim they provide bacceriologically safe drinking water. Sampling and monitoring initiatives are currently being put in place to provide safe water to all of Queensland's population. Dr Brenton Nicholson of the South Australia Engineering and Water Supply Departments, Australia Centre for Water Quality Research discussed disinfection by- products - are these the next major water quality issue ? the current chinking on guidelines for THMs and ocher disinfection by-produces were presented. le is predicted chat to meet proposed guideline values, chlorination DBPs such as dichloracecic acid and chloral hydrate will be of greatest concern as their guideline values will be hardest to meet. The next session covered several disinfection technologies. Bruce Copper, Manager of ICI Wacercare, scared chat the intention of his paper was co present the faces and remove some of the fallacies regarding chlorine. He suggests char there has been over-emphasis on negative points against chlorine. le is apparent chat there is no 'ideal' disinfectant but chlorine, ch loram ine (or possibly chlorine dioxide) come closest to the mark for potable water. In the area of wastewater disinfection a number of points such as effectiveness and toxici cy were refuted . The presentation concluded chat after considering all points and all the evidence, there is no valid reason for preventing the use of chlorine. Professor Hans van Leeuwen of the University of Pretoria presented an overview of the technology of ozonacion. In summary it was concluded chat ozone is a powerful disin-

fectanc, however, due co its instabi lity i1 cannot provide a protective residual durin! potable water distribution and has co bf supplemented with another disinfectant usually chlorine or chloramine. With waste¡ water disinfection it is an effective and apparently environmentally safe disinfectant. Two presentations on UV disinfeccior followed. The first of these was by Angu, MacDougall of Process and Po llucior Control. This paper discussed the role o indicator organisms for monitoring disinfection efficiency. le was concluded chat onli UV disinfection can give the security of reasonably uniform inactivation of pathogens. Rob Wilson of UVS Ultra Violet Pcy lee continued the case for UV disinfection. Thii presentation covered materials and technological aspeccs , research and development bioassays and the operational requirements 01 UV units. The conclusions were chat th( bioassay was che only true measure of the performance of a UV system and char UV ii effective but the system muse be purpos( designed for each application co guarantee perfor'"mance. Rhett Butler of Memcec led unfortunately could nor present chis paper due cc illness. However the Symposium proceedingi include his very comprehensive paper on th( capab iliti es of municipal microfilcracor systems. The latest generation of CMF unici has greatly improved the economics ol chis process. He concluded chat membram technologies like CMF will become cht "treatments of choice" for small communities. Rural Queensland and New Sourt Wales communities are prime candidates fo1 evaluation. The final session was on wastewater effluem disinfection. Catherine Hamilton of the South Australia Health Commission gave an overvie\\ and national perspective . Reviews by a number of wastewater authorities have led cc the conclusion chat alcernacive(s) to chlorine need co be developed so chat there are cost effective options available for environmentally sensitive areas. The Australian Centre fo1 Water Quality Research in South Auscralia ii co undertake the development of guidelinei for wastewater disinfection. The two priority areas are protection of human health and projection of che environment. Some additional areas chat wi ll need to be addressed in the project are the coses of monitoring the disin-

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Profile for australianwater

Water Journal December 1993  

Water Journal December 1993