Water Journal January - February 1998

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WASTEWATER

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Volume 25 No 1 January/February 1998 Journal Australian Wat er & Wastewater Associat ion

Editoria l Board F R Bishop, Chairman B N Anderson, G Cawston, M R Chapman P Draayers, W J Dulfer, GA Holder M Muntisov, P Nadebaum, J D Parker AJ Priestley,] Rissman , EA Swinton

General Editor Margaret Metz AWWA Federal Office (see address below)

Features Editor EA (Bob) Swinton 4 Pleasant View Cres, Glen Waverley Vic 3150 Tel/Fax (03) 9560 4752

Branch Correspondents ACT - Ian Bergman T el (06) 248 3133 Fax (06) 248 3806 New South W ales - Mitchell Laginestra Tel (02) 9412 9974 Fax (02) 9412 9686 Northern Territory - Bill Bean Tel (08) 8924 7201 Fax (08) 8941 0703 Queensland - Tom Belgrove Tel (07) 3810 7967 Fax (07) 3810 7964 South Australia - P eter Martin Tel (08) 8303 8723 Fax (08) 8303 8750 T asmania - Ed Kleywegt T el (036) 238 2841 Fax (036) 234 71 09 Victoria - Mike Muntisov Tel (03) 9600 1100 Fax (03) 9600 1300 Western Australia - Jane Oliver Tel (09) 420 2462 Fax (09) 420 3178

Advertising & Administration AWWA Federal Office Advertising: Margaret Bates Graphic Design: Elizabeth Wan PO Box 388 Artannon NSW 2064 Level 2, 44 Hampden R oad, Artarmon Tel (02) 9413 1288 Fax (02) 9413 1047 Email: awwa@inta.net.au

Water (ISSN 0310 • 0367) is published six times per year:J anuary, March, May,July, September, November by

Australian Water & Wastewater Inc ARBN 054 253 066

Federal President Greg Caw ston

Executive Director

CONTENTS From the Federal President .. ...... ....... ...... ................ ............. .... .. .. ................. 2 From the Executive Director .... ... ..................................... .. ................... ......... 4 MY

POINT

OF

VIEW

The Cost of Salt .... .. .................... ............... .... ...................... .. ........... ........... .... 3 D Blackmore INDUSTRY

PEOPLE

Profile-Marika Calfas ........................ ...... ................ ......... ............................. 7 C Porter WATER

[:!'. Who Drinks What? Potable Water Use in South Australia ...... .... .._. ........ 9 J S H eyworth, E J Maynard, D Cunliffe ~ Cyanobacteria in a Small Tropical Reservoir .............. .. .. ....... .. ............. 14 D J Griffiths, M L Saker, P R H awkins WASTEWATER

r,- The Cost of Australian BNR Plants ......................................... .. ...... .. ...... 20 K J H artley \..

Werribee Treatment Plant: Born 1897 and Still Going Strong .. ..... .. .. .. .... 23 EA (Bob) Swinton ~ Reuse of Sludge From a Dairy Factory Lagoon .... ................... .. .... ........ 25 P R L M osse, L V Rawlinso n IE Retrofit of a Trickling Filter Plant to BNR Standard ... ...... .. .. ...... ... .. .... . 29 S Morgan, R Farley ~ VFA Production in Australian and Canadian Prefermenters .. ............. 34 E v Mi.inch, F A Koch ENVIRONMENT

Chris Davis Australian Water & Wastewater Association assumes no responsibility for opinions or statements of facts expressed by contributors or advertisers and editorials do not necessarily represent the official policy of the organisation .

Display and classified advertisements are included as an information service to readers and are reviewed by the Editor before publication to ensure their relevance to the water environment and to the objectives of the Association. All material in Water is copyright and should not be reproduced wholly or in part without the writ ten permission of the Editor.

Subscriptions W.1ter is sent to all members of A WWA as one of the privileges of membership. Non-members can obtain Water on subscription at an annual subscription rate of S39 (surface mail). lti) This signifies a paper has been refereed.

iii Minimising the Impact of Pesticides on the Riverine Environmen t Using the Cotton Industry as a Model ................................. .. ..... .......... ...... 37 N Schofield, V Edge, R Moran BUSINESS

11:1. Melbourne's Bulk Water Supply Agreements .................... .. .. ... ... .. ........ 42 B Bayley, T Kelly DEPARTMENTS From the Bottom of the Well ..... .. .................................................................. 4 International Affiliates ....... ....... .. ... .. ... ... ...... .... ........... .. ... ......................... .. .. 5 New Products ................ .............. ........................... ..... ..... ... ..... ..... ... ... .. .. ...... 45 Water Index 1996-1997 .. .... .. .. ........................ .. ... ........................... .. ........ ... . 46 Meetings ........ ..... ... ........... .. ........ .. ..... .. ... .......... ........ .. .. ... .......... ... .. ............... 48 OUR COVER: Was Werribee the first wastewater treatment plant in

Australia?J ust 100 years ago, M elbourne 's sewage started to be p umped from Spotswood to Brooklyn, then by gravity 20 km to 'the Farm ', wh ere it was treated by land filtration before discharge of the drainage water to Port Phillip Bay. Note the rivetted wrought iron sections of the rising main , still in place below the remains of the old steam pumps (see our story on page 9).

Photos by D avid Lorum, courtesy ofScienceworks, Museum ofVictoria.

m

WATER

Abstract A survey of 3014 people across South Australia was undertaken to determi ne the sources of water for drinking and cooking. Overall, rain water was found to be the main source of water used for drinking- 42.2% of households used tank water for drinking, followed by mains supply at 40.3% . For cooking, mains supply was used by 64.3% of households, followed by 29. 9% of households using rain water from tanks. In the metropolitan area, on average 25.6% of households used rain water fo r drinking, w hereas in rural areas, on average 81.5% of households used rain water, with use in some areas approaching 100%. T he extensive use of rain water highlights the need to consider rain water storage in tanks as part of the strategic planning of potable water supplies, particularly fo r ru ral communities. However, first th e potential health risks associated with rain water fro m tanks need to be addressed.

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Key Words Water supplies, health risks, rain water from tanks, consumer survey

II

Introduction The availability of safe water supplies for drinking, cooking and other household uses is well recognised as essential to protecting the public's health. Even in the urban setting where water is comprehensively treated to minimise adverse health impacts, there is increasing concern about the quality of water and its impact on health in Australia and internationally (World H ealth O rganization, 1993; National Health and Medical Research Council/ Agriculture and Resource Management Council of Australia and New Zealand (NHMRC/ARMCANZ), 1996; Watson, 1997; Payment et al., 1991; Payment et al., 1997). For rural areas in Australia, provision of an assured quality of water presents additional problems, including those associated with the distances involved, the small size of the communities and a lack of good quali ty sources of water. T he recent N H MRC/ARMCANZ guidelines w hich promote higher quali ty for water supplies will heighten these problems.

Rain water collected in domestic tanks is an important source of potable water for rural South Australia, with 77 to 84 per cent of households, depending upon region, using rain water from tanks as a source of water (Australian Bureau of Statistics, 1994). In Australia as a w hole, 30-85 per cent of rural

POTA LE WATER USE IN SOUTH AUSTRALIA J S Heyworth, E J Maynard, D Cunliffe

households, depending o n region, and 12.6 per cent of all ho useholds (approximately 818,505 households) use rain water from tanks. While the use of rain water from tanks is substantial, little is known about the associated health risks.

In the main, attention has focused on the health risks associated with reticulated water supplies rather than on alternative water supplies such as rain water.

Nevertheless, the safety of all water sources is of major concern to health au thorities.

Domestic Rain Water Quality Water stored in rain water tanks is usually collected from roof catchment areas. Potential sources of contamination include faecal material from birds, rodents, possums and other animals;

accumulated fallout from air pollutants; breakdown products fro m roofing material; and organic deb ris from overhanging trees. Several studies of rain water from tanks have investigated the physical, chemical o r microbiological quali ty (Fuller et al. , 1981; Thomas and G reene, 1993; Edwards 1994).

Edwards (1994) investigated the prevalence of indicator organisms in rain water tanks from 32 households in the Noosa Shire in Q u eensland, where 3500 (13.8%) residents were dep endent on tank rain water. Of the 64 samples taken, eleven contained 1 o r more E. coli per 100ml, 24 greater than 10 coli forms per 100ml an d 24 had standard plate counts greater than 500 organisms per 100ml. Studies such as this show microbiological quali ty to be WATER JANUARY/ FEBRUARY 1998

9

WATER below guideline values. H owever, the implications regarding pathogen densities, i.e. organisms known to be harmful to human health , in tank rain water are uncertain. The subsequ ent risk o f illness, in pa rticular gastrointestinal disease, is unknown, but may well be important judging from the levels of organisms indicating the presence of faecal contamination.

Data on the numbers of pathogens in tank rain water and associated health o utcomes is limited. For exa mple, C rabtree et al.. (1996) investigated the p revalence of Cryptosporidium and Giardia species in tank rain water in the Virgin Isla nds and de tected Cryptosporidium oocysts in 48 p er cent of tank rain water samples (n=44) and Giardia cysts in 26 per cent of samples, but did not consider disease outcomes.

Other re ports relate to investigations o f specific disease outco mes. In an outbreak of salmonellosis in Trinidad the cau sative agent, Salmonella arech evalata, was isolated from tank rain water (Kaplan et al. , 1978). Clostridium botulinum was isolated from samples of rain water and soil in the hom e environs of two ou t of four children diagnosed with botulism in N ew South Wales between 1980 and 1981 (Murrell and Stewart, 1983). Rain wa te r, however, was not confir med as the source of th e disease- causing organism s.

The desirability for a study of potential health risks in South Australia was evident and this study is the precursor to a larger study in South Australia to assess the microbiological health risk associated with the consump tion of rain water from tanks. Before examining the h ealth impacts of rain water use it was necessary to determine the extent of the use of rain water from tanks and to clarify regional differences in use across South Australia. T he opportunity was also taken to investigate the use of water more generally. T he obj ectives of this component of the study were therefore to identify the main sources of water used for drinking and cooking and to determine the extent of th e use of water from rain water storage tanks.

Survey Design The data was collected during May 1996 via SERCIS (Social, Environm ental and Risk C ontext Information System), a computer assisted telephone interview syste m (CAT I) and conducted by the South Australian H ealth Commission (Taylor et al. , 1996). A sample of 4500 telephone numbers was randomly selected from the Adelaide and country regions electronic white pages telephone listings. Within each h ou sehold, the person who had their birthday last, and was eighteen years or over , was selected for telephone inter10

WATER JANUARY/ FEBRUARY 1998

interviewer's contacts were selected at random for validation. T his involved a supervisor monitoring interviews and confi rming that the person selected was the person in the household who had the last birthday.

view. The survey included questions on the main sources of water for both d rinking and coo king used in t he household. Demographic data was also collected. Before the main survey, a pilot survey of fi fty responden ts was undertaken and t he questions were modified appropriately.

The telepho ne interviews were administered by trained interviewers an d conducted in English , Italian, Greek, Vietnamese or Spanish . At least five attempts were made to contact the appropriate person at each telephone number selected before classification as a non-contact. T en per cent of each

Results Response Of the initial sample of 4500 hou seholds there were 532 ineligible for sampling (359 had telephone numbers which were not connected, 135 were non-residential numbers and 38 were fax/ modem numbers). With an eligible

Table 1 Main sources of water for drinking and cooking in South Austral ian households Source of Water

Cooking

Drinking

% (95% confidence

n

% (95% confidenc~

n

interval)

interval) Rain water only

1271

42.2 (40.4-44.0)

901

29.9 (28.3-31 .5)

Public mains supply only

1215

40.3 (38.5-42.1)

1939

64.3 (62.6- 66.0)

421

14.0 (12.8-15.2)

60

2.0 (1.5- 2.5)

Bottled or spring water Rain water and mains supply

58

1.9 (1.4-2.4)

58

1.9 (1.4- 2.4)

Ground or bore water

14

\ , 0.5 0.3-0.7)

21

0.7 (0.4- 1.0)

River or lake water

13

0.4 (0.2-0.6)

19

0 .6 (0.3- 0.9)

0

0

3

0.1 (0.0- 0.2)

22

0.7 (0.4-1.0)

13

0.4 (0.2- 0.6)

Rain water and river or lake Other sources1

1. Other sources includes a mixture of water sources such as bottled and mains, rain/spring water and distilled water. A few respondents did not cook at home, and are included in 'other sources.'

Table 2 Main sou rces of drinking water across South Australia (percentage of households) Area

Mains

Rain water

Bottled or spring water

Other sources#

N

%

%

%

%

310

54.5

26.1

15.8

3.5

1780 165 64 19 97 222 72 18 74 67 31 29 37 7 22

52.8 5 .5 3.1 0 .0 14.4 12.6 2.8 5.6 8.1 64.2 32.3 6.9 5.4 0 .0 0.0

25.3 82.4 93.8 100.0 73.2 81.5 95.8 94.4 82.4 28.4 67.7 93.1 83.8 100.0 90.9

18.7 8.5 3.1 0.0 11.3 2.7 1.4 0.0 1.4 4.5 0.0 0.0 2.7 0.0 0.0

3.2 3.6 0.0 0.0 1.0 3.2 0.0 0.0 8.1 3.0 0.0 0.0 8 .1 0.0 9 .1

Metropolitan Adelaide

1. Northern Metro area (Elizabeth and North) 2. Rest of metropolitan area 3. Adelaide Hills 4. Lower North 5. Strathalbyn and Milang 6. Fleurieu Peni nsula 7. Mid-north plus York Peninsula 8. Riverla nd 9. Murray Mallee 10. South-east without Mt Gambier 1 1. Mount Gambier 12. Port Lincoln 13. Rest of Eyre Peninsula 14. Areas served by other small supplies 15. Areas with no public water supply 16. Remote Areas

# Other sources includes groundwater or bore, and mixtures of sources such as rain water/ mains, bottled/ mains, rain water/spring water. The categories 'rain water plus river' and 'river or lake' were omitted because no respondents indicated using these water sources as their main supply for drinking, apart from respondents in Mt Gambier where the main supply is lake water.

WATER some comparison between households, household consumption was divided by the number of people in the household to provide an estimate of con su mption per person. If there were children under 5 years and adults over 70 years in the household, questions were also asked about their specifi c co nsumption patterns.

Table 1 shows that rain water from tanks is a major source of water for drinking. Overall, 42.2 per cent of households used it as the major source of drinking water, compared with 40 .3 per cent that used mains supply water.

Bottled or spring water was also a notable source of drinking water amongst 14.0 per cent of respondents.

Other sources made up 3.5 per cent.

Public mains su pply was the main source of water for cooking.

Comparisons of water consumption for drinking and cooking by region, as categorised by the source of public

sample of 3968, 3014 interviews were completed, a response rate of76.1%.

Approximately 74% of the 3014 interviews were conducted in metropolitan Adelaide (n=2224) and 26% in country South Australia. The reasons for nonresponse were refusals (8.7% ), noncontact after five attempts (10.4% ), respondents unable to speak English, Italian, Greek, Vietnamese or Spanish (1.4%), incapacitated (3. 2% ) and terminated interview (0.2%) .

Sources of Water R espondents were initially asked to nominate the main source of water used for both drinking and cooking in their h ouseholds (Table 1). R espondents indicating rain water from tanks as a main source of water for drinking and cooking were then asked about the n umber of cups co n sumed in the househ old per day for cold drinks, hot drinks and coo king. In order to provide

Table 3 Main sources of water for cooking across South Australia (percentage of households)

n

%

Rain water %

310

81.3

15.5

1.0

2.3

1780 164 64 19 97 222 72 18 74 67 31 29 37 7 22

82.1 21.3 15.6 0.0 38.1 31.5 6.9 11.1 12.2 77.6 51.6 6.9 13.5 0.0 0.0

12.8 72 .6 82.8 94.7 54.6 62.6 93.1 88.9 70.3 20.9 45.2 89.7 73.0 100.0 90.9

2.8 2.4 0.0 0.0 4.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

2.3 3.7 1.6 5.3 3.1 5.9 0.0 0.0 17.6 1.5 3.2 3.4 13.5 0.0 9.1

Area

Mains

Bottled or spring %

Other sources# %

Metropolitan Adelaide 1. Northern Metro area (Elizabeth and North) 2. Rest of metropolitan area 3. Adelaide Hi lls 4. Lower North 5. Strathalbyn and Milang 6. Fleurieu Peninsula 7. Mid-north plus York Peninsula 8. Riverland 9. Murray Mallee 10. South-East without Mt Gambier 11. Mount Gambier 12. Port Lincoln 13. Rest of Eyre Peninsula 14. Areas served by other small supplies 15. Areas with no public water supply 16. Remote Areas

# Other sources includes bottled or spring water, groundwater or bore and a mixture of water sources such as rain water/mains, bottled/ mains, rain/spring water, rain water/ river and river or lake. It also includes ' no cooking.'

Table 4 Consumption of rain water per person for drinking or cooking and by age (cups* per day) All persons Cups per day

Cold drinks n=1329

<1 cup 1 to 4 cups 5 to 9 cups 10 to 14 cups 15 or more cups don't know

n 57 862 334 42 14 20

% 4.3 64.9 25.1 3.2 1.1 1.5

Mean Median

* a cup is defined as ca. 250

3.9 3.3 ml

Ch ildren aged <5 years

Both drinking and cooking

Hot drinks or Cooking n=1348 n 98 711 400 99 26 14

% 7.3 52.7 29.7 7.3 1.9 1.0 4.5 4.0

Adults aged >70 years

n=135 n 10 79 35 6 3 1

% 7.4 58.5 26.7 4.4 2.2 0.7 4.0 4.0

n=268 n 3 49 118 51 39 8

% 1.1 18.3 44.0 19.0 14.6 3.0 9.1 8.0

mains water, are shown in Tables 2 and 3. In rural areas the primary source of drinking water was rain water. Overall, 81. 5 per cent of households used rain water as their main source of drinking water, compared with 25. 7 per cent of households in m etropolitan Adelaide.

Apart from Mt Gambier, where only 28.4 p er cent used rain water from tanks as the main drinking wate r supply, consu mption in co untry South Australia ranged from 67. 7 per cent in Port Lincoln to 100 per cent in the Strathalbyn/M ilang area and those areas with no public supply (Table 2). For cooking, 70. 1 per cent of rural South Australian households used rain water as their main source of water compared with 15.0 per cent of households in m etropolitan Adelaide (Table 3). U se of rain water from tanks as the main source of water for cooking ranged from 20.9 per cent in Mt Gambier to 100 per cent in those areas with no public supply.

Consumption of Rain Water from Tanks ( For those households reporting use ofrain water (n=1348), the extent ofuse for cold drinks ve rsus hot drinks/ cooking was inves tigated as it was con sidered that any gastrointesti nal health risk may be reduced by heating or boiling water (Table 4). The average number of cups (ca. 250 ml per cup) consumed per person p er day was estimated as 3.9 for cold drinks (about 1.0 litre) and 4.5 for hot drinks or cooking (about 1.1 litres).

Consumption amongst young children and the elderly, both considered as groups pote ntially at higher ri sk of gastrointestinal disease, was also investigated (Table 4). Amongst households in w hich rain wate r is co nsumed, 135 (10 .0%) households had children aged under 5 years and 268 (19.9% ) households included people aged .over 70 years. For children the average reported con sumption of rain water as either hot or cold drinks p er day was 4 cups (l litre) and for adults over 70 years, the average reported consumption was 9 cups per day (2.2 litres).

Discussion This study indicates that rain water from tanks is the major source of water fo r drinking and an important source for cooking in South Australia. More households use rain water from tanks as the major source of drinking water than households that use mains water (Table 1). Rain water is clearly the primary source of drinking water for rural South Australia with an overall consumption ofrain water from tanks of81.5 per cent outside the metropolitan area.

It is postulated that regional differences in the consumption of rain water WATER JANUARY/FEBRUARY 1998

11

WATER from tanks for drinking and cooking across country South Australia are a reflection of differences in the aesthetic quality of m ains water. Unfiltered supplies in South Australia, particularly from the River Murray, have always had problems associated with physical appearance, taste and odour. Until the filtration plants were installed from 1977 onwards, this had also applied to areas of metropolitan Adelaide.

Waters supplied to the Eyre Peninsula and many South-East towns have salinities generally over 1000mg/L, thus reducing the palatability of the water (NHMRC/ARMCANZ 1996).

On the other hand, Mt Gambier, which has a low use of tank rain water, is supplied with lake water of a high aesthetic quality.

High levels of consumption of rain water from tanks across the State may also result from concerns about the use of chemicals in water treatment. A number of studies have indicated that this is an important con cern amongst the public (Baxter, 1990; Slovic, et al.

1993; SAHC, 1990) . A health omnibus survey of the public in South Australia found that 'chemicals in drinking water' was most frequently ide ntified as the water pollution con cern most likely to affect health; 24 per cent of responden ts named 'chemicals' as a concern compared with 11 per cent w ho believed 'germs' to be a problem (SAHC 1990).

The use of rain wate r from tanks is greater in South Australia than in other States (Australian Bureau of Statistics, 1994). This grea te r use appears to reflect a historical dissatisfaction with

the aesthetic quality of public water supplies in South Australia. In an environmental issues survey (Australian Bureau of Statistics, 1994), South Australians showed the highest level of dissatisfaction with mains supply water, with 51 per cent indicating they were not satisfied with the quality of mains supply water compared with 33 per cent for Australia as a w hole. Similarly, a survey conducted by the Australian Environment Council (1988) found that in South Australia 'poor tasting water' was the most important environmental concern, whereas elsewhere in Australia it was 'noise.' In recent years this has been addressed to a large extent by the installation of a number of filtration plants. By the year 2000, 80 per cent of the population will be supplied with filtered w ater. However, the poor reputation persists.

T he level of use of bottled or spring water as a main source of drinking water was higher than expected, at 14 per cent (Table 1). Increasing use of bottled water has also been reported in the United States and Great Britain (Baxter, 1990; Select Committee on the European Communities, 1996), where a number of reasons were suggested for this increase: a con cern about the purity and safety of tap w ater ; improved technology leading to increased detection and reporting of ch emical contaminants by water authorities; increased scie ntific knowledge of substances not previously thought to be harmful; as well highly publicised incidents of bo th chemical and microbiological contamination of water.

f

BOOKS Freshwater Algae in Australia T J Entwistle, J A Sonnennan, S H Lewis. ISBN O 646 31408 4. 242 pages. AS. Available from Sainty & Assoc. Pty Ltd, PO Box 1219 Potts Point NSW 2011. Cost $30 soft, $40 hard, including postage.

This excellent handbook is not a text book but an illustrated guide to the freshwate r algae commo nly en countered throughout Australia, aimed at assisting aquatic managers and scientists in diagnosis.

The first 20 pages briefly summanse: • the 13 divisions identified by Day et al. (1995) • their habitats, ranging from attachm ent to animals, rocks etc. to occurrence in muds, rivers, reservoirs and even snow • collection, storage and identification, including use of microscopes 12

WATER JANUARY/ FEBRUARY 1998

• a brief page on management • their ecological signficance.

Then follows 85 double pages of description o f each genus with excelle nt coloured micrographs or diagrams, followed by a list of 125 valuable references.

The genera are arranged in a novel format of vegetative groups rather than the conventional system atic order , w hich makes it easier for non-experts to identify specimens to genus level.

Diagnosis is assisted by an illustrated key based on schematic diagram s of gen eral appearance.

The Australian Society of Lirnnology, Royal Botanic Gardens M elbourne and the CRC for Freshwate r Ecology supported the authors. The list of acknowledgements spans a wide range of the institutions involved in both ecology and water supply.

EA (Bob) Swinton

Potential Health Effects Concerns have been raised about the contribution of mains water to endemic gastrointestinal disease and studies are being carried out on the impact of mains water on health. Canadian studies have reported that water complying with water quality standards is associated with an increased risk of gastroenteritis (Payment et al., 1997; Payment et al., 1991). A randomised control trial in Montreal of the impact of reverseosmosis water filters on the incidence of gastrointestinal symptoms found that the inciden ce was 33- 35% higher in those households without a filter fitted, even though the w ater met current standards (Payment, 1991). A study of a similar design is under way in Melbourne (Hellard and Fairley, 1997).

Rain water, however, seems to have been overlooked.

U se of rain water by the young and the elderly h as been specifically examined because of the increased risk of gastrointestinal illness in these groups (Gangarosa et al., 1992; HoogenboomVerdegaal et al., 1994; Stevens et al. , 1995), and because drinking water has been shown to be associated with an increased risk of gastrointestinal disease amongst young children (Payment et al., 1997). In the prospective study of the impact of drinking water on endemic gastrointestinal disease in Montreal, Payment et al. (1997) found that the number of episodes of gastrointestinal illness in children aged 2-5 years was 1.29 episodes per person-year com-pared with 0. 96 episod es per person-year amongst children consuming purified water (RR=l.34).

Conclusions The policy implications o f the findings presented in this paper are significant. Substantial reso~rces are committed to supplying water and maintaining the infrastructure for rural water supplies. Furthermore, these systems may require upgrading at considerable cost to comply with the 1996 Australian Drinking Water Guidelines (NHMRC/ARMCANZ, 1996). Yet this study has indicated that 81.5 per cent of con sume rs in country regions do not use mains water as their main source of drinking water. While some people choose not to use mains water, others, including those in remote Aboriginal communities, do not have access to a public supply. These communities are dependent on rain water collection, gro undwater and private surface water collections. It therefore seems appropriate to review the use of rain water storage as an alternative water supply, p articularly as it has been shown to be a community preference for drinking water. The promo-

WATER tion of rain water storage as a water supply where supply is limited or of dubious quality is consistent with the principles of conservation and sustain-

ability. However, the safety of rain water from tanks must be a prime consideration in promoting this source of water.

Research to date has indicated that rain water from tanks may be of poor quality (Fuller et al., 1981; Thomas and Greene, 1993; Edwards, 1994).

However, little data on adverse health

outcomes is available. Throughout Australia, especially in South Australia, use of rain water from tanks is substantial, but there is little understanding of the quality in terms of potential health risks. A formal assessment is needed to identify the risks, if any, associated with consumption of rain water. In particular, an assessment is needed of the contribution of rain water from tanks to endemic gastrointestinal disease and the methods of preventing or reducing the risk. The South Australian Health Commission and Flinders University of South Australia are proceeding with such a project. This data will provide a basis for the development of guidelines on the safe use of rain water from tanks.

References Australian Bureau of Statistics (1994) Environmental Issues. People's Views and Practices. Canberra, Australian Bureau of Statistics.

Australian Environment Council (1988) Community Response to Noise in Australia: Results of the 1986 National Noise Survey. Canberra, AGPS. Baxter R (1990) Some Public Attitudes About Health and the Environment.

Environmcnt.11 Health Perspectives 86: 261-269.

Crabtree K, Ruskin R et al. (1996) The Detection of Cryptosporidium Oocysts and Giardia Cysts in Cistern Water in the US Virgin Islands. Water Research 30 (1): 208-216.

Edwards R (1994) A Microbiological Investigation into the Degree of Contamination of Water in Domestic Rain Water Storage Tanks with Residents of Noosa Shire, Solely Supported by Tank Water 1993, 54th Annual State Conference of the Australian Institute of Environmental Health (Qld Division), Ipswich, Queensland, AIEH, Qld Division.

Fuller C, Martin T, Walters R (1981) Quality Aspects of Water Stored in Domestic Rain Water Tanks (A Preliminary Study). Adelaide, Engineering and Water Supply.

Gangarosa R, Glass R, Lew J, Boring J (1992) Hospitalisations Involving Gastroenteritis in the United States, 1985: The Special Burden of the Disease Among the Elderly. American journal of Epidemiology 135 (3): 281-290.

Hellard M, Fairley C (1997) Gastroenteritis

in Australia: Who, What, Where, and How Much? Australia New Zealand Journal ofMedicine 27: 147-149.

Hoogenboom-Vcrdegaal A, De Jong J, During M, Hoogenveen R, Hoekstra J (1994) Community-based Study of the Incidence of Gastro-intestinal Diseases in The Netherlands. Epidemiological Infections 112: 481-487.

Kaplan J, Deen R, Swanston W, Tota B (1978) Contaminated Roof-collected Rain Water as a Possible Cause of an Outbreak of Salmonellosis. Journal ,of Hygiene 81: 303-309.

Maynard EJ, Heywonh JS (1990) Environmental Health Risk Perception.

Adelaide: South Australian Health Commission unpublished data.

Murrell W, Stewart B (1983) Botulism in New South Wales, 1980-1981. Medical Journal ofAustralia 1: 13-17.

NHMRSC/ARMCANZ (1996) Drinking Water Guidelines. Canberra: National Health and Medical Research Council and Council/Agriculture and Resource Management Council of Australia and New Zealand.

Payment P, Richardson L, Siemiatycki J, Dewar R, Edwardes M, Franco E (1991) A Randomised Trial to Evaluate the Risk of Gasrto-intestinal Disease Due to Consumption of Drinkmg Water Meeting Current Microbiological Standards. American Journal of Public Health 81 (6): 703-708.

Payment P, Sicmiatycki J, Richardson L, Renaud G, Franco E, Prevost M (1997) A Prospective Epidemiological Study of Gastro-intestinal Health Effects Due to the Consumption of Drinking Water.

International journal of Environmental Health Research 7: 5-31.

Select Committee on the European Communities (1996) Drinking Water.

London, HMSO. Slavic P, Flynn J, Mertz C, Mullican L (1993) Health-Risk -Perception in Canada, Minister of Supply and Services Canada.

Stevens M, McConnell S, Nadebaum P, Chapman M, Ananthakumar S, McNeil J (1995) Drinking Water Quality and Treatment Requirements: A R.iskbased Approach. W.1tcr December, 12-16.

Taylor A, Dal Grande E, Wilson D (1996) SA Country Health Survey, March April 1996. Adelaide, Behavioural Epidemiology Unit. SA Health Commission.

Thomas P, Greene G (1993) Rain Water Quality from Different Roof Catchments. Water Science and Tcclmology28 (3-5): 291-299.

Watson C (1997). Safe Drinking Water.

Medical Journal of Australia 166: 285-286.

World Health Organization (1996) Guidelines for Drinking Water Quality, Geneva: World Health Organization.

Authors Jane Heyworth is a PhD student at

Flinders University of South Australia undertaking a risk assessment of rain

water consumption in collaboration with the South Australian Health Commission (SAHC) (PO Box 6 Rundle Mall, Adelaide SA 5000, fax (08) 8226 7102.

She has extensive experience in environmental health, having worked with state and local governments and as a lecturer in environmental health at Flinders University. Dr Ted Maynard is a public health physician and Manager of the Special Programs Section of the Public and Environmental Health Service, SAHC and Dr David Cunliffe is a Scientific Officer with the Environmental Health Branch of that Service. He has over 15 years experience in water and waste water microbiology.

rn,n~ 1111~

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WATER Providing innovative and cost effective solutions for the sustainable development of our region's water resources.

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WATER JANUARY/FEBRUARY 1998

13

Abstract

Introduction

Solomon Dam on Palm Island off the coast of northern Australia is subj ect to re curring blooms of cyanobacte ria.

Artificial destratification by the forced introduction of air into the lower part of the water column has been effective in preve n ting summer blooms of Cylindrospermopsis raciborskii but less effective in preventing winter, dryseason blooms of othe r cyanobacterial species. Extensive drawdown of the reservoir during the dry seaso n restricted the depth at w hich the aerator could be deployed, resulting in considerable O}..')'gen depletion at the base of the water column. This favoured mobilisati on of nutrients from the sediment w hich, during the mid-year natural deep mixing, became entrained into the water column and triggered phytoplankton blooms. Major components of the mid- year blooms were the cyanobacteria Anabaena circinalis and Microcystis aemginosa and the colonial green alga, Volvox.

Diatom blooms dominated by species of Synedra were largely restricted to the summer mo n ths, resulting in severe silica depletion if the summe r rain inflows were delayed.

Zooplankton grazing pressure may be a factor contributing to the dominance of the winter dry- season blooms by large colonial species, including some potentially toxic cyanobacterial species.

The most spectacular growth over recent years in our knowledge of toxic cyanobacteria has been in identifying and characterising the toxins and defin ing their health effects. Less spectacular, but no less important, has been the growth in the body of information now available to us on the condi tions that lead to the formation of cyanobacterial blooms in water bodies. This information will provide a framework from which to develop effective management procedures to coun te r the harmful effects of these organisms.

Management of toxic cyanobacteria may take one of two forms. T he first is 'crisis management,' wh ich involves¡treating cyanobacterial-affected raw water to remove the offending organisms and/or to neutralise the toxins.

The second is 'preven tative management,' which n1anages the conditions in the water body and catchment to prevent cyanobacterial blooms fomung.

We have used both these management approaches at Solomon Dam on Palm Island off the east coast of northern Australia (18°45' S; 145°35' E). We have attempted to manipulate t he phytoplankton compositio n in the water body by artificial aeration. As a backup, we have relied on standard water treatment procedures. Even at times of strong cyanobacterial blooms, these procedures have proved effective in preventing toxic contamination of the water supply to the island community. This paper discusses the results of a

Key Words Cyanobacte rial blooms, zooplankton, artificial aeration, tropical lakes 14

WATER JANUARY/FEBRUARY 1998

biological sampling program w hi ch monitored t he effectiveness of the aeration procedures tried at Solomon Dam.

Materials and Methods Solomon Dam serves as the main water su pply fo r a commu nity of more than 2,000 people at Palm Island. lt is a small reservoir wi th a maximum volume of0.5 x 106 1113 and a maximum depth of 13.4 m. The p rimary sampling site (Site 1) was situated close to the offtake tower near the deepest point.

Other sites were established at varying distances and different directions from this point (see Figure 1).

Water samples were tak<in from different depths using a Va n Dorn bottle and sedimen t samples with an Ekman bottom dredge sample r.

Measurements of temperatu re and dissolved O}..')'gen concen tration were made w ith a Hydrolab Datasonde II submersible multi- parameter instrument with data-logging faci li ty.

Phytoplankton in water samples were concentrated by settlement after treatme n t with Lugol's solution (a saturated solution of iodine in a saturated aqueous solution of potassium iodide). The concentrated sample was transfe rred into a Sedgewick-Rafter chamber for counting. The contribution of different components to the to tal phytoplankton biomass was computed from cell numbers and estimated cell volumes as determined from microscopic measurements and approximation of the nearest simple geometric solid.

WATER proved effective in removmg Zooplankton samples were 12° the cyanobacterial cells and collected by duplicate 6 m . . . km protecting the water supply vertical hauls (net diameter 50 from contamination by cm, mesh size 70 µm ). For ) toxins.

More recently, as a counting, the sample was Townsvillc I further precaution, this has reduced to ca. 100 ml using a ) been supplemented by treatt--~~~c~~nFolsom sample spli tter and ment with activated carbon. preserved in 5% formalin.

1 QUEENSLAND ·-7 The preserved sample was Artificial 28° L--·-·--~~~~~,! concentrated by sedimentaDestratification tion and subsampled with 3• Sampling Sites a wide-bore 1 ml piston An aeration system was - s - Depth in metres pipette for counting in a installed in late 1983 to Sedgewick-Rafter chamber. disrupt the vertical stability of Chlorophyll a and bacterithe water column. This ochlorophyll were estimated involved forced introduction spectrophotometrically after of air into the lower part of filtering 500 mL wate r the water column through samples through glass fibre duplicate 25 m long perfodiscs (Whatman GF/C) and rated tubes suspended from extracting w ith cold 90% flo tation buoys (Brown and acetone or 90% m ethanol, Jory, 1985). Compressed air using the equations of Parsons (200 KPa) was supplied to and St rickland (1965) and each tube through separate .,.,,' Tailing and Driver (l 963) fo r lines from a compressor delivt I O 100m 50 chlorophyll a and Stanier and ~) ering 50 Ls- 1 . This mechaI '----'---L-~~ Smith (1960) for bacterinism, based on the design of Figure 1 Location of sampling sites (1-6) and t he aerator oc hlorophyll. Total-P and Tolland et al. (1978) prorelative t o depth isopleths (m below full capacity} soluble reactive PO 4-P in duced a curtain of air bubbles water samples were estimated rising to the surface from a spectrophotometrically by the molyb- nalis and M icrocystis aeruginosa. depth which at the time of the original Cylindrospernwpsis raciborskii was installation was 1 m above the bottom denum blue method, NH 4- N by the phenate method an d Si by atomic isolated from water samples, grown i n (see Figure 2) . culture and its toxicity was con firmed absorption spectrom etry (APHA, 1985).

The effect of artificial mixing on the Carbon, ni trogen and phosphorus in by mouse bioassay (H awki n s et al. , phytoplankton dynamics of the resersedim en t samples were determined 1985). The first step in management of voir has been previously reported spectrop hotometrically; carbon after the water supply was taken in August (Hawkins and Griffiths, 1993) and is chromic acid digestion (H eanes, 1984), 1983 w ith the commissioni ng of a slow su mmarised in Figure 3, which comnitrogen after Kjeldahl digestion sand filtration system consisting of a pares the phytoplankton population in (APH A, 1985), p h osphorus after a number of concrete enclosures provid- April 1983 in the unaerated water modified Kjeldahl digestio n procedure ing a large bed area of fine sand to trap column (a, c) and April 1984 in the suspe nded mate ria l. T his filtration aerated water column (b, d) . In April (Allen, 1974). process, fo llowed by chlorination , 1983, w hen the water column was History of Blooms in Solomon strongly stratified , with a largely anoxic Dam hypolimni on, there was a distinct chlorophyll maximum at 1 m depth (see In 1979 there was an outbreak of Figure 3a). From 6.5 111 depth to the hepatoenteritis in the Palm Isla nd bottom, the dominant pign1ent was comm unity resulting in hospitalisation bacteriochlorophyll (see Figure 3a). The of many children (Byth, 1980). The maj or contributor to the su bsurface problem was traced to the water supply, peak of chlorophyll a was the cyanoand attri buted to an earlier alga l bloom, bacterium C. raci borskii (Cyan. in although the causal organism had not hi stogram Figure 3a), whilst in the been identified (Bourke and Hawes, hypolimnion the dominan t organism 1983; Bourke et al., 1983). It was was the anaerobic photosynthetic presumed that the problem had been bacte riu m Chlorobium Jimicola. In compou nded by t he use of co pper April 1984, after four months of aerator sulphate as an algicide. operation (8 h day- 1 from 0800 h), there This event served as the trigger for a was a fairly unifo rm temperature distristudy of the reservoir which began in bution down the water colu m n and 1981. Towards the end of that year, only a small dissolved 02'.')'gen gradient Solomon Dam experienced a strong with depth (see Figure 3d). Chlorophyll w ith Cylindrospermopsi s bloom a was fairly uniformly distributed with raciborskii as the dominant organism. depth , and the phytoplankton popThis was t he first reco rding of ulation was now dominated by diatoms C. raciborskii in Australia, although it (Bae. in histogram Figure 36) w ith was known to occur in the Indo- Malay Synedra as the dominant genus (5. tenera region. T here were recurring blooms of var. tenera, S. ulna var. chaseana). this organism in 1982 and 1983 Artificial aeratio n also produced an with occasional blooms of two other Figure 2 Artificial aerator used to destratify increase in the total chlorophyll a cyanobacterial species, Anabaena circi- the water co lumn

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WATER JANUARY/FEBRUARY 1 998

1,5

WATER

4

yan

t

(d)

0

4

20

40

60

80

0 , (%)

100

80

100

Figure 3 Depth profiles for chlorophyll, temperature and oxygen in the unaerated (a, c) and artificially aerated (b, d) water column at Site 1. See text for f urther explanation

concentration m the water column.

This took t he form of an initial large increase, evident from integration of the pigment profiles (see Figu res 3a, 36). The increase was followed by a lesser effect which, with large temporal fluctuatio ns, persisted for at least nine months after the start of artificial aeration (Hawkins G riffiths, and 1993). Increases in p hytoplankton c hlorophyll a concentrations immediately after the onset of artificial destrati6.cation and moderately elevated values thereafter are not uncommon (Steinberg, 1983). They have bee n vari ously

(b) Cyli11drospetmopsis raciborskii

(a) A,,abaena circinali.f

attributed to an initial entrainment of nutrient-rich hypolimnetic water, an increased rate of oxidation and decomposition of organic matter (Fast, 1971), and to more long- term effec ts related to changes in the species composition induced by the altered water column dynamics (Reynolds et al. , 1983, Trimbee and Harris 1984).

The incidence of cyanobacterial blooms over the periods 1981-1984 and 1993-199 5 confirms the effectiveness of artificial aeration (stippled bar) in preventing blooms of C. raciborskii (see Figure 4). T he only recorded bloom of this species since early 1984 coincided with a period of temporary malfunction of the aerator in December 1993.

Responses to Artificial Aeration In order to avoid di sturbance of bottom sediments and settling of the aerator tube on to the bottom at times of maximum drawdown of the reservoir, more recent destratification trials have tes ted th e effectiveness o f a shallower deployment of the diffuser tubes. For the profiles shown in Figure 5, the diffuser tubes were suspended at 5 m depth. T emperature and dissolved O>..)'gen profiles are shown for Si te 1, w ith and w ithout aeration, at a time of year wh en water column stability might b e expected to be at its maximum. Also

(c) Microcys/is aeruginota

1981

1982

1983

I

1984

1993

1994

1995

100

100

cells mL¡' x 10-3 200

100

Figure 4 Cya nobact erial blooms, 1981-1995, 0.5 m depth sa mples, Site 1, before and after artificial aeration (stippled bar in middle panel)

16

WATER JANUARY/ FEBRUARY 1998

WATER species like Volvox which R eynolds shown are the respective profiles at Phytoplankton in Deep-mixed (1983) has described as a 'sophisticated varying distances from the aerator.

Water Column r- strategist ,' and some cyanobacteria.

T h ere i s approximately a 1° C O ver recent years periods of deep tempe rature diffe rence between t he mixing-u sually between M ay and Promine nt among the latter are M. surface and 2 m depth at all sites located A ugu st, whe n artifici al m ixing is aeruginosa w hich usually coexists with som e distance away from the ae rator overtaken by natural mixing-charac- Volvox and A. circinali s which may o r (see Figure Sc). H owever , there is no teristically produce p hytop lank ton may n ot coexist with the other two evidence at any site, w ith the possible blooms. In 1994 and 1995 the blooms species an d always persists longer in the exception of Site 6, of the characteristic were of the colonial green alga Volvox water colum n (see Figure 7). tempe rature profile evide n t in t he and some cyanobacterial species, most u naerated water column (see Figure Sa) . notably A. circinalis and M . aeruginosa Zooplankton Population The dissolved oxygen profiles con fi rm (see Figure 7).

Dynamics the effec tiveness of artificial aeration in It is interesting to note that diatoms T h e dominant zooplankton grou ps extending th e region of OA')'genation have n ot been a significan t component in Solom on Dam ove r the Aprildown the water column, but there is in recent years of th e m id-yea r, Au gust pe riod were c op ep od s and considerable oxygen depletion of that M ay-August p hytop lan kton popularo tifers (see Figure 9). Bo th groups part of the water column lying below tion . Bloom s of Synedra have appeared comprise specialised feeders able to the diffuser tubes. O A')'gen demand in only during t he su mmer m o n ths selec t pre fer red prey specie s. This the lower part o f the water colum n (N ovember-J anua ry) wh en , becau se of favoured dominance of the phytoplankclearly exceeds the ra te at which oxygen their large size relative to many other ton p opulation by n on- targe ted o r can be repleni shed from above. phy topla n kton speci es, th e diatom s It is likely therefore that unle ss th e account fo r a large component of the resistant species. In addition to their aerator is placed close to the bottom, p hytoplankton biomass (see Figure 8) . capacity for rapid growth , large colonial stro ng oxygen deple tion will occur j ust T he diatom bloom s cau se seve re sibca green algae are also resistant to ingestion above the sedim ent, even in a vigor- depletion of the wate r column , by filter feeding zooplankton (R eynolds o u sly aerated wat er c olu mn. Und er although recovery fro m su ch episodes and Rodge rs, 1983). The large colonies these conditions, considerable mobili- of silica depletion quickly follows th e of M. aemginosa would also be immune satio n of certain nutrie n ts from the we t season inflows of J anu ary and to ingestion as w ell as being potentially sedim ents is to be expected (Martinova, February (see Figure 8). Therefo re , the toxic, at leas t to some cladoc erans absence of Synedra , or any ot her (D eM ott et al. , 1991) .

1993; Brunberg, 1995).

T he zoop lankton population of the T hat the sediment in Solomon D am diatom s in significa nt quantity, from su m me r months was dominated by the mid-year blooms is unlikely to be represents a substantial po tential resercladocerans and copepods in early 1994 voir of nu trient elements is evident due to silica limitation.

In Solomon D am, the conditions in and by rotife rs in early 1995 and may from the concentrations of C , N and P midyear (April- August) do not favo ur have been a co ntributing factor in the recorded in sam ples take n from the upper 15 cm (see Figure 6a, b , c). The diatoms, as might be expected in a weJl- failure of Synedra to re- es tablish valu es, altho ugh showin g ma rked mixed wa ter column w ith substantial dominance late r in each year when silica fl uctuations be twee n samples, are internal nutrient loading (T rimbee and and o ther nutrients from deep nuxm g generally within th e range know n to be H arris, 1984), but o ther opportunisti c were again available. typical of highly productive lakes Temp. ("C) (Gorham e t al. , 26 30 27 28 29 32.73 33,52 197 4, P enning(a) ton 1978) .

It is also apparen t t hat after a long period o f - 3 oxygen deple tion 4 of the bottom 6 w aters, there is 2 6 considerable mobilisation of P04-P 4 and N H 4 -N from the sediment inincreasing dis1ance from aerator 40°' (%) 60 to the overlying a w 86. 1 84.0 water (see Figure ~ (d) 2 (b) 66, C, d - f).

Entrain m en t of this nutrient- rich 4 water into t he aerator tube rest of the water d <plh column , as must 6 inevitably occur when conditions '------1 20% 0 sal. permit deep mix8 ing, has the potential to trigger increased phytoplankton growth Figure 5 Dept h profi les for summer t emperature and dissolved oxygen at Sit e 1, no artif icial aeration (a, b). Similar (see Figure 6g, h). summer profiles with aerat ion (c, d) at Sit es 1 - 6

*

2

WATER JANUARY/ FEBRUARY 1998

17

WATER Conclusion In the artificially destratified Solomon Dam the blooms of the cyanobacterium C. raciborskii which characteristically dominate the summer phytoplankton in the un managed reservoir are replaced by diatom s with Synedra species as dominant components (H awkins and Griffi ths, 1993). In this respect, therefo re, Solomo n D am conforms with the now well d ocumented responses of these two major phytoplankton groups to ch ange in water colu mn stability (R eyn olds et al. , 1983; Steinberg, 1983; H arris and Baxter, 1996).

The other major cyanobacterial species A. circinalis and M. aeruginosa tend to bloom during th e dry season w inter m on ths. Fo r at least part of thi s p eriod the reservoir is naturally mixed to the bottom. This natural mixing is in addition to the artificial mixing, which circulates the upper 5 m or so. U nder these conditio ns it appears that diatoms cannot compete with the two cyanobacterial species or w ith Volvox, even w he n silica and other nu trients are abundant. The reasons for this are not clear. They may be related to the greater resistance of the large colonial species to grazing by zoopla nkton. Copepod nauplii and rotifers, present in consider-

able numbers at this time and known to be capable of high grazing impacts in eutrophic lakes, may exert a ' top-down' control of the more palatable phytoplankton species (Quibler-Lloberas et al. , 1996). It may also be significant that in another Queensland water storage, North Pine Dam nea r Brisbane, compared with Cylindrosperm opsis, Microcystis has been shown to occur more abundantly at times when the water column is less stable (H arris and Baxter, 1996).

Whilst this pap er confirms the effectiveness of artificial destrati fica tion in preven ting summer dominan ce of the phytoplankton by the potentially highly toxic C. raciborskii, it highlights the limitations of this management technique in eliminating the w inte r blooms of so me other equally troubleso m e cyanobacterial sp ecies (A. circinalis and M . aeruginosa). Artificial destratification, unless it also reduces anoxia and nu trient release fro m the sedime nts, may actually stim ulate phytoplankton bloo ms, including blooms of those cyanobacterial species that are more tole rant of vertical mix ing.

T he results described in this paper confirm that the phytoplan kton composition in Solo mo n D am, and i ts

, 560 400

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References AJJen SE, Chemical Analysis of Ecological M aterials, Blackwell Scientifi c P ub lications, Oxfo rd (1974) 565 pp.

APH A (1985) Standard M ethods for the Examination o[ W.1ter and Wastewa ter.

16th Edi tion. American Public Health Association, Washington , 1268 pp.

'a·:r·- .,!

C

IO

b

u

In its early years this proj ect was fu nded by the Q ueensland D epartment of Local G ove rnment and enj oyed logistic support from the Q ueensland D epartment of Aboriginal and Islander Affairs through th e Palm Island C ouncil. M ore recen tly it has received fundi ng and technical support from the Q u eensland D epart me n t of P rimary Industries (Water R esou rces).

:r··-1

300

.3 200<r

.§

Acknowledgement

:~,~-~-

(a) Car bon

100

seasonal succession, is governed by a complex interaction of climatic, hydrological and biotic factors and that no single management techniqu e is likely to be equally successful under all conditions. Backup management procedures, including slow sand filtration, treatment with activated carbon and chlorination, must therefore remain as important components of the management strategy for this water storage.

1, .L.

Olher c~oOOcn:ria

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0

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(c) Phosphor u s

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2

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:~,,,_

0

.,

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80 1994

20 40 2

60

(d)>eb

IO

Figure 6 C, N, P in surface sedi ment sam ples at Site 1 (hist ograms). Soluble NH 4 -N (b) and P04 -P (c) in water samples f rom 0.5 m (open circles) and 7.0 m depth (closed circles) compared with 1995 dissolved oxygen profi les

18

WATER JANUARY/ FEBRUARY 1 998

Figure 7 Concentrations of maj or phytoplankton groups at 0.5 m depth , Site 1 with artificial aeration

WATER (â&#x20AC;˘) N.D.-1

[993

l995

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N.D.

'v Nauplii ..t. Eggs

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(b) Cladoccran,

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;z (b)

Figu re 8 Concentrat ions of soluble silica (open circles) and of Synedra (vertical lines) at 0. 5 m depth, Site 1 (a) and daily rainfall (b)

Bourke ATC , Hawes RB (1983) Freshwater Cyanobacteria (Blue-green Algae) and Human H ealth. Medical Journal of Australia. 1: 491-492.

Bourke ATC, Hawes RJ3, N eilson A, Stallman ND (1983) An Outbreak of Hepato Enteritis (the Palm Island Mystery Disease) Possibly Caused by Algal Intoxication. Toxicon 3 (Suppl,): 45- 48.

Brown IK, Jory AG (1985) T he Use of Artificial Mixing to Control Iron and Manganese in Urban Water Supply Storages.

Institute of Engineers, Australia, National Co11fere11ce Publication No. 85/14, Melbourne.

Brunberg AK (1995) Microbial Activity and Phosphorus Dynamics in Eutrophic Lake Sediments Enriched with Microcystis Colonies. Freshwater Biology 33: 544-555.

Byth S (1980) Palm Island Mystery Disease.

M edical Journal ofAustralia 2: 40-42.

Demott W1:i..., Zhang QX, Carmichael WC (1991 ) Effects of Toxic Cyanobacteria and Purified Toxins on the Survival and Feeding of a Copepod and T hree Species of Daph11ia. Limnology a11d Oceanography 36: 1346--57 .

Fast AW (1971 ) The Effects of Artificial Aeratio n on Lake Ecology. Enviro11me11tal Protectio11 Age11cy, Water Pollutio11 Co11trol R esearch Series 16010 EXE 12/71. 470 pp.

Gorham E, Lund JWG, Sanger JE, Dean WE Jr (1974) Some R elationships Between Algal Standing Crop, Water Chemistry and Sediment Chemistry in the E nglish Lakes. Limnology a11d Ocea11ographyh 19: 601-617.

Hawkins PR, Griffiths DJ (1993) Artificial Destratification of a Small Tropical Reservoir: Effects Upon the Phytoplankton. Hydrobiologia 254: 169- 181 .

Hawki ns P R, R unn egar MTC, J ackson ARB , Falconer JR (1985) Severe by the H epatotoxicity Caused Tropical Cyanobacterium (Blue-green Alga) Cylindrospermopsis raciborskii

Figure 9 Abundance of major groups of zooplankton (6 m hauls) at Site 1

(Woloszynska) Seenaya and Subba Raju Isolated from a Domestic W ater Supply Reservoir. Applied and Environmental Microbiology 50: 1292-1295.

Harris GP , Baxter G (1996) lnterannual Variability in Phytoplankton Bio- mass and Species Composition in a Subtropical R eservoir. Freshwater Biology. 35(3): 545-560.

Heanes DL (1984) Determination of Total Organic-C in Soils by an Improved Chromic Acid D igestion and Spectrophotometric Procedure. Communica tions in Soil Science and Plant Analysis, 51: 1191-1 21 3.

Martinova MV (1993) Nitrogen and Phosphorus Compound s in Bottom Sediments: M echani sms of Accumulation, Transformation and R elease.

Hydrobiologia 252: 1-22.

Parsons TR, Stricklahd JDH (1965) Particulate Organic Ma tter. Ill. I. Pigment analysis. Ill. II. D etermination of Phytoplankton Pigments. Joumal of the Fisheries Research Board, Canada.

18: 117-127.

Pennington W (1978) R esponses of Some British Lakes to Past Changes in Land Use on their Catchments. Verhandlungen Internationale Vereinigung Limnologie 20: 636--641.

Quiblier- Lloberas C , Bourdier G, Amblard C, Pepin D (1996) Impact of Grazing on Phytoplankton in Lake Pavin (France): Contribution of Different Zooplankton Groups. Joumal of Plankton R esearch 18: 305-322.

Reynolds CS (1983) Growth R ate Responses of Volvox aureus Ehrenb.

(Chlorophyta, Volvocales) to Variability in the Physical Environment. British Phycologica!Joum al 18: 433-442.

R eynolds CS, Rodgers MW (1983) Celland Colony- division in Eudorina (Chlorophyta: Volvocales) and Some Ecological Implications. British Phycological Joum al 18: 11 1-119.

R eynolds CS, Wiseman SW, Godfrey BM, Butterwick C (1983) Some Effects of Artificial Mixing on the Dynamics of

Phytoplankton Populations in Large Limnetic Enclosures. Journal of Plankton Research 5: 203-234.

Stanier RV, SmithJ H C (1960) The Chlorophylls of Green Bacteria. Biochimica and Biophysica Acta 41: 478-484.

Steinberg C (1983) Effects of Artificial Destratification on the Phytoplankton Populations in a Small Lake . Journal of Pla11kton Research 5: 855-864.

Tailing JF, D river D (1963) Some P roblems in the Estimation of Chlo rophyll a in Phytoplankton. In: Proceedings, Conference on Primary Productivity Mea suremen ts, Marine and Freshwater, 1961 (M. Doty, editor). U.S. Atomic Energy commission, Division of T echnical Information (TID-7633) , 142-146.

Tolland HG , Davies JM , J o hnson D , Coll ingwood R W (1978) Design, Installation and Assessment of a Perforated P ipe Dcstratification System at Sutton Bing ham R eservoir (Wessex Water Authority). Water R esearch Centre Enqui1y R eport. ER591, Medmenham.

Trimbee AM , Harris, GP (1984) Phytoplankton Population D ynamics of a Small Reservoir: Effect of Intermittent Mixing on Phytoplankton Succession and the Growth of Blue-green Algae. Journal of Plankton Research 6: 699-713.

Authors Professor Dilwyn Griffiths is H ead of the Department of Tropical Plant Sciences at James Cook U niversity of North Queensland, Townsville Qld 4811, tel. (077) 81 5751, fax (077) 25 1570. Martin Saker is a PhD student in the same department. Dr Peter Hawkins obtained his PhD from that department. H e is now on t he staff of Australian Wate r Technologies, PO Box 73, West Ryde, NSW and associated with t he Cooperative Resea rch C entre fo r Water Quality and T reatment.

WATER JANUARY/FEBRUARY 1998

19

m

WASTEWATER

THE COST OF AUSTRALIAN

BNR PLANTS K J Hartley Introduction

Capital Costs

T he number of biological nutrient removal plants in Australia is increasing rapidly (Kelle r and H artley, 1997).

Six teen plants were commissioned in 1997 alone, bringing the total nu mber operating to 29. T wo more are starting up early in 1998. What is the cost of th is new technology and how is it affected by effluent quali ty standards and the new methods of proj ect del ivery?

A cost analysis conducted in 1994 w he n only eigh t BNR plan ts were op erating in Australia indicated that effluent phosphorus concentration had a signifi can t effect o n capital cost (H artley, 1995).

T his short paper presents an analysis of the larger cost data base that is now available.

Table 1 lists the 31 BNR plants constructed in Au stralia. Contract construction costs for most of the plants have been obtained from the owners and escalated to 1997 values. The parameters w hich could affect cost: • design capacity in equivalent persons. In some cases some plan t components are sized for a larger capacity • fifty percentiles for nitroge n and phosphorus concentratio ns in the effi uent. Depending o n the data avai lable, either design values or reliable operating values are listed • the project delivery method , classified as ei ther traditional (design followed by competitive constructio n contract), or competitive design and construct contract

• whether the project involved a predominantly new plant or whether it was an upgrade project in w hich existing tankage was incorporated in the new process train . This classifica tion i s subjective but has allowed a useful co st corre lation fo r new plants to be developed • the year com pleted. This parameter has been used to look for learning curve effects (Peck, 1984).

T he results of the analysis of new plant costs are shown in Figu re 1. T he data for the upgrade proj ects are n ot sh own b u t these are mu ch more scattered and generally lie below the n ew plan t valu es. The corre latio n s developed relate a fu nction of cost and effluent quali ty to plant design capacity.

Over the effluen t quali ty range of the data (3-10 mg/L for N, 0.2-3 mg/L for

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WATER JANUARY/ FEBRUARY 1998

WASTEWATER Table 1 Australia 's BNR Plants ID

PLANT

OWNER

PROCESS

COST ($M) 1997 YEAR NEW or PROJECT EFFLUENT 50%iles (Note 2) CAPACITY COMPLETED UPGRADE DELIVERY At year Escalated p (kEP) (Note 1) METHOD completed to 1997 N (Note 3) (mg/L) (mg/L)

1

Albury

Albury City Council

3 Stage Phoredox (combined anoxic/ aerobic reactor)

40

1987

u

Traditional

1.5

2.3

3.55

2

Ballarat South

Central Highlands Regional Water Authority

High rate P removal (A/ 0 )

69

1988

u

Traditional

2.6

5.1

7.33

3

Banora Point

Tweed Shire Council

Modified UCT

50

1995

N

Traditional

4

3

17.5

18.66

4

Bathurst

Bathurst City Counci l

PWD Modified IDEA

39

1997

u

Traditional

15

1

5

Bendigo

Coliban Region Water Authority

Modified UCT

120

1991

N

Traditional

6

1.5

30

35.03

6

Brendale

Pine Rivers Shire Council

UCT, prefermentation , filtration

20

1990

u

Traditional

10

2

3 .95

4.88

7

Capalaba

Redland Shire Council

Modified UCT, prefermentation

30

1997

u

Traditional

5

2

3.6

3.60

8

Caboolture Regional

Caboolt ure Sh ire Council

Modified UCT

38

1997

u

Traditional

5

1

7.3

7.3Q

9

Coolum

Maroochy Shire Council

3 Stage Phoredox, prefermentation

25

1997

u

Traditional

5

1

8

8.00

10 Dalby

Dalby Town Council

CASS

15

1997

N

D&C

10

1

2.4

2.40

11 Lilydale

Yarra Valley Region Water Authority

50

1998

u

D&C

15

1

13

13.00

12 Loganholme

Logan City Council

Modified UCT, perfermentation

50

1995

u

Traditional

5

2

10.7

11.41

13 Maroochydore

Maroochy Shire Council

Modified UCT, perfementation

85

1997

u

Traditional

10

2

35

35.00

14 Merrimac

Gold Coast City Council

Modified UCT

60

1994

N

Traditional

5

2

15

16.55

15 Moe

Gippsland Region Water Authority

IDEA

40

1997

u

Traditional

5

0.5

6

6.00

16 Nambour

Maroochy Shire Council

Modified UCT, prefermention

18

1997

u

Traditional

10

2

10

10.00

17 Neerim South

Gippsland Region Water Authority

BioDenipho

0.6

1997

N

D&C

10

0.5

1.2

1.20

18 Noosa Coastal

Noosa Shire Council

Modified UCT, prefermentation, filtration

45

1997

N

D&C

5

1

18

18.00

19 Penrith

Sydney Water Corporation Johannesburg, prefermentation

25 50 75

b.st stage: 198L 12nd stage: 1981 13rd stage: 199'

N

Traditional

4

2

6 5.2 6.9

52

1997

u

Traditional

5

1995

N

D &C

26.05 20 Port Macquarie Hast ings Council

PWD Modified IDEA

21 Rottnest Island Rottnest Island Trust

CASS

22 Rouse Hi ll

Sydney Water Corporation Modified UCT, prefermentation

23 St Marys

Sydney Water Corporation

24 Selfs Point

Hobart City Council

BioDenipho

25 South Caboolture

Caboolture Shire Council

CASS

26 South Windsor

Hawkesbury City Council

27 Thomeside

25

5

0.5

1 .5 _

3

0.2

35

38.61

1.60

1994

N

D&C

50

1993 1997

u u

Traditional

45

D& C

5

1.5

9

9 .00

40

1997

N

D &C

5

1

9 .1

9 .10

Johannesburg, prefermentation

14

1992

N

Traditional

2

3 .3

3 .75

Redland Shire Council

3 Stage Phoredox, prefermentation

30

1997

N

Traditional

5

2

9 .5

9 .50

28 Warragul

Gippsland Region Water Authority

BioDenipho

20

1998

u

D &C

10

0.5

5

5 .00

29 West Wodonga

Kiewa Murray Region Water Authority

UCT, filtration, prefermentation

N

Traditional

10

1.5

30 Wetalla

Toowoomba City Council

Modified UCT

31 Winmalee

Sydney Water Corporation CASS, fil t ration

81 11st stage: 198E {hydraulic) bnd stage: 1981 13rd stage: 199~ ~th stage: 199<

10 total 1989 values)

13.28

60

1997

N

Traditional

5

1

19

19.00

60

1997

u

D&C

6

0.1

22.5

22.50

Notes: 1. BNR facilities at a pre-existing plant classified as new if no old process units incorporated in BNR plant.

2. Operating data or design values. Where necessary, 50%ile taken as half of 90%ile. N Blank where no specific standard required .

3. Costs escalated using Australian plant cost index, Brennan DJ & Greenfield PF (1996). 1997 index assumed to be 227.8.

WATER JANUARY/FEBRUARY 1998

21

WASTEWATER

-7

reactor processes (3 plants, all using the proprieta ry CASS process). Excellent D correlation co- effici en ts result.

Several observations can be made: I y = 0.7518XO'il3:2S • N seems to have a R2 ; 1 greater impact than P on cost • there appears to be no significant difference in the 1000 100 10 0.1 cost of the various fo rms of PLANT CAPACITY (kEP) continuous process oConlinuoos (Trad!tlooal) • SBR (D&C) • Contlnvous(D!.C) • the sequencing batch Figure 1 Constru cti on cost of new BNR plants in reactor (SBR) plants conAustralia (1997 values) structed to date have been P), the function giving the best correla- substantially cheaper than the continution was found to be: ous process plants. Figure 1 suggests that the plant costs may cross at a capacity (Nos9 * p o.29) * COST well above 100 000 p ersons. However, the relative slopes of the two lines may where: with more data. It is also worth change COST = contract construction cost, S noting that the SBR plants have only million in 1997 values recently bee n commissioned and the N = efiluent 50 percentile nitrogen of the process is not yet proven reliability concentration (mg/L) • fo r the conti nuous process, plan ts P = eilluent 50 percentile delivered by design and construct have phosphorus concentration not been cheape r than those delivered (mg/L) by the tradi tional method. H owever, It is also evident that the data fall into the three SBR plants were ail delivered two groups, one for continuo us by design and construct. This suggests processes (11 plants), th e othe r for that the use of design and constru ct interm ittent or sequencing batch contracts could lead to step changes in 1000 1

I

I

~ - ,- J

technology rather than the refinemen t of established approaches • attempts to incorporate date or order of construction in the correlation led to poorer correlation coefficients. There does not appear to be any learning curve influence to date.

Many project-specific facto rs affect th e cost o f a particula r project.

H owever, the simple relatio n ships presented here should prove useful for project planni ng purposes.

References Brennan DJ, Greenfield PF (1996) The Transparency of Cost Data, Chem Eng in Aust ChE21 , 4, 6-7.

Hartley KJ (1995) Biological Nutrient Removal Plants: Review of Full-scale Operation, UWRAA Res Rpt No 94.

Keller J , H artley KJ (1997) Biological Nutrient Removal: P resent Status and Future Directions, Water 24, 5, 39-40. · Peck GM (1984) T he Principles of Leaming and Forgetting and their Influence on P roductivity and Cost, IEAust Multidisciplinary Trans, pp. 95- 106.

Author Ken Hartley is Project Manager, Water Tech nology with the Advanced Wastewater Manage me nt Ce n tre, Chemical Engineering Department, University of Queensland 4072, tel.

(07) 3365 4305), fax (07) 3365 6932.

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WERRIBEE 'On 5 th February 1898, the Go vernor, Lord Brassey, raised th e p enstock at the Australia Wh arf, which released the Ci ty's p ent-up sewage to flow into the M elbourn e Main, th e H obson's Bay M ain, on to Spotswood and eventually W erribee.

Brassey and his g uests-who included th e Premier, Ministers, MP's, Mayors, Presidents of Shires and others-then symbolically folJowed the sewage on its journey. Th ey boarded the Lady Loch and steam ed around to Spotswood to insp ect the pumping station before going on to W erribee, where they wen t alongside the newly completed j etty.

A commem orative silver m edal was issued to all guests'. (from a history of the Melbourn e M etropoli tan B oard of W orks Vital C onn ections by Tony Dingle and Carolyn R asmussen, 1991) This was, of co urse, t he o fficial opening of the sewerage system, the Rising Main and the Outfall Sewer which carried sewage 30 km to the treatment system at the W erribee Farm, but, as all engineers will recognise, the system had been completed well b eforehand , with the first flows in Augu st 1897. O ne doesn't take risks by combining sewage w ith such an array of notables.

The Sewerage System In fact, work commenced in 1892, d espite incredible difficulties with finance due to a seve re recession.

Starting at the downstream end, the Farm was carefully graded into 20 acre blocks surrounded by channels and drains. The gravity Outfall sewer, 17 miles long, w as divided into seven contrac ts. One thousand three hundred men w ielding picks and shovels moved nearly 500 ,000 m 3 of earth and rock, and replaced i t with ten- foo t diameter pipe and open channel. Apart from a four-span brick aqu educt over Kororoit Creek, the job was fi nished in a year.

The shaft for the Rising Main, from Spo tswood to the high point at Brooklyn , h ad to be drive n mainly through basalt, by blasting and hand.

(H appily, a legacy of gold mining experience helped). T he rising m ain itself was composed of four-foot and six-foot diameter wrought iron rivetted sections.

In 1894, sinking of the pump wells in 'Spotiswoode' comme nced , again

The National Trust-listed pump station at Spotswood, now a major feature of Sclenceworks

dow n through the basalt edge of the River Yarra, and above ground the magnificent 'monumental' pum p station was built. Four massive reciprocating pumps made by T hompso ns o f Castlemaine, each drive n by a 300 horsepower steam engine, were installed , and the first was trialled in February 1897, and progressively m odified as they commenced intermittent operation on infiltration water.

T he typical Victorian archi tecture of the pump station can be seen in the photograph ab ove. Each o f the mirror image buildings housed the pumps: the coal- fired boiler house was adj acent to the wharf. At a later stage a microbiology laboratory w as h oused behind the tiny dormer window of the building on the left. No 5 pumping e ngine, installed in 1901 to supplement the four Thompson pumps, is show n on page 24. It is a Hathorn- D avey, imported from the UK. This pumping engine is the oldest of its type in the world and is still in good working order.

The bran ch sewe rs were laid by teams of subcontractors and the Board's

own day-labour laid the ston eware reticulatio n pipes. By the middle of 1899 more than 36 miles of mains and branch sewers had been laid, together with 273 miles of reticulation. 'Five years of frantic burrow ing.' Eve n further ' up the track ' t he sanitary appliance manufacturers and domestic plumbers were h ard at work.

T he first property connected to the new sewers was the All England Eleven H otel in Port Melbourne and the 'first flush ' commenced on 17 August.

All this fran tic activity took place at a time w hen the financial situation was never stable. As the result of a frenzied property 'bubble' in the 1880s, there was a severe recession. The unemployment rate was about 30%. Fitzgibbon, elected at the age of 65 as C hairman of the newly constitu ted Board (he had been T own Cle rk o f the C ity of Melbourne), drove the venture through, wea the ring one financial c risis after another. At on e despe rate stage h e sailed to London personally to raise a loan of two million pounds, but was foiled by the simultaneous float of WATER JAN UARY/ FEBRUARY 1998

23

WASTEWATER another government loan, and had to settle for only one million, on p oor terms. On his return he deposited the money between three local banks, but the crux of the D epression forced them to close their doors, so that the money was inaccessible. Somehow, work continued. The C hief Engineer, Thwaites, was forced to take a salary cut, from 2000 pounds to 1500 pounds (about $160,000 down to $120,000), but Fitzgibbon refu sed to budge from his 2000 pounds.

The main outfall sewer lasted until 1993, when the new W estern Trunk Sewer was fully commisioned.

War that the population actually attai ned this level, it was a courageous decisio n , both financially and hydraulically. ~ In fact it was found that, even _g when th e Farm was gradually ~ extended to 10,000 ha, irrigation c3 alone could not cope with the ~ jncrcased flows, so in the l 930s .c a. 'grass filtration' was added as a supplement in winte rtime, and Guy Parker (the founder of the Water journal) instituted the lagoon systems. In 1975 a quarter of the flow was diverted to the Easte rn Treatment Plant at Carrum, leaving the Wes tern Treatment Plant to cope with an average of 450 ML/d of a much stronger sewage. The three treatThe Treatment System ment systems of irrigation, gras,s There had been previous sewerNo 5 pumping engine at the Spotswood Pumping filtration and lagoons are still Station, now part of Sclenceworks age proj ects in Australia, but so fa r working a hundred years later, as can be ascertained, they m erely reducing a strong sewage containdi scharged to the ocean. It was M ansergh and T hwaites designed for ing a large proportion of trade wastes the combined opinions of Thwaites, a 45-year horizon, estimating a populafrom averages of BOD: 400-500 to 30 together with the imported consultant, tion increase from 0.4 to 1. 7 million by mg/L, SS: 400 to 30 mg/L, TKN: 55 to Baron Mansergh , that disc harge of 1935 . (Whether they took into acco unt 24 mg/L and P: 11.5 to 8mg/L. They M elbourne's raw sewage to the ocean at the e.p. of the massive amo unts of trade also provide the pasture for the largest either Cape Schanck or Point Lonsdale waste generated in the industrial zone is live-stock operation in Victoria, returnwas too expensive. Instead they opted not recorded). The first flow was going ing a substan tial profit. for a 'sewage farm' of about 3500 ha, to be about 150 ML/d, and it was anticA credit to t he fores ight of the with discharge of the purified drainage ipated to rise to 580 ML/d. Although it engineers of the 1890s, followed by the water into Port Phillip Bay . was not until after the Second World dedication of their successors!

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WATER JANUARY/FEBRUARY 1998

WASTEWATER

~

REUSE OF SLUDGE F OM A DAIRY FACTORY LAGOON P R L Mosse, L V Rawlinson

Abstract

Introduction

Lagoons have traditiona lly been regarded as convenient, low-cost trea tment systems. As w ith other systems, sludge in lagoons eventually accumulates to levels w hich hinder the operation of the lagoon. This paper describes th e desludging of a dairy factory trade waste treatment system.

The sludge was initially pu mp ed from the first aerated lagoon to the second lagoon, which was later taken off- line. T he in tention was to dry the sludge on- site , bu t concerns about possible odours over the h ot sununer period required a mo re immediate solution.

Settled sludge was pu m ped to a closed 20,000 litre tank using fire hoses to encourage the flow. The thinner sludge was directly injected into soil using a Bioplow, or discharged to land from a tanker and incorporated into the soil using a disc plough within eight hours of surface application.

Sludge application rates were determined according to the d raft New South Wales Environment Protection Authority (NSW EPA) Environmental M anagement Guidelines for th e Use and Disp osal o[Biosolids Products. The biosolids were applied to an area of 37 h ectares w hi ch w as lat er plo ughed , harrowed and sown w ith mixed pasture.

Maffra is a small regional centre in eastern Vi ctoria. T he town has a populatio n of arou nd 5000 and is the site of a dai ry fac tory operated by Murray Goulburn Co-operative Limited.

T h e factory processes milk fo r ten months a year, with a peak intake of2.3 Ml/d and a low intake of 0.6 Ml/d.

B etween 50,000 and 60,000 tonnes of skim milk powder, anhydrous milk fat and bu tter products are produced each year, primarily for the .export market.

Wastes from the town are treated in two separate lagoon systems.

Domestic and minor trade waste is treated in an ae rated lagoon and pumped to a winter storage lagoon. The treated effl u ent is u sed to irrigate agncultural land owned by Gippsland Water and a cou ncil reserve.

Key Words Biosolids guidelines, beneficial use, reuse, trade waste, desludgi ng

Table 1 Average influent and effluent quality of t he Murray Goulburn trade waste system f rom January 1995 to June 1997 Parameter BOD (mg/I} Suspended Sol ids (mg/I) Ammonia N (mg/I) Nitrate (mg/I) Orga nic N (mg/I) TKN (mg/I) Total P (mg/I) pH Alkalinity (mg/I) sulphate (mg/I) sulphide (mg/I} TDS (mg/I} E. coli (orgs/100ml)

Influent

Effluent

1300 490 3.6 80

40 1 70 4.5 0.5 19 22 21 9.3

93 25 >11 870 38 <0.1

-

-

1800 1400

The Maffra Industrial W astewater Treatment Plant receives wastewater from the Murray Goulburn Cooperative fac tory at an average flow rate of 1.54 ML/d. The treatment train consists of an aerated lagoon, a high rate trickling filter and two facu ltative ponds. Average influent and current efflu ent quality of the trade waste system are given in Table 1.

T he fi nal eilluent is discharged to th e Macalister River. The volume di scharged is determined by the combinati on of river flow, anm1onia concentration and temperature as sp ecified in an EPA licence fo r the site.

T he industrial waste lagoon system has required desludging twice. T his was first done in 1991-92, when the second lagoon was taken offiine and the sludge allowed to dry. Swamp dozers were used to turn the sludge and the dried sludge was stockpi led beside the lagoons and landscaped on the site in 1996.

In August 1996 it was recognised that the sludge in the fi rst (aerated) lagoon had reached quite h igh levels and was interfering with the operation of the lagoon. . D esludging of the first lagoon was tuned to coincide with a six- week fac tory closure at the end of the season.

Due to the limited time available fo r removal, the sludge was allowed to settle and then pumped to the second trade waste lagoon. A total volume of 30,000 m 3 was dredged and transferred from the aerobic lagoon to the seco nd lagoon over ten days.

WATER JANUARY/ FEBRUARY 1998

~5

WASTEWATER Biosolids Classification

Figure 1 Bioplow system inject ing biosolids into t he reuse area

Figure 2 Tanker discha rging biosolids to t he reuse area

Three samples of biosolids from the Maffra trade waste lagoon were obtained using an oceanographic sampling bottle and chemically analysed. Results of the analyses and the biosolids gradings are given in Table 4.

Based on these results, the overall contaminant grading of the Maffia trade waste biosolid product is category B. The stabilisation grade ofbiosolids is based on the reduction of pathogens and 'vector attraction,' or the likelihood of the product to putrefy and attract pests. Stabilisation grade can be established by treatme n t process and/or microbiological testing. Three gradesA, B, and C-are defined (see Table 2).

T he biosolids produced at the Mafi"ra trade waste lagoon system ach ieved stabilisation grade B. T his was based qn t he fact that they had undergone extended aeration to reduce pathogens and continuous aeration for more than 20 days with lagoon storage for more than six mon ths to redu ce vector attraction.

The fi nal classification of the biosolids is therefore Restricted U se 2 (see Table 2). Such a product is suitable for agricultural reuse. As the contaminant grade ofbiosolids may change over time, testing should be repeated periodically to confirm the conta1ninant grade.

Reuse

Figure 3 The desludged refu rbished lagoon prior to recommissioning

The second lagoon supernatant was drained and the lagoon was taken oflline with the intention of allowing the sludge to dry on- site. H owever, because of complaints abou t odours possibly originating from the exposed sludge, it was decided to remove the thickened sludge and apply it to agricu ltural land owned by Gippsland Water.

The solids removed represented nine years of operation of the lagoon.

Rationale for Reuse at the Site In the absence of any Victorian guidelines, the local regional office of the Victorian EPA approved the use of the NSW EPA's draft Environmental Management Guidelines for the Use and Disposal of Biosolids Products 26

WATER JANUARY/FEBRUARY 1998

(NSW EPA, 1995) to determine the reuse practices in this project. Under these gu idelines applicatio n ofbiosolids requires consideration of: • the quality and quantity of biosolids produced • the soil type and initial contaminant levels • application rates which will supplement fertiliser use but not contaminate the soil • land area and buffer zones required.

Biosolids are classified according to both the contaminant and stabilisation grades. The five classes and allowable land application uses are given in Table 2.

Contaminant acceptance concentration thresholds are given in T able 3.

Several areas, totalling some 37 ha, with suitable slope, appropriate buffer distances and no prior irrigation history were identified on the property.

D etailed soil sampling of 30% of this 37 ha was carried out in accordance with schedule 3 of the NSW EPA guidelines (see Table 5 for results).

Final biosolids application rates are based on contaminant and nitrogen loading rates. The contaminant limited biosolids application rate (CLBAR) prevents excessive loading of contaminants. The nitrogen limited biosolids application rate (NLBAR), w hich is calculated on plant nitrogen requirements, reduces the amount of nitrogen available to be leached.

The NSW EPA (1995) requires the CLBAR to be determined by limiting the maximum allowable soil contaminant concentration and applying biosolids at a rate below the maximum level. T he maximum CLBARis the lowest application rate determined of all the contaminants. The CLBAR in this in stance was 59 dry tonnes/ha due to the biosolids and soil dieldrin concen trations.

The NSW EPA (1995) also requires the nitrogen loading from the biosolids applied to a site to be limited by the nitrogen requirement of the crop grown on the site. Nitrogen is available m

WASTEWATER biosolids in easily leached from the soil, organic nitrogen is released slowly over time, largely by the action of soil bacteria. The mineralisation rate of anaerobically digested biosolids was used to calculate the available nitrogen from the biosolids, as the NSW EPA guidelines do not provide a value fo r lagooned biosolids.

The NLBAR was calculated by determining the amount of available nitrogen in the biosolids and consider-

ing the crop requirements. The crop requirements were based on NSW Agricu lture rates for ryegrass pasture (Rawlinson 1997). An NLBAR of 19 dry tonnes per hectare was estimated.

The maximum application rate for biosolids application is determined by comparing the CLBAR and NLBAR and applying at the lower rate, which was 19 dry t/ha. Based on a measured solids content of8% of the sludge in the lagoon, this equates to 238 kl/ha.

Table 2 Classification of biosolids products (draft, NSW EPA 1995) Biosolids Classification

Mi nimum Quality Grades

Allowable Land Application Use

Contaminant Grade

Stabilisation Grade

Unrestricted Use

Home lawns and gardens Pu blic contact sites Urban landscaping Agriculture Forestry Soil and site rehabilitation Landfill d isposal Surface land d isposal

A

A

Restricted Use 1

Publ ic contact sites Urban landscapi ng Agricultu re Forestry Soil and site rehabilitation Landf ill disposal Surface land disposal

B

A

Restricted Use 2

Agricultu re Forestry Soil and site rehabilitation Landfill disposal Surface land d isposal

C

B

Rest ricted Use 3

Forestry Soil and site rehabilitation Landfill disposal Surface land disposal

D

B

Not Suitable for Use

Landfill disposal Surface land disposal only withi n t he boundaries of the sewage t reatment plant site

E

C

Table 3 Contaminant acceptance concentrat ion thresholds for biosolids (draft, NSW EPA 1995) Contaminant

Arsenic Cadmium Chromium (total) Copper Lead Mercury Nickel Selenium Zinc DDT/DDD/DDE Aldrin Dieldrin Chlordane Heptachlor HCB Lindane BHC PCBs

Grade A (mg/kg) (dry weight) 20 3 100 100 150 1 60 5 200 0.5 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.30

Grade B (mg/kg) (dry weight) 20 5 250 375 1 50 4 125 8 700 0.5 0.2 0 .2 0.2 0.2 0. 2 0 .2 0.2 0 .3

Grade C (mg/kg) (dry weight) 20 20 500 2000 420 15 270 50 2 500 1.00 0.5 0.5 0.5 0.5 0 .5 0.5 0.5 1.00

Grade D (mg/kg) (dry weight) 30 32 600 2000 500 19 300 90 3 500 1 .00 1 .00 1 .00 1.00 1.00 1 .00 1.00 1.00 1.00

Sludge Handling and Application The sludge was removed usmg a wet- well chopper pump mounted on a small floating barge. The pump was driven by an 11 kw motor. Fire hoses were u sed to make the sludge slump and flow to the pump, as without hosing the biosolids would not flow sufficiently to allow pumping (see photograph on page 25). The diluted sludge was stored in a closed 20 000 L tank.

The Bioplow is towed by a tractor and has a tank volume of 70001 and a 2.5 metre injection width (see Figure 1). The unit has four soil cutting discs with associated hydraulically controlled injection tynes. The application rate of 238 kl/ha was to be achieved by delivering the full load ¡over a distance of 11 7 metres. However, the actual application achieved was about one third of that planned. This was due to a combination of factors. The ground was very dry and hard, making it difficult for the injectors to penetrate the soil. The sludge solids content was also significantly less than 8% at the time of application. The biosolids were th<:'. refore applied w ith three passes over the same area, the first two at 90° to each other and the th ird and final pass at a diagonal to the earl ier passes. The injector depth was set to around 10 cm-12 cm, but this was not always achieved because of the hardness of the ground. The application was con trolled to minimise spillage of the liquid onto the ground surface during injection.

A second, less-controlled, application m e thod involved tankering the sludge to the identified area and pouring it onto the surface (see Figure 2). A trial of this method was approved

Table 4 Contaminant grade and quality of Maffra t rade waste biosolids Contaminant (mg/kg) Arsenic Cadmium Chromium (total) Copper Lead Mercury Nickel Selenium Zinc DDT/DDD/ DDE Aldrin Dieldrin Chlordane Heptachlor HCB Li ndane BHC PCBs

Biosolids Qua lity 1.1 1.5 39 341 5 0.5 11 0.25 415 0.42 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.25

Contaminant Grade A A A B A A A A B A B B B B B B B A

Quality = mean + ax standard deviation (NSW EPA, 1995) where a is the sampling coefficient dependent on t he number of samples taken (defined in Table S2-1 NSW EPA, 1995)

WATER JAN UARY/FEBRUARY 1998

~7

WASTEWATER Table 5 Contaminant concentrations of soil measured on-site Maffra Soi l Levels ( mg/kg)

Contaminant

1.4

Arsenic Cadmium Chromium (total) Copper Lead Mercury Nickel Selenium Zinc DDT/ DDD/ DDE Aldrin Dieldrin Chlordane Heptachlor HCB Lindane BHC PCBs

< 0.5

7.4 2.9 4 .9 < 0 .2 1.4 < 0.5 9.2 < 0.02 < 0.02 < 0 .02 < 0.02 < 0 .02 < 0.02 < 0 .02 < 0 .02 < 0.1

Ta ble 6 Costs incurred in the desludging and reuse operation Item

Cost

Dredging of sludge from aerated lagoon to second lagoon

Costs

Gippsland Water labour Bioplow hi re and labour Tanker cartage Miscellaneous equ ipment Cultivat ion and sowi ng

TOTAL

by the regional EPA. A rough estimate of applicatio n was made and the product was allowed to discha rge directly from the tanker. The product soaked into th e ground and was incorporated within eight hours using a discplough. Approximately 20% of the handled biosolids were applied in this way. The enti re operation took 49 days over the hot summer period. No odour problems were encou n tered d uring application and no formal complaints were made by the public to the EPA. T he desludged and refurbished lagoon is shown in Figure 3.

The fields we re later ploughed, harrowed and sown with a mixture of pasture species. A small amou n t of superlime was added to assist in establishment of the seedlings. D espi te drought conditions in Gippsland over much of the summer and winter and initially poor ge rmination, spring growth was lush and prolific.

33,000 11,000

The total cost of the operation was $198,000 (see Table 6).

94,000 45,000 3,500

Conclusion

12,000 198,500

Based o n t he NSW EPA draft Environment Management Guidelines for the Use and Disposal of Biosolids Products, the desludging of a trade

SPECIALISING IN ENVIRONMENTAL SERVICES ..,._ Environmental AudiVSite Investigations ..,._ Contamination Assessment & Remediation ..,._ Environmental Risk Assessment ..,._ Hazardous/Industrial Waste Management ..,._ Solid Waste Management ..,._ Information Management ..,._ Environmental Impact Statements ..,._ Environmental Management Planning & System Development

CMPS&F ENVIRONMENTAL CONSULTING ENVIRONMENTAL ENGINEERS & SCIENTISTS Offices throughout Australia and South East Asia

28

WATER JANUARY/ FEBRUARY 1998

waste lagoon and reuse of the sludge on land was achieved without odour problems using the Bioplow and landspreading followed by discploughing.

References NSW EPA (1995) Environmental Management Guidelines for the U se and Disposal of Biosolids Products. NSW Environment Protection Authority, Sydney, October 1195 Draft Rawlinson L V (1997) Biosolids land application for Gippsland Water. Report prepared by L V Rawlinson an d Associates fo r Gippsland Water.

Acknowledgements The authors thank Bill Hugg of Gippsland Water for on- site management of the desl u dging. IL and H Murdoch, RMB 1790, O ld Marrandera Rd via Wagga NSW 2650 provided the pump and Bioplow system. ¡

Authors Dr Peter Mosse is Technology Manager, Gippsland Water, PO Box 348, Traralgo n Vic 3844. Lisa Rawlinson is an Agricultural Scientist and Principal of L V Rawlinson and Associates, PO Box 255 Berry NSW 2535. She was forme rly Operations Manager for biosolids land application in Sydney Water and now specialises in biosolids reuse.

KNOW YOUR POETS PRIZE Yes- there are people w ho actually read Water out there! (Well, there are at least two that we know of.)

T he inaugural Know Your Poets Prize and an AWWA tie goes to Warren Traves of Gutteridge.Haskins and D avey in Brisba ne, who correctly spotted the an omaly in Mitc hell Laginestra's article, Gulgong of the No'verflow in the November/ December 1997 issue of Water. The bastardised excerpt from The Colt from Old Regret in the article was, of course, pen ned by AB (Banj o) Paterson and not H enry Lawson.

Carl Peterson of Mudgee Shire Council, our second Know Your Poets respondent, will receive a bonus prize (another AWWA tie) fo r coming up with the right answer and correcting another error-Gulgong is about 30 km from Mudgee and not the 20 km printed in the article.

Once again, readers are invited to submit general interest stories for publication.

Margaret Metz

m

WASTEWATER

Abstract Until early 1997 sewage from the Sandy Bay area south of H obart was macerated prior to discharge into the Derwent Estuary and is now being treated at the Selfs Point Wastewater Treatment Plant. This plant, which was built to treat sewage from the northern New Town area, has now been upgraded from a trickling filter process treating 4.1 ML/day to a hybrid trickling fi lte r/biologi cal nutrient removal treatment train with a capaciry of 10.4 ML/day treating the combined sewage. T he plant is presently undergoing process testing to meet a performance guarantee.

Introduction H obart City Council has three separate catchment areas in its reticulated sewerage network (see Figure 1).

The northern area encompassing the suburbs of New Town an d Lenah Valley is predominantly residential in nature and also includes a milk processing plant. The sewage from this area was previously treated by p rimary treatment and trickling fil ters at Selfs Point. Sewage from the central area, including the Central Business District, is treated by high rate biological filters at Macquarie Point. The southern area, including the suburbs of Sandy Bay and Mou nt Nelson, is primarily residential and light commercial. Until early 1997 this southern catchm ent flow was discharged after maceration into the D erwent Estuary at Blinking Billy Point through an ou tfall diffuser 750 metres offshore.

During the 1980s and early 1990s Hobart City Council investigated a range of options for greater treatment of Sandy Bay sewage within that catchmen t. N umerous sites were considered but no ne was deemed acceptable due to the lack of adequate buffer areas.

Council decided to pump the sewage from the Sandy Bay catchmen t northwards through the ciry to the Selfs Point Wastewater Treatment Plant, which would have to be increased in capaciry.

By 1994, the Tasmanian D epartme nt of Environment and Land Management (DELM) required significantly tighter discharge licence conditio ns than had previously prevailed, including limits for nutrient parameters. It also required the combined treated effluent to be pumped back southwards to Blinking Billy Point for discharge.

These constraints necessitated the installation of a sewage rising main fo r the Sandy Bay catchment, a return effluent pipeline and associated pumping stations. The route is indicated in Figure 1. Each 500 m m diameter

OF A TRICKLING

FILTER PLANT TO BNR STANDARD S Morgan, R Farley

pipeline is 10.5 kilometres in length. A significant upgrading of the plant at Selfs Po int was also requ ired to meet the tighter licence limits.

Design Criteria The major design parameters were set by the requirements of the new environ me n tal licence for the Selfs Point Plant. The concentrations given in T able 1 indicate a rypical infl uent composi tion, the previous Selfs Point licence condition s, the new licence conditions and the effluent concentrations specified m the contract documents.

The initial licence conditions were set at ' never to exceed' levels. H owever, these proved too difficult to design for and were replaced by a comprehensive perfo rmance evaluation w hich required 95% compliance. Both the phosphorus and faecal coliforms design effluent standards were reduced to enhance the range of options fo r effluent reuse.

Th e plant performance will be confirmed with a comprehensive evaluation requiring 95 per cent compliance.

T his will consist of two separate sixweek periods during which composite samples of effluent are analysed every second day. Samples are included if the day's flow is less than the designed 10.4 ML. The plant performance will pass the evaluation if 20 out of 21 samples meet the contractual co n ce ntra tion limits: i.e. one failure only is permitted on each parameter. There were several design considerations particular to the

Selfs Point catchment and site: • Hobart City Council wished to maximise the use of the existing treatment plant infrastructure as these assets were still in good condition • the site is located on a former landfill comprising unconsolidated material • the groundwater i s very salty and corrosive, requiring treated timber piles • the nearest residen tial zone is about 250 metres away across a bay and industrial operations adj oin the site. These required relatively tigh t noise and odour control specifications • the layout was to make efficient use of the available area to allow fur future expansion of treatment plant capacity.

Catchment Characteristics The Sandy Bay and New Town catchments are p redominantly residential with some light commercial areas and few industries discharging to sewer.

A milk processor in the New Town catchment is the only significant industrial effluent contributio n , providing 2-3% of the total flow to the plant and 10-15% of the organic load. The New Town catchment is a gravity collection system with a mean sewage residence time of 2-3 hours. The Sandy Bay catchment is similar in size, with steeper topography. T he transfer to Selfs Point increases the average residence time before treatment to 4-10 hours.

The peak diurnal flowrate is in the range 180-2401/s, w hile the minimum flow is abou t 40L/sec. T h e B OD concen trations are u sually five times WATER JANUARY/ FEBRUARY 1998

29

WASTEWATER labour workforce was successful in winning the contract for one of these section s.

Expressions of in terest were invited from sui tably qualified companies to provide process solutions for the upgrading of the Selfs Point plant to BNR standard, which mad e u se of the existing trickling filters. C ouncil did n ot specify a particular process type but was keen to en sure that the selected process technology was well proven and represented the world's best practice in cost-effective nutrient rem oval wastewa ter treatme nt.

Afte r an initial review, selected organisations were given the oppo rtunity to expand on their expressions of interest in DERWENT presentations to C ouncil officers.

RIVER Afte r an evaluatio n o f these Blinking Billy p rese nta tio ns three co m panies ~ Point Outfall were invited to prepare tenders 1 km for the treatment plant proj ec t.

A twelve- week tender period Figure 1 Locat ion of Hobart Council wastewater was considered appropriate and treatment plants tenderers were provided with an information package to accomhigher at pea k flow compared to pany the specifica tion. The information overnight levels and thi s resu lts in a very package provided comprehen sive details wide organic load flu ctuatio n over a of the characte ristics of the wastewater typical day. from t he two catchm en ts and the performance of the existing Selfs Point Project Delivery trickling filter plant. A pe rformance The C o uncil ch ose design-and - evaluatio n was incorporated into the construct in acco rdan ce with AS4300 as specification , which required a bond of the method of project delivery for the 20% of th e co ntrac t value, to be treatm ent plant upgrade. This was to released on successful completion of th e give process designers a large degree of evaluatio n. flexibility and scope fo r in novation in A thorough tender evaluation proceth e fi nal design. Council's engineering dure was developed to assess th e offers. department had a considerable level of T he analysis covered m ore than 40 exp ertise in wastewate r t rea tm en t, individual parameters including the w hich allowed it to prepare the tender areas o f process flexibility, proven documentation and manage the proj ect technology, quality of equipment, ease with inhouse resources. of maintenance, capital cost, life cycle The pipeline system was designed by cost and approach to projec t delivery.

AN I-Krtiger was awarded the conC ouncil's engineering department and constructed in a number of discre te tract fo r the design and con structio n of packages. Council chose to construct th e new Selfs Point BNR plant in the politically sen sitive section of the D ecember 1995. T he co n trac t sum p ipeline through the cen tral business including allowance for con tingen cies di strict of H obart and let the re maining was $9.7 million. This compares to a sections by public tender. Council's day cost estimate range of $ 12- 17 million Table 1 Influent and effluent parameters for the Selfs Point Plant Pa ra meter 80D5 Suspended solids Ammonia as nitrogen Total nitrogen Total phosphorus Oil and grease Faecal coliforms

Units

Influent concentration

Previous licence

New licence

Design effluent

mg/L mg/L mg/L mg/L mg/L mg/L cfu/ 100 m l

265 200 39 41 9 25* 106 -10 8

40 60 no limit no limit no limit no limit 1000

15 20 2 10 3 5 750

15 20 2 10 2 5 10

* This value is based on very limited data

30

WATER JANUARY/ FEBRUARY 1998

(1993 dollars) for a n ew plan t to treat th e w hole flow.

T he total project cos t was $20 .3 million. T his included the treatmen t plant up grade, pip elines to and from Sandy Bay, pum ping stations and an environmental laboratory at the Selfs Point site.

Description of Upgraded Treatment Plant Inlet Works T he process for the liquid streams at the plant is illustrated in Figure 2.

After flows from the two catchments combine, raw sew age p asses through a protection screen and a 10 mm self cleaning bar screen prior to the inlet wet well. The raw sewage pumps d riven by variable speed drives lift the screened sewage to a fo ur- chamber aerated grit chamber. Grit is removed from the cham ber by air lift pumps and separated in a Spirac grit classifier. While the aerated grit removal does add a small amou nt of di ssolved oxyge n, the slight negative impact on phosphorus removal is co nsidered to be far outweighed by the reliability and effectiveness of the systen1. Both grit and screenings are removed for disposal to landfill.

After grit re moval the raw sewage flows to the existing primary sedimentation tanks. A t the discharge of these tanks, adj ustable weirs split the flow between the trickling filters and the biological nutrie nt removal (B N R ) section of the plant. T h e raw sludge colJected in the primary sedimentation tanks is transferred to the prefe rmenter.

Trickling Filters T he two trickling fil ters have been re tained with only m inor refurbi shm ent. Each filter is 30 m etres i n diameter and filJed w ith stone media. The eilluent from the filters is pu mped, without settling, direct to th.e inlet of the BNR aeration reactors. Trickli ng filter eilluent bypasses the anaerobic zon e of th e BNR system as the high nitrate co nce n trati on of this stream wou ld redu ce its effec tivene5s . The filters provide good BOD removal and a significant degree of nitrificatio n (app roxima te ly 60% conve rsion of ammonia to ni trate at a sewage temperature of 13°C ), t hus significantly reducing the aeration en ergy required in the BNR p rocess.

Biological Nutrient Removal Process T he BN R system incorporates the Bio-De nipho process developed by Kruger in D enmark. The system at Selfs Point includes an anaerobic zone which is followed by three aeration reactors and two circular clarifie rs.

Primary eilluent, the prefe rm enter

WASTEWATER liquid fraction, return sludge from the clarifiers and filtrate from the dewatering systems are combined at the inlet of the anaerobic zone. Phosphorus concentrations in excess of20 mg/Lare being achieved in effiuent from the anaerobic zone, indicating significant biological phosphorus activity. Microscopic analysis has confirmed this result by observation of high numbers of phosphorus-accumulating bacteria.

Trickling filter effluen t i s added prior to the flow entering one of the first two aeration reactors. The flow is switched between these tanks on a timed cycle. The tank being fed is operated in the denitrification cycle without aeration. No supplementary carbon is added. T he third aeration reac tor operates in series with whichever inlet reactor is being fed.

Aeration i s achieved by surface rotors, which also provide good mixing.

While the rotors may be less energyefficient than fine bubble diffused air systems, they are far simpler to access for maintenance and were assessed as having a lower life cycle cost.

Two clarifiers operate in parallel to settle t he effiuent from the third aeration reactor. They are each 26 metres in diameter and have a sidewall depth of 4.5 metres with surface scum collection.

Disinfection The effluent from the clarifiers undergoes ultraviolet light disinfection before being pumped to the Blinking Billy Point outfall. The UV system has been designed to achieve <1 0cfu/ 100mL faecal colifo rms at two times average dry weather flow. T he UV unit is a 32 lamp Trojan UV4000, which is self cleaning with a low consumption of cleaning agent. Advanced co n trol minimises power co n sumption and maximises lamp life by adjusting the UV dose to match transmissivity and flow rate. The UV system performance has been enhanced by the relatively high transmissivity of the effiuent, which has averaged approximately 75%.

The existing chlorine disinfectio n system wi ll be retained , with a reduced storage volume of chlorine, in case it is found necessary to provide a residual to meet effiuent reuse standards.

Solids Treatment Processes Raw Sludge T he sludge collected in the primary sedimentation tanks is transferred from the tan k hoppe rs under sequence control to the prefe rmenter. The prefermenter provides condition s to allow partial hydrolysis of the sludge, creating a liquid fraction with a high concentration of readily biodegradable

Figure 2 Process flow sheet for Selfs Point plant

organic material. After prefermentation the sludge passes through a Kri.iger rotary drum thickener. The thickened sludge of 5-6% solids is transferred to the anaerobic digesters. The thickener can be operated unattended. T he filtrate from the thickening process is transferred to the inlet of the anaerobic zone.

T he thickener is presently being run during t he period 3am to 7am to provide additional carbon to the BNR process w hen the influent load is at its lowest.

Waste Activated Sludge Activated sludge is wasted daily. A rotary drum thickener of the same size as the prefermenter thickener is used to increase the solids con tent of the sludge from 0.8% to 3-4%. O nce thickened, the sludge is pumped to the anaerobic digesters for further stabilisation, while the filtrate is returned to the anaerobic zone of the BNR plant. The thickeners, which are compact, fully enclosed units, have proved to be trouble-free and suitable for unattended operation.

Digestion and Dewatering The two thickened sludge streams are co-digested in two. existing anaerobic digesters. The digesters, each 700 1113 in volume, were refu rbished as part of the plant upgrade, including repair and recoating of the floating gas storage covers . The two digesters are now linked and operated in parallel with a design detention time of 23 days. The design solids content of 5.5% was not achieved initially but modifying piping to draw from higher in the digesters has made this possible. The digested sludge is dewatered by a full y enclosed Kruger belt filter press. A sludge cake of 22-26% solids is conveyed by a shaftless screw to a skip bin fo r transport off-site.

T he plant has also been configured so that waste activated sludge can be directly dewatered by thickener and belt press if required. The sludge dewatering system is fully automatic and has been operated unattended for several hours, the only limitation being the capacity of the skip bin.

T he anaerobic conditions in th e digesters usually result in some release of phosphorus into the liquid phase. A

dosing system has been installed so that an iron or aluminium salt can be added to the belt press filtrate sidestream if it is found necessary to achieve effiue nt licence limits fo r phosphorus. Stable operation of the digesters in their new mode of 5-6% solids concentration has yet to be ach ieved, so it is still n.o t certain what degree of metal salt addition, if any, will be required in the longer term.

Cogeneration O nce the digesters achieve consistent operation they w ill produce digester gas in excess of that required for digester heating. Rather than wasting the heat to atmosphere it was assessed that cogeneration would be economically viable.

T he design-and-construct contract has been extended to include the installation of two purpose-built 15kW cogeneration units w hich are expected to provide over 200 MWh of electricity annua lly for u se in the plant. The cooling water from the u nits will be used to heat the digestion system.

Control and Instrumentation All automatic operations in the plant are controlled through programmable logic controllers (PLCs) and the operator interface is through a Citec t Supervisory Control and Data Acquisition (SCADA) system. The-plant can be monitored and controlled remotely.

The contract specification called for the plant to be capable of unattended operation for a conti nuous period of 64 hours. Under normal operation the plant will only be staffed from Monday to Friday during day-time working hours.

In addition, the SCAD A system can be used to monitor the Sandy Bay rising main pumping stations delivering raw sewage to the plant and Council's other wastewater treatmen t plant at Macquarie Point.

Online instrumentation measuring suspended solids, turbidity, phosphorus, ammonia, nitrate, BOD and COD has been installed to monitor the process. Once instrument performance has been proven, some of these measurements may be used for online control within the plant.

WATER JANUARY/ FEBRUARY 1998

~1

WASTEWATER Power Supply The upgraded plant required an increase in the mains electric power supply from 500kVA to 1500kVA, comprising two 750 kVA transformers.

In addition, due to the sensitivity of the process to upsets of even a few hours, a backup diesel generator has been installed.

This generator has a capacity of 200kVA w hich is sufficient to maintain aeration and all major pumping duties within the plant at up to two times average dry weather flow-. This will ensure that the biomass will remain active during any p ower outage and the plant will be able to meet all licence

B0D5 (mg/L) 50 . - - - - - - --

-

- - --

---

40 30 20

i?"Licence Limit

.........

10

,. •,. ,. •

--.; •

Apr

•

Jun

Aug

Oct

Suspended Solids (mg/L}

50 , - - - --

- - - ---'----'----~

40 30

1'f Licence limit

20 .., • 10 0

....

...... .... . ····...·....

.L.---- - - -·__;.••!.;•:......c._:._ _...i Apr

Jun

Aug

Oct

Ammonia Nitrogen (mg/L}

30

-r--- - - - -- - - - - - -

25 20

15 10

/

5 0

Ucen:e Limit

• •. •

t ::::~.c...~.•:;:;:......-.;::;:-~;:;.:'~::::::::~;:-.•=•--,·--=-··~-.;:,-~~·-·::.~· Apr

Jun

Aug

Oct

Total Nitrogen (mg/L)

40 30 20

-r------- -- - - -- •.,

••

/

Licence limit

·····...... . ·-·~~---=-· ... -..... ·~

10 -1------L-J?_ __

__,c.--=•

Total Phosphorus (mg/L) 20 . - - - - - - - - - - - - - -

15 10

............. . ... ...... . .. ..

4------------~ Licence Limit

0

Apr

Jun

Aug

Oct

Figure 3 Effluent conce ntrations for Selfs Point plant

32

WATER JANUARY/FEBRUARY 1998

conditions as soon as mains supply 1s resumed.

The control system computers and PLCs are operated from an uninterruptible power supply incorporating sufficient battery backup to maintain power until the diesel generator starts up.

Effluent Reuse The efiluent passes 10 .5 kilometres through Hobart, giving relatively ready access to a variety of potential users.

Opportunities have been identified for reusing the high quality efiluent along the pipeline rou te. It is believed that the low nutrient concentrations and high disinfectio n level will result in the effiuent being acceptable for many reuse applica tions. T he Royal Tasmanian Botanical Gardens has indicated that they would be prepared to irrigate most of the Gardens with treated efiluent, if funding can be found . Irrigation reuse with effluent is regulated by the Coordinating Group for Effiuent R euse in T asmania and resu lts from six months o f op erations are required before reuse proposals will be approved.

Irrigation reuse is expected to occur once this tria l pe riod has been completed . One factor counting against large-scale reuse is the relatively low cost of potable water in Hoba rt and economic viability is expected to be the major deterrninant of reuse volumes.

During winter months there is a potential for up to 3 ML/day of reuse, while in summer a maximum consumption of 6 ML/day may be real isable.

A novel use of efiluent is as a heat source (or sink) for heat pump system s.

Two sys tems have recently been commissioned that use treated efflu ent from Selfs Point. O~e system heats swimming pool water and provides space and hot water heating at the new Hobart Aquatic Centre and the other provides space heating at a retirement village. D u ring winter the effluent is expected to have a minimum temperature of 10°C. H eat pump systems can readily use effluent at this temperature as a heat source providing a very energy- efficient heating system. Discussions are to be held with other businesses close to the pipeline route for greater use of the heat capacity of the effluent.

problem organics such as pesticides, so there is potential for biosolids reuse.

Biosolids from the plant are transported to a Council-operated vermiculture operation. After addition of about 20% by weight of conditioning agents, the biosolids are processed into vermicast. The operation requires a degree of financial support at this stage and the level of cost recovery in the future will depend on the market's demand fo r the product.

Odour and Noise Odour and noise were both of significant concern throughout the design stages as the nearest domestic reside nce is approximately 250 metres away across New Town Bay and t here are businesses and rowing club sheds adjacent to the Selfs Point site.

A compre h ensive odour co ntr"o l system has been installed . The inlet screen, grit tanks, prefermente r, filtrate tank and all dewatering equipment are fully enclosed and ventilated. The collected fo ul air is passed through a diffuser in the aeration reactors, which provides a high odour rem.oval efficiency. No odour complaints have been received since commissioning of the plant. Nearby residents invited to inspect the plant commented on its lack of offensive odours.

T he potential for increased noise was addressed with a tight specification in the contract documents. B affling of the surface aeration rotors , acoustic insulation of the effluent pu mp station and enclosure of other motors has meant that the site boundary noise requirements have easily been met.

Process Start-up A number of potential seed sludges were evaluated fo r the startup of the BNR sectio n o f the plant. Microscopic analysis indicated that none was of a suitable quali ty, with some containing excess numbers of filame ntou s bacteria and others with very old over-oxidised sludges. To initiate b iomass buildup, solids were retained in both the primary and secondary sedimentation tanks fo r several days before being fed to the activated sludge system. Wastewater was introduced to the new tanks on 5 March 1997.

Biosolids Quality and Reuse

Results

The biosolids generated at the augmented Selfs Point Plant will have undergone mesophilic anaerobic digestion, meeting USEP A Part 503 Class B pathogen requirements . T he production rate is about 40 1113 per week at 22-25% solids. The na ture of the catchment results in relative ly low concen trations of heavy metals and

The effluent BOD and suspended solids concentrations d ropped to values below licence requirements within a few days (see Figure 3). The ammonia concen tration in the effluent began dropping three weeks after the start of feed to the aera tion tanks and was meeting the licence conditions by the fifth week. Nitrate concentration rose

WASTEWATER with increased nitrification and then fell as process control was amended to encourage denitrification. Efiluent total nitrogen was less than the environmental licence limit by the seventh week.

Biological phosphorus removal steadily improved, with effluents of 1-2mg/L occurring in the twelfth week, wh en problems with sludge removal led to an excess of biomass in the system.

Control of the plant then had to focus on preventing sludge carryover into the effluent. Process commissioning and optimisation is continuing prior to the contractual perfom1ance evaluation period. Summary p erforman ce data for the plant during the process establishmen t period is presented in Figure 3 . The plant met ammonia and nitroge n removal licence conditio ns during the mid- winter period when wastewater temperatures dropped to below 12°C. In late September a fire at the milk processing plant resulted in a shutdown of m ilk production. This led to a significant reduction in the organic load to the plant, which in turn resulted in an increase in total phosphorus and nitrogen concentrations in the effluent. M ilk production resumed in late O ctober and efflu ent nu trien t concentrations dropped back to low levels in a week.

Conclusion The project has proved successful in the provision of high quality sewage treatment to both the Selfs Point and Sandy B ay catchments.

Although still undergoing final process commissioning, the new Selfs Point plant has demonstrated a high level of performance and it is anticipated that it w ill meet aJl contractual performance requirements.

Maintaining the trickling filters as an integral part of the biological process has delivered an energy- efficient and flexible plant which has minimised both the total project cost and future plant operating budget.

The decision to implement the treatment plant upgrade on a design-andconstruct basi s has proved to be a successful method of project delivery.

T he active partnering arrangement between Council and ANI-Kriiger has produced a versatile plant based on the contractor's process expertise and tailored to suit Council's requirements.

C lose consultation through out t he contract kept problems to a minimum and delivered the project within budget and on time.

Authors Scott Morgan , a Chemical Engineer with H obart C ity Council, was the client officer responsible for th e implementation of the augmentation of the Selfs Point plant. He can be contacted at GPO Bsox 503E, Hobart TAS 7001, tel. (03) 6238 28 16, fax (03) 6231 9369.

Ray Farley is th e Operation s Manager of Hobart City Coun cil's wastewater treatment plants.

CORRECTION In Table 2 in the article On-site Wa stewater Treatment: A Sou th Australian Survey p ublished in the November/ D ecember 1997 issue of W ater, the n umber of complying readings for combined chlorine for the H eathfield and Hahndorf WWTPs were given as 5 and 3. In fact, those numbers were indicating the readings

that did not comply with >0.5 mg/L co mbined c hlorine criterion. A correction is therefore made to Table 2 as the number of complying readings for combined chlorine (0.5 mg/L) for the Heathfield and HahndorfWWTPs being 47 and 49 respectively instead of 5 and 3. With apologies from the author N Mehlika Kayaalp.

KEY INVESTMENT REFLECTS PHILMAC'S INDUSTRY COMMITMENT Philmac has reinforced it's long-term commitment to supply role in Australia 's burgeoning water industry and t he Austra lian water industry w ith a $1 million investthis move reflects our understanding of that,' he ment in new manufacturing te ch nology. The investment sa id . 'Thi s new technology w ill a llow Philmac to represents th e opportunity for further expand its water-related © IVIO~@r~~~'i'I the company to expand its activ it ies and co ntinu!l our ILACRON product range and further reputation as a user of leadingce ment its reputatio n as a key edge technology.'

Philm ac was na med Manusupplier to the wa ter industry.

As part of the tec hno logy fa cturer of the Yea r last year by the South Australian Centre for investm ent, t wo new mo ulding machi nes and a n electronic Manufacturing for its quality lath e, a ll cons idere d stat e-of-theapproach to the manufacture of art man ufacturing equipment its products. 'That award was have been purchased and w ill be wo n based o n our commitment in ope ratio n by October. Philmac is a world-c lass to innovatio n and quality. The acquisitio n of thi s new desig ner and m anufacturer of qua lity pipe system eq uipment further emphasises thi s approach,' Mr Stathy products for the contro l and movement of liquids, gases sa id. 'Thi s new eq uipment w ill further reinforce and other material s.

Philm ac·s international reputation as an innovative Philmac's marketing development director, M r Chris manufacturer of some of the world's best quality valves Stathy, sa id the initiative reflected th e company's confiand fitting s.' dence in the future growth of th e Australian wat er Th e new eq uipment is bein g in st a lled at the industry. 'We are increasing ly playing an im portant company's North Plympton factory in South Au stralia.

For more information, please contact Chris Stathy, Philmac, tel (08) 8300 9200, fax (08) 8300 9390.

WATER JANUARY/FEBRUARY 1998

3.3

m

WASTEWATER

VFA PRODUCTION IN AUSTRALIAN AND CANADIAN

PREFERMENTERS E v. Miinch, F A Koch

Abstract

long as the bio-P performance of the plant is good, it is assumed that the preferrnenter must be working well.

B u t is th e prefermen te r actually working efficiently? Is there scope for improvement of its performance?

We have compiled recent data from nine full-scale prefermente rs in Australia and Canada, and used the rate of volatile fatty acids (VFA) production to compare preferme nter efficiency.

The design parame ters of importan ce are the prefermenter configuratio n , the fraction of total flow that is fed to the prefermenter, the prefe rmenter volume and the hydraulic and solids residence time (HRT and SRT). All sidestream prefermenters compared in this study have relatively similar rates of VF A production (typically 14-28 Thorneslde, activated primary tank mg/ L/ h), which indicates that they ail perform with Should the same type of prefermenter similar efficiencies, indep endent of be built again next time? These are all their type. questions that can be answered by a detailed analysis of existing p referKey Words menter performance.

Prefermente r, VFA, BNR, fullT his paper compares the perforscale, rate ofVFA production mance of nine full-scale p refermenters in Australia and Canada. T he intention Introduction and Methodology of the survey is not to judge the various prefermenter designs and plant operaPrefermenters are becoming increastions but to colJate th e data upon which ingly popular to improve the performance of existing or new biological readers can make informed decisions. nutri en t removal (BNR) plants, especially in Australia, where BNR Note: This is a shortened version of a is still a relatively new technology. paper presented at the BNR3 conferHowever, o nce the prefermenter is ence in Brisbane from 30 Novemberbuilt and operating, very little attention 4 December 1997. is usually paid to its performance. As 34

WATER JANUA RY/FEBRUARY 1998

Preferm enters increase the fraction of readily biodegradable com pounds in the wastewater. These compou nds are th e preferred substrate for the bio-P bacteria (Gujer et al., 1995; H enze et al., 1995). A maj or co mpo n ent of this material usually co nsists of the volatile fatty acids, C 1 to C 5 (VFAs), which can be analysed by gas chromatography.

Consequently, we have chosen to compare the efficiency of prefcrm enters on the basis of the ' rate of VFA production ' (v. Mtinch and Lant, 1997).

This ca n b e a yardstick by which th e effi cie ncy of utilisation of available reactor volume can be assessed, similar to the organic removal rate in anaerobic digestion. For a con tinuous prefcrmenter at steady state, the rate ofVFA produc tion is calculated as follows:

HR.T Where rvFA is the rate o f VFA production (mg/L/ h) and C~J are VFA co ncentrations in prcfermenter eillue nt and influent respectively (mg/ L). A m easu re of preferm enter o utput in absolute terms is the total mass ofVFA produced per unit time (in kg/d). This measure depends o n the size of the plant. A prefe rmenter outpu t that is independ ent of th e size of the overall

WASTEWATER wastewater treatment plant is the VFA preservati on and storage for VFA con centration increase in the total plant analysis, as samples can quickly deterioflow due to th e action of the prefer- rate if the biomass in the sample is not menter (Barnard, 1992).

In thi s paper, all VFA concentrations are quoted as chemi cal oJ>--yge n demand (COD). This is done because the effectiveness of substrates for bio-P removal is usually compared on the basis of its COD equivalents. Secondly, tod ay's commonly used mathe matical models of the BNR process, such as for exa m.pie the IA WQ Activated Sludge Model No. 2 (Gujer et Kelowna, static fermenter al., 1995), express all organic constituents as equivalent amounts of COD. The inactivated. A reliable me thod is to COD equivalents for each VFA are (all ce ntrifuge the sample (if necessary), in gCO D/g) 1.067 for ace tic, 1.514 for filter the su pernatant through 0.22 µ m propionic, 1.818 fo r butyric and 2.039 membrane filters and finally to acidify th e sam.ple with phosphoric acid. VFA for valeric acid.

Care mu st be taken with sample analysis should be performed by gas

chromatography. The commonly u sed distillation method has a low accuracy and cannot distinguish individual VFAs.

Comparison of Nine Full-scale Prefermenters Tables 1 and 2 give an overview of the design data and opera ting characteristics for the prefermenters compared in this study. Only VFA data that was measured by gas chromatography (and not the distillati on method) 1s reported. All samples were grab samples.

The columns of Table 1 and Table 2 ate explained below the cables. The columns of the tables are identified by numbers.

Discussion and Conclusions The most efficient prefermenter (highest rate of VF A production) of the prefermenters compared in this study

Table 1 Prefermenter design and operating data in 1996.

Columns (identified by column number) are explained below. N/A means 'not analysed' (1) Plant

(2) Prefermenter type

(6)

(7)

(8)

(9)

(10)

(11)

TS

pH

(%)

(-)

(3)

(4)

(5)

QT

Qp

# of

VPC

VP,

(ML/ d) (ML/ d ) fer m.

(m3)

(m3)

4-8A 882 5.4/6.5 N/A

SRT CTCOO. raw (d)

(mg/L)

267

Kelowna

Static fermenter

25

1.56

1

618

Penti cton

Complete-mix with

14

0.7

2

350 10-14 408

Static fermenter

2.6

0 .605

1

334

4-8

470 5.0/6.1 N/A

APT

3

1.5

2

350

3-5

350

N/A

5

13

Complete-mix with

87

2.64

1s

1803

4-6

344

6 .3

N/ A

234

N/A

28.5 285

primary c larifier

Westbank

Salmon Arm

Bonnybrook

206

dedicated thickener

Penrith

Complete-mix

17

0 .16

2

280

1 .8

630

5 .2

92

758

Rouse Hill

Complete-mix

1

0.032

1

220

6.9c

200

6.1

1 69

891

32

2

1

2281 4.5-8 500

6 .1

145 394D

3

3

1

2000

7.5E

N/A

Loganholme Complete-mix with dedicated thi ckener

Thorneside

APT

12

420

N/ A

• Based on wasting a certain fraction of prefermenter volume each day (neglecting solids in primary clarifier and primary effluent).

8 The plant has got two prefermenters, but in 1996 only one prefermenter was on-line, receiving a flow of 110 m3/ h from both primary clarifiers. c During 1996, different residence times were trialled. This residence time is currently thought to be optimal.

0 Measured value in the thickener supernatant (diluted by spray-water that is added to fermenter thickener at a flowrate of 1.5 to 2 Ml./d).

E Only preliminary data j ust after start-up of prefermenter (11-21 July 1997).

(1) Plant location. Kelowna, Penticton, Westbank, Salmon Arm, Bonnybrook are in British Columbia or Alberta, Canada; and Penrith, Rouse Hill, Loganholme and Thorneside are in New South Wales and Queensland, Australia.

(2) Prefermenter type.

(3) Total flow to plant. For the Bonnybrook plant, only the flow to the new BNR process train is given (about 26 % of the total flow to the plant).

(4) Flowrate to prefermenter. In cases where there are two prefermenters, this is the fl owrate to each prefermenter.

(5) Number of prefermenters at that plant. In cases where there are two prefermenters, there are usually also two primary clarifiers.

(6) Prefermenter volume. This is the volume of each prefermenter (in cases where there is more than one prefermenter). For two-stage prefermenters, this volume is the combined volume of the complete-mix tank plus the fermenter thickener, as the thickener also adds to the costs.

(7) Nominal SRT. For static prefermenters, SRT is typically used as a control parameter (the operators vary the SRT to adjust effluent VFA concentration).

(8) Total COD concentration in the raw wastewater.

Yearly average TCOD of screened and degritted raw wastewater. For the Bonnybrook and Salmon Arm plant, it was assumed that TCOD is about twice the BOD5.

(9) pH value in the prefermenter. For static fermenters, the first value quoted is in the sludge blanket and the second in the supernatant. For two-stage prefer· menters, the pH value in the complete-mix tank is given.

Generally, the higher the VFA concentration, the lower the pH value (v. Munch and Greenfield, 1997).

(10) Prefermenter influent VFA concentration. Where this value is not currently being measured, we have assumed it to be zero for calculation purposes, even though there is usually some VFA in the primary sludge.

For a complete-mix with primary clarifier prefermenter, the influent VFA concentration is estimated to be around 10 %of the fermenter effluent VFA concentration (dilution of recycled fermenter effluent with raw sewage).

(11) Prefermenter effluent VFA concentration. VFA concentrations in this paper are always given as mgCOD/l.

WATER JANUARY/FEBRUARY 1998

35

WASTEWATER Table 2 Prefermenter performance measures calculated from the measured values shown in Table 1.

Columns (identified by column number) are explained below

t:J.CVFA

Yo

(mg/L)

(%)

Sampli ng period for VFAs (# of samples)

fQP/QT

HRT

(VFA

MVFA

(%)

(h)

(mg/L/h)

(kg/d)

Kelowna

6

10

28

416

17

2

Jan 96 - May 97 (16)

Penticton

10

12

21

359

29

7

Feb 96-Jan 9 7 (10)

Westbank

23

13

16

125

48

10

Jan 96-May 97 (18)

Salmon Arm

100

6

1.4

24

13

4

May 95 (15)

Bonnybrook

3

16

14

618

7

2

Jan 96- Dec 96 (171)

Penrit h

2

42

16

213

14

2

June 97 (10)

Rouse Hill

3

165

4

23

29

14

June 97 (10)

Loganholme

6

27

23F

1 286

49F

10

Apr 95-Nov 96 (205)

100

16

N/A

N/A

N/A

N/A

-

Thorneside

(15)

(18)

(13)

Plant

(14)

(17)

(12)

(16)

F Taki ng into account that VFA concentration in prefermenter thickener had been diluted about twice ,

(added spray-water).

appears to be the static prefermenter at Kelowna followed by the two- stage prefermenter at Loganholme. The latter has also got the highest increase in VFA concentration in the entire wastewater flow. All sidestream p refermenters compared in this study have relatively similar rates ofVFA production (14 to 28 mg/L/h , with the exception of Rouse Hill), which indicates that they

perform with similar efficiencies independent of the type of sidestream prefermenter used. An APT can be a very simple and cheap option, with usually a relatively low rate of VFA production. This can still be acceptable, since the APT is treating the entire wastewater flow and a small increase in VFA concentration can thus represent a large mass ofVFAs p roduced. Generally

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(12) Fraction of total plant flow that is used as feed for prefermenter. Prefermenter feed flowrate divided by total flow to plant. In cases where there are two prefermenters, the total flow to the prefermenters is taken.

(13) Hydraulic residence time. Calculated by dividing column (6) by column (4). Unlike for the other prefermenter types, the HRT in an APT is not con-stant, but will vary with the daily flow f luctuations.

(14) Rate of VFA production. This value is used to compare efficiencies of prefermenters. Calculated by Eqn. ( 1).

(15) Mass of VFA produced per day. Calculated by multiplying the rate of VFA production with the reactor volume and the number of prefermenters.

(16) Increase in VFA concentration in the entire wastewater flow. Calculated by multiplying column (12) with column (11) and neglecting any VFAs in the raw wastewater or the primary effluent.

(17) Overall VFA 'yield.' Calculated by dividing column (16) by column (8). This is the increase in VFA concentration in t he entire wastewater flow due to prefermentation divided by the total COD in the raw sewage.

(18) Sampling period for VFA. For some of the plants, very little VFA data was available and the number of samples taken was limited. The rate of VFA production calculated for those plants might not be representativ.e for the whole year.

speaking, with the exception of Loganholme, Canadian prefermenters seem to outperform their Australian counterparts, especially when considering the disadvantage of the colder climate for the Canadian prefermenters.

Acknowledgements This work was partly fu nded by the Cooperative Research Centre for Waste Management and Pollu tion Control.

References Barnard J (1992) D esign of Prefermentation Processes. In: D esign and R etrofit of Wastewater Treatment Plants for BNR, C W Randall, J L Barnard and H D Stensel, eds., Technomic Publi shing Company, 85-95.

Gujer W, H enze M, Mino T, Matsuo T, Wentzel M C and Marais G v. R (1 995) T he Activated Sludge Model No . 2: Biological Phosphorus Removal. Wat. Sci. Tech. 31 (2), 1-11.

Henze M, Gujer W, Mino T, Matsuo T, Wentzel M C and Marais G "· R (1995) Wastewater and Biomass C haracterisation for the Activated Sludge Model No. 2: Biological Phosphorus Removal.

Wat. Sci. Tech. 31 (2), 13-23. v. Mt:inch E and Greenfield P F (1997) Estimating VFA Concentrations in Prefermenters On-line by Measuring pH. Water Research (in press). v. Mt:inch E and Lant P A (1997) Prefermenter Design and Performance Evaluation Based on Rates Instead of Yields. CHEMECA '97, 28 Sept.-1 Oct., Rocorua, New Zealand.

Authors Elisabeth v. M unch is a PhD student in the Advanced Wastewater Management Centre, The University of Queensland, St Lucia, QLD 4072, tel. (07) 3365 4729, fax (07) 3365 4729.

Frederic Koch is a research associate m the Department of Civil Enginee ring, 2324 Main Mall, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.

DI

Abstract Pesticides are u sed extensively in cotton production and their presence in the river system in northern New South Wales and Queensland is well documented. This paper describes a major R&D Program to determine the transport and fate of cotton pesticides and their impact on aquatic biota.

Pesticides were shown to move on-farm mainly due to runoff following irrigation and storms. Pesticide levels did not build up in soil from season to season and there was no evidence of leaching through the soil profile. Other transport m echanisms were drople t drift after spraying, move ment of vapour for p esticides such as endosulfan, and windborne du st particles. The most important method for off-farm transport appears to be uncontained runoff following major storm events, while droplet drift is the most important aerial transport m echanism.

The effects of pesticides used in cotton production on aquatic biota are still not resolved and research is continuing. At this stage no clear deleterious effects have been demonstrated, but a possible link b etween levels of end osulfan in the Namoi River and certain mayfly and caddis fly larval populations was indicated in a one- year study. The Program is also focusing on the developme nt of strategies to minimise the impact of pesticides on the riverine environment and their adoptio n through best management practice by the cotton industry. This aspect of the Program is being progressed in close

ENVIRONMENT

consultation with the indu stry and regulatory authorities.

Key Words Cotton, rivers, endosulfan, pesticide transport, pesticide degradation

Introduction Pesticides and Rivers C hemical pesticides are currently an essential component in the management of pests (insects, mites, weeds and diseases) of most crops. Modern agriculture frequ ently ¡ requires largescale efficient production systems w hich require so phisticated p est m anagement systems, including the use of pesticides. Preharvest crop losses worldwide to pests would total about 40% without effective pest management (Harris and Kennedy, 1996).

Many factors affect the u se of p esticides in agriculture, including the cropping system, crop value, p est pressure, environmental conditions and industry culture. Although nonchemical pest management techniques such as cultivation, crop rotation, resistant cultivars and biological control are widely used, most industries rely on some chemical use to maintain commercial viability.

Australia's p esticide usage has increased about fivefold over the last 30 years, mainly due to the increased u se of herbicides and expanding production.

Total pesticide sales in Australia increased from $90m in 1978 to $757m in 1993 (Avcare , 1995). The agricultural sector is the main pesticide user,

with herbicides comprising about 65% of the total. Public concerns over potential impacts of pesticides on the environment have increased during the same p eriod, especially in relation to the presence of chemical residues in food, water and air. The recent o ccurrence of H eJixR (chlorflurazuron) pesticide residu es in beef cattle that were fed trash from cotton sprayed w ith HelixR highlighted this issue and resulted in temporary problems for beef exports from Australia. In respon se to these problems, co tton growers voluntarily stopped using H eJixR. C urrently, the re is only limited information available about pesticide u se and its environmental impact in Australia. Some m onitoring otpesticide residues in waterways has been carried o ut, but this is not comprehensive enough to provide a detailed overview of the quality of Australia's surface water. A maj or difficulty in determining the sources of pesticide contamination in river systems is the widespread u se of pesticides in urban and agricul tural environments. Fish kills in rivers are the most obvious sign of possible pesticide contamination, and although difficult to link to a specific source, have been associated at times with p esticide use o n farms. H owever, other factors can contribute to fish kill s, including deo xygenation , high turbidity and urban efiluent.

Cotton Industry The cotton industry has grown since the 1960s to b ecom e the nation's fourth-largest rural export earner, WATER JANUARY/ FEBRUARY 1998

37

ENVIRONMENT

Figure 1 A caterpillar of t he heliothis mot h, Hetiothis armigera, a major pest of cotton in Aust ra lia (source: John Green, CSIRO)

grossing ab ou t Sl. 2 billion in 1996-97.

About 1500 growers usually plant over a quarter of a million hectares of cotton ann ually, mainly in a belt that reaches from the Darling Rive r in central New South W ales northwards into central Q ueensland. Australia's cotton crop is the highest yi elding of t he wo rld's major cotton producers, w ith 90% of production relying on irrigation.

Pests are a m aj or impedimen t to cotton p roduction in Australia. W ithou t effective ma nagem en t program s, losses caused by pests, pa rti cula rly insects and mj tes, would be so devastating that cotton productio n would not be eco no mically viable . Abo u t 60 ch emical i nsect icides, miticides and herbicides are used in cotton production in Australia and over 180 com me rcial fo rmulations of these are registered.

H owever, most fa rmers only use 10- 14 of these chemjcals.

The m aj or p ests of cotton in Australia are caterpillars of two sp ecies ofheliothis moth (see Figure 1). These insects can devastate whole crops if not quickly and effectively controlled .

Control is m ainly achieved by sp raying with a range of insec ticides, including e n do sulfan early in the season.

R educing pesticide use is a major aim of the cotton indu stry, both to minimise environmental im pacts and to lessen the development of insecticide resistance in pest species.

In partnership with governme nt agencies, the cotton industry has initiated and strongly suppo rted research into alternative pest management strategies including transgenic (B.t.) cotton, disease- an d in sect-resista n t varieties, biological control agents and strategic u se of insecticides.

The allocation of 50% o f the cotton industry's substantial R&D budget to 'integrated pes t management' has already led to a reduction in pesticide use and, over time, is expected to lead to a declining role fo r chemicals in crop protectio n . Alth o ugh pes ticide use should be reduced by 50% by the year 2000 , the cotton industry will still n eed to rely on ch emical pes ticides for economically viable production.

38

WATER JANUA RY/ FEBRUARY 199 8

Figure 2 Sprayi ng cotton with insecticide at Moree, NSW (source: N Woods)

Health of Rivers in Cotton Growing Areas Arthington (1994) reviewed the state of rivers in cotton growing regions and concluded that they are generally in a ' poo r state of health.' This review pointed out that pesticide contamination is on ly one of a number of facto rs affecting river health . O ther impacting activities include land clearing, fertiliser use, effl uent discharge, animal grazing, water extraction, river regulation and invasive exotic pests like carp. Impacts to rivers can be in the form of damage to vege tation, river ban ks and stream habitats and biota, and i nc reased sedimentation, turbidity and nutrients.

These all contribu te to algal blooms and other disturbances to river ecosystems.

It is diffi cu lt to separate out the sp ecific impact of pesticides i n thi s environm ent.

Research on Pesticides and the Riverine Environment The Programs In response to conce rns over the state of rivers and the p erceived connection wi th pesticide u se, the Land and W ater R esources R esearch and D evelopme nt C orporation (LWRRDC), the C otton R esearc h and D evelopment Corporation and the Murray- D arling Basin C ommission (MDBC) began in 1991 to plan a cooperative study to minimise the impact of pesticides on the riveri ne e nvironment using the cotton industry as a model.

T h e R&D program fo rma lly commenced in Ju ly 1993 and and is due for completion by D ecember 1997. Its goals are to: • assess the im pact, if any, of current pesticide use on the riverine environment • develop prac tical and eco nomic m ethods to reduce the transport of pesticides from application sites, and m inimise effec ts o n th e riverine environmen t • provide a scien tific b asis for the development of managem ent guidelines and regulatory codes.

The p rogram co n si sts of three overlapping phases:

• Phase I, w hich de termines and quantifies the major pathways of pesticid e m ovement to rivers and the imp act of pesti cides o n river biota.

• Phase II, which identifies and tests po te ntial m et hods fo r am elio rating problems associated with pesticides.

• P hase III , w hich develops and imp}ements best managem ent p ractices to minimise pesticide contamination.

Phase I-Pesticide Transport and Impact T he research in Phase I has focu sed on identi fying the transpo rt m echanisms and fate of pesticides, particularly endosulfa n , on cotto n fa rms and transpo rt off- fa rm (Scho field and Simpson , 1996) .

Transport Spray drift In Au stralia most pesticides are applied co cotton as sprays.

Aircraft are used extensively to apply insecticides (see Figure 2). T he use of aerial application i n cot ton is directly related to the large scale o f operations of many fa rms and the problem s associa ted with ground applicatio n , particu larly related to irrigatio n/ rain fall, sp ray timing and soil compaction. Four main factors affect the movement of p esticide droplets after spraying: • drople t size-smaller drop{ecs (<100 um) are more likely to be affected by wi nd and air tu rbulence than larger droplets around 250 um • weather conditions such as surface temperature inversions and u n stable conditions can contribute to spray drift • height of aerial spraying affec ts the spread of spray droplets away from th e crop , as do vortices from aircraft wings • droplet deposi tio n , partic ularly of small droplets, is affected by turbulence w hich can increase deposition on the crop, as compared to bare soil. D roplet size manipulation and th e use of buffer zones can reduce the impact of drift.

R esults indicate th at spraydrift is potentially a significant contributor to n venne contamination and that improved applicati on prac tices are essen tial to reduce the off- farm m ovement on pesticides in sensitive areas (see Figure 3) .

ENVIRONMENT Volatilisation Pesticides can volatilise from plant surfaces, the soil surface, from within the soil pore spaces and from pesticides adsorbed onto soil particles. Volatilisation is affected by the saturation vapour pressure of the pesticide, adsorpti on to substrates, wind velocity, temperature, soil water content, pesticide diffusion and advection through the soil and the application method. Research has established the potential of volatilisation of endosulfa n to contaminate nearby rivers. H owever, its contribution is likely to be sign ificantly less than either spraydrift or runoff (Edge, 1996). Nevertheless, it does provide a 'background' inpu t.

Airborne dust Soil particles on w hi ch pesticides are deposited are subject to suspension in the atmosphere from air disturbances and activities such as tillage and vehicular traffic. R esearch has clearly shown that dust movement on farm s can reloca te pesticides.

H owever, this pathway is likely to be far less important than spray dri ft in the off-farm aerial transport of pesticides.

Surface water and suspended sediment Pesticides can be transported

off farms in solution or as attached to suspended sediment (see Figure 4), and this is a m ajo r factor in pesti cide contamination of rivers, particularly as storm runoff (see Figure 5). Eve n modern farm s wh ich ca n full y recycle irriga ti on drainage water on-fa rm are not designed to withhold large storm even ts. A nu mber of fa rms that do not have adequate recycling and on- farm storage facilities may still release contaminated tailwater to rivers and lagoons in min or storm even ts. Wh ile models have been developed to predict pesticide export off cotton fields and farm s, the movemen t and fate of pesticides between th e field/farm boundary and rivers is an area of contin uing research.

Percolation

to

groundwater

Gro u ndwate r ca n pote n tiall y be contaminated by pesticide percolation th rough t he soil. Although th is is unlikely to be a problem fo r most pesti-

cides in the clay soils typical of cotton farm s, the Australian Geological Survey Organisation has identified herbicide contamination of groundwater beneath some other irrigated systems (Bauld, 1996).

Impact Degradation and fate The mechanics of pesticide breakdown involve complex chemical, photochemical and microbiological processes. For .instance after spraying, endosulfan can be transformed in soil and on the plant from the parent alpha and beta isomers into the equally toxic breakdown product endosulfan sulfate. T his pathway does not appear to occur in water w here hydolysis to the non-toxic endosulfa n diol occurs. R esearch in this program has shown that neither endosulfa n nor endosul fa n sulfa te accumula tes in soil from year to yea r (see Figure 6). Peak concen trati on s occur during the spraying season initially as alpha and beta endosulfan and subseque n tly as th e sulfate. T he concentration of pesticid e in ru no ff is closely related to the soil concen tration at the time. Once .in the river system , endosulfan either rem ains in the w ater colum n , volatilises or binds to bottom sediments and subsequently d egrades. There is also no evidence that endosulfa n build s up in river systems from year to year (Cooper 1996a).

River bio-monitoring and ecological impacts The resea rch in this area .is

aimed at assessing the impact of pesticides on aquati c ecosystems principally by moni toring changes in populations of macroinvercebrates in rive rs an d undertaking laboratory and mesocosm experime n ts to assess dose-toxicity responses. A study of water quality in rivers i n the Central and North West Regions of NSW during the 1995/96 irrigation seaso n by th e NSW Department of Lan d and Water Conse rvation showed that there were minor changes in macroinvercebrate community stru ctu re and decreases in d ive rsity at sites adjacent to cotto n fa rms during the pesticide spray season

Figure 3 Wind-borne drift of pesticide after aerial spraying (source: N Woods)

(Cooper, 19966). Populations of sensitive species tended to decrease, but some species appeared to be tolerant.

These changes did not occur at sites upstream of irrigated agriculture.

There were significant correlations between a nu m ber of e nvironmental variables and macroinvertebrate communities, but not with endosulfan levels in th e water. Endosulfan is the most freq uently detected cotton pesticide, w ith 73% of sa mples take n in the 1995/96 cotton spray season exceeding the current accep ted wate r quality guideline of0.01 microgram/litre established for the protection of Australian aquatic ecosystems.

Brooks and Cole (1996) concluded that the biomonitoring study has not clea rly established pesticides as the ca u sal fac tor in th e disturba nce of macro.invertebrate communities. More defini tive studies by the D epartment of Land and Water Conservation and the Centre for Ecotoxicology (of the NSW EPA and U niversity of Sydney) are continuing.

Chemical monitoring The wate r quali ty monitoring study in the Central and N o rth West Regions of N ew South Wales fo und that increases in pesticide levels correspond with the beginning of the cotton growing season (Coope r, 1996a). Pesticide monitoring, ta ken over five growing seasons from-1991 to 1996, found that the appearance of endosulfan in rivers is closely tied to its use in cotton (see Figure 7). Several other pesticides were also detected in rivers during the study. Atrazine, which is not used in cotton, con tinues to be the most widely detected pesticide in the study area, excep t in the Macquarie valley, where it is rarely fou nd.

Phases II and Ill-Applying the Research to Fix the Problem

Figure 4 Collecting soil from tail drains on a cotton farm (source: B Simpson)

The ultimate aim of the R &D program is to minimise the impact of pesticides o n rivers and this means ensuring that the cotton industry adopts improved practices as a result of the research. The 'best practice' m ethod of m anagemen t is being used as the most effective way to facilitate this process (Doak, 1995) .

Phase II involves the development, WATER JANUARY/ FEBRUARY 1998

3$

ENVIRONMENT

Figure 5 Pesticides are transported into

Figure 6 The degradation of endosulfan in

Figure 7 Endosulfan in rivers is linked to

rivers during storms (source: Department of Land and Water Conservation, NSW)

soil over time (source: B Simpson)

its use on cotton (source: Department of Land and Water Conservation, NSW)

• Soil

Impact on a Hidden Resource.

Proceedings 23rd Hydrology and Water R esources Symposium, Hobart 21-24 May 1996, pp 143-147.

Cooper B (1996a) Central and North West R egio ns Water Quality Program: 1995/96 Report on Pesticides Monitoring. Department of Land and Water Conservation, Technical Services Directorate; TS96.048. ISSN 1327-1032.

Cooper B (19966) Central and North West R egio ns Water Quality Program: 1995/96 Report on Biological Monitoring. Department of Land and Water Conservation, Technical Services Directorate; TSD96.094. ISSN 1327- 6255.

Doak J (1995) .Minimising Pesticide Impacts-A Best Practice Management M odel for the Cotton Industry.

LWRRDC Occasional Paper No. 05/95.

Edge VE (1996) E nvironmental Issues Facing the Cotton Industry Related to Pesticide Use. Proceedings of the Eighth Australian Cotton Conference, Gold Coast, Australia. 14-16 August 1996, pp. 47-54.

Harris Rand Kennedy I (1996) Pesticides in Perspective, Cotton Yearbook 1996, The Australian Cotton Grower, pp. 98-102.

Harrison S R and Tisdell J G (1996) U pdating an Ex Ante Evaluation of the Impact of Research Projects R elating to Au stralia's Natural Resources. Consultancy Report to LWRRDC. Schofield N J and Simpson BW (1996) Pesti cides-An Emerging Issue For Water And The Environment. 23rd Hydrology and Water ..Resources Symposium, H obart, Australia , 21-24 May 1996, pp. 229-236.

Workshop on Best Practices: Minimising the Impact of Pesticides on the Riverine Environment. Conference held at Australian Cotton Research In stitute, Myall Vale on 28 March 1996 (unpublished).

testing and evaluation of prospective practices that have emerged from the research or any other so urce. A workshop held in March 1996 identified and ranked potential best practices requiring further study. A number of studies have been funded to develop these potential 'solutions' to the point of being recommended b est practices.

In Phase III a best practice manual is being developed for use by growers and consultants as the main delivery mechanism for achieving the program's goals.

The m anual will advocate practices that minimise the amount of pesticide transported off farms, and consequ ently minimise the impact of pesticide in the riverine environment. The need for cotton growers to communicate effectively w ithin their local communities and with oth er industries is also emphasised.

Some examples of p otential best practices that are curre ntly being formulated are: • Pesticide application Growers will be responsible for all pesticide spray application decisions and protocols and for keeping neighbouring properties informed ab out these matters. Pesticides must be applied in such a way that they do not cause damage to adjacent areas, taking account of weather and environmental conditions and by using buffer zones when appropriate • Farm design Furrow length and gradients are to be designed to reduce erosion from water runoff, and tailwater drains must have low gradients to reduce water runoff velocities. Stormwater management plans will be used to reduce water runoff. This involves maximising the capacity of farms to retain stormwater and preventing this w ater from reaching natural wate rcourses, wetlands and billabongs • Integrated pest management Pest managem ent strategies will be used which reduce the need for chemical p esticides. These include the use of transgenic cotton, managing crops to early maturity, preserving be n eficial insects, managing the development of p esticide resistance destroying the overwintering pupae of heliothis by cultivation 40

WATER JANUARY/FEBRUARY 1998

and

water

management

Growers will minimise soil erosion by retaining stubble, redu cing in-crop cultivation , main taining soil orga nic matter and adopting minimum tillage fanning systems w hich are compatible with pupal destru ction to maximise soil surface cover. The runoff of pesticidecontaminated water is to be mini1nised by controlling and scheduling irrigation to cake accou nt of soil and weather conditions.

Conclusions Clearly, recommendations of best practices are not su fficien t in themselves to bring about the required changes in the cotton industry. At the August 1996 Australian Cotton Growers Conference (attended by 1300 delegates, including many cotton growers) a clear resolution to adopt the best practice approach was made. The program is now actively reviewing and developing the most appropriate implementation framewo rk.

As Harrison and T isdell (1996) have commented , 'This research program should produce real benefits for both the Australian e nvironme nt and the cotton industry. It is unique in evaluating all aspects of an environmental problem by combining expertise from diverse backgrounds, pursuing a participative approach with the industry, and continuously briefing resource managers and regulators of progress. This holistic approach can serve as a model for other research involving complex agricultural ecosystems.'

For a full list of the research proj ects involved in the program Minimising the Impact ofPesticides on the Riverine Environment: Using the Cotton Industry as a Model see the 1997 Listing of L WRRDC Funded R&D Programs (ISBN 0 642 26709 X).

References Arthington A (1995) State of the Rivers in Cotton Growing Areas: Northern NSW and the Border Rivers with Queensland.

L WRRDC Occasional Paper No. 02/95.

Avcare (1995) 1995 Figures and Facts, 3rd edition, Avcare-National Association for Crop Protection and Animal Health, 2 pp.

BauldJ (1996) Groundwater Quality: Human

Authors Dr Nick Schofield is the P rogram Manager for Water Resources and Coordinator of the joint Cotton Pesticides Program at the Land and Water R&D Corporation, GPO Box 2182, Canberra ACT 2601. Dr Vic Edge is Deputy Chief of Plant Industry Administration w ith the Cotton R&D Corporation (NSW Agriculture , Orange, New South Wales) . Russell Moran is a communication consultant working for the LWRRDC m Canberra.

m

BUSINESS

MELBOURNE'S BULK WATER SUPPLY AGREEMENTS B Bayley, T Kelly In a lively joint platform presentation at A WWA's 17th Federal Convention Brian Bayley, Melbourne Water Corporation's General M anager, Water, and Tony Kelly, Yarra Valley Water's General Manager, Asset Services, reported on the legal and operational intricacies surrounding the disaggregation of Melbourne Water in January 1995. Both held executive positions with the authority before it was split into a business to perform the wholesale function and three retail water supply businesses.

The relationship between the wholesaler and each retailer was defined primarily by a legal contract which set the terms and conditions under which the wholesaler would provide bulk water to the retailer.

The presentation addressed the preparation and content of the Bulk W ater Supply Agreement and some of the issues that have been encountered in working with the Agreement.

BAYLEY: Prior to its disaggregation in January 1995, Melbourne W ater was an integrated business providing water, sewerage and m ain drainage services. For the provision of water supply itself, the organisation was internally structured into a Wholesale Division and three Regions providing retail services. The wholesaler had a strong engineering focus, the regions a strong customer focus. Charges were levied upon the Regions for the provision of wholesale services, but the transfer price was not a business driver.

As a result of a comprehensive restructure of the industry by the Victorian Government, Melbourne's water supply and sewerage services are now supplied by four independent corporate entities. Ownership of all the businesses remains with the Victorian State Government.

Three n ew lice nsed retail companies, each with an assigned area, compete in the provision of retail services to domestic and commercial customers.

Competition is achieved through comparison of key customer service performance indicators sponsored by the Office of the Regulator General, and through comparison of financial results. The retail companies do not compete directly fo r each other's customers.

T he fourth business, retaining the name Melbourne Water, provides wholesale water supply and sewerage disposal services to the three retail companies. The price of these services has a fixed and variable component. Each retailer is charged different rates.

This provision of w holesale water supply services is governed by Bulk Water Supply Agreements. These are legally binding contracts and their workings and prices are fundamental to the disaggregated industry model. The contracts were produced by M elbourne Water in D ecember 1994.

The contracts are designed to ensure that a reliable supply of safe drinking water is maintain ed, institute quali ty improvement projects, define standards at interfaces, control leakage, achieve accuracy in billing, price to allow for service improvements and achieve sp eedy resolution of disputes.

KELLY: In Yarra Valley Water's case, charges for wholesale water and sewerage services payable under its Bulk Water Supply Agreement represent two thirds of Yarra Valley Water's annual operating costs.

The current industry structure effectively prevents Yarra Valley Water from securing any reductions in these costs.

BAYLEY: Interim Bulk Water Supply Agreements between 42

WATER JANUARY/ FEBRUARY 1998

Melbourne Water and the retail companies were prepared in h ouse be twee n June and December 1994. The initial documents were further refined through management and legal review and finally fo rmed into a binding, though interim, contract. It made specific reference to the obligations of the parties to attempt to negotiate a new long- term Agreement during the first six months operation. However, for various reasons, this review never effectively occurred and the interim Agreements remain in place. The three major factors to be considered were asset split, service levels and charges.

It was necessary for the water supply assets to be spli t to enable the assignment of responsibilities. General rules were agreed with Government on th e w holesale and retail functions. The criteria fo r the asset split were that the separation of headworks (wholesale) and service delivery (retail) func tions and associated assets should satisfy one or more criteria for determining headworks functions . These cri teria included annual security of supply; storage to provide a balance between inflow and outflow (demand) over several months; transfer of water to or between storages, or river regulation; transfer; and water quality control.

Where works have multi-purpose fu nctions, the determinate should be the principal or most critical function . Where supply is to more than one retailing business and bulk supply cannot reasonably be achieved through commercial agreements/contracts, then associated works should be defined as headworks.

Retail assets were then assigned to a retail company by virtue of their location. Finally the asset split was endorsed by the Government.

For each retail business an Allocation Statement was prepared to transfer responsibility for assets and liabilities to the retail companies. In addition to assets the Allocation Statement also allocated land, contracts, land lease agreements, supply agreements, works offers and software. Assets w hich were not allocated remained with Melbourne Water.

A list of Melbourne Water's assets is contained in the Bulk Water Supply Agreement, and in addition an Asset Interface Register was prepared for each retail company. The register consists of a series of sketch plans w hich show in detail the location of interfaces between Melbourne Water's and Yarra Valley Water's assets. The original Asset Interface R egister is h eld by the Regulator General. C hanges to a Register can be made by a joint submission from both Yarra Valley Water and Melbourne Water to the R egulator General.

BUSINESS In general there has been little dispute over asset allocation since disaggregation.

The Agreement specifies performance obligations for bulk water supply. In all cases, service levels were not to be below those w hich existed in Melbourne Water in the twelve months prior to disaggregation. While thi s was accepted in theory, in some cases those service levels may not previously have been well defined or measured. Service levels are specified for pressure, flow, water quality and emergency response.

Charges to be paid in return for the w holesale services were intended to recover t he cash requirements for Melbourne Water at the time of the disaggregation. The cash requirement was made up of operational co sts, capital investments (as no borrowings are allowed) and debt repayments.

In satisfying Melbourne Water Corporation's cash requirement its return on capital ended up slightly higher than the retailers.

The charges are divided into two components-a variable compo nent based on the long run marginal cost (to provide a signal on cost of augmentation) and a fixed component calculated as the difference between the total economic cost and expected receipts from the variable component (to ensure full co st recovery). The variable charge is p aid weekly and the fixed charge monthly.

T he Agreement provides for M elbourne Water to improve water quality in a number of specified areas, and prices will be discou nted if this is delayed .

The initial chalJenge for the two types of business post- di saggregation was to develop the necessary skills required fo r working with a commercial agreement. No longer w ere d ealings represented by a fictitious transfer price, but involved real payments. The obligations of each party needed to be unde rstood and translated into actions by a number of people w ithin both the w holesale and retail organisations. Since m any of the senior managers in both arms had been part of the original corporation, the cultural change required to work effec tively with a conunercial agreement of this nature presented qui te a challenge.

The initial challenges were compounded by different interpretations of the Agreement and different expectatio ns by the individuals involved as to what was or should have been included within the Agreement. The definition of service level obligations was loose in a number of areas such as water quality standards and meter accuracy. T here were, and still are, a number of issues encountered by the parties.

Of major significance was the issue of responsibili ty for funding capital works. Yarra Valley Water maintained that the wholesaler was obliged to fu nd certain capital works ' rem embered' to have been included during the drafting of the interim pricing basis. However, these works had not bee n specified in the interim Agreement, and the basis of the pricing was not open to review or re-negotiation.

Compounding this was the challenge of determining an appropriate location for the interface between Melbourne Water and Yarra Valley Water for new assets.

The issu e was brought to a h ead by disagreement over w hich party should fund works required to overcome certain water supply and quality problems. As a result of the difference in positions, significant conflict emerged between the parties. T his has since been resolved by mutual compromise-a process facilitated by each party gai ning a better understanding of the basis fo r th e other's position.The key lesson from this experience was that any performance obligations including outcomes from capital works w hich are built into the price must be fully specified .

Omissions from the Agreement made at the time of disaggregation represent a new status-quo. Independent businesses have an obligation to optimise their position from this new position, h ence such omissions will be difficult if not imposKELLY:

sible to correct, and may be the source of conflict.

The water quality performance standards for each water supply zone specified in the current Agreement represent the standards that were achieved by Melbourne Water in the twelve months prior to disaggregation. In determining standards to be specified in any future Agreement it will be necessary to have regard to performance standards that Yarra Valley Water must meet as part of its licence, the requirements of the Regulator and the Department of Health and Community Services, customer expectations and national water quality guidelines.

The volume of water delivered to Yarra Valley Water is currently calculated as the volume measured through the exdams meters less the volume delivered to the other retail companies. No allowance is made in the bulk water price for leakage and unaccounted water in Melbourne Water's ow n supply system.

The existing meters used to measure these volumes were originally installed for operational requirements, not for billing to retail companies. Given the dependence on volume of the wholesale charges, the accuracy of the meters has a major bearing on the amount payable by Yarra Valley Water.

It will be necessary to reach agreement on accuracy standards and on how these standards may be achieved in practice.

At the retail company boundaries some volumes are estimated . These are based on the number of customers, relative area, o r equivalent meter readings. Failu re to specify the operating conditions under which the estimation formulae are valid can result in significant estimation errors.

C ommitments have been made by Melbourne Water Corporation to eliminate the areas for w hich the volume is estimated by the installation of additional m eters.

Following the allocation of asse ts between wholesaler and retailer, there are now sites which contain both Yarra Valley Water and M elbou rne W ater assets. The businesses need to work togeth er to ensure security of the site, access fo r the other party, maintenance of the site and individual assets, and payments fo r power and telephone services.

BAYLEY: Gene ral provisions were made within the interim Agreement to facilitate price variations. H owever, the appropriateness of these variations dep ends entirely upon the structural arrangements within the industry w hich are external to the Agreement itself. To progress, coordinated w holesale and retail pricing reviews are requ ired. These are not expected until mid 1998.

T he funding of capital works required to service growth in water consumption is an issue. The cu rre nt price iucludes a variable component based on the Long Run Marginal Cost of water supply system augmentation. While this provides an economic signal as to impending augmentation costs, the Agreement does not specify a process for ensuring adequate return to the w holesaler for growth works.

KELLY: More consideration could have been given to defining a mechanism to ensure that system pla nning and associated capital works are performed efficiently and effectively. In this regard M elbourne W ater could adopt an open or closed book approach.

The closed book approach would lead Yarra Valley Water to be suspicious of the outcomes. Concerns would include the possibility of M elbourne Water setting prices higher than those required to recover a reasonable return for the investment, or 'gold-plating' the investment to increase its costs and hence the required return.

In con sidering an open book approach M elbourne Water needs to have regard to commercial confidentiality, the potentially significant intrusion of the retail comp anies into the decision processes within the organisation, and the problem s of seeking agreement to a capital works program from three retail companies, each with different priorities.

WATER JANUARY/FEBRUARY 1998

43

BUSINESS Stronger linkages between the price and the service level may serve to enhance compliance with the Agreement. This could take the form of a performance bonus for achievement, or penalties for non-achievement of specified service levels.

As stated earlier, the initial Agreement was intended to have a term of six months. Yarra Valley Water pursued renegotiation vigorously during the months following disaggregation. A radical new Agreement was prepared collaboratively

by M elbourne's three retail water companies to provide a new basis for renegotiatio n.

T o date, the parties have not succeeded in executing a new Agreement and under these circumstances the initial interim Agreement continues to apply.

BAYLEY:

The key difficulty with re- negotiation is establishing a new price system.

When the Agreements were initially prepared, the service obligations and the price were developed largely independently. Negotiation on revisions to the service obligations is relatively non-contentious. However, real progress requires changes in price to be considered. To date, negotiation on price has not occurred due to uncertainty over arrangements for future regulation of the w holesale price and the low probability of reaching agreement between the parties.

KELLY:

BAYLEY: Capturing the operational knowledge of a large water supply organisation into an Agreement is a significant challenge. It is perhaps unrealistic to expect to capture all issues correctly in the first executed version of the Agreemen t. Under these conditions it is important that good adjustment procedures are either built into th e Agreement or into the stru ctural relationships surrounding the Agreement.

The early problems in working with the Agreement caused a deterioration in relationships between Melbourne Water and Yarra Valley W ater. This resulted in less goodwill and cooperation over issues that were not formally part of th e Agreement, since there was a tendency for all dealings to become adversarial.

Throughout this phase, h owever, both parties reiterated their strong commitment to ensuring that solutions were least community cost. This important principle has not been clouded by disagreement over issues such as who might fund capital works. The knowledge that both businesses continue to have the same sha reholder has perhaps helped to maintain a constructive attitude.

Despite the sh ortcomings and teething problems with the Agreeme nt, it is our judgement that it provides a superior

The Churchill Trust invites applications from Austnl.ians, of 18 years and over from all w:illcs of life who wish to be considered for a C hurchiU Fellowship to undertake, during 1999, an ovcrn:as study project chat will enhance their usefulness to the Australian community.

No pttoaibed qu.u.i.lication1 arc: required, merit being the primary test, whether based o n past ach.ievements or demonstrated ability for future achievement.

Fellowships are awarded 11nnu.uly to those who have al.ready established themselves in their ailing. They arc not awarded for the purpose of obtaining higher academic or formal qualifications.

Detail.a may be obtained by sending a self addressed stamped envelope (12x24ans) to:

The Win1ton Churchill Memorial Tru.r 218 Northbourne Avenue, Braddon, ACT2612.

Completed application forms and reports from three referees must be submitted by Saturday 28 February, 1998.

44

WATER JANUARY/ FEBRUARY 1998

basis for an effective w holesale/retail relationship than operation within a vertically integrated supplier.

The advantages result primarily from the improved focus of the separated businesses and the need for the parties to communicate effectively and formalise their relationship.

Some of the specific advantages are as follows. Each business is able to concentrate on the condition, capacity, perfo rmance and returns of its assets. D ecision-making is clearer with a real pricing signal instead of an internal transfer price. Real debate on solutions is promoted leading to b etter technical solutions at a lower cost. Behaviour i s less bureaucratic in the smaller businesses, leading to efficiency gains. Lower overall co sts have been and will be produced within the industry. Better customer service has resulted. Business autonomy h as generated pride and staff commitment.

Throughout all the negotiations, there has been a clear spectrum of agreement on the fundame ntals of meeting commercial obligations under the existing agreements; developing an effective commercial relationship; monitoring performance to ensure contracts are met; and working together on enhancements.

Addressing the issu es, there is a plan to negotiate on a project basis to agree new standards; install bulk water m etering; institute a leakage study in the bulk supply system; report service level compliance by the wholesaler; review performance annually; resolve issues and build relationships through workshops; institute new protocols for billing variations.The nex t phase of the reform program is under way.

D uring this phase, the reforms will focus on structural, regulatory and pricing issues.

It is expected that the Bulk Water Supply Agreements between Melbourne Water and the retail companies will be reviewed as part of this phase. Issues to be considered include whether the obligations of both parties in the Agreements are clear, whether the responsibilities of the parties are allocated explicitly and whether the risks are borne appropriately. A further issue is whether the current pricing structures create appropriate incentives for optimising asset utilisation and efficient long- term investment.

It is unlikely that Melbourne Water's current posi tion as an unregulated monopoly will p ersist. One alternative is that it may be issued with an operating licence and be subject to economic regulation. Other parameters include the allocation of Bulk Water Entitlements, and the possibility of a competitive access regime.

The reform program will ensure that Melbourne remains in the forefront of the national water industry.

FURTHER VICTORIAN REFORMS As this issue of Water goes to press the Victorian Government's $ 1.3 billion water reform package is about to be implemented. Under the package the Government w ill assume $850 million of metropolitan water industry debt and $450 million w ill be invested in capital works.

Starting on 1 January 1998, there will be a major injection of infrastructure funding to speed progress towards improving water and environmental standards in country Victoria and provide an average 18 per cent reduction in water bills throughout the State.

Key elements of pricing changes that bring M elbourne into line with regional Victoria are the abolition of property-based water and sewage rates for all domestic and non-domestic customers, the introduction of a flat fixed fee for each property, and a user-pays approach to pricing through water and sewage disposal charges which will now apply to all business and household customers.

As reported in Crosscurrent (10 November 1997), Premier J eff Kennet has denied that the Government is preparing the way for the privatisation of the water industry, stating that such a move is off the agenda' before the next State election in 2000.

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MODEL DRT-15CE PORTABLE TURBIDITY METER

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MODEL 5570 INTERFACE LEVEL MONITOR

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RECOVERABLE RESOURCES AWWA VICTORIAN STATE CONFERENCE

7-9 MAY 1997 RICH RIVER GOLF CLUB MOAMA,NSW Managers and practitioners who are Interested In the potential to recover resources from the water cycle will benefit by attending this conference.

Intending authors are Invited to submit abstracts of 250 words to AWWA, PO Box 1033 Caulfield North Vic 3 I 6 I or fax (03) 9509 8243 by 30 January 1998

WATER JANUARY/FEBRUARY 1998

45

WATER

INDEX

As with all other AWWA publications, including convention proceedings, these titles can be searched through the AWWASEEK computer disk. Disks can be obtained from and updated by P W illiams, Faculty of Environmental Science, Griffith University, Nathan Qld 4111.

Business Community Ownership and Confli ct Resolution in Planning M Dugdale Jan 1996 The Consumer's Perspective J Simpson Jan 1996 Sydney's Choices Consultation S Love Jan 1996 Communicating w ith Customers: Research T echniques N Roseth Jan 1996 Community Education Program R Whately Jan 1996 Community Education: Grass Roots A Colliver Jan 1996 Wastewater 2040 Revisited G V H arris, EJ Murphy, BS Sanders Jan 1996 Water T rading in Victoria: Possible Controls J McMullan Jan 1996 Transforming Government Business Enterprises A P ender M ar 1996 Australia Exports Electromagnetic Flowmeters T Spurling M ay 1996 Public C onsultation R J Morrison, P Ricci, DE Lewis, D Calvert July 1996 Due Diligence and Contaminated Land Risk Ranking T Bates, F Sack July 1996 Five Years of Industry participation with Cleaner Production R Scott July 1996 Transferable Water Entitlements: Early Lessons from South Australia H Bjornlund,J McKay Sept 1996 Sydney Water Corporatisation-A Model for R eform?

V J ackson Sept 1996 Contracting Out-Another Management Fad? G Hodge No v 1996 Alliance Type Contracts in the Water Industry S Brown, G Simpson, J Ricketts Nov 1996 Quality Accreditation in the Water Industry R Cooper N ov 1996 Liability of Authorities and their Consultants N H emmings Jan 1997 WaterLog D Cummins M ar 1997 Performance Management-The Key to Organisation Effectiveness P R enfrew May 1997 A Strategic Review of the Water Treatment Industry D Bainbridge July 1997 Corporate Governance and Stakeholder Expectations N Scheinkestel July 1997 A Quantum Increase in Water Prices J Crockett, L Carroll Sept 1997 Water in California: Comparing Private and Public C ompanies B Adamson Nov 1997 Water Industry Operator Training Nov 1997 J Park When in R ome ... Water Engineering in 97 AD. R Goldfinch Nov 1997 Reports Antipodean Team to UK Water Industry C Davis Mar 1996 Networking the Gem1an and Australian Water Industries I Bergman May 1996 Australian-Indonesian Activities in Water and the Environment I Bergman Jan 1997

Water Water Resources Water Resource Management in Western Australia R Payne Water Conservation Strategy in Western Australia

46

WATER JANUARY/ FEBRUARY 1998

Sept 1996

1996-1997

L English, J Schlafrig Sept 1996 Kalgoorlie Boulder-The Water- efficient City R Botica, S White Sept 1996 Drought Management for Victorian Urban Water Supplies R Moran Nov 1996 Macaque: Regional Scale Modelling of Water Yield from Forests F Watson, R Vertessy, R Grayson, L Band, T McMahon M ar 1997 Reservoir Sedimentation D ata in South Eastern Australia J Davis, I Rutherford, B Finlayson Mar 1997 Towards Reducing the Uncertainty in Design Flood Estimation P Hill, R G Mein, PE Weinmann Mar 1997 Recent Advances in Estimating Extreme Design RainfaLls PE Weinmann Mar 1997 Improvements in Real-time Flood Forecasting J ELiiott Mar 1997 Domestic Non-Potable Reuse-Why Even Consider It? I B Law May 1997 Aquifer Storage and Recovery ofStormwater Runoff P Dillon, P Pavelic, X Sibenaler, N Gerges, R C lark May 1997 Needs, Challenges and Health Benefits of Drinking Water R H elmer Sept 1997 Reports Groundwater Centre Builds East-West Link P Martin Sept 1996

Water Supply Second Boot Plant Commissioned EA (Bob) Swinton Condition Assessment of Water M ains P Ferguson, M Heathcote, G M oore, D Russell Predicting Underground Pipeline Failure G Constantine, ] Darroch, R Miller Prospect Water Filtration Plant G H enderson Reports Australasian Corrosion Association D N icholas South Australia's Pipelines E A (Bob) Swinton Some Overseas Impressions P M osse

Jan 1996 Mar 1996 Mar 1996 Jan 1997 Mar 1996 Mar 1996 N ov 1996

Water Treatment Removal of Algal Toxins using Membrane Technology M Muntisov, P T rimboli M ay 1996 Biological Iron and Manganese R emoval: An Untapped Potential I Cameron May 1996 Granular Activated Carbon Pilot Plant Studies G Newcombe, A Collett, M Drikas, B R oberts May 1996 From Catchment to Tap (The C R C WQ & T Program) D BursiLI, A J Priestley Sept 1997 Natural Organic Matter- the C urse of the Water Industi3/ M Drikas Sept 1997 A Survey of Water Treatment Plants in NSW M van Anen, H B Dharmappa Nov 1997 Reports Ozone T echnology Seminar J Giannopolous Nov 1996

Water Quality Bacterial R egrowth Potential in German and Australian Waters N Withers, M Drikas, B Hambsch July 1996 Aluminium, Water and Alzheimer's Disease R M Douglas July 1996 D etecting Protozoa in Water: A Comparison of methods B Faulkner, R Thurman, D Veal, A Champion Jan 1997 Contamination of Samples for DOC Analysis J van Leeuwen, M Drikas, D BursiLI, B Nicholson Jan 1997 Trials of the Colilert System PW Adcock, C Saint Mar 1997 Drinking Water and Public H ealth M Muntisov M ay 1997 Aluminium in a Water Supply: Parts 1 and 2 B A Coller, J Lin May 1997 Recreational Water Guidelines for Cyanobacteria LS Pilotto, MD Burch Sept 1997 Blue-green Algae and D rinking Water Quali ty

WATER

INDEX

D Steffensen, B Nicholson, M Burch, M Drikas, P Baker Sept 1997 Beyond Coliforms-Measuring Human H ealth M Hellard, M Sinclair, G Ranmuthugala, L Pilotto, A Padiglione, B Robertson, C Fairley Sept 1997 Predicting and Maintaining Water Quality in Distribution Systems Sept 1997 G Kastl, I Fisher Aluminium in a Water Supply, Part 3.

J Lin, B A Coller Nov 1997 Reports Public Health Priorities in Water Quality and Treatment R M Douglas May 1997

Wastewater Sewerage Systems Management of Wastewater in Small Coastal Communities SK Twartz, M Wood Jan 1996 PIRAT-Non-Subjective Sewer Inspection and Assessment G Campbell, K Rogers, J Gilbert Mar 1996 Assessing M elbourne's CBD Sewer System SC Carne, AM Norrish Mar 1996

1996-1997 R TWilliams Gulgong of the No'verflow M Laginestra

Nov 1997 Nov 1997

Biosolids Global Atlas of Wastewater Biosolids Use and Sludge Disposal July P Matthews Biosolids 2000 PS Machno July Dewaterability of Activated Biosolids I H Bane May Heavy Metals Leaching from Biosolids P R Ginige, A Shanableh Nov

1996 1996 1997 1997

Industry Wastes PETWINTM_A Modelling Tool for the Petroleum Industry AJ Baker Jan 1997 Bioremediation-Current Status for P AHs, PCP, PCBs and Dioxins July 1996 McConnell, M Stevens, P R Nadebaum Current Clean- up Technologies and Practices in the USA M E Peterson July 1997

Wastewater Treatment

Environment

Iron Chlorides for Filamentous Bulking: Laboratory Investigations I Sosa-Sanchez Mar 1996 Overview of CRC for Waste Management and Pollution Control I Fergus May 1996 Advanced Wastewater Management J Keller May 1996 Advanced Constructed Wetlands: An Ecotechnology Option H J Bavor May 1996 Modelling Aerobic Denitrification Ev Munch,J Keller, P Lant M ay 1996 Sewer Overflow Treatment-a Viable Alternative to Treatment NA Booker, AJ Priestley July 1996 On-line Wastewater C haracterisation Sept 1996 S Couper, R Pearson Aerated Septic Tank Systems: Field Survey of Performance MA Khali fe, H B D harmappa Sept 1997 The IDEA Plant at Black Rock, Geelong G C H Williams May 1997 Power Generation from a Large Covered Lagoon GR Nicholas, P R Harris July 1997 Wastewater Treatment by Lime and Sea Salt Brine A Shanableh July 1997 Biological Nutrient Removal-Present Status and Future Directions July 1997 J Keller, K J H artley Reports Innovation in Sewage Treatment/Tokyo Style May 1997 P Gross Sweet Smell of Success fo r Odour Interest Group M Laginestra Sept 1997 Microbiology Enters the Wastewater Industry in Earnest T Flapper Nov 1997

Environmental Monitoring Problems with Stream Sampling Jan 1996 M J Lich on Key Issues for Irrigated Agriculture in Australia J S Abbott Mar 1996 Measuring the H ealth of Our Rivers May 1996 N J Schofield, P E Davies Environmental Auditing of Wastewater Treatm ent Plants May 1996 P Nadebaum, P Drew, W Drew Environmental Management System, Waste Service NSW A Thakur,) B Cook July 1996 Spurious Correlation and Pollutant Export R elations R G Millar Sept 1996 Port Phillip Bay Environmental Study EA (Bob) Swinton Nov 1996 Catchment Management within Agencies: Bottom up/Top D own J Howard Jan 1997 Control ofCyanobacterial Blooms in Weir Pools I Webster, G Jones, R Oliver, M Bormans, B Sherman Jan 1997 Sampling and Analysis: The Australian Water Quality Guidelines Jan 1997 W Maher, C leGras, A Wade Predicting the Water and Salt Dynamics Beneath Eucalypt Plantations R P Silberstein, RAVertessy, J Morris, L D Connell M ar 1997 Environmental Performance of Sydney's Deepwater Outfalls T Pritchard Mar 1997 Saline Disposal Basins K Narayan Mar 1997 CDS-A New Screening Technology for the Environment RA J ago May 1997 Attenuation of Landfill Discharges in Sandstone Steams M Petrozzi May 1997 Victoria's Groundwater Protection Policy July 1997 D Strudwick Environmental Regulation of Perth's Groundwater BJenkins Nov 1997 Reports Rivers Down the Drain Sept 1996 C Davis Technology Tight O n-Site Nov 1997 C Davis Australia's New H orizons Oceans P olicy May 1997 M Metz

Effluent Re-use MED LI - Bringing Effluent Irrigation Design into the 21st Century R Davis, E Gardner M ay 1996 Membrane T echnology for Wastewater Reuse AW Day May 1996 Appropriate Technologies for Wastewater Treatment and R euse G Tchobanoglous July 1996 R ecovery and Reuse ofWastewater using Australian Natural Zeolite EL Cooney, NA Booker July 1996 Irrigation Impacts at Nowra R Lawrie July 1996 The FILTER Technique for Land Treatment of Sewage Effluent N S Jarwardane, J Blackwell Nov 1996 R ecycling of Reclaimed Water in South Australia N M Kayaalp Jan 1997 On-site Wastewater Treatment: A South Australian Survey N M Kayaalp Nov 1997 Reports Reuse of Sewage Effluent P Martin M ar 1996 Gorillas and R ecycled Water M Laginestra J uly 1997 Water Reuse in Spain

Stormwater Urban Stormwater Mangement G White , LJuginis, M Beharrell , C Young The Pollutec Stormwater Pollution Trap: Field Trials RA Allison, TH F Wong, TA McMahon Modelling Urban Run-off and Pollutants F H S C hiew, T A McMahon Leaf Litter in Stormwater: A Major Source of Nutrients?

RA Allison, F H S Chiew Pollutant R emoval by Storage: Analysis of Data H P Duncan

July 1996 Nov 1996 Mar 1997 M ar 1997 M ar 1997

WATER JANUARY/ FEBRUARY 1998

47