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RASSOCIATION

FEBRUARY 1993


t AUSTRALIAN WATER & WASTEWATER A.SSOCIATION

Australian Water & Wastewat6.Associat ion Incorporated ARBN 054 253066

ISSN 0310-0367

Volume 20, No. 1, February 1993

CONTENTS 3 My Point of View Association News

FEDERAL SECRETARIAT Executive Di rector - Chris Davis Business Manager - Margaret Bates PO Box 388, Artarmon 2064 Telephone (02) 413 1288 Facsimi le (02) 413 1047

PRESIDENT Barry Sanders, Phone (09) 420 2453

4 5 8 10

Features

12 17

SECRETARY/TREASURER Greg Cawston, Phone (02) 597 0503

BRANCH SECRETARIES Canberra, ACT Alan Wade, D.E.l.P PO Box 1119, Tuggeranong 2901 Phone (06) 207 2350 New South Wales Nick Apostolidis, GCEC, 39 Regent Street Rail way Square 2000 Phone (02) 699 9922 Victoria John Park, Ci- Water Training Centre, PO Box 409, Werribee 3030 Phone (03) 741 5411 Queensland Don Mackay, PO Box 412, West End 4101 Phone (07) 840 4844 South Australia Neil Palmer, Ci- State Water Laboratories, E&WS Private Mail Bag, Salisbury 5108 Phone (08) 381 0268 Western Australia Bill Chapman, WAWA PO Box 100, Leedervi lle 6007 Phone (09) 420 2462 Tasmania Annette Ferguson, GPO Box 503E, Hobart 7001 Phone (002) 28 2757

Northern Territory Lindsay Monteith, PO Box 351 , Darwin 0801 Phone (089) 81 5922

EDITORIAL CORRESPONDENCE EA (Bob) Swinton, 4 Pleasant View Crescent, Glen Waverley 3150 Office Phone-Fax (03) 560 4752 Home (03) 560 9306

ADVERTISING Ann Sykes-Smith, Appita, 191 Royal Parade, Parkville 3052 (03) 347 2377 Fax (03) 348 1206

News from the Executive Association News IAWQ Industry News

23 26 29 32 35

The AWWA Environment Award Health Risks from Pathogens in Untreated Wastewater Sludge RA Gibbs and G.E. Ho Nepean Reservoir Destratification G. Schadlow, J. lmberger, J. Patterson and I. Fisher The ANZECC Guidelines for Water Quality M. Lag inestra reports Ion-Exchange and Adsorption Bob Swinton reports Wetland Systems in Water Pollution Control Lance Bowen reports IMSTEC '92

Of Interest

36 Book Reviews 38 Product Information 40 Conference Calendar

OUR COVER "This environment is worth preserving" This was the caption for th is peacefu l scene in Albany Harbour, in a brochure put out by the Environment Protection Authority of Western Australia. In 1988 the harbour was being rapid ly degraded by influx of nutrients and other po flutants from industry, mun icipality and agricu lture. Rap id act ion, by al l three contributors, to reduce their discharges to levels calculated by the EPA is solving the problem. One of the industries was the fert il iser factory of CSBP & Farmers Ltd. The waste audit and subsequent design of nutrient management for the factory by Sinc lair Kn ight & Partners was the WA submission for the AWWA Nat ional Environment Merit Award . Summaries of all the seven Branch submissions is the lead article in t his issue. The winner wil l be announced at the 15th Federal Convention. [Photo courtesy of the EPA of WA]

r, Wa1 ---~~-

PUB LI CAT ION Water Is bl-monthly. Nominal distribution times are the third weeks of February, April , June, August . October. December.

,

IMPORTANT NOTICE PRODUCTION EDITOR John Grainger, Appita, 191 Royal Parade, Parkville 3052 (03) 347 2377 Fax (03) 348 1206

The Australi an Water and Wastewater Association assumes no responsibility for opinions or statements ol facts expressed by contributors or advertisers , and editorials do not necessaril y represent the official policy of the organisation. Display and classified advertisements are included as an inlormational service to readers , and are reviewed by the editor before publication to ensure !heir relevance to the wate r environment and to the objectives of the Association. All material in Water is copyright and should not be reproduced wholly or In part withou t the written permission of the editor.

WATER February 1993

1


TECHNOLOGY

HEALTH RISKS FROM PATHOGENS IN UNTREATED WASTEWATER SLUDGE Implications for Australian Sludge Management Guidelines by R. A. GIBBS and G. E. HO SUMMARY Literature concerning pathogen densities in untreated wastewater sludge was reviewed to aid an assessment of the health risks associated with the use of municipal sludge. No information on pathogen densities in Australian sludges was found so risks were assessed using pathogen densities in other countries and infection rates in Western Australia. Based on information from other countries it was estimated that an individual handling sludge and ingesting 0.1 g of sludge would have a greater than 1OJo chance of becoming infected with Giardia, less than 25% chance of contracting a helminth infection, approximately 1OJo chance of becoming infected with an enteric virus and less than 1OJo chance of contracting a Salmonella infection. However a qualitative risk assessment based on reported infection rates in Western Australia suggested that enteric viruses in wastewater sludge pose the most risk followed by Salmonella and Giardia. These risk assessments and a limited amount of epidemiological evidence suggest that digested wastewater sludge is not suitable for unrestricted marketing to the public. Guidelines in the US and UK follow this philosophy. Two issues of concern for Australian sludge guidelines are the use of indicator organisms to predict pathogen densities and the possibility of Salmonella regrowth in composted wastewater sludge.

Robyn Gibbs is a Research Fellow in Environmental Science at Murdoch University and has eight years experience in water and wastewater microbiology. She is conducting research on the die-off of human pathogens in stored municipal wastewater sludge and sludge applied to land.

Goen Ho is Associate Professor in Environmental Engineering at Murdoch University. Since joining the University in 1976 he has carried out teaching and research in the treatment and utilisation of industrial, agricultural and municipal wastes.

INTRODUCTION The purpose of this review was to assess the potential health risks associated with the use of final sludge from wastewater treatment plants. Sludge products from different plants will vary depending on wastewater and sludge treatments but for assessing the risks this review concentrated on mesophilic anaerobic digested sludge. The effect of sludge treatments on pathogen concentrations was not covered in this review. Two risk assessments were carried out. Firstly the risks were assessed by looking at the following questions. • Which groups of people could be at risk from exposure to sludge? • What densities of pathogens have been found in wastewater sludge? • What is the infectious dose for these pathogens? • Therefore what are the risks to exposed people? A separate assessment of risk based on the incidence of disease in Western Australia, estimated excreted loads, persistence of pathogens in the environment and infectious doses was also conducted. These risk assessments were then used to examine possible sludge management strategies and guidelines in Australia. Epidemiological studies were also summarised. It is recognized that the major route of infection for most enteric pathogens is person to person contact. However this does not negate the possibility that exposure to wastewater sludge may be another potential route of infection.

PEOPLE AT RISK FROM EXPOSURE TO SLUDGE People at risk from exposure to wastewater sludge can be divided into two groups, those directly exposed and those indirectly exposed (Block, 1986). Directly exposed people might include wastewater and sludge treatment plant workers, sludge transporters and handlers, members of the public using garden products containing sludge, farm workers using sludge and landscaping workers. People directly exposed to wastewater sludge could ingest pathogens contaminating their hands or clothes. Children exposed to sludge are probably most at risk because they are more likely to directly ingest sludge or eat without removing sludge contamination from their hands.

Indirect exposure to sludge might come from consuming crops grown ~n sludge-amended soil or consuming meat or water indirectly contammated from sludge. The following discussion will concentrate on direct exposure to wastewater sludge as there was not enough published information to quantitatively or qualitatively assess the health risks associated with indirect exposure to wastewater sludge. The transmission of pathogens through agricultural application of sewage sludge is therefore not covered in this review but it is an area where more research would be valuable.

PATHOGEN DENSITIES IN WASTEWATER SLUDGE During an extensive literature search no information about pathogen densities in Australian sludges was found. Work on quantifying pathogens in wastewater sludge in Perth was recently commenced and will be reported separately. A limited number of studies have been carried out in the USA UK and France and the results are summarised in Table 1. The enteri~ viruses shown in Table 1 are probably from the enterovirus group which includes poliovirus, echovirus and coxsackieviruses. Other viruses reported by Fradkin et al. (1985) to be present in wastewater and sludge, but for which no quantifiable densities were found, included rotavirus, hepatitis type A, reovirus, adenovirus and parvovirus. Other bacteria reported to be present were Shigella, enteropathogenic E. coli, Yersinia enterocolitica, Vibrio cholerae and Leptospira. 1 The types of pathogens in Australian sludges sho uld be similar to those from the USA, UK and France. An example of what might be expected in Australian sludges is shown in Table 2 which shows the number of reported cases caused by different pathogens in the Perth metropolitan area and for the whole of Western Australia in 1991. Complete data was not available for the whole of Australia so Western Australia was used as an example. Pathogen densities

WATER February 1993

17 ,


in sludge should reflect the numbers of people in the community infected by enteric pathogens as infected people excrete the pathogen causing the infection. This will vary seasonally and from comm,unity to community. Other factors apart from the number of infected individuals will also affect pathogen densities in sludge. Two of these factors are the numbers of pathogens excreted by infected individuals and persistence of these pathogens in the environment. Estimated data for these are shown in Table 2. In the Perth metropolitan area in 1991 there were more reported cases caused by the bacterial pathogens Campylobacter, Clostridium difficile and Salmonella, and the protozoa Giardia than by any other enteric pathogens. The numbers of reported helminth infections were relatively low. Table 1 Summary of Pathogen Densities in Digested Wastewater Sludge Group

Viruses

Pathogen

Emeric viruses

Bacteria

Salmonella

Protozoa

Campylobacter Entamoeba Giardia

Helminths Nematodes

Ascaris

Trichuris

Toxocara

Toxascaris Cestodes Taenia •

t

No. of Organisms/ kg* Mea n Range

30 550 1900 200 8IO;

0-60 l0-5859 300-4 I00 NSt < 0.9-7500

3-11 00 NS NS 0-95 0-3720 70-3 .0xIO• 8321 I.9xlO't 3000- l.23x l05 NS 95 4IO 25-775§ 2030 NS 9700 NS NS 11 0-1200 2785-6415§ 5100 360 NS 1400 NS NS 0-230 4IO 125-695§ NS 1730 IOI0-3400 NS 1200 NS 480 NS NS 0-160 10 NS NS 0-330 1250-3150§ 2200 480 16 620 60 NS

Schwartzbrod and Mathieu, 1986 Goyal et al., 1984 Berg and Berman, 1980 Carrington et al., 1991 Soares et al., 1992 Jewell et al., 1980 Lue-Hing et al., 1977 Stern and Farrel, 1977 Jones et al., 1990 Fox and Fitzgerald , 1977 Sykora et al., 1991 Soares et al., 1992 Schwartzbrod et al., 1987 Barbier et al., 1990 Arther et al. , 1981 Reimers et al., 1986 Fox and Fitzgerald, 1977 Barbier et al., 1990 Arther et al., 1990 Reimers e1 al., 1986 Fox and Fitzgerald, 1977 Barbier et al., 1990 Art her et al., 1981 Fox and Fitzgera ld, 1977 Reimers et al., 1986 Art her et al., 1981 Fox and Fitzgerald, 1977 Schwartzbrod et al., 1987 Fox and Fitzgerald, 1977 Barbier et al., 1990

in some cases conve rted from numbers/ L by assuming that I L of slu dge weighed I kg

not stated co nverted from number/ g dry weight using a dry we ight / wet we ight rat io of 0.03 geo metric mea n

§

950/o confidence intervals

To assess how representative results from Perth were for the rest of Australia the incidences of notifiable enteric diseases in Perth, Melbourne and the Kimberley region of Western Australia were compared. Data was not available for all enteric pathogens but for those shown in Table 3 the incidence of reported enteric infections in Melbourne was approximately half that for Perth. This may have reflected the true incidence but is more likely to have been due to differences in notification rates. The relative infection rates for different pathogens in Perth and Melbourne were similar. The dominant enteric pathogens were Campylobacter, Giardia and Salm onella. Infection rates for notifiable helminths were low. In the Kimberley region infection rates were considerably higher than in the cities. Giardia was the dominant enteric pathogen. It appears that results from Perth may be representative of other cities but not necessarily of regional areas, particularly northern parts of Australia. If the incidences of enteric infectious diseases in other cities are similar to Perth and Melbourne then Australian municipal sludges would not be expected to contain the high concentrations of helminths shown in other countries. For the helminthsHymenolepis nana, Ascaris lumbricoides and Strongyloides stercoralis, which only have a human host, the numbers of cases and numbers of pathogens excreted by infected individuals in Perth are such that they couldn't give the concentrations shown in other countries unless the number of people with unreported infections is very high. Taenia saginata eggs which originate from infected humans will not infect other people but may present a risk to cattle.

WATER February 1993

Group

Pathogen

Viru ses

Rotavirus Adenovirus E nteroviruses Hepatitis A

Bacteria

A uthors

t

18

Table 2 Number of Persons Infected by Enteric Pathogens in the Perth Metropolitan A rea and for the Whole of Western Australia for 1991 (Public Health and Enteric Diseases U nit of State Health Laboratory Services, 1992) and Estimated Excreted Load and Persistence of these Pathogens (Shu val et al. , 1986)

Protozoa

Helminths

No. of Cases Met ro. State Area Total

Campylobacter species Salmonella species Clos1ridium difficile Shigella species Aeromonas species Enterotoxigenic E.coli Giardia intestinalis Blastocystis hominis1 Cryptosporidium species En/amoeba species Hymenolepis nano (dwarf tapeworm)

Strongyloides stercoralis Trichuris trichiura (whipworm) Hookworm ova

Exc reted load*

Persistencet

10' NS

NS NS 3 months NS 7 d ays 2 months NS l month NS 3 months

NS NS NS NS 11 56 376 438 49 35 0 514 353 67 49

259+ 206 + 194+ 142+ 1579 785 520 21l 5 54 27 1014 494 273 70

10' 10' 108 NS 10' NS 10" 10' NS NS 10'

25 14

178 132

NS IO

NS 3 weeks

ll 5 26

127 125

10' 10'

9 months 3 month s

12 l

16 l

[04

l year 9 mon ths

10'

25 days NS NS 25 days

Ascaris lumbricoides (roundworm)

Taenia saginata

104

Typical number of organis ms per gram of faeces Estimated max imum life of infecti ve stage at 20 to 30oC in water, wastewater, so il and on crops

t t

Reports From two laboratori es (may not be for the whole state), Hargreaves (1992) Pathogen status not es tab li shed

NS

Not stated

INFECTIOUS DOSES Infectious dose information is scarce because infectious dose studies depend on human volunteers. There are also problems with using infectious dose information as outlined by Block (1986) . Some of these problems are: 1. Infectious doses vary depending on the health_of the individual. 2. Infection can be measured in-different ways including clinical symptoms, shedding of pathogens in faeces and serological response, so data from different studies may not be comparable. 3. Ingestion of laboratory grown organisms may not replicate ingestion of organisms in environmental samples. Rose and Gerba (1991) and Shuval et al. (1986) summarised infectious doses for different organisms and these are shown in Table 4. In interpreting this data the above limitations need to be kept in mind. Table 4 shows that the probability of becoming infected by consuming one organism is higher for viruses, protozoa and helminths than for bacteria, and the number of organisms required to cause infection in a certain percentage of the population is less for viruses, protozoa and helminths than for bacteria.

RISKS FROM EXPOSURE TO FRESH SLUDGE Tables 2 and 4 were used to quantify the health risks of direct exposure to pathogens in wastewater sludge. The risk assessment was based on exposure to fresh sludge rather than treated or stored sludge. Two ass umptions were made. Firstly it was ass umed that Table 3 Incidence of Enteric Infectious Diseases per 100 000 Population (1991) Pathogen

Melbournet Hepatitis A

Campylobacter species Giardia species Salm onella species Shigella species Taenia saginata & hinococcus species (hydatid disease) •

14 58 20 23 2.0 0.2 0.03

lncidence/ 100 000* Pertht Kimberl eyt NS 103 46 34 4.4 0 ,0')

0

NS 448 1062 712 418 0 0

Population statistics from the Australi an Bureau of Statist ics, 1988 (Pert h and Kimberley) and 1990 (Melbour ne)

Infect ious Diseases Uni t, Hea lth Department Victoria (1 992)

Public Healt h and Enteric Diseases Uni t or State Health Laboratory Services (1992)


Table 4 Infectious Doses for Enteric Pathogens Probability

Pat hogen

Dose to Cause Incidence of

of Infection

from Exposure to

10/'o*

1-250/ot

26-500/ot

51-750/ot

76-1000/ot

1-10

10-100

100-1000

103.104

1-10 1-10

10-100 10-100

100-1000 100-1000

103.104 103-104

100-1000 103-104 104.105

104.105 105.106

l Orga nism*

Enteroviru ses Poliovirus 1 Poliovirus 3 Echovirus 12 Rotavirus Norwalk Agent Hepatitis A virus Salmonella species Salmonella typhi Salmonella newport Salmonella derby Salmonella pullorum Shigella dysenteriae Shigella flexneri Vibrio cholera Escherichia coli (pathogenic) Clostridium peifringens Campylobacter Entamoeba histolytica Giardia lamblia Ascaris lumbricoides Ancylostoma duodena le Trichuris trichiura

l. 49x10· 2 3.Jx10· 2 l.7x10" 2 3. lx10· 1 2.3xl0· 3 3.8x10·5

0.67 0.32 0.59 0.03 4.3 263 104.105 107.108

4.97xl0·4 lx10·4 7x10· 6

20 100 1428

103.104 105.106

10-100 100-1000 102.103 103.104 103-104 104-107 10 3-tcf

108-109 108-109

7x10· 3 2.8xl0· 1 l. 98x10· 2

1.4 0.04 0.5 100-1000

109-10 10

104-106 1-10

10-100

1-10 1-10

10-100 10-100

from Rose and Gerba (1991) t from Shuval et at. (1986)

pathogen densities in Australian sludges are similar to those from other countries. As discussed above this may not be true for helminths. Secondly, for the purposes of estimating the risk, it was assumed that the maximum amount of sludge that any individual would ingest at one time was 1 g and that a more realistic amount that an individual might ingest was 0.1 g. In the worst case it was assumed that Australian sludges contain the maximum numbers of enteric pathogens found in any of the studies from other countries and that an individual handling sludge would ingest 1 g of sludge. The results of this calculation are shown in Table 5. The percentage of individuals likely to become infected with the worst case dose was taken from the infectious dose information given in Table 4, and this is also shown in Table 5. A slightly more realistic infection rate was calculated by assuming that sludge contains the mean number of pathogens shown in Table 4 and that an individual might consume 0.1 g of sludge when handling sludge. This is still likely to be an overestimate as it is unlikely that many people will ingest 0.1 g of sludge. This estimate also does not take into account protozoa and helminth viability. Keeping the assumptions in mind it can be seen from these estimates that for an individual handling sludge and consuming 0.1 g of sludge then there is an approximately 1OJo chance of becoming infected with an enteric virus, less than 1OJo chance of contracting a Salm onella infection, greater than 1OJo chance of contracting a Giardia infection and-less than 25% chance of contracting a helminth infection . These calculations suggest that if Australian sludges contain the concentrations of enteric pathogens found in digested sludge in the USA, France and UK, then they pose a risk to the health of people handling sludge which has not been treated further than mesophilic anaerobic digestion. The greatest risk appears to arise from Giardia Table 5 Estimated Infection Rate from Handling Sludge

Enteric viruses Salmonella Giardia Ascaris Trichuris

Table 6 Criteria Used to Classify Number of Cases in Western Australia, Excreted Load and Pathogen Persistence Classification

.

Pat hogen

and helmi~ths in sludge. In Australian municjpal sludges the risks from helmmths should not be as great but risks of Giardia infections may be similar. A qualitative risk assessment was also carried out. Rather than using data from other countries the assessment was based on reported infection rates in Western Australia. This was used in conjunction with estimated excreted loads and persistence of pathogens in the environment as shown in Table 2. Some of the pathogens shown in Table 2 were not included in the qualitative risk assessment. Taenia saginata was excluded because it is not transmitted directly from person to person but needs an intermediate host. Clostridium difficile was not considered to present a risk from faecal-oral transmission. Blastocystis hominis is not a clearly established pathogen. Ascaris lumbricoides was considered to present a negligible risk relative to the other pathogens because of the low number of cases in Western Australia. Information in Table 2 was classified into low, medium or high as outlined in Table 6. Infectious dose classifications were taken from Shuval et al. (1986). The classifications were then combined to rank the pathogens into groups. Group 5 contains the pathogens which presented the most risk with the risks decreasing to group 1 which contains the pathogens of least risk. The classifications and groups of pathogens are shown in Table 7.

\Vorst Case: Sludge Contains

Average Case: Sludge Contains Mean Number of Pat hogens

Number in

Percentage of

Nu mber in

Percentage of

1.0 g

Exposed People Infected

0.1 g

Exposed People Infected

1-250Jo < IOJo 1-250Jo 26-500Jo 26-500Jo

O.Q7

7.5 2 123 9.7 5.1

0.04 1.0 0.4 0.22

< IOJo to lOJo < 10Jo > IOJo <250Jo <250Jo

Excreted Load

Persistence

less than 100 103 and less I month and less 100 10 500 104 and 10 5 greater than 1 month to 3 months 5 greater than 500 greater than 10 greater than 3 months

Low Medium High

This risk assessment is obviously very general and based on a number of assumptions. Some of the assumptions were that: 1. Each of the different factors had equal weight (number of cases, excreted load, persistence and infectious dose). 2. Reported cases reflected symptomless and unreported cases. 3. Input into wastewater from infected animal waste was not significant. 4. Where data was not available it was estimated from data for similar pathogens. 5. Any pathogen which resulted in less than 2 cases per 100 000 people per year was considered to present negligible health risk in wastewater sludge. 6. Levels of immunity to viruses were not significantly higher than for other pathogens. 7. Salmonella regrowth potential was not significant. Based on the qualitative risk assessment and with these assumptions in mind then the pathogens of most concern in Western Australian sludges are enteric viruses. The next group of pathogens which are of concern are Salmonella, Giardia intestinalis and Trichuris trichiura. Most of the Trichuris trichiura infections were Table 7 Relative Health Risks of Different Groups of Pathogens Gro up

Group 5 (highest risk)

Group 4

Maximum Number of Pathogens

No. of Cases

Group 3

Group 2

Pathogen

Rotavirus Adenovirus Enterovirus Hepatiti s A Salmonella Gia,dia intestinalis Trichuris trichiura Campylobacter Shigella Cryp/osporidium Hookworm ova Hymenolepis nana Ent amoeba Strongyloides stercoralis Enterotoxigenic £Coli

No. of Cases Excreted Persistence Infectious in \Vestern Austra lia in 1991

Load

medium medium medium medium high high medium high medium medium medium medium low

high high high high high medium low high hi gh medium low low medium

medium medium medium medium medium low high low low low medium 1 low low

low low low low high low low high medium low low low low

medium low

low high

low medium

low high

Dose

Group 1 (negligib le risk) Ascaris lumbricoides

WATER February 1993

19


associated with travellers and recent immigrants so infection rates in the resident population appear to be low. This organism was therefore not considered to present a major risk from transmission through sludge. Most of the hookworm, Hymenolepis nana and Strongyloides stercoralis infections reported in Western Australia were from patients in the Kimberley region. The risk of infection from helminths in Perth sludges would therefore appear to be low. This may be similar in other southern cities in Australia. In northern Australia the risk of contracting helminth infections through contact with sludge may be higher. The qualitative risk assessment using infection rates in Western Australia gave a different result to the quantitative risk assessment based on pathogen densities in sludge in other countries. The quantitative risk assessment suggested that Giardia and helminths presented more of a risk than enteric viruses and Salmonella. One reason for the differences may be that poor recoveries of pathogens in sludge resulted in an underestimation of pathogen densities in sludge in other countries. Measured enteric virus concentrations in sludge may have been particularly low. Another reason is that methods used to detect Giardia did not assess viability. However the differences may also underline the general uncertainty attached to the results due to the assumptions made and lack of data which . could be used in the risk assessment. The conclusions of the qualitative risk assessment differ from those of Shuval et al. (1986). They proposed a model to predict the relative infectiveness of pathogens in causing infections through wastewater irrigation in developing cou ntries. The risks from pathogens were ranked in the following way. Helminths Bacterial infections Protozoan infections 3. Least Viral infections. In contrast the ranking developed in this study (shown in Table 7) suggested that viruses present the highest risk, fo llowed by bacteria and protozoa with helminths presenting the least risk. There are probably two main reasons for the difference which are due to the Shuval et al. (1986) model being developed for developing countries. Firstly Shu val et al. (1986) assumed that the prevalence of helminth infections was very high. Shuval et al. (1986) used figures of 600Jo prevalence for both Ascaris and Trichuris. Based on reported cases then the prevalence of Ascaris and Trichuris in the Perth metropolitan area in 1991 was 0.001 and 0.01 OJo respectively (Public Health and Enteric Diseases Unit of State Health Laboratory Services, 1992). The second reason is that Shu val et al. (1986) assumed that due to poor hygiene most infants would be exposed to enteric viruses and subsequently immune to enteric virus infections. This assumption was not made for this study so immunity was not treated as a significant factor in the risk assessment. 1. High 2. Lower

EPIDEMIOLOGY Epidemiological studies are another way of assessing the risks from pathogens in sludge. However epidemiological information is limited because the costs involved in epidemiological studies are extremely high. In studies described by Jakubowski (1986) costs ranged from US$21 000 to US$107 000 for retrospective studies, and US$178 000 to US$2 000 000 for prospective studies. These studies were carried out in the late 1970s and early 1980s. There are a greater number of studies involving exposure to wastewater and these were summarised by Shuval et al. (1986). Block (1986) could report only four epidemiological studies of exposure to sludge rather than exposure to wastewater. One of these was a study of sludge compost workers described by Clark et al. (1984). Workers directly involved in composting showed evidence of an immune response to antigens which was higher than groups not involved with compost activities. More symptoms of burning eyes and skin irritation were also reported among compost workers. However these may have been associated with high dust levels rather than the sludge. Jakubowski (1986) described an epidemiological study of farm residents on farms with anaerobically digested sludge spread on their fields. No significant differences were observed between the test and control groups for reported illness and serology. The author noted that health risks might have been higher with a higher rate of expos ure. Another study described by Block (1986) reported hepatitis A infections in four men who spread wastewater sludge on farmland. It is probable that the men were infected during the course of their work.

20

WATER February 1993

In a review of the epidemiology of Salrrwnella, Pike (1986) found only one published outbreak of salmonellosis which involved the use of sludge. This involved 98 human cases drinking unpasteurised milk from a farm in Scotland. Sludge containing effluent from a chicken factory had been sprayed on grassland and cattle reintroduced shortly afterwards. Cows, calves and domestic pets were found to be infected with S. typhimurium. Another milk-borne epidemic in Czechoslovakia (Raska et al. 1966) appeared to have been caused by sludge spread on land. Cesspool wastewater was spread on fields and this resulted in contamination of the water supply into a dairy. This appeared to lead to contamination of the milk and an infectious hepatitis A epidemic. In 1986 European Community round table discussions were held on the risks associated with the agricultural use of wastewater sludge (EC Panel, 1986). A Salmonella panel stated that wastewater and wastewater sludge were the source of infection in 12 reported outbreaks of salmonellosis. How many of these outbreaks were actually associated with municipal wastewater sludge is not clear. At least three of them which occurred in the UK were associated with animal wastes, wastewater or .septic tanks rather than municipal sludge. The conclusions of the panel were that sludge presented a hazard to the health of animals and men and that it should be treated to destroy pathogens or restrictions imposed on the use of land after sludge was applied. A parasite panel agreed that sludge spread on land can act as a vector of Ascaris and Taenia saginata. A virus panel concluded that there were only two relevant reports of wastewater sludge acting as a source of infection for the spread of enteric viruses. These were the two hepatitis A outbreaks described above. On the basis of the limited number of studies that have been carried out it appears that human infection has occurred through handling sludge or the use of wastewater sludge in agriculture. However if guidelines are followed which include sludge treatment or restrictions on the use of sludge-amended soil and public access, then the health risks appear to be low.

SLUDGE GUIDELINES A number of countries have guidelines for the use of wastewater sludge on land but the formulation of guidelines is a difficult process because there is very little information available. As shown above epidemiology has not provided enough information to state conclusively whether past sludge management practices have resulted in any diseast in exposed humans. There does seem to be some evidence that wastewater sludge has been associated with a few cases of infection, but not in cases where the sludge had been treated or where use restrictions were imposed after sludge was applied to land . Studies in the USA, France and UK have demonstrated that sludge which has not been treated past mesophilic anaerobic digestion may contain pathogenic viruses, bacteria, protozoa and helminths. Estimated infection rates among exposed populations consuming 0.1 g of sludge were approximately 1OJo for enteric viruses, < 1OJo for pathogenic bacteria, > 1OJo for Giardia and < 250Jo for helminth ova. The epidemiological information and reported pathogen densities from other countries therefore suggest that sludge which has only been treated by mesophilic anaerobic digestion is not safe for unrestricted use by the public. Legislators in other countries have adopted this philosophy and responded to it in two ways. The first is by requiring that sludge undergo further sludge treatment before unrestricted use. The second is by imposing restrictions on the use of partially treated sludge. These restrictions include requirements such as subsurface injection or tilling of sludge into soil, limitations on access and withholding periods for sludge amended soil. There are differences between the guidelines in different countries. and this is illustrated by examining the US and UK guidelines. Sludge guidelines in the USA are in the process of change so there are present guidelines (US EPA, 1989a) and proposed new regulations (US EPA, 1989b). The proposed regulations may be modified again and were expected to be promulgated towards the end of 1992. There are differences between the US and UK guidelines (DOE, 1989) in three major areas. The first difference is in the way that sludge {s classified. In the UK sludge is classified as treated or untreated and in the US sludge is classified as untreated, treated by a process to significantly reduce pathogens (PSRP) or treated by a process to further reduce pathogens (PFRP) . The second difference is between the restrictions placed on the use of the different classifications of sludge. The US allows the unrestricted use of sludge which has been treated by a


process to further reduce pathogens such as composting. The UK The reviewed studies do not provide any basis for using the does not seem to allow the unrestricted marketing of any type of densities of faecal ipdicator bacteria in sludge to predict the presence sludge. In the UK untreated sludge can b_e used in agriculture with _ or absence of enteric pathogens. associated use res trictions. The US does not allow the use of Salmonella Regrowth in Composted Wastewater Sludge untreated sludge in agriculture. The third difference is between the In the US, sludge which has been treated by a PFRP process can monitoring and classification requirements. Sludge guidelines in the be marketed without restrictions. Acceptable PFRP processes are UK specify acceptable sludge disposal practices with land use composting, heat drying, heat treatment, thermophilic aerobic restrictions but do not require any monitoring for pathogens or digestion , beta ray irradiation , gamma ray irradiation and indicator organisms. The present US 40 CFR Part 257 guidelines pasteurization (US EPA, 1989a) . are also based on acceptable processes and procedures. However the Laboratory studies have demonstrated that Salmonella can regrow new US proposed regulations have requirements which specify in composted wastewater sludge (Russ and Yanko 1981). The results acceptable pathogen densities, but also specify alternative process of a fi eld study also suggest this (Yanko 1988). In the field study plus indi cator organism density requirements. the finished product from a wi ndrow composting facility contained very few Salmonella but blended compost products contained high levels of Salmonella. The authors measured Salm onella levels in the IMPLICATIONS FOR AUSTRALIAN GUIDELINES other blending products and concluded that nutr'ent related regrowth Australia is in the process of formulating guidelines for sludge of Salmonella was the only explanation for these high levels. In the management. These guidelines are not yet available for public described study Salmon ella was regularly detected in composted comment so the details are not discussed here. However the fo llowing sludge meeting PFRP criteria. Mixing with other products and discussion concerns issues which may be raised in the guidelines. baggi ng seemed to be conditions which favoured regrowth. These studies suggest that some composted sludges have the potential to Pathogens of Concern support Salmonella reg rowth. Composted sludge may appear The qualitative risk assessment based on the incidence of disease Salmonella free but contain low levels of Salmonella which can grow in Western Australia (Table 2) produced a ranking of the relative after bagging. As recommended by Yanko (1988) additional research risks of different pathogens in wastewater sludge (Table 7). Enteric to better understand what conditions give rise to So!monella regrowth viruses were considered to present the greatest health risk in is warranted. Management practices may significantly alleviate any wastewater sludge. Also of concern were Salmonella and Giardia. potential hazards associated with Salmonella in compost. Pathogens such as Campylobacter, Shigella and Cryptosporidium Yanko (1988) also discussed the results of two studies which presented a lower risk. The risk of infection from helminths in suggested that seeded laboratory cultures of Salmonella may not municipal sludge was considered to be low. predict the regrowth of indigenous Salmonella. This study raises questions about what form of monito ring could adequately assess Indicator Organisms as Predictors of Pathogen Densities and prevent the marketing of sludge products with unacceptably high in Wastewater Sludge densities of Salmonella. A laboratory test of regrowth potential may After assessing the use of indicator bacteria for predicting not be an adequate predictive tool. pathogen densities in sludge Pederson (1981) and Lewis-Jones and Winkler (1991) did not recommend the use of indicator organisms. CONCLUSIONS Pederson (1981) evaluated the available literature and concluded that An epidemiological review and assessment of the health risks no single indicator organism maintained a density level which was associated with municipal wastewater sludge sug&ested that untreated constant relative to that of pathogenic organisms. In a later review digested sludges are not suitable for unrestricted marketing to the Lewis-Jones and Winkl er (1991) co nclud ed that severa l public due to unacceptably high risks associated with enteric viruses, microorganisms in raw and treated sludges could be used as S almon ella, Giardia and some h elminth s. However both indicators of other organisms but the true extent of sludge epidemiological i,nformation and studies,.o f pathogen concentrations contamination could only be assessed by direct determination of in sludge were scarce. The risk assessment was based on data from the relevant organisms. other countries so a qualitative risk assessment based on reported Berg and Berman (1980) studied the effect of anaerobic digestion cases in Western Australia was carried out. This suggested that enteric on viruses and indicator bacteria indigenous to domestic sludges. viruses in sludge present the greatest risk fo llowed by Salmonella They found that indicator bacteria were destroyed more rapidly than and Giardia. Two issues are of concern for Australian guidelines. viruses and large variations in the numbers of viruses occurred over Firstly the use of faecal indicator bacteria to predict pathogen narrow ranges of faecal coliforms, total coli forms and faecal densities in sludge was not supported by the literature. Secondly the . streptococci. The rates of destruction of faecal streptococci by regrowth potential of sludge treated by composting or other forms digestion were closest to those of virus destruction so they concluded of further treatment needs further discussion . Research in these two that faecal streptococci may by useful process indicators. Lewis-Jones areas would be of benefit. and Winkler (1991) came to a similar conclusion. They described a study which examined the relationship between enteroviruses, ACKNOWLEDGMENTS Salmonella, coli forms, faecal streptococci and fRNA phages in raw The review documented here was part of a project funded by the and treated sludges. Faecal streptococci appeared to be reliable Water Authority of Western Australia and Urban Water Research indicators of virus contamination . A significant correlation between Association of Australia . Members of the steering committee for Salmonella and viruses suggested that Salmonella could also be used this project were Mr Hugh Rule, Mr Ivan Unkovich and Dr Richard as a virus indicator but fRNA phages and coliforms were no t good Lugg. The opinions expressed here are those of the authors and do indicators of enteric viruses. not necessarily reflect those of the steering committee, Water In contrast to the results for viruses, Lewis-Jones and Winkler Authority of Western Australia or Urban Water Research Association (1991) found that faecal streptococci were no t good indicators for of Australia. Salmonella as their susceptibility to sludge treatments varied. Yanko (1988) found that there were significant correlations between REFERENCES Salmonella and total coliforms, faecal coliforms and faecal streptococci. Linear regression was used to predict that Salmonella Art her R.G., Fitzgerald P.R . and Fox J.C. (1981). Parasite ova in anaerobically digested were below the detection limi t ( < 0 .2/g) when indicator sludge. Journal of the Water Pollution Control Federation, 53(8), 1334-1338. concentrations were below 240 MPN/ g, 43 MPN/g and 73 MPN /g Barbier D., Perrine D. , Duhamel G., Doublet R. and Georges P. (1990). Parasitic hazard with sewage sludge ap plied to land . Applied and Environmental Microbiology, for total coliforms, faecal coliforms and faecal streptococci 56(5) , 1420-1422. respectively. Berg G. and Berman D. (1 980) . Destruct ion by anaerobic mesophilicand thermophilic These studies indicate that faecal streptococci may be useful digestion of viruses and indicator bacteria indigeno us to domestic sludges. Applied 1 and Environmental Microbio logy, 39(2), 361-368. indicators of enteric virus densities in sludges. Faecal and total coli forms did not appear to be good indicators which suggests that Block J.C. (1986). Biological Hea lth Risk s of Sludge Disposal. In Epidemiological Studies of Risks Associated With the Agriculturol Use of Sewage Sludge: Knowledge E. coli may also be a poor indicator. However the results were not and Needs. Ed. by J.C. Block, A. H . Havelaar and P. L'Hermite, Elsevier Appli ed conclusive. No studies were found which examined the relationship Science Publishers, London and New York. between faecal indicators and parasites. This is an area where more Carrington E.G., Pike E.B., Auty D. and Morris R. (1991). Destruction of faecal bacteria, information is needed as the risk assessment suggested that Giardia enteroviruses and ova of parasites in wastewater sludge by aerobic thermophilic and anaerobic mesophilic digestion. Water Science and Technology, 24(2), 377-380. may be a pathogen of major concern in sludge. WATER February 1993

21


Clark C.S., Bjornson H.S., Schwartz-Fulton J. , Holland J.W. and Gartside P. S. (1984). Biological health risks associated with the co mposti ng of wastewater treatment plant sludge. Journal oft he Wa1er Pollution Control Federal ion, 56(12), 1269-1276 . DOE (1989). Code of Practice for Agricultural-Use ofSewage Sludge. HMSO, London. EC Panel (1986). Conclusions and recommendations from panel discussions. In Epidemiological Studies of R isks Associa1ed With the Agricultural Use of Sewage Sludge: Knowledge and Needs. Ed. by J.C. Block, A.H. Havelaar and P. L'Hermite, Elsevier Applied Science Publishers , London and New York. Fox J.C. and Fitzgerald P.R. (1977). Parasite content of municipal wastes from the Chicago area. Journal of Parasitology, 63, 68-69. Fradkin L. , lutkenhoff S., Stara J., Lomnitz E. and Cornaby B. (1985). Feasibility for performing a risk assessment on pathogens. Journal of the Water Pollution Control Federation , 57(12), 11 83-11 88 . Goyal S.M., Schaub S.A., Wellings F.M ., Berman D. , Glass J. S., Hurst C. J. , Braesher D.A., Sorber C.A., Moore B.E. , Bitton G., Gibbs P.H. and Farrah S.R. (1984). Round robin investigation of methods for recovering human enteric viruses fro m sludge. Applied and Environmental Microbiology, 48(3), 53 1-538. Hargreaves J. (1992). Annual report of the CDI 'Viruses' report ing scheme, 1991. Communicable Diseases Intelligence, 16(10), 206-221. Infectious Diseases Unit, Health Department Victoria. (1992). Surveillance of Notifiable Infect ious Diseases in Victoria. Hea lth Department Victoria . ISSN 1037-1532. Jak ubowski W. (1986). US EPA sponsored epidemiological studies of health effects associated with the treatment and disposal of wastewater and sewage sludge. In Epidemiological Studies of Risks Associated With the Agricultural Use of Sewage Sludge: Knowledge and Needs. Ed . by J.C. Block, A.H. Havelaar and P. L'Hermite, Elsevier Applied Science Publ ishers, London and New York. Jewell W.J., Kabrick R.M and Spega J.A. (1980). A uto heated Aerobic Thermophilic Digestion with Air Aeration. US EPA, Cincinnati, Ohio. R804636. Jones K., Betaieb M. and Telford D.R. (1990). Seasonal variation of thermophilic campylobacters in sewage sludge. Journal of Applied Bacteriology, 69, 185-189. Lewis-Jones R. and Winkler M. (1991). Sludge Parasites and Other Pathogens. Ellis Horwood, London , Sydney. Lue-Hing C., Sedita S.J. and Rao K.C. (1977). Viral and Bacterial Levels Resulting From the Land Application of Digested Sludge. Report No. 77-21. Metropolitan Sanitary District of Greater Chicago. Pederson D.C. (1981). Density Levels of Pathogenic Organisms in Municipal Wastewater Sludge -A Literature Review. US EPA, Cincinnati , Ohio. EPA- 600/ S2-81-170. Pike E.B. (1986). Recent UK research on incidence, transmission and control of Salmonella and parasitic ova in sludge. In Epidemiological Studies of Risks Associated With the Agricultural Use of Sewage Sludge: Knowledge and Needs. Ed. by J.C. Block, A .H. Havelaar and P. L'Hermite, Elsevier Applied Science Publishers, London and New York. Public Health and Enteric Diseases Unit of State Health Laboratory Services (1992). Western Australia n 1991 enteric pathogen report. Comm unicable Diseases Intelligence, 16(8), 154-159. Raska K., Helcl J., Jezek J. , Kubeika Z., Litov M., Novak D. , Radkovsky J., Sery V., Zejdl J. and Zikmud V. (1966). A milk-borne infectious hepatitis epidemic. Journal of Hygiene, Epidem iology, Microbiology and Immunology, 10, 413-428.

RIVER MURRAY SALINITY MITIGATION SCHEMES IN SOUTH AUSTRALIA by R J Newman We apologise to both the author and readers for the transposition of the captions on page 25, and the occlusion of the 'continuation from page 26 to page 36'. The graph labelled Fig. 4 should have the caption Fig. 2. The diagram labelled Fig. 2 should have the caption Fig. 3. The map labelled Fig. 3 should have the caption Fig. 4. The fo llowing References have been added to the paper. REFERENCES Co ll ingham E.B. (1986), Woolpund a Groundwater Interception Scheme; Geotechnical Report for disposal (of saline groundwater) to a basin at Stockyard Plain. EWS Dept 86/ 55. Collett A. (1987), Woolpunda Groundwater Interception Scheme; Report on River Flow and Salinit y studies, EWS Dept 87/ 45. Kinhill Engineers (1987), Woolpunda Groundwater Interception Scheme, Draft Environmental Impact Assessment. Murray-Darling Basin Ministerial Cou ncil (1988), Draft Salinity and Drainage Strategy, Discussion paper No. 1. Newman R.J. (1987), Woolpunda Groundwater Interception Scheme; Project Design Report, EWD Dept 87/ 46 . Social & Ecological Assessments (1989), Waikerie Salt Interception Scheme, Public Environmental Report. Telfer A . (1987), Woolpunda Groundwater Interception Scheme; Hydrogeology Executive Summary. EWS Dept 87/ 42 . Telfer A. (1989), Waikerie Salt Interception Scheme; Final design report, H ydrogeology. EWS Dept 90/ 14.

Reimers R .S., McDonnel D.B., Little M.D., Bowmann D.D., Englande A .J. and Henriques W.D. (1986). Effectiveness of wastewaler sludge treatment processes to inactivate parasites. Water Science and Technology, 18 , 397-404. Rose J.B. and Gerba C.P. (1991). Assessing potential hea lth risks from viruses and parasites in reclaimed water in Arizona and Florida, USA. Water Science and Technology, 23, 2091-2098. Russ C.F. and Yanko W.A . (1981). Factors affecting salmonellae repopulation in composted sludges. Applied and Environmental Microbiology, 41, 597-602. Schwartzbrod L. and Mathieu L. (1986) . Virus recovery from wastewater treatment plant sludges. Water Research, 20(8), 1011-1013 . Schwartzbrod J., Mathieu C., Thevenot M.T., Baradel J.M. and Schwartzbrod L. (1987) . Wastewater sludge: Parasitological and virological contamination. Water Science and Technology, 19(8) , 33-40. Shuval H.J., AdinA., Fattal B. , RawitzE. and Yekutiel P. (1986). Wastewater Irrigation in Developing Countries, Health Effects and Techn ical So lutions. World Bank Technical Paper Number 51, The World Bank, Washington D.C. Soares A .C., Gerba C.P., Josephson K.L and Pepper I.L. (1 992). Effect of anaero bic digestion on the occurre nce of enteroviruses, Giardia cysts and indicator bacteria in sewage sludge. Presented at IAWPRC Conference, Washington D.C., May. Stern G. and Farrell J.B. (1977). Sludge disinfection techniques. In Proc. of Na t. Conj on Composting of Municipal Residues and Sludges, Washington D.C. Information Transfer, Inc., Rockville, MD. Sykora J.L., Sorber C.A ., Jakubowski W., Casson L.W., Cavaghan P., Shapiro M.A. and Schott M.J. (1991). Distribution of Giardia cysts in wastewater. Water Science and Technology, 24(2), 187-192. US Environmental Protection Agency (1989a). Control of Pathogens in Municipal Wastewater Sludge for Land Application Under 40 CFR Part 257. US EPA, Cincinnati, Ohio. EPA/ 625/ 10-89/ 006. US Environmental Protection Agency (1 989b). Standards for the disposal of sewage sludge: Proposed rule. Federal Register, 54, 5746-5901. Yanko W.A . (1988). Occurrence of Ftlthogens in Distribution and Marketing Municipal Sludges. US EPA, Ci ncinnati, Ohio. EPA/ 600/ 1-87/ 014 .

AWWA-WMAA 2nd NATIONAL HAZARDOUS AND SOLID WASTE CONVENTION ACHIEVEMENTS AND CHALLENGES Melbourne May 8-11, 1994 CALL FOR PAPERS Technical Program, The technical program will focus on achievements and case studies, and the problems and challenges that remain. Abstracts are requested which address the following key issues relating to industrial, commercial and municipal wastes:

Hazardous Waste

• Solid Waste

• Waste minimisation, recycling, clean technology • Treatment and disposal technologies - biological treatment - options to incineration - problem wastes - emerging technologies

• Waste minimisation • Recyling - marketing, economics, collection , sorting • Resources recovery - materials and energy • Landfill sifting and operation • Pricing - collection, disposal • Regulations issues

• Control of air emissions • Obtaining environmental Contaminated Land approval • Risk assessment and site-specific • Community involvement solutions • Clean-up technologies • Government - regulations and role • Environmental auditing Typewritten abstracts, not exceeding 250 words, of proposed papers to be presented verbally or in poster session , must be received by the Convention Secretariat by 31 May 1993 . Abstract submittal forms available from Secretariat.

Deadlines 31 May 1993 Abst ract submittal Selected papers will be notified 30 August 1993 Final manuscripts by 18 December 1993 Convention Secretariat 2nd National Hazardous & Solid Waste Convention Secretariat PO Box 388, Artarmon NSW 2064 Telephone (02) 413 1288 Facsimile (02) 413 1047

Aquatic and Environment Chemistry Articles Wanted for August Supplement Th e August 1993 issues of Water and Chemistry in Australia wil l co ntain a joint suppl ement usin g th e successfu l format of the August 1992 su pplement. Th e editors are seekin g art icles and short items. Artic le titles and a short summ ary should be submi tted by Apri l 1 to Bob Swinto n (phone-fax (03) 560 4752) or Bru ce Gui se ph (052) 21 3294 Fax (052) 21 7971 . For ad vertis in g, co ntact th e AWWA Federal Sec retari at.

22

WATER Feb ru ary 1993


TECHNOLOGY

NEPEAN RESERVOIR DESTRATIFICATION by G. SCHLADOW, J. IMBERGER, J. PATTERSON and I. FISHER ABSTRACT The Nepean Reservoir has been used as a case study for artificial destratification. A new design methodology, founded on the behaviour of bubble-driven buoyant plumes rising in a stratified environment, identified a higher efficiency design than earlier empirical methods. The designed system was shown to effectively break down the thermal stratification in two successive summers. A two dimensional, simulation model of destratification gave excellent agreement with field measurements.

INTRODUCTION ¡Density stratification of water storage reservoirs is a common occurrence. When the duration of stratification is sufficiently long, oxygen depletion can occur in the hypolimnetic waters that have become isolated from the water surface. The consequences of this oxygen depletion can include the formation of iron and manganese compounds in solution and suspension, and the release of nutrients into the water from the sediment. Artificial destratification has been practised to counter the effects of density stratification. Bubble plume destratification is one of the more common methods used. Here, compressed air is forced through a diffuser located at depth in the reservoir. The rising columns of bubbles are accompanied by the entrainment of ambient water to form a combined bubble and water plume. When the buoyancy supplied by the bubbles is no longer sufficient to cause the heavier entrained water to rise, the plume sheds its excess heavy fluid which falls to an intermediate depth where it intrudes horizontally. It is through the rise of entrained water that the potential energy of the water column is increased, leading in time to the breakdown of the stratification. The Sydney Water Board currently operates approximately 12 storage reservoirs throughout the Sydney, Illawarra and Blue Mountains regions of New South Wales. One of these, Nepean Reservoir was selected by SWB as a case study for a detailed investigation into the use of aerators to assist in water quality management. The Centre for Water Research (CWR) at The University of Western Australia was commissioned by Sydney Water Board (SWB) to carry out the research and development program aimed at establishing a_sound basis for the design and operation of bubble plume destratification systems.

PROBLEM DEFINITION Nepean Reservoir, constructed in 1935, has experienced a number of water quality problems. These problems include oxygen depletion, high levels of manganese and iron in the supply and intermittent algal blooms, and are not dissimilar to those experienced in a number of other SWB storages. These problems have also been experienced in other parts of Australia and overseas. Aerator systems have been previously installed in other SWB storages (for example Avon Reservoir) in an attempt to destratify the reservoir over the summer months. These systems were designed without due reference to the dynamics of bubble plumes or to the local physical conditions. As a consequence, the designs have not been optimal.

SOLUTION METHODOWGY Nepean Reservoir was used as a case study to determine the most effective strategy to destratify the Board's water storages and then monitor and manage these storages in their destratified state. SWB, in consultation with CWR, instigated a program for the development, testing, implementation and monitoring of destratification strategies. The solution methodology consisted of defining component programs that would lead to an improved understanding of the physics of the destratification processes. These components were:

Geoff Schladow is a Senior Research Fellow at the Centre for Water Research, in the Department of Environmental Engineering, University of Western Australia. His research interests are in the area of environmental fluid mechanics. In recent years, he has been focusing on the study of processes that determine water quality and in developing computer models to represent them.

Ji>rg Imberger is a professor in the

Department of Environmental Engineering at the University of Western Australia and is Director of the Centre for Water Research and the Special Research Centre for Environmental Fluid Dynamics.

John Patterson is an Associate Professor in

the Department of Environmental Engineering at the University of Western Australia. His research interests include natural convection and the modelling of lakes and reservoirs. ,.

Jan Fisher is a Principal Scientist with

Australian Uilter Technologies, Science and Environment, the new trading name of the Sydney Water Board. He has been with the Board for five years, prior to which he was a Senior Lecturer in the Department of Resource Engineering, University of New England, NSW. He received his PhD from the University of Melbourne.

Laboratory experiments: Experimental research aimed at understanding the dynamics of the mixing processes associated with bubble plume entrainment in a stratified water column and its efficiency compared to other devices. Environmental monitoring: Ir.::allation of an extensive data collection network on Nepean Reservoir to provide essential data for the design and evaluation of the destratification system and validation of the model. The network included meteorological stations, water column profiling and inflow and outflow monitoring. Development of the simulation model: The development of the two dimensional (2D) DYRESM reservoir simulation model, incorporating destratification design routines was the central component of the research program. The associated development of a user interface will allow ready application to any reservoir in the Board's water storage network.

WATER February 1993

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Design of destratification systems: The aerator design, produced as part of the present project, was based on the understanding gained during the initial part of this project and refined from experience · gained from aerator design at other reservoirs. Performance monitoring: The destratification system installed in Nepean Reservoir has been monitored by the Board's AWT Science and Environment Division during the 1990/ 91 and 1991/92 summers, in order to evaluate its performance.

OBSERVATIONS The results presented in this paper relate primarily to the performance monitoring at Nepean Reservoir. The reservoir has a maximum depth of 63 m, a storage capacity of 70 170 ML and a surface area of 325 ha. The designed destratification system comprised two 150 Ls-1 compressors connected to a 75 mm polyethylene air distribution line. When destratification commenced the response was almost immediate, with hypolimnetic temperatures rising by as much as 0.1 °C each day. Surface layer temperatures declined, with a marked increase in temperature fluctuations, indicating the very active mixing associated with the bubble plumes. The mean lake temperature rose considerably as a result of the reduced heat loss from the surface. · Complete, sustained destratification occurred up to 2-1/2 months sooner than under normal conditions. Figure 1 illustrates these results. The numerical model DYRESM predicted the response of the lake to the meteorological forcing and the destratification . A comparison between measured and predicted results is shown in Figure 2. The measured results were taken from a thermistor chain located 500 m from the aerator.

60 50

50

I 40

40

z0 l;i JO

JO

~ 20

20 10

10

70 , - - - - - - - - - - --

- - --

-

- - - - --

-, 70 60 50

50

40

JO 20 10

10

oL-J--'-'-'-'-..w.._J_-1--LU......L--'-'-..ll....u..-'-'-.L...J.L-J--'--'-'-.L.l.-'-_.__u_,_Jo 0

60

120

180

240

DAYS SINCE 91256 (1J September, 1991)

Fig. 2 - Isotherms for the period 13 September 1991 to 16 February 1992 based on measured thermistor chain data (upper) and numerical model result (lower). Destratification was taking place intermittently throughout this period.

- 2m ·····34m 25.0

E ~

l

E ~

15.0 300.0

~ 0

~

0.0

5.0 1989

1990

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Time

• Both the one dimensional (ID) and two dimensional (2D) versions of the reservoir model DYRESM, including the new bubble plume sub-model, are complete. Comparisons of measured Nepean Reservoir data with model outputs for 1991/92 show excellent agreement. The ID model was proven to be satisfactory for the purpose of designing the aeration system. The 2D model, with its demonstrated ability to track the !notion of water masses, gives considerably better simulation results for elongated reservoirs such

Fig. 1 - Temperature traces at depths of 2 m and 34 m below the water surface (left axis) and free airflow rate (right axis) for the period monitored. (a)

Mixing was accomplished by the entrainment of fluid by the rising bubble plumes and the insertion of the mixed fluid about one or more levels in the density profile. Each intrusion drove a pair of circulation cells, which extended the length of the lake whenever a vertical density gradient persisted. This is shown schematically in Figure 3. The integral plume model used to describe the bubble plumes provided a good description of the evolution of the process of destratification, including the main features of this circulation . The entrainment pattern was such at Nepean, that there was a net transport of fluid from the surface layer to the hypolimnion, ie. there was net erosion at the base of the thermocline. As a consequence, the process of artificial destratification was characterised by the hypolimnion growing at the expense of the epilimnion. This was totally opposite to a natural lake overturn. Eventually when the temperature difference across the thermocline was sufficiently small , total lake mixing occurred. The thermal response of the Jake to removal of aeration differed depending on whether this occurred in the first or second half of summer. During the first half of summer, when the lake surface was cooling naturally, the destratified lake state was generally self maintaining .

PRINCIPAL RESULTS • The designed aerator effectively broke down the summer temperature stratification which developed during the 1990/ 91 summer in a period of approximately three weeks. During the 1991/92 summer, the aerator was run intermittently using both a long and short diffuser and was able. to maintain destratified conditions while being operated for only 46% of the time at the design air flow.

24

WATER February 1993

(b)

Fig. 3 - An inferred lake circulation resulting from artificial destratification. (a) No internal detrainment points. (b) One internal detrainment point.


as Nepean, and should prove to be valuable in future water quality studies. • A new aerator design methodology, founded on the behaviour of bubble-driven buoyant plumes rising in a stratified environment has been developed. This provides an estimate of the number of plumes, the air flow rate per plume and the spacing between plumes required to dismantle stratification in any reservoir at the optimum efficiency. The aerator configuration that can achieve both rapid destratification of a large temperature gradient, and use the minimum volume of air to maintain a destratified condition is considered to be the best design. This new approach is a major advance on earlier empirical approaches and leads to higher operating efficiencies. • The direct cost savings that can be realised through the use of a high efficiency design are very significant. With a more efficient design, both operating and capital costs would fall roughly in proportion to the gain in efficiency. If the water quality benefits of destratification are fully realised (for example, reductions in manganese concentrations) then the savings in costs of conventional chemical treatment are likely to be many times higher than the total cost of a destratification system. As the design methodologies are general, and can be applied to any reservoir regardless of depth or strength of stratification, substantial cost avings can now be readily extended to other reservoirs. • Technology transfer has been given a high priority in the present project. An intensive training course in the use of the DYRESM model was conducted at CWR in June 1990 and was attended by two of the Board's staff. A further training course was conducted at the Head Works Section of SWB in June 1992 to complete the project. • The incorporation of a "friendly" user interface for DYRESM has been completed. It includes bar selection menus and input data windows, extensive validation procedures for input data to guard against run time errors, extensive error diagnoses and recovery procedures, and interactive graphical output. This interface allows for a greatly reduced training time for new users of the model by making many of the processing steps invisible to the user and by allowing simulations to be run in an interactive mode.

CONCLUSIONS A bubble plume destratification system has been shown to be capable of rapidly breaking down the thermal stratification that develops in a temperate lake over the spring and summer. It can do this by virtue of the fact that on average the work performed by the bubble plume in mixing the water column is greater than the surface stratifying fluxes. It appeared to make little difference to the ultimate thermal state of the lake, whether destratification commenced early in the stratifying season and used intermittently as required, or used later in the season when the maximum thermal gradient had been established. There may, however, be important differences in respect of water quality parameters. A two dimensional model of the reservoir's thermal structure gave an excellent match to the observations. Destratification as an economical and effective means of alleviating water quality problems can now be applied to many water storages. The methodology to design such high efficiency systems has been pioneered at the Centre for Water Research and is now being used effectively around the world. ACKNOWLEDGMENTS Funding for this research was provided by the Sydney Water Board. George Kastl and Rod Frenda were responsible for the collection of the field data. The processing and verification of the data, together with the running of the model was due to the efforts of Kerry Greenwood. REFERENCES Asaeda, T. and Imberger, J. (1993) - Structures of bubble plumes in stratified environments. In press, J. Fluid Mech. Lemckert, C. and lmberger, J. (1993) - Bubble plumes in arbitrary stratification. In press, ASCE J. Hyd. Eng. Sch ladow, S. G. (1992a) - Bubble plume dynamics in a stratified medium and the implications for wa ter qualit y amelioration in lakes. f#iter Resources Research, 28 (2), 313 - 321. Schladow, S. G. (Ed.) (1992b) - Nepean Reservoir Destratification Project - Final Report. Report to Sydney Water Board. Centre for Water Research Report WP 662 GS. Sch ladow, S. G. (1993) - Lake destratification by bubble plume systems: A design methodology. In press, ASCE J. Hyd. Eng. Schladow, S. G. and Fisher, I. C. (1993) - the response ofremperate lakes 10 anificial destratification: Physical Limnology. Submitled to limnology and Oceanography.

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ENVIRONMENT THE ANZECC GUIDELINES FOR WATER QUALITY FORUM, 30 NOVEMBER -1 DECEMBER, 1992, CANBERRA A Report By MITCHELL LAGINESTRA The Forum was set up to enable discussion and presentation of different perspectives of the document released on November 30th . This report is a continuation of that published in the December issue of this Journal. After the introduction by Dr Ian Lambert, and the explanation of the rationale for the criteria by Professor Barry Hart (see previous report), the following speakers discussed their reactions from many different angles. Chris Bell, of the E.P.A. Victoria, was a major contributor to the document as chairman of the Advisory Committee. His address was Achieving Water Quality Outcomes. He said that the National Strategy has the overall objective of ecologically sustainable water management. Some would argue that the only means of achieving this are strong regulation and powerful enforcement capacity. In contrast there is the philosophy of the competitive market. The answer must lie somewhere between. We need legal standards where appropriate, and goals, guidelines and codes of practice where greater flexibility is desirable. The Strategy was initiated in part because of a community perception that Australia's water quality was deteriorating. It is difficult to say this with certainty. It has certainly changed since European settlement, the question is whether it is still deteriorating, and this can only be answered by analysing trends. In Victoria the monitoring network shows about twice as many increases as decreases in N and P concentrations, and this may well be the case nation-wide, but definite answers are not yet available. However, such data is meaningless unless compared with the values which the community places on its water bodies. Management cannot proceed without clear setting of objectives. Identification of .problems is easy, the difficulties arise in implementing options which reflect not only the environmental but also the social and economic objectives. Therefore the first step is public consultation . The next stage is to translate these desires into practical objectives. The Victorian system establishes State Environment Protection Policies for defined areas, on catchment basis. After research and consultation, the Government eventually sets out agreed beneficial uses, the necessary water quality objectives, and a catchment management plan developed to achieve them. In some cases, the reality that it is impracticable to attempt rehabilitation may well be accepted, in others that a stream should be restored to a higher level of protection. The ANZECC Guidelines are designed to provide reference values

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The catchment plan must address all contributory sources. The control process for point sources is a combination of Best Practice Environmental Management, Cleaner Production/ Waste Minimisation, Codes of Practice, and Technology. Benefit/ Cost analysis must be applied to unify economic and environmental goals. Control of point sources might reflect BACT, CAT, or a forcing formula, and for individual cases will take into account dispersion, interaction with other sources, cost effectiveness of further reduction, age of plant, and the plant's past history before licence conditions are set. However, the impact of diffuse sources is more difficult to control. For non-point sources, BPEM also applies, and this is assisted by the Landcare programs. Farmers do not want to lose their soil any more than the community wants it in the waterways. There are opportunities in new urban design, but existing areas may be too difficult to fix. This could lead to the need for further reductions in point sources, including diversion, closure or relocation of an industry. A relatively new approach is tradeoff of continuing discharge from the source in question with emissions from other sources whose reduction or elimination may be more cost-effective. However, management plans based on an assumed assimilative capacity may ignore low level accumulations which could lead to unacceptable ecosystem degradation. However, in a benefit/ cost analysis there is no figure which can be set for degradation, either of land or water. Internalising of externalities is still in its infancy, but the role of the 'market' in pollution permits, allied to taxes and charges, will assuredly grow. Chris concluded with a discussion of the different ways to act in the public arena, to attain the cooperation and interest of the public in clarifying the goals of 'ecologically sustainable water resources management'. It is still a long way off, although the Guidelines assist by defining parameters, and the tools are available for governments to use. Specific aspects of the possible impact of the Guidelines were discussed by other speakers. Ian Smalls, Principal Scientist of the Environment Branch of the NSW Department of Water Resources, in his paper Use of the Guidelines for Water Resources Management asked the questions: Why should we meet the Guidelines? How do we? and Can we? the last being the most difficult to answer. Management must identify pollutants, determine sources, forms and fate, relate consequences to causes, manage to reduce these consequences . . . and monitor success.

His examples concentrated on two issues which affect the Murray-Darling system, algae and pesticides. Community awareness has increased and Governments are being pushed into stricter regulations, but eutrophication is too multifaceted for a simplistic approach. The bluegreen algal blooms in the Darling made international headlines and had many economic ramifications. The cause was a combination of drought and high levels of nutrient inputs. Algal guidelines for human use of water are currently based on cell counts of 2000/ mL as an alert level, mainly for taste and odour, followed by a level of 15000/ mL for potential toxicity (domestic and stock). However, it would be more useful to have easy direct measurements of toxins or odours. Nutrient concentration guidelines are normally based on phosphorus concentrations, e.g. For clear lakes and reservoirs, 20 µ,g / L Clear running water 50 µ,g / L Turbid waters 100 µ,g / L Current information suggest that bluegreens prefer N/P ratios of less than 25:1. However, other factors such as climate, seasonal factors, morphology and sediments enter into the equation. Consideration of annual loads rather than spot concentrations would seem to lead to better catchment management strategies. Ian quoted the multi-pronged attack on eutrophication of the Carcoar Dam. Pesticides in the Upper Darling tributaries have become a matter for concern, and a mutual study program has been established, with particular emphasis on Endosulfan, used mainly for cotton. The ANZECC Guidelines suggest a limit of 0.01 µ,g/L, derived from North America, and this level is frequently being exceeded in the Darling system . Questions are: • Is this level derived from methods using older persistent pesticides? • If partitioning to sediments affects bioavailability, does this apply to the very turbid Australian rivers? • Are the Guidelines applicable, and achievable? If the answers are in the affirmative, than either Endosulfan must be retained on the land, or substituted by a more benign material. (The cotton industry is working on the former by instituting improved farm management practices). In both examples, a cooperative interaction between government and the community is leading to steady improvements. Guidelines interpreted as legally enforced Standards could be counterproductive. On Day 2, the opening address, Setting the Water Industry Scene, was by Neil


McDonald and June Maurer of t he Intergovernmental Relations Section of the DPIE, which has been involved in the AWRC and ANZECC Water Quality Management Strategy. The Strategy is integrated with the ANZECC Guidelines, which concentrate on the quality of the source and receiving waters, and the NHMRC Drinking Water Guidelines. (The outline of the Strategy was published in the December issue of this Journal.) The paper by John Cou rt discussed 'assimilative capacity' in terms of a different concept, the 'Water Quality Margin' (WQM) . John was for many years a principal manager in the SPCC, and chaired the NHMRC committees on Air and Water Quality. He is now op erat in g as a consultant. The paper was entitled Translating Water Quality Guidelines into Effl uent Requirements. He defined WQM as the

difference between the Objective and the poorest in-stream quality resulting from the discharge of an effluent, and using this concept he presented a logical discussion on the various options open to the community and its legislators. The Strategy objective is 'to achieve sustainable use ... while mai ntaining economic and social development'. In the current circumstances there is a tension between pursuit of improvement, or accommodation of degradation, and the economy. There are four possible approaches: • Total Protection . . . not even temporary increase in contamination, anywhere. The question is whether this ideal is desirable, or even realistic. • Progressive Improvement . .. application of improved technology and management, but allowing localised degradation in 'mixing zones'. The question is whether the overall improvement offsets the local · degradation. • Optimisation . . . some environmental benefits are foregone to realise desirable eco nomic benefits (th e dominant approach in recent times). The question is whether the trade-offs can be adequately assessed. • No Protection ... the approach in years gone by . .. no longer espoused. Setting Water Quality Objectives involves two elements: Environmental values (or beneficial uses) which become the Goals for specific water bodies ... a task of the Community. Quality Criteria , which become the quality objectives for the selected Goals ... the task of the scientists, as developed in the ANZECC Guidelines. There are some disadvantages in using such Objectives: • the uncertainties of the local scientific data. • they encourage WQM to be used to its limit. • they present problems in equitabl e a lloc ation to present and fu ture dischargers. (John drew attention to the need to address the aspect of the very variable flow of streams in Australia, a complex issue which needs considerable development, but has to be ignored for the present) .

The tools for achieving the Goals decided upon are: • regulation of point source effluents, by licensing quantity and concentration • for non-point pollution, the persuasive processes of TCM, and planning controls. However, a question still to be fully addressed in our Strategy is whether to focus on receiving water quality, or end-of-pipe effluent limits. After two decades, USA has decided to consider both, with a set of criteria for defining the relationship. The answer will depend on how close the receiving water is to its Goal. In this respect, the term 'assimilative capacity' may encompass both mere dilution and true assimilation (e.g. of BOD). The concept of Water Quality Margin, the difference between the Objective and the situation measured after mixing of the effluent into the water body, (in the case of an assimilating pollutant, at its peak in the stream), is a neutral term and does not imply that the environment is there to be used for treatment of a discharge. John then discussed at length the question of whether the Guidelines should be applied as 'black letter law' or as advisory criteria. Probably the optimum in Australia would be to adopt: • goals and objectives for the ambient, which carry some legal obligation 'to be taken account or in granting approvals for discharges or activities • te chnolo gy- base d regu lations for discharges, with 'black letter' licences. Technology-based li cences mu st be technically achievable, and enforceable by prosecution . They can apply state-wide or be catchment-speci fic, general or industry specific.. Advantages: They are unambiguous, and enforceable, they are perceived as providing a 'level playing field' , and if based on BATEA or BMP they can lead to progressive improvement. Disadvantages: They bear no relation to the condition of the receiving waters, so in some cases could lead to degradation, they may incur costs not justified by benefits, they limit the scope for flexibility. John then discussed at length the various concepts for putting the Guidelines into practice, to protect or improve a receiving water. His recommendations were: • New effluent or run-off should not cause Objectives to be exceeded ... but offsets could be considered . • If the WQM is already negative, i.e. worse than the Objective, then no discharge should be allowed without a corresponding, or better, offset. • Priority should be given to reducing existing negative WQM situations. • Positive WQM should be managed in a precautionary manner. • Both direct regulation and economic incentives to be used. • Waste Minimisation and Resource recovery to be pursued at source. Failure to develop adequate institutional, regulatory and policy responses at all levels of Government could leave the National Water Quality Strategy as mere bureaucratic

prose. The next stens should be to : • a dopt the m ecJ-iani sms for se tting Goals/ Objectives as Jaw • adopt a mechanism for relating effluent limits to Objectives • translate the various AWRC Guidelines into regulations • develop catchment management for nonpoint sources Ian Lawrence is the Principal Environmental Planner for ACT, and he spoke of Alternative Mechanisms, aimed at Catchment Management Strategy. TCM involves co-ordinated use of land and water to ensure minimal degradation of soils, water quality and ecology. The issues include not only determination of the appropriate discharge standards and best management practices, but also the relative contributions to pollutant loadings, and the social equity and economic implications of allocations across all the activities in the catchment. TCM requires a systematic analysis in order to determine the environmental values, and resolution of potential conflicts. The analysis will need to incorporate: • inventory of bio-physical components • analysis of impacts on the ecosystem • distribution of benefits and costs across communities • opportunity costs in respect of future generations • prediction of performance in short and long term • consideration of confidence, risk and irreversibility. In discussing the sustainability of a waterway he presented the example of the complexity of nutrient transport, which involves internal recycling and mediation in both sediments and biomass. In particular, event-based systems are very difficult to assess, given time lags, antecedent factors and other contributors. To determine sustainable limits three methods are available: A systems approach is difficult because we still do not have full understanding of geomorphological and ecological processes. A comparison between similar water bodies, or different reaches of the same stream, but with different inputs, can yield a pragmatic guide. Trend analysis requires long-term data, which may not be available for a particular decision , but will be needed for review. The options available for application of a TCM strategy comprise: • Limit or constrain certain land uses, either by prohibition or restriction in location • Modify management practices, including technical , economic and administrative control over discharges • Improve levels of comp li ance and performance • Review appropriateness of the chosen environmental values from time to time. Decisi ons will comprise a mix of solutions, guided by cost-effectiveness, social equi ty, community acceptance, technical and financial viability, and administrative and political viability. Ian's full paper deals with each of these aspects in detail, including institutional planning, strategic planning, social and

WATER February 1993

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economic issues, administrative considerations and consultation strategies. Finally he stated that there is the need for clear documentation, developed in association with all the agencies and groups within the catchment, to ensure effective implementation, together with the need for a joint monitoring program and periodic review. The follo\ving papers expressed concern on the method of application of the Guidelines. Dr Harley Wright is the Environment Manager for the paper company Kimberley Clark. For the previous seven years he was the manager of the Chemicals and Wastes Section of the NSW State Pollution Control Commission. His paper was entitled Minimising Risks and Costs with Impact Assessment and Tradeable Permits.

He argued that the approach of 'Best Practicable Means', (which has become BATEA), imposes standards which are based on technology, (and commercial economics) not on environmental impacts. His paper developed the toxicological approach, embodying the concepts of assimilative capacity, degradation, movement into sinks, including bioconcentration, and dynamic equilibria. Use of these concepts should allow management of discharges to avoid any unacceptable harm, with the flexibility to choose the pollution control technology which bests suits a particular situation. Adding the concept of tradeable permits, where applicable, should minimise the total cost to society of achieving a targeted level of control, since companies could have the option between purchasing permits from other sources, or investing in more expensive technology. Ecotoxicity measurements on sensitive biota can be translated into environmental criteria, by applying appropriate safety factors, which can range from 10 to 1000 depending on the reliability of the data. More often than not environmental criteria tend to be set at the 'No Observable Effect Level', but statistics show that however negligible, there can never be a zero risk. With industrial discharges, benefits demanded by the community have to be paid for by the company. Setting excessively stringent criteria can impose excessive costs, which are ultimately borne by the wider community in terms of increased prices, or closure of the business, yet with negligible benefit to the local community. Discharge criteria and the concept of tradeable permits must also depend on the type of pollutant. These can be classified as dilutable, degradable, conserved, nonconserved, bio-concentrating, complexing and partitioning. The philosophy in USA on point discharges to freshwater streams is that even within the mixing zone, the effluent must not reach the LC 50 of the grazer Ceriodaphnia magna, whatever the downstream dilution. BOD, signifying organic substances which are oxidised rapidly, is by definition degradable, as well as dilutable, and the natural assimilative capacity of a receiving water can be utilised by careful management. (He quoted a case in USA where a paper mill discharging secondary effluent (15 mg/ L BOD) into a hydro-power river is permitted to oxygenate the river upstream

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of the discharge to ensure that oxygen sag does not occur during periods of low DO). BOD is one pollutant where the concept of tradeable permits can easily be applied should there be several discharges competing for the assimilative capacity. Salt is a conserved substance, and is a prime concern in the Murray-Darling system. Since it remains in solution, it eventually is discharged to the sea, but since the river has to be utilised for irrigation and domestic supply, the present levels in the river must be reduced. Since salt is neither bound nor lost in the system, its environmental impairment can be reasonably estimated. The salinity credit strategy being tried is an application of economic trading to ensure that total community resources are applied to salinity interception schemes, which show the highest benefit/ cost ratios. Phosphorus is a 'sticky' pollutant, i.e. it can transfer into and out of sediments and biomass, which makes its immediate impairment difficult to estimate. However, a tradeable credit system is being tried in Colorado, where credits may be earned for measures to reduce, as well as point discharges, diffuse sources. However, because of the uncertainties, the latter only earn half points. Toxic materials include both inorganics such as heavy metals and arsenic, and organics which either do not degrade rapidly, or are bioconcentrated. In this case, the aggregate load on the river has to be managed, irrespective of distance between discharges. Trading is not applicable except between similar sources. For both 'sticky' and bioconcentrating substances it is essential to establish a monitoring program to maintain an open decision-making framework. His conclusion was that given that care and caution are used in selecting ambient criteria, there is usually an assimilative capacity for single or multiple discharges of like substances. When feasible, this allows the concept of tradeable permits to meet society's environmental goals in a least-cost manner. Harvey Baker, Environmental Director of the Australian Cotton Foundation, spoke on the Cotton Industry's perspective. The industry had received adverse media attention during the algal bloom episode in the Darling, with much of the blame placed upon it. He expressed concern about lack of involvement in the drafting of the Guidelines, and was worried that some of the criteria would become standards. For example, the current guidelines for pesticides are chemically/analytically unattainable. Endosulfan is pivotal to the industry, and allows continuation of predator/prey relationships in insect control, but it kills fish at 0.1 Âľg /L. The guidelines require a limit of one tenth of this, which he maintained is below the limit of detection. None the less, the industry is aiming for BPM, and having achieved containment of excess irrigation water on the farms, is setting the pace for other agriculture. Much money is being spent on monitoring, and research into new pesticides to lessen environmental impact. He concluded that guidelines are of benefit, but setting of goals should be on the basis of both economic factors and sound ecological data.

THE WORKSHOPS Workshops were held during the conference. The first was devoted to Interpretation of the Guidelines. There was some discussion of the definition of 'ambient' when referring to highly modified systems . There are differences due to geography, seasonal variation, designated use / protection valu es, morphology, variability, species present/ecosystem and the extent of the current disturbance. It was noted that in the USA, all waters must be swimmab le and fishable, minimum standards for designated use are set nationally, and driven by discharge permits. In Australia, the Guidelines set national goals, with the aim being to standardise discharge practices. It was felt that every State and Territory should adopt the same standards. Hopefully the Guidelines should foster this. However, the rationale of setting standards, when performed by the States, is more important than the specific numbers. The signing of an intergovernmental agreement by the State Premiers gives the power to the NEPA to over-ride some local aspects. Workshop 2 addressed application of Guideline values. One success story was Albany Harbour, where values from the draft were applied, and because of their legitimacy, local dischargers agreed to reduce pollution accordingly. There was some discussion on parameters employed for heavy metals, set because of their conservative nature. However, since costs for rehabilitation would be excessive, precaution should be applied. The use of biological indicators in Australia is still in its infancy. Definitions of number of samples and acceptable variations in diversity are still not decided. Geoff Noonan of the EPA of NSW guaranteed that the Guidelines would become standards, and his authority is studying how best to incorporate them into a legal framework. However, there was considerable discussion on the appriateness of single values for national application, in view of the wide variations in climate, etc. The local community must be involved. However, if this proves ineffective, or even too expensive, then the national Guidelines should apply. The final workshop addressed different approaches to water quality management. In view of the hot debates if prosecution is adopted, it was asked if there was a more productive method of resolving problems. Total loading for cumulative effects, and partnership solutions were tabled . It was accepted that point sources are easier to regulate, whereas for the Darling River, 50% of nutrients came from diffuse sources. Financial incentives were discussed. In Victoria, licence fees are directly related to licence limits. In USA, the EPA is not allowed to give financial incentives, but it has been found that publication by the EPA of a success story in the media has indirect benefits to the company concerned. The conference organisers expressed the hope that the Guidelines would be recognised as such, not as immutable standards, given the problems of definition of effects, the natural variability of waters in a huge continent, and the many societal factors involved.


TECHNOLOGY

ION-EXCHANGE AND ADSORPTION A Brief History of Some CSIRO Developments in Water and Effluent Technology A Report by BOB SWINTON INTRODUCTION Dr D E Weiss, who served as President of AWWA Victorian Branch in 1973-4, President of IAWPR, Australian National Committee, in 1979, and as Australian President of RACI in 1983, retired from CSIRO in 1984. He was the intellectual dynamo who led the CSIRO team which invented Sirotherm, Sirofloc and other processes for treating, not only water, but mineral processing streams. In July 1992, after many other honours, he was accorded an award by the Solvent Extraction and Ion Exchange Group of the UK Society of Chemical Industry, 'in recognition of his innovative work in the field of ion-exchange technology and its application in practice'. Later, at a special function in Melbourne, with the RACI, the SCIV, AAS, AATS&E, Dr. Weiss reminisced on the 40 years of his research career, and paid particular thanks to his ex-colleagues at CSIRO, and to the many industrial collaborators, including the Water Authority of Western Australia (WAWA) . This article is an edited version of his address. His theme was that a string of seemingly unrelated inventions had, in fact, a continuous and evolving thread which was applied according to the needs of the time, and that close contact with the leaders of the chemical, mineral and water industries provided the stimuli for commercial application.

EARLY WORK -

ADSORPTION

On graduation from the University of Adelaide, in 1945, his first job was as shift chemist at APPM, Burnie, where his attention from production was distracted by observing the separation of various dyes in the foams below the paper machines. Despite his lack of formal post-graduate research training, he decided to leave production for research, and after a one ;ear stint at Commonwealth Serum Laboratories, he applied for a job at the CSIR Division of Industrial Chemistry, then led by Dirk Zeidler, (later to be knighted as the Chairman of ICI Australia). He accompanied his application with a suggestion, and a cardboard model, of a multistage centrifuge for the extraction of penicillin broth. (This idea was later developed independently overseas). However, on starting at CSIR he concentrated on developing that chance observation of fractionation in foam into a usable process. With active involvement from his previous employer, CSL, he developed a process whereby activated carbon was treated to become, in effect, an ion exchanger 1• When this was incorporated into a foam, as in mineral flotation 3 , he showed that it could extract streptomycin reversibly. Later, instead of using a foam, the activated carbon was coated over the surfaces of discrete bubbles of air, which floated up a column against a rapid downflow of broth, thus achieving countercurrent extraction 2 • Further development replaced the air bubbles by coarse quartz particles, coated with water-wet diatomaceous earth, held tenaciously by surface forces 4 • Moving a bed of this material down against a rising flow of solvent enabled countercurrent purification of crude penicillin, similar to fractional distillation. To move the bed of particles steadily against the upflow, the principle of the mineral dressing jig was used, whereby a pulsation was applied to the upflow, generating a semi-fluidised, but non-turbulent, bed 5 •

ION-EXCHANGE This valuable property was then applied to ion-exchange, and a continuous water softening system was developed 6 • When this was demonstrated to delegates from the Fifth Empire Mining Congress in Melbourne in the early 50s, some rapid negotiation led to a security clearance and a visit to some uranium extraction plants operating

in the Colorado desert, using ion exchange. Dr. Weiss was informed of the need for a better technology for extracting the uranium from an unfiltered leach liquor. With support from Conzinc Riotinto, a pilot plant was developed and satisfactorily demonstrated the ability to pass a desanded slurry, containing 20% w/ w of slimes, countercurrently through a pulsated bed of ion exchange resin 7•8 • The process was patented and licensed to Permutit, U.K. , who built a full -scale, 1.2 m diameter plant in London, then erected it at the uranium mine in Rum Jungle, NT. Despite frantic efforts by a joint team, it failed to work satisfactorily by the appointed deadline. In the quiet fortnight which followed, the cause was traced to a minor change in the system, instituted in London for reasons of economy, which caused air to enter the system and attenuate the pulsation. However, the work thus begun continued elsewhere, in both Russia and Japan. Asahi developed from it the first commercially successful continuous ion-exchange process for boiler feed and industrial water treatment. A similar project, supported by Comalco for their Wei pa project, proved that a slurry of lime passed through a bed of ion exchange was capable of producing dilute caustic soda solution without the concomitant chlorine9, but concentration proved to be too expensive. A project supported by APM showed that it was feasible to recover sodium sulfite from certain pulping effluents, and thus reduce the salinity of the effluent.

DESALINATION Attention then switched to the use o ion-exchange for desalination of brackish water in saline catchment areas, such as Western Australia, and of saline effluents to permit re-use. What was required was replacement of the expensive, and polluting, regenerant chemicals by a physical system, such as electricity or heat 10 • Following on active carbon studies 11, concentration on electrical regeneration, in conjunction with Union Carbide Australia, led to the pioneering synthesis of polymers which were good conductors of electricity 12 . However, they could not be applied for desalination 13, so the emphasis shifted to regeneration by heat. A clue was obtained from a study of biological processes where cell energy is used to move substances against concentration gradients (a relevant example being the ability of sea birds to perform desalination). Observation of changes in pKa in a basic dye attached to a protein 14 led to realisation that organic bases show marked changes in basicity with increasing temperature. From this emerged the concept of the 'Sirotherm' process, whereby salt is extracted from brackish water by a mixture of weak acid and certain weak base resins, which are then rinsed with hot water. Heating the weak base changes its basicity causing the adsorbed ions to be released as a more concentrated effluent. The first laboratory results, in 1962, using various combinations of resins, showed only a small thermal effect. Predicting behaviour by matching the titration curves of individual resins made systematic study feasible. By this means a breakthrough was achieved. Utilising commercial resins, and synthesising others, combinations of resins were devised which had acceptable working capacity 15 • However, the process, utilising mixtures of resins with bead sizes designed for fixed bed plants, was far too slow. It needed to be at least a hundredfold faster. When the resins were ground very fine, the transfer of the vital hydrogen ions between the acid particles and the basic particles did proceed at an acceptable rate, but the hydraulics were quite impracticable. The solution adopted was the 'plum pudding resin'.

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The active resins in micron size, were 'plums' dispersed within a porous matrix, the 'pudding' of an inert but water-permeable polymer formed into beads of the standard size 16 •

THE 'SIROIHERM PROCESS' ICI Australia then became an active collaborator, lending their expertise in radiation polymerisation, and later, catalytic polymerisation, to manufacture the preferred polytriallylamine and polyacrylic acid particles in micron sizes. Under contract, the AEC, AMDEL, the University of Adelaide and RMIT in Melbourne became involved. After much work, and testing, pilot batches of the plum pudding resin were manufactured , sufficient to operate a fixed bed pilot plant. In 1970, with the co-operation of the Water Authority of Western Australia, this was installed at a bore in Perth. It ran for some months, and showed that alkaline waters can be treated 17 • CSIRO and ICI co-operated to commercialise the process, with negotiations proceeding in Japan, Europe and USA. The Water Reuse Centre in Tokyo successfully operated a fixed-bed pilot plant for the partial desalination of sewage effluent, and in 1976 ICI operated the first commercial plant at its Osborne factory, as a precursor for boiler feed treatment 15 . Unfortunately, the second OPEC crisis and subsequent world recession stopped the project. Important improvements, the need for which were indicated by experience at Osborn, were not commercialised. Improved thermal stability was achieved through resin modification. The porous inert matrix was dispensed with thus simplifying resin production and improving working capacity 18 • However, the development of a continuous process using magnetic micro-resins was continued. (During the late 60s an alternative process to thermal regeneration was explored in the laboratory. In the 'Sirocarb' system, a mixture of weak acid carboxylic resins and Type II strong base resins could be regenerated by a solution of carbon dioxide at quite low pressures, but this process was never scaled up 21) .

WATER PURIFICATION PROGRAM About this time, the Water Purification Program was formed with interests steadily extending beyond desalination into all aspects of water and wastewater treatment. Dr Weiss became the Chief of the Division of Chemical Technology, including this Program, which became the responsibility of Dr B A Bolto.

MAGNETIC MICRO-RESINS Work continued in the laboratories of CSIRO and ICI Australia on the development of magnetic resins. The concept had first arisen during a period of co-operative research with Union Carbide Australia in the mid-60s, before ICI Australia became the sponsor of the Sirotherm project. The concept was to achieve rapid reaction rates by using microbeads of resins, each bead containing a proportion of a magnetic oxide. After dispersion in the reaction medium, they could be flocculated by magnetism, and recovered for regeneration far more rapidly than by normal gravity sedimentation21 •19 . In collaborative work a number of such resins were prepared and evaluated, for use in Sirotherm, dealkalisation of water, recovery of heavy metals from mineral solutions 31 , colour from pulping effluents, and even in food processing, in a joint project with Kraft Australia 19 • 'Whisker resins', where the active component was grafted on to surface of inert magnetic beads, were much faster, and suitable for use with colloids, but had low capacity 19 .

CONTINUOUS ION-EXCHANGE Utilising such resins, a practicable continuous ion-exchange process was developed, and after pilot plant investigation at ICI's Deer Park factory, a demonstration plant was designed by Davy McKee, and with the co-operation of WAWA, but financed by DITAC, erected in Leederville, where it demonstrated that a continuous Sirotherm process could operate, provided that the pretreatment system for removal of divalent ions, which was a countercurrent regeneration fixed-bed ion exchange process, could be maintained at high efficiency 20 .

A beginning arose from earlier exploratory work associated with magnetic resins when it was shown that gamma iron oxide, which was the magnetic component of the resins, could adsorb colour from acid waters and release it under alkaline conditions 21 • Gamma iron oxide by itself is so magnetic that once magnetised, it is impossible to re-disperse, but the idea of developing special magnetic resins which could reversibly adsorb colour and turbidity was born. A whisker resin with a surface coating of an aluminium complex achieved this but regeneration by brine was expensive23 . A cheaper system utilised ordinary magnetite, which can readily be magnetised and demagnetised, so finely ground particles were coated by a layer of precipitated iron oxide gel, which had the same charge behaviour of gamma oxide. This adsorbed colour, micro-organisms, and clay particles at pH 6, and released them at pH 10. However, the gel wore off during repeated cyclesM. It was then discovered that it was only necessary to pre-treat the surface of the magnetite particles with alkali to develop a surface which changed to therequired positive charge below pH 7, but to ally this with small amounts of inorganic or organic flocculants. The finely ground magnetite particles, when passed through a magnetic field , clump together and settle out in a far smaller clarifier than for conventional flocculation. The slurry is then stripped with weak alkali in a system of magnetic drums, and the magnetite returned for re-use 22 ,25 • From these findings the 'Sirofloc' process emerged on a laboratory scale 22 •26 ·27 . With strong encouragement from WAWA it was first successfully demonstrated, after pilot plant and further physical chemistry studies28 , in a commercial plant at Mirrabooka, built by Austep in 1981, with the co-operation of WAWA. The process has since been further improved and is in operation in a number of plants both in Australia and abroad 19•29 • It has also been applied to sewage treatment 30 and to recovery of heavy metals from mineral processing effluents 19,31 •

SUMMARY Thus the CSIRO team, initially under the leadership of Dr D E Weiss, and later, of Dr BA Bolto, has shown that ion-exchange and adsorption processes • can operate continuously with fine or standard size resins • can directly process slurries as well as elarified solutions • can operate in systems with electron-conducting, as well as insulating polymeric networks • can be regenerated by heat instead of acid and alkali • can process particulates and co+loids as well as soluble ions The thread has continued from antibiotics to water and sewage treatment, based on the application of active materials in particulate form . The role of Dr Weiss until the late 70s was not only as the leader of a research team, and as a fount of ideas, but also as an entrepreneur, ever alert to opportunity, and skilful at finding collaborators for commercial development. Currently, in the Division of Chemicals and Polymers, what is now termed the Water and Wastewater Treatment Program headed by Dr Bolto, is still active in ion exchange and adsorption technology, but the activities of the group have expanded into many other fields of water and waste technology, such as nutrient removal by biological means, the biodegradation of industrial effluents, dispersed air flotation and the recovery of coagulant from sludges.

SELECTED REFERENCES I. 2. 3. 4. 5. 6. 7. 8. 9. IO. II. 12. 13 . 14. 15. 16.

COWUR AND TURBIDITY Attention then switched in the mid· 70s to finding a better process for removing colour and turbidity from ground apd surface waters.

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D. G. D. D. D.

E. Weiss, Discuss. Faraday Soc. No.7, 1949, pp. 142- 151. Moir, M. Ross and D. E. Weiss, Aust. J. Appl. Sci., 1953, 4, pp. 543 - 551. E. Weiss, Proc. Royal Aust. C hem. Inst. , 1967, 34, pp. 261- 271. W. Minty, M. Ross a nd D. E . Weiss, Aust. J. Appl. Sci., 1953, 4, pp. 519-529. W. Minty, R . McNeill, M . Ross, E . A. Swinton and D. E. Weiss, Aust. J. Appl. Sci., 1953, 4, pp. 530-542 . R. McNeill, E. A. Swinton a nd D. E. Weiss, J. Metals N.Y., 1953, 7, pp. 912- 921. E. A. Swinton and D. E . Weiss, Aust. J. Appl. Sci., 1956, 7, pp. 98- 112. T. V. Arden, J. E. Davis, G. L. H erwig, R. M. Stewart, E. A. Swinton and D. E. Weiss, Proc. U.N. Int. Conf. Peaceful Uses Atomic Energy (2nd) Geneva, 1958, 3, pp. 396- 414. G. L. Herwig, E. A. Swinton and D. E. Weiss,Aust. J. Appl. Sci., 1963, 14, pp. l-21. D. E. Weiss, 8.A. 8olto, R. McNeill, A. S. MacPherson, R . Suidak, E . A. Swinton and D. Willis, J. Inst. Eng. Aust., 1965, 37, pp. 193- 199. V. A. Garten a nd D. E . Weiss, Rev. Pure Appl. Chem., 1957, 7, pp. 69-122. R. McNeill a nd D. E . Weiss, Aust. J. Chem., 1959, 12, pp. 643-656. A. S. MacPherson, R. Suidak, D. E. Weiss and D. Willis, Aust. J. Chem., 1965, 18, pp. 493 - 505. M . Klot z and V. H. Stryker, J. Am. Chem. Soc., 1960, 82, pp. 5169- 5172. 8. A. 8olto a nd D. E. Weiss, "Prog. in Ion Exchange and Solvent Extraction" Vol. 7, J. Marinsky and Y. Marcus, Marcel Dekker, New York, 1976 , pp. 221-289'. 8. A. 8olto, A. F. G. Cope, G. K. Stephens and D. E . Weiss, Proc. Soc. C hem. Ind . Conf. "Theory and Practice of Ion Exchange", Cambridge, U.K., Jul y 1976, pp. 29 .1-29. 11.

continued on page 35


TECHNOLOGY

WETLAND SYSTEMS IN WATER POLWTION CONTROL The IAWQ Conference, Sydney, 30 November-3 December, 1992 A report by Lance Bowen As reported in the December issue, this conference held at the University of New South Wales, was attended by nearly 300 registrants.

OPENING The Chairman of the Conference Committee, Professor David Pilgrim, welcomed delegates and guests to the Conference and introduced the official party. Mr Chris Davis, Executive Director of the Australian water and wastewater Association, drew attention to the current trend to favour natural treatment systems and this ¡ Conference was very timely and was well supported by the number of registrants. Professor Bert Lijklema, Vice-President of the International Association on Water Quality, described the range of Specialist Groups now operating, ie, over 30, and how these were operating conference and seminar programs to meet real water quality needs. Dr Hans Brix, Chairman of the Specialist Group, explained the operating principles of the Specialist Group and related his experiences in Australia whilst on a six month working experience in Australia some two years ago. Professor John Niland, ViceChancellor and Chairman of the NSW Environmental Protection Authori ty, welcomed the Conference to the University and pointed out that the University had been involved in environmental matters for many years and was running a variety of appropriate post graduate courses including Environmental Engineering. It was also the initiator and the host of the new Co-Operative Research Centre for Waste Management and Pollution Control involving some 14 partners. Ms Penny Wensley, Australian Ambassador for the Environment, who headed the Australian delegation to the recent Rio Conference, explained the co-operative efforts at the conference by the 178 countries represented. She explained that water quality was essential for a variety of uses, Australia being the 2nd driest continent, related the events of 1835 when Melbourne was stricken by epidemics of cholera and typhoid due to pollution of the Yarra and how this was eventually resolved by the construction of Werribee Farm, which is stocked with 13 500 cattle and 6000 sheep and which has international status as a bird sanctuary and wetland. She highlighted the importance of water quality in inland Australia by referring to the 1991 cyanobacterial bloom in the Darling River which made international headlines. The current efforts to redress water pollution could be traced to the Stockholm Summit in 1972 leading to the concept of sustainable development dealt with at the Rio Summit, in particular, and to the 800 page Agenda 21. Issues highlighted in this document include the importance of water resources, pollution of the seas by sources on the land, management of solid wastes and toxic and hazardous materials. All these had relevance to the Wetlands Conference. It was clear from the general agreement reached at the Conference that there would be international cooperation on an unprecedented scale and much practical work was necessary to achieve the goals identified at the Conference. This Wetlands Conference was an excellent example of international cooperation and technology transfer on a natural method of treatment leading to recycling of a valuable resource. Wetlands appeared to have widespread application to developing countries in providing safe handling of wastes. Ms. Wensley concluded by saying that she was honoured to be invited to speak at the Conference and congratulated all those involved.

KEYNOTE SPEAKERS A number of keynote speakers had been invited to the Conference to focus the attention of delegates on particular topics, these included Professor Richard Kadlec from the University of Michigan. He presented a perspective of where the technology of constructed wetlands for water purification had been (identifying those mistakes made along the way), where the technology was at the moment and where it was headed. He emphasised that we were moving from what

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he described as a 'transposed digit' method of system design to a more rational design basis with a solid foundation. He pointed out how different this was to the early attitude to wetlands where they were likely to be filled in, drained, filled with garbage or loaded with poorly or untreated liquid wastes. Dr Hans Brix, Chairman of the Specialist Group, provided a review of the European wetlands scene where several hundred constructed wetlands were in use for the treatment of municipal wastewater, most were soil based sub-surface horizontal flow systems planted with reeds but surface and, more recently, vertical flow systems had also been constructed. The treatment efficiency for surface flow systems was good for BOD and SS at 20 m2 PE-1, for sub-surface at 10 m 2 PE-1 but nutrient removal was low and nitrification was marginal. Newer designs of vertical flow systems with intermittent flow were able to fully nitrify at 5 m 2 PE-1â&#x20AC;˘ Phosphorus removal could be obtained by careful selection of a medium with a high P-binding capacity or by adding chemicals, Al, Fe or Ca salts. Denitrification could be obtained by passing nitrified effluent from vertical flow beds through sub-surface beds. Constructed wetlands have direct application to European countries that have no or very poor treatment of municipal wastewater from the smaller villages with limited funds. Associate Professor John Bavor, University of Western Sydney, Hawkesbury, reviewed developments in constructed wetlands in Australia, including a range of wetland formats which were proving successful for treatment of effluents and in urban and rural runoff management applications. The development of high efficiency, 'reduced footprint', formats was the aim of a number of groups and progress was being made in applications in the urban cityscape context. The use of larger surface flow systems was discussed and illustrated in the utilisation of uch systems in coastal areas, particularly where natural treatment methods were preferred by local residents. Both treatment reliability and efficient buffer capacity were required in these situations, an example of this was the large experimental system at Byron Bay. Dr Donald Hammer, Tennessee Valley Authority, provided an overview of the performance of a number of constructed wetlands in the USA and the reasons why many of them had not maintained their initial performance. This was due, in his view, to a poor understanding by the designers of the importance of long term hydraulic conductivity, particularly for sub-surface flow systems. This was due to incorrect selection of the media used, insufficient attention to the hydraulic gradients used and to ignorance of the biological fouling of the surfaces of the medium used. In spite of this there were many systems which had been successfully operating for up to 20 years and a detailed study of these could provide guidance on how to achieve more consistent performance and a longer operating life. Professor George Tchobanoglous, University of California at Davis , presented a thought provoking discussion on the appropriateness of a number of 'lumped' parameters which were routinely used in the design and evaluation of constructed wetland treatment s stems. He questioned the reliance on traditional parameters such as BOD and SS, highlighting the relatively arbitrary nature of the determinations. A range of 'novel' or alternative design parameters, such as RACOD or specific organic compounds was suggested, he emphasised that the future of constructed wetlands The Wetlands forum: 'Woody' Reed, with Hans Brix, Don Hammer, Bob Kadlec


depended on a better understanding of the processes occurring within the wetlands themselves. Plants act to manipulate their environment to their own best advantage, they cause turbulence and will only grow to the extent that they get what they want. Other issues raised ¡ included the use of retardation theory rather than the use of first order kinetics, process control strategies, stability analysis and statistical approaches - looking at the probability of pollutant levels being exceeded rather than lumped efficiency levels. Professor Peter Cullen, University of Canberra, raised the issue of the still largely experimental nature of wetlands for wastewater treatment. Within this context wetlands should be only used where they were appropriate. He made the distinction between pulsed and continuously operating systems, ie, urban drainage versus municipal wastewater treatment. There are still a number of critical questions that need to be answered with regard to wetland design, use and understanding of the processes occurring within them. Questions that need answering include: are wetlands a sink for nutrients or merely a reservoir? what is the true role of plants? how important are factors such as flow paths, residence times and depths? and what role does the substrate play? Design issues include: what inflows and outflows are relevant? what options are there for different configurations that will suit different problems? what loading rates arl! relevant? what vegetation management strategies need to be developed? Other factors that need to be considered include: the need to look at whole plant cycles, management of wetlands to release phosphorus under specific conditions and intervals, the importance of hydrology and mass balances to understanding their behaviour. Other issues include: different hydraulic behaviour of different types of systems, the development of non-uniform flow systems, interaction between plant senescence and flow rates which could drastically influence nu trient uptake and release. The importance of what a wetland is to be used for should not be ignored, the treatment performance that it delivers must be seen in the broader context of its effects on the receiving waters into which it feeds.

PLATFORM PAPERS There were 65 platform papers and seven poster papers presented at the Conference. Preprints are available from the AWWA Office, Artarmon at a cost of $100. It is expected that a selected number of these will be published by IAWQ in its Journal Water Science and Technology Series in the coming year, the full keynote papers are expected to be included. Selected papers are summarised below, using Author's abstracts where suitable.

Engineering - Design and Hydraulics DESIGN CRITERIA FOR CONSTRUCTED WETLANDS by R W Crites Summary of design criteria for hydraulic performance of free water surface and subsurface flow wetlands. Design methodology based on detention time, BOD loading rate, water depth and aspect ratio. Detention time determination based on plug flow assumptions and first order kinetics. Aspect ratio should be between 4 to 1 and 6 to 1 for free water surface systems. For subsurface flow systems BOD loading should be less than 75 kg/ ha/day, entry zone loads should be below 0.2 kg/ m-2/day BOD and 0.08 kg/ m-2 / day SS. Performance of three operating systems from the US were presented: Gustine, Sacramento and Mesquite. The problem of inlet clogging for systems that have been operating for two or more years. Systems with BOD load rates in excess of 0.2 kg/ m-2/day were found to suffer from inlet clogging problems.

FWW CHARACTERISTICS OF CONSTRUCTED WETLANDS by R Netter Presented the findings of hydraulic experiments conducted on subsurface flow wetlands in Germany. Dye tracing was performed in three subsurface flow wetlands: two with a gravelly sand medium, one with a sandy gravel medium. Five tracers (bromide, uranin, eosin , lithium and tritiated water) were used. Bromide was found to be the most reliable tracer, uranin and eosin (both fluorometric dyes) were found tq suffer from

sorption and photolysis decay. Lithium was also found to be unconservative. It was fo und that increased hydraulic load rate gave increased permeability. Plug flow behaviour was observed as was longitudinal dispersion. There were also distinct preferred flow paths present.

Urban and Agricultural Runoff Management CONSTRUCTED WETLANDS FOR RIVER WATER QUALITY IMPROVEMENT by R H Kadlec and D L Hey Reports on the Des Plaines open water wetland in Illinois, USA. The wetland has been the site for a research project on treatment of non point source river pollution. Monitoring started in 1989 and is still continuing. It has been found that only 25% of the wetland system provides effective treatment. Two different hydraulic models were used to fit the data: Large dead zones exist to the side of a main channel; and small dead pockets are uniformly distributed through the wetland. Both could be used to model the system well. The wetland behaved in neither a well mixed nor a plug flow manner, but intermediate to these extremes. The nominal residence time was seven days but it took three weeks to clear the wetland of tracer.

CARCOAR WETLAND - A WETLAND SYSTEM FOR RIVER NUTRIENT REMOVAL by G. C. White, I. C. Smalls and P. A. Bek During December, 1991 the NSW Department of Water Resources initiated construction of an artificial wetland at the upstream end of Carcoar Dam near Blayney in central western NSW. The principal function of the wetland is to reduce nutrient inputs, especially phosphorus, from the Belubula River into Carcoar storage and consequently lower the incidence of blue green algal blooms which occur most summers . The wetland is a multi-faceted project involving substantial research and community involvement. Construction of the wetland weir and earthworks components were completed during April, 1992. The wetland planting program commenced in October and will continue into next year. The wetland is not fully operational and the various research programs have only just begun. However, even at this early point in the project, significant experience has been gained in design, construction and planting of large wetland systems and the establishment of comprehensive community involvement programs in NSW. This paper outlined the background to the wetland, the design of the wetland system and its construction primarily as a solution of nutrient pollution in the Belubula River. The paper also outlines the direction of research undertaken and the role and nature of community involvement in various aspects of the project.

Municipal Effluent Treatment NUTRIENT REMOVAL AND DISINFECTION PERFORMANCE IN THE BYRON BAY CONSTRUCTED WETLAND SYSTEM by H. J. Bavor and E. F. A ndel A constructed wetland system has been developed for polishing of treated sewage effluent at Byron Bay, northern New South Wales, Australia . Nutrient removal and disinfection performance of the system has been monitored in preliminary investigations and has been found to be promising. The system, monitoring program and ongoing research program are described.

Urban and Agricultural Runoff Management MANAGING URBAN SURFACE WATERS THROUGH WETLAND TREATMENT by D. Diessner The City of Bellevue, Washington, has been a leader in surface water management since 1975. The City's Storm & Surface Water Utility department alleviates flooding, protects surface water quality and enhances aquatic wildlife habitat for the enjoyment of all citizens. After analyzing various alternative surface water management strategies, the Utility selected an integrated approach. This approach WATER February 1993

33


includes the use of pollutant source controls and treatment measures to protect naturally occurring wetlands, streams and lakes. The City has been a leader in urban surfa.ce water quality and wetl.a nds research, and has developed design standards for and monitors the effectiveness of surface water pollution control facilities. The effects of urban surface water on naturally occurring wetlands is being documented. Research continues on how to increase the pollutant removal effectiveness of constructed wetlands. Protection of wetlands through pre-treatment and source controls has been investigated. Practical examples of various pollution technologies are being demonstrated including biofiltration, soil filtration/underdrains, infiltration, oil/water separators, maintenance practices, surface pond systems and wetland treatment measures.

WETLAND CONCEPTS APPLIED TO URBAN LANDSCAPES: CONSTRUCTED "SOURCE" WETLANDS by B. Hopkins and R. Argue A class of wetland was introduced which employs engineering practices and installations to collect, store, dispose of, retrieve and use stormwater, at source, in the urban landscape. Two Adelaide, South Australia examples of "source wetlands" are described. At New Brompton Estate, roof runoff from (eventually) a cluster of 18 residences is diverted to a 106 m gravel-filled trench in a central reserve. The collected water sustains a row of deciduous trees bordering the reserve and provides frequent (winter) charges, via a bore, to a Quaternary aquifer at depth 30 m. At Northfield a swale/ trench system which handles all storm runoff from a residential street (including domestic contribution) will be trialled. Runoff seeping to a trench from the swale will be of high quality and will provide charges of water to a 5 m Quaternary aquifer. Some runoff of good quality will pass from the catchment in large storm events. In both cases, New Brompton and Northfield, water retrieved from the Quaternary aquifers in summer will be used for open space irrigation. Constructed source wetlands offer a valuable new option in urban stormwater quantity/ quality management.

WETLAND SYSTEMS IN STORMWATER POLLUTION CONTROL by J Klunder A need has been firmly established in Adelaide to introduce a multi objective approach to the management of stormwater. Protection of life and property from the effect of flooding must remain a top priority but the emerging requirement is that it be achieved in an environmentally and socially acceptable manner. The diversion of stormwater through wetlands in one procedure within an integrated catchment management approach which offers multiple benefits including water pollution control. Differing water quality objectives and the constraint of land availability are both placed into an Adelaide perspective by reference to nine recently constructed or proposed wetlands.

Overview of Systems and Perform:\Oce INVENTORY OF CONSTRUCTED WETLANDS IN THE UNITED STATES by D. S. Brown and S. C. Reed During 1990 and 1991 the U.S. Environmental Protection Agency (EPA) sponsored an effort to identify existing and planned constructed operating systems. In addition to inquiries by telephone and mail, the effort included site visits to over 20 operating subsurface flow constructed wetlands. The inventory documented the presence of over 150 constructed wetland systems for wastewater treatment, including both free water surface (FWS) and subsurface flow (SF) systems. The majority of the systems identified were SF systems for treating municipal wastewater. FWS systems were separated into three groups based on the design level of effluent water quality. SF systems were separated into three groups based on the basic design approach. The inventory indicated that neither between nor within these groups was there consensus regarding basic hydraulic and engineering design criteria, system configuration, or any other aspect, such as, type of vegetation, size and type of media, or pretreatment. Information on location, type of systems, design approach, hydraulic and organic loading rates, costs and other aspects is presented. Information gathered and "lessons learned" from the site visits are presented. Insufficient oxygen for nitrification appears to be a problem for both FWS and SF systems. Insufficient hydraulic design appears to be a problem for SF systems.

CONCLUDING FORUM The conference was concluded by arranging an open forum, chaired by Dr Sherwood Reed, which was summarised by Dr David Mitchell. Hans Brix The effects that wetland plants have on the physical environment of the wetland cannot be ignored. They reduce wind velocity, temperature and radiation at the water surface which must affect the treatment processes that occur. Understanding plant processes is vital to optimising the performance of these systems. This is especially so in small systems with low load rates. ' Robert Kadlec Issues of the long term viability of wetlands must be further examined. Some systems have bee,p operating now for up to 20 years as constructed wetlands while some natural wetlands have been "treating" waters for 30 to 90 years. Studies need to run for a minimum of five years to give any insight into the sustainability of the processes. Donald Hammer Many vital issues still need to be explored. Such elementary factors as flow resistance caused by plants and differences between different species and the gradients required to allow flow rates to be sustained. Department of NSW with its coastal wetlands polishing municipal effluents. Other displays were provided by the Co-operative, Research Centre for Waste Management and Pollution Control, CSIRO Water Resources and the Waikato Region in New Zealand.

TECHNICAL TOURS A TRIAL WETLAND SYSTEM FOR URBAN RUNOFF TREATMENT IN THE BLUE MOUNTAINS OF NEW SOUTH WALES by P. Swanson The Sydney Water Board is trialling a constructed wetland system for the treatment of urban runoff in the Blue Mountains of New South Wales. The paper presents preliminary results from 18 months of performance monitoring. Initially, the formation of surface mats of algae and the subsequent export of these algae from the wetlands ponds resulted in poor treatment performance. Upon the decline of these algal scums, there was substantial removal of phosphorus, nitrogen and suspended solids from base flow urban runoff. Stormwater concentrations of these deterrninands were also generally reduced by the wetland ponds. Increases in aquatic macrophyte density appeared to be important in controlling algal growth and the associated nutrient and suspended solids export. There is significant potential for the use of wetland systems for the treatment of dry and wet weather urban runoff, provided that an adequate proportion of these flows can be contained. The long term treatment capacity of such systems requires further investigation.

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This gave the opportunity for delegates to meet and mix as soon as possible during the Conference and commenced with a visit to the Botany wetlands which are being restored after some 100 years of urban runoff impact. The Penrith Lakes and wetlands of the Nepean River floodplain were then inspected before visiting two sites in the Blue Mountains, one at Katoomba involving treatment of urban runoff and the other at North Katoomba STP used for polishing municipal effluent. The day also involved a visit to the Echo Point look-out and a bush dinner at the Hawkesbury campus of the University of Western Sydney.

NEXT CONFERENCE A proposal was made by Dr K P Hu from the South China Institute for Environmental Science of the Peoples Republic of China to hold the next wetlands conference in the city of Guangzhou some time in 1994. The actual date, venue and program topics will be covered in the first brochure to be circulated by the local organising committee. Details will also be provided in IAWQ's Conference Calendar. Thanks to Michael Waters and Richard Ouvrier for providing notes for this report.


CONFERENCES International Membrane Science and Technology Conference IMSTEC '92 IMSTEC '92 was held at the University of New South Wales in November, 1992. The Conference was organised by the Centre for Membrane Science and Technology which is based in the Departments of Chemical Engineering and Biophysics. The Conference was opened by Dr J. Saunders (Director of NSW State Development), followed by the Hon . Ross Free, Federal Minister for Science, who announced that the Centre had just received the title, UNESCO Centre for Membrane Science and Technology. The International flavour of the Conference was emphasised as the 250 delegates, representing over 30 countries, were addressed by the first plenary speaker, Professor Enrico Drioli, President of the European Membrane Society. His presentation also picked up a strong theme of the Conference as he spoke about 'Membrane Technology for a Clean Environment'. The other first-day plenaries were by Professor Heiner Strathmann (U. Twente, Netherlands and U. Stuttgart) who gave an overview of Industrial Applications of Electrodialysis, and Professor Erno Pungor, who is the Hungarian Minister for Science as well as being a membrane scientist. Professor Pungor spoke about Ion-Selective electrodes. The Conference was a full three days, with over 130 papers presented orally and in poster session. The topics covered illustrate the very extensive application and interest in membrane technology. A summary of the sessions gives a picture of the contents, Environmental/ Wastewater/ Water (37 papers), Pervaporation and Membrane Distillation (16), Gas Separations (13), Novel Membranes and Characterisation (16), Membrane Fou lin g (6), Membrane Processing of Proteins/ Biomass (14), Ionic Separations (8) , Microporous Membranes (7), Inorganic Membranes (4), Charged

Membranes (5), Biological/Biomimetic Membranes (12). One of the many highlights of the conference was the interest in 'environmental' and 'water' applications. Several papers described the treatment of organic wastes using coupled bioreactor/ membrane systems, and others covered the removal of heavy metal ions, oils and trace organics. The strong interest in Gas Separations, Pervaporation and Membrane Distillation was reflected in papers on membrane development and application. In a plenary lecture (day two) Professor Yuri Yampoliskii (Russian Academy of Sciences) gave an account of the very substantial developments in membrane technology in Russia. In another plenary lecture, on day two, Professor Georges Belfort (Renssellear Polytechnic Institute) presented theoretical and experimental evidence of the advantages of generating fluid instabilities within membrane modules to achieve enhanced performance. The problems of membrane fouling were addressed in a special session which included the combined talents of Hans-Curt Fleming (U. Stuttgart) and Harry Ridgway (Water Factory 21) unravelling some of the features of biofilm formation. Dr Michael Lysaght had the difficult task of presenting the plenary on the morning after the Conference Dinner. He did a superb job explaining the use of hollow fibre membranes packed with cells for therapeutic purposes. His presentation opened up the exciting applications of membranes in biomedical applications. Also on the final day a session was held on Biological and Biomimetic Membranes in conjunction with the Annual Meeting of the Australian Society of Biophysics. The 'overlap' between the interests of synthetic and biological membraneologists was emphasised through

presentations by Uwe Sleytr (U. Bodenku lter, Vienna) on Molecu lar Nanotechnology and George Belfort who closed IMSTEC by talking about Molecular Interactions between Proteins and Polymer Membranes. IMSTEC had 'social' functions each evening, with the highlight being the Conference Dinner at Taronga Park Zoo. The journey to the zoo included a harbour crossing and a cable-car ride to the function centre. Professor Mike Archer (UNSW Biology) gave a breath-taking after dinner talk on the Wonders of Palaeontology in Australia and South America. In conjunction with IMSTEC was a preconference workshop on Membrane Science and Technology that attracted 70 delegates. Speakers included Georges Belfort , Bill Eykamp, Marianne Nystrom and Tony Fane. The final day of the membrane-packed week was a PostConference tour arranged in collaboration with Memtec Ltd. The tour included a visit and inspection of the 2 mL/ day Membio demonstration plant at the Water Board site at Cronulla. The process involves a 2-cell, fixed-film bioreactor in series with about 1000 m 2 of Memtec microfilter. The scale and level of sophistication impressed all the visitors. The tour also took in a visit to Memtec's head office and production facility at Windsor, outside Sydney. All in all the IMSTEe '92 week was memorable, and the convenor is looking for a volunteer to organise the next event. NOTE: Proceedings of IMSTEC '92: A limited number of Proceedings (500 pages) are available for $60. To obtain a copy contact Professor Tony Fane (c/ - Centre for Membrane Science and Technology, UNSW, Fax: (02) 662 1587 or Tel: (02) 697 4315).

ION-EXCHANGE AND ADSORPTION Continued from page 30 17. S. D. Hamann and N. H . Pilkington, Desalination, 1979, 28 , pp. 43- 48. 18. B. A. Bolto, K. H . Eppinger, M. B. Jackson and R. V. Suidak, Desalination , 1980, 34, pp. 171-188. 19. B. A . Bolto, Waste Management, 1990, 10, pp. 11-21. 20. B. A. Bolto, E. A. Swinton, P. R. Nadelbaum and R. W. Murtagh , Water Sci. Jech., 1982, 14, pp. 523 - 534. 21. N. V. Blesing, B. A . Bolto, D. L. Ford, R. McNeill, A. S. MacPherson , J. D. Melbourne, F. Mort, R. Suidak, E. A. Swinton, D. E. Weiss and D. Willi s, " lonExchange in the Process Industry," Society of Chemical Industry, London, 1969, pp. 371-381. 22. L. 0 . Kolarik, A. J. Priestley and D. E. Weiss, Proc. 7th Fed. Convention Australian Water and Wastewater Association , 21- 24 Sept. 1977, pp. 143-161. 23. N. J. Anderson, B. A. Bolto, R. J. Eldridge, L. 0. Kolarik and E . A. Swinton , Water Res., 1980, 14, pp. 967 - 973. 24. N. J. Anderson, L. 0. Kolarik, E . A. Swinton and D. E. Weiss, Water Res. , 1982, 16, pp, 1327-1334. 25. L. 0. Kolarik, Water Res., 1983, 17, pp. 141-147. 26. N. J. Anderson and A. J. Priest ley, Water Res. , 1983, 17, 1227- 1233. 27. N. J. Anderson and B. A. Bolto, N. V. Blesing, L. 0 . Kolarik, A. J. Priestley and W. G. C. Raper, Water Res., 1983, 17, pp. 1235- 1243 . 28. D. R. Dixon, Water Res., 1984, 18, pp. 529-5 34. 29. B. A. Bolto, Chem. in Aust., 1990, 17, p. 172. 30. A. J. Priestley and M. A. Woods, Water, 1987, 14, pp. 13-15. 31. D. R. Dixon, Process and Control Eng., 1989, 42, pp. 88- 90 .

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Water Journal February 1993  

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