Water Journal July - August 1995

Page 1


Volume 22, No 3 July/August 1995 Editorial Board F R Bishop, Chairman cf- CMPS&F, 12th Fir, 390 St Kilda Road Melbourne Vic 3004

CONTENTS ASSOCIATION NEWS From the Federal President From the Executive Director Association Meetings

2 4 5

B N Anderson, G Cawston, M R Chapman P Draayer s, W J Dulfer , GA Holder M Muntisov, P Nadebaum, JD Parker A J Priestley, J Rissman

Features Editor E A (Bob) Swinton Tel/Fax (03) 9560 4752

MY POINT OF VIEW What's This New Association About


Dr John Langford

Advertising Sales & Administration


AWWA Federal Office PO Box 388 A.rtarmon NSW 2064 Level 2, 44 Hampden Road Artarmon NSW 2064 Tel (02) 413 1288 Fax (02) 413 1047

Sludge Beneficial Use of Biosolids in the Sydney Region


A Kanak, G Osborne, EA (Bob) Swinton Best Practices in Biosolids Land Application


J Walsh, L V Rawlinson Destruction of Sludge in Supercritical Water


A Shanableh

Coastal Environment Algal Blooms in Australian Coastal Waters


G Hallegraef Controlling Marine Introductions: Crimp


R E Thresher, R Martin Translocation: The Ballast Water Problem


G Rigby

Management Algal Management Strategy - Delivering t'h e Vision


T J Verhoeven

Technology Floating-Medium Downflow Flocculation with Coarse Sand Filter - A System for a Small Community


ACJr -Alan Wade Tel (06) 248 3692 Fax (06) 248 3623 New South Wales - Mitchell Lagineatra Tel (02) 412 9974 Fax (02) 412 9876 Northern Territory - Graeme Reed Tel (089) 82 7346 Fax (089) 82 7221 Queensland - Lyndsay Chapple Tel (07) 835 0222 Fax (07) 8326335 South Australia - Phil Thomas Tel (08) 259 0244 Fax (08) 259 0228 Ta.smania - Dao Norath Tel (002) 332 596 Fax (002) 34 7 559 Victoria - Mike Muntisov Tel (03) 600 1100 Fax (03) 600 1300 Western Australia -Alan Mall8 Tel (09) 420 2465 Fax (09) 420 3178

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OUR COVER Toxic micro-organisms, known as the dreaded "blue-green algae"

are already only too familiar to most practitioners in water supply. Less wellknown are those micro-organisms which inhabit the estuarine and coastal waters and reefs, and our cover contains photo-micrographs of some of them. Some of these are dangerous to the other denizens of these waters, ie fish and shellfish, and through the food chain, even to humans. Some of them secrete toxins, or the damage can be wrought by the anoxia caused by massive blooms. Larger organisms can also be a problem, and trans location of both types of organism from the northern hemisphere into our waters is an ever-present threat. Our feature on Coastal Environment introduces readers to a wider dimension than our usual interests, noting that we can have an impact on such coastal waters through our nu,trient discharges, whether intentional or through natural outlets. Photographs courtesy of Dr David Hill, School of Botany, University of Melbourne


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BENEFICIAL USE OF BIOSOLIDS IN THE SYDNEY REGION A Kanak, G Osborne*, EA (Bob) Swinton The principal authors presented papers at the BNR2 Conferenc e in October. Based on their presentations, with updates by the authors, this paper was produced by the Editor.

Keywords Sludge, biosolids, agriculture, sludge treatment, compost

Abstract Current uses of biosolids produced in the Sydney/Illawarra region are composting, land application for agriculture and forestry, with a significant component processed by mixing with quicklime and cement dust, and a small amount with crushed steelworks slag for local landscaping at Port Kembla. Sydney Water is collaborating with the NSW Department of Agriculture and State Forests in a number of research projects to assess the impact of use of biosolids, in their various forms.

Beneficial Use Options Beneficial use of sludge products involves taking advantage of one or more characteristics of the sludge so that a benefit is obtained. Higher value beneficial uses are obtain ed wh en t h e gap between the value of the benefits and the cost of the related activities is at its most favourable. To illustrate this concept, the soil improvement and agronomic value of land-applied sludge products can be compared to the transport, energy and management costs associated with the supply of the product for this purpose. Typically this will indicate a comparable ratio of costs and benefits but still not a profitable one in dollar terms. Incineration of slud ge may produce electricity, but the cost of oper ation will far outweigh the value. However, specific circumstances may still make this the favoured option. To date in the Sydney region beneficial use options involving land application of products after limited further process in g have been preferred lar gely because this strategy is simple to implement, involves low capital costs and is a fl exible option. It also shows favourable net costs compared to oth er options. Importantly it has a high degree of community support. At present about 200,000 tonnes of WATER JULY/AUGUST 1995

Biosolid products (processed sl ud ge products capable of beneficial use) are produced a nnually in the Sydney/Ill awarra region . About 90 % of this amount is utili sed for beneficial land application in the market sectors of horticulture, agriculture, silviculture and land rehabilitation. Some elaboration on each of these sections is given below: Horticulture. This market sector utilises composted products, which are produced from sludge in large quantities by contractors, but also at one of the Sydney Water treatment plants. Typically these products are produced via an outdoor turned-windrow system, involving the use of wood and or garden waste mixed with dewatered sludge at a ratio of up to 2.5 to 1 by volume. Natural biological processes cause a time temperature relationship of over 50°C for an extended period which is suffi cient to reduce pathogens to prescribed levels which are deemed to be safe by the regulatory authorities and which permit the use of these products for land scaping, gardens and ornamental horticulture. Frequently the composted Biosolids are not used 'as is', but as one ingredient in varioos organically enriched soil additive products. In Sydney these products have been used for high profile projects such as aesthetic improvement of railway stations, for establishment of the grass verges at the 3rd r unway project of the Federal Airports Corporation, and in small quantities in the Royal Botanic Gardens. The composted Biosolids are presently batch tested for heavy metals, presence of organochlorine pesticide residues and for pathogen contro l comp liance before dispatch to market, as well as for plant nutrient levels. Germination tests are also conducted from time to time. Agriculture. Agriculture utilises

liquid and dewatered biosolids, and alkali-treated biosolid s to obtain fertiliser value, pH adjustment and other soi l improvement benefits. Usually dewatered sludge cake is applied at 10 dry tonnes/ha which under typical conditions approximates agronomic needs with 80100 kg of availab le nitrogen for plant uptake in the first season, with the balance becoming availab le progressively (see below). At present, pasture, cereal and oilseed production are favoured and Bioso lid s are not applied where root crops such as potatoes and carrots are grown, or where the edible portion is in contact with the soil such as lettuce and cabbage production. However the use of Biosolids products for such vegetable production is the subj ect of some current research. Meanwhile the present position represents prudent practice, which is appropriate in the absence of hard data. ' Although the agronomic data we have so far are limited, it is evident that Biosolid~products have a valuable role to play in the management of many agricult ural enterprises, and can reduce reliance on mineral ferti lisers and improve soil characteristics. At present in NSW both agricultural and other land app li cation is regulated by the NSW Environment Protection Authority. Silviculture. Collaborative r esearch work in NSW with State Forests began in 1991 and is exploring the impacts of ¡applying Biosolid products to radiata pine plantations. Inve stigation s have focussed on environmental and forest productivity impacts at a number of sites of differing soil and rainfall characteristics to the south and west of Sydney. As it is not possible nor desirable to cultivate the floor of an existing forest the operating methods are somewhat different from agriculture, and not all plantations are physically suitable. Access by the pub li c for recreation is also an inhibiting factor. However the percentage of suitable sites amongst the total forested area is more than sufficient to utilise 30,000 tonnes of dewatered product annually. To date no environmental problems have been demonstrated even after heavy rains in intensively moni-

Unloading biosolids cake into a bunded storage area

* Organic Waste Recycling Unit, Locked Bag 4, Richmond 2753


tored catchments and forest productivity gains appear impressive, with research work indicating up to a 50% diameter increase in 3-5 year old trees, and a 28% increase in merchantable timber in older trees one year after Biosolid application to poor performing forest sites. Further work is continuing, and it is true that there is considerable interest in woodlots as a beneficial "sink" for products from sewage treatment not only by the Water Board in Sydney but also at Wagga in NSW and at Branxton in NSW at one of the Hunter Water Corporation's treatment plants. Land Rehabilitation. The challenges which frequently exist to rehabilitate degraded land are often suited to the use of Biosolids products because poor soils are usually deficient in organic matter, trace metals and plant nutrients. In some trial sites it has been found that Biosolid products significantly outperform mineral fertilisers; this is especially so when the topsoil is missing, such as is the case when open cut mine sites require revegetation, or where severe soil erosion is being remediated. Although this is not a large market or one of predictable year-round demand it is worth pursuing because of the high value of the Biosolid addition that can be demonstrated. Also where the land zoning or other regulations prescribe special site management procedures, such as is typical with a mine site, it may be possible to utilise Biosolids with somewhat higher levels of contamination than are desirable for agriculture, especially in one-off applications.

Impact of Nutrient Removal Processes Although the majority of Sydney's wastewater is routed to the ocean via the primary treatment facilties at North Head, Malabar, Cronulla , and Bondi, a significant and growing proportion of treated wastewater must be discharged to the Hawkesbury-Nepean River system, which is suffering from a number of pressures as the population expands in this catchment. Consequently, full treatment including nutrient removal has been implemented recently at a number of STPs. Currently Sydney Water operates biological nutrient removal (BNR) plants at Penrith, St Marys and the new Rouse Hill development, and utilises

chemical precipitation at several other plants. Both systems produce sludges which have somewhat different characteristics from the sludges produced by anaerobic digestion of conventional primary and secondary sludges. It has been found at the Penrith plant of the Water Board that BNR performance can only be optimised if the sludge residence time is kept quite short, typically 10-15 days, otherwise the P returns to solution. Most of the continuous flow Biological Reactor facilities such as IDAL plants have only a slightly greater sludge age, where 20 days is typical. This short sludge retention interval contributes to a situation where the sludges tend to be more odorous, more difficult to dewater to a level suitable for physical handling, and more attractive to insects, and perhaps to rodents. Odour. Problems seem to be related to incomplete reduction of proteins and fats which can result in generation of unpleasant mercaptans from the sludge over a period of days or even weeks, depending on temperature and storage conditions. Laboratory testing of these sludges shows that myriads of gaseous compounds are involved, including those with evocative names like putrescine and cadaverine. This problem of odour potential should not be underestimated and depending on the severity and plant location some additional processing may be mandatory. Such additional processing techniques could include aerobic digestion, chlorination, anaerobic digestion, lagooning, alkali stabilisation or drying to about 90% solids. Anaerobic digestion suffers in that the phosphorus captured by the biomass is released back into the liquid phase. Large scale open-air composting of these sludges with typical wood waste additives is not a sustainable year-round option unless the site for this work is well isolated from neighbours, due to odour complaints. No single option can be recommended, each case requires specific assessment. Based on limited experience at two STP's it does seem that improved separation of grease and scum from the solids at the treatment plant will help the progress of sludge digestion towards completion, which can be important

Table 1 Chemical content of typical sludges (mg/kg of dry matter)

Total Kjeldahl N Phosphorus Potassium Calcium Magnesium Copper



BNR (Penrith)

IDAL (Q. Hill)

Primary (Cronulla)

68,000 29,400 9,690 10,700 6,900 630 470

50,000 34,000 2,530 9,710 3,300 500 510

42,000 22,500 820 19,700 2,520 1,220 1,020

when sludge residence time is short. Dewatering. Conventional anaerobically digested sludges are generally dewatered to 20% solids or greater to permit the transport and handling by conventional equipment. A recent development, the 'bladder press', has enabled 40% solids to be attained with conventional anaerobically digested sludges. However BNR sludges are far more difficult to dewater, even with high polymer addition rates and well maintained presses or centrifuges. Certainly 18% solids is at the lower end of what could be called "spadeable" and if the solids level is lower. than this, the product is difficult to transport by conventional trucks. At 18% solids the product will tend to slump thixotropically to an angle of repose of 15-20°. Sludge at 25% solids will by comparison have an angle of repose of about 40°. More polymer is not the answer as a gelatinous and more expensive product is the likely end result. The dewatering difficulty is related to the lack of sludge age and is made more understandable when it is appreciated that the water in a volume of sludge exists in four forms: free water, capillary water, colloidal water and intracellular water Gravity separation and dewatering are effective for removing the first 3 categories of water but the higher proportion of intracellular water in short age sludge can only, be removed effectively by further digestion or by thermal treatment, which is rapid, but expensive due to the energy involved. Extended lagooning will help in this and other regards, however the decanted fraction can threaten the otherwise high performance of a BNR facility. However, this can be carefully managed in the same way as the centrate from dewatering processes, eg by lime precipitation. In some instances the sludge in liquid form but thickened to 6-10% solids may be suitable for injection into subsurface soil to improve soil characteristics, and this technique has been practiced by Sydney Water for about five years now, with good success, and injection rates of up to 9000 L in 2 minutes . However, transport and year round "weatherproof" operations can be significant hurdles. Vectors. In-so-far as insect attraction is concerned, BNR sludges, if insufficiently stabilised, can be intensively colonised by fly larvae quite rapidly and in one case this effect was in evidence within ten days of dewatering¡ the sludge. This characteristic is not acceptable if the sludge i& destined for land application or composting because it would certainly alienate customers. Options such as drying, alkali stabilisation, incineration or sub-surface liquid injection are ways around this problem. Better still is to treat the cause and not WATER JULY/AUGUST 1995

the symptom and to produce a more stable and usable product by an integrated processing system. Sufficiently stable products can be put to multiple beneficial uses, provided they ar e satisfactory in other regards, such as with respect to contaminant and pathogen levels . In Sydney, apart from the properties discussed above, it has bee n found that nutrient removal sludges are fairly similar to sludges obtained from other treatmen t plant configurations, and so me indicative analyses are shown in Table 1.

Alkali Stabilised Biosolids Reference has already been made to the use of alkali stabilised Biosolids and in Sydney such products are produced at North Head STP by the N-Viro So il process (Bio-recycle Pty Ltd), and at Malabar STP via the addition of quicklime. During 1995 the RDP process will be installed at North Head by Thiess, involving both lime addition and supplementary heating. The resulting products are readily useable, despite their lower levels of nitrogen (1%) due to loss of ammonia, than in untreated dewatered product (34%) The reason these products are valuable, despite their r educed fertiliser value, is because they offer some potential to replace or augment agricultural lime used for acid soil amelioration, and they simulta n eo usly offer trace elements, organic matter and some nutrients. From the tr eatment plant operators perspective th ey produce a low odour, relatively dry product (45%, or more, solid s is typical) from sludges which may initially have been objectionable to handle, which can be stored and transported. The use of such processes for BNR or extended aeration sludges can be recommended if product stability is a problem, and the transformation in product char acteristics is quite major, as is demonstrated at the North Head Plant, Sydney, where the raw slud ge feed is dewatered immediately after thickening, then alkali-treated. Should there be a requirement for a low or nil pathogen product the alkali addition processes can accomplish this by a combination of elevated pH and temperature.

Agricultural Research As mentioned above, the NSW Department of Agriculture has been involved in beneficial use of biosolids for over ten years, as well as programs for re-use of effluent water. In 1991, following a review of all available scientific literature, the Sludge Application Program (SAP) was established at Richmond. Usually sludges contain 2-4% total nitrogen and 2-4% total phosphorus, a low concentration. The extent to which even these amounts are avail able for WATER JULY/AUGUST 1995

plant uptake is a function of their chemical forms, partially dependent on the processes used at the treatment plant. At 10-30 tonnes (dry matter) per hectare, crop or pasture demand for these nutrients may, or may not, be satisfied. It must be stressed that any recoupment of costs will depend on the profit that primary producers obtain in the first TWO years followin g application, when mo st of the nitro ge n in the Biosolids becomes available. Although the organic a nd fibrous matter will increase productivity, this will only occur in the longer term and is difficult to quantify. Application rates (of either Biosolids or effluent) must not be so high as to exceed the combined ability of the agricultural system - crop, pasture and soil to use the nutrients and absorb or detoxify any pathogens or contaminants without leakage to the wider environment, damage to the site, or migration into the food chain.

Spreading dewatered cake

(listed below). In doing s0,1 the Department had in mind the need for competitiveness, for sustainability, and for preservation of the State's r eputation for contaminant and pollution free food. As discussed in the paper by Walsh and Rawlinson in this issue, it has also been necessary to re-draft the guidelines for the u se of biosolids , with som e emphasis give n to the USEPA Ri sk Pathway approach. As the re search developed n ew research areas were to be identified, and t he need to maintain so me long-term studies would be determined. Research proposals were solicited from within NSW Agriculture. Meetings of a NSW Agriculture-Water Board review panel were held in 1992 to consider the proposal s r e ceived. Nineteen projects wer e approved and funding commenced in November 1992.

Summary of Projects (Note, further explanation is appended to some of these titles) Project 1: Pathogen survival in NViro Soil. • Evaluation of product homogeneity with regard to pH and total solids • Determination of the nature of heat production in N-Viro Soil in windrows (is it chemical or biological ?) • Determination of the pre sence of a suitabl e colonisation barri er against Salmonella spp in mature N-Viro Soil. Project 2: Sewage products as nitrogen and phosphorus fertilisers in coastal NSW.

Maize in biosolids study at Berry

With regard to the question of 'heavy metals', the work of Chaney (1990) is often quoted. He maintained that there was no evidence of phytotoxicity from Cu, Zn, Ni at pH above 5.5. However, the situation in most of Australia is very different from that in North America and Europe, where most agriculture is conducted at pH 6.5. A large proportion of our agriculture is based on soils which are acidic, even down to pH 4.5, and we have developed crops which do not demand liming. Topsoils are mostly shallow, low in organic matter and in cation exchange capacity. In consequence of this different regime, the Department, in a consultative proce ss, a nd on the advice of Professo r s Pa ge a nd Chang of California, has outlined nine areas of long-term r esearch. These were developed into a range of spec ific projects

The overall objective is to develop systems for the safe and efficient use of sewage products as fertilisers for crops and pastures in high rainfall coastal districts of NSW. Project 3: Sewage sludge products as fertilisers and soil ameliorants in deciduou s orchards. (Apple, pear and peach) Project 4: Fertiliser value and conta minant leve ls of dewatere d sewage sludge cake on mature apple trees. Project 5: Effectiveness of N-Viro Soil, dewatered sludge cake, cane filter mud, lime and inorganic fertiliser s as nutrients and ameliorants for sugar cane soils. Project 6: The deve lopm e nt of sewage sludge compost quality standards for application to horticulture and landscaping. The overall aim is to produce a series of quality standard s to enabl e sludge compost to be produced and marketed to its full potential and to prevent the sale of composts that are unsuitable for use in horticulture and which would curtail, through reputation, existing and potential markets. Project 7: Utilisation of sewage sludge compost as a soil conditioner and 11

fertiliser for vegetable production. Project 8: The agronomic and economic value of sewage slud ge in cropping systems on the acid soils of Central NSW. To determine the potential benefits from the use of N-Viro Soil and sewage sludge cake for cropping on the acid soils of Central NSW. A cereal crop will be used to see if these products can economically increase yields on these problem soils. The research will also be looking for potential long term benefits such as reduced acidity and/or increased organic matter. Project 9: The chemistry of sewage sludge-derived heavy metals in a typical acid soil of the Sydney region. Project 10: Plant growth and metal uptake from sewage sludge amended acidic soils. Project 11: Selection, characterisation and monitoring of field trial sites including catchments for the study of environmental pollution following the application of sewage sludge. Project 12: Soil and plant sampling procedures to detect significant changes in heavy metal concentrations when different methods are used to incorporate sewage sludge. Project 13: Interaction of sewage sludge with biological N 2 fixation and mineralisation of legume N. To de termine types and rates of sludge which do not jeopardise the viability and effectiveness of Rhizobiumlegume symbiotic N2 fixation and mineralisation of legume nitrogen. Project 14: Survival of pathogenic bacteria in processed sewage sludges. Project 15: The economics of sewage sludge products use in agriculture. To summarise overseas and Australian economic studies on the value of sludge products use in agriculture. To summarise the cost structures for a range of alternative slud ge products, from their point of departure from the Sydney sewage treatment plants to, and including, the incorporation of the product on farm. To identify areas where further technical and economic research is required. Project 16: The growth and yield response to sewage sludge of a range of summer crops. Project 17: The growth and yield response to sewage sludge products of winter wheat (Triticum aestivum var). To determine the fertiliser value, in terms of plant growth and crop of sludge products (N-Viro Soil and sludge cake) under wheat grown in the central west of NSW. Project 18: Evaluation of sewage sludge products for use in extensive livestock production. To assess the potential for use of organic waste products as an economic and sustainable soil ameliorant and fer-


tiliser for extensive livestock production systems in the Sydney catchment area. Project 20: Survival of human parasites in processed sewage sludge. • To investigate the ability of helminth parasites of humans (round worms and tape worms) artificially seeded into sludges, to survive the common treatment processes. • To determine the longevity of worm ova which have survived stage 1, by seeding them into in treated sludges applied to the soil by different methods and, collaborate with the Environmenta l Pathogens Unit of the Water Board to extend these techniques to investigate the survival of protozoan oocysts in sludges. • To develop a standard test using the most resistant helminth egg as an indicator of pathogen survival in different sludge treatment processes. Reports on these contract research projects are being regularly supplied to the client, Sydney Water , but it is beyond the scope of this brief review to cover them all. However, preliminary results of wheat trials in Condobolin and Gilgandra were published in the Proceedings of BNR2 conference, demonstrating the spread and variability of plant responses that are possible.

brown colour of sludge. In conventitmal STPs, only a small proportion of the P in wastewater is captured by the s ludge , but nutrient removal processes deliver most of the P to the sludge. However , if this is achieved by precipitation by alum or iron salts, the P will not be readily available and any overdosing will have the adverse effect of fixing any phosphorus already present in the soil. BNR sludges (aerobic sludges) provide more available pho sphoru s (Amundson and Jarrell, 1983).

Conclusions There is no doubt that land application of sludges from domestic STPs is more beneficial than land-fill or incineration, but there is little prospect that the benefits will totally cover costs of transport from the large cities to suitabl e cropping areas. Development of horticultural products by composting techniques will provide an outlet for a proportion of sludge. Alkali treatments provide a product which can be stored and transported, and which can provide value in their liming content. Silviculture also has some potential. The research projects in progress should enable a rational set of guidelin es for agricultural use to be established.

Nutrient Quality


Agricultural benefits of sludge application are not as simple as might be first imagined, since the availability of the prime nutrients N and P depends on the method of treatment of the sludge Nitrogen. The nitrogen content is expressed a total N, but can be in three forms: o~ganic nitrogen, nitrate and ammonia. Nitrate is immediately available to plants, but can be lost by leaching, or microbial denitrification in the soil. Ammonia can be taken up by some species of plants, or fixed to clay colloids. However, it is at risk by loss to the atmosphere. Organic nitrogen becomes available as it is steadily broken down by soil microbes into nitrate or ammonium ion. The plant-available nitrogen is referred to as mineralisable nitrogen . Parker and Sommers (1983) in an overseas study compared sludges from 24 treatment plants when applied to a silt loam soil. The percentages of the organic nitrogen avai lab le were 25 % from raw/primary sludge, 40 % from waste activated sludge, 15% from anerobically digested sludge and 8% from composted sludge. Aerobic (or BNR) sludges should have higher nitrogen contents but published data is scarce. Phosphor us. Phosphorus is expressed as total-P. Plant-available phosphorus cannot be determined by the usual colorimetric test because of the

Amundson, R G and Jarrell, W M (1983) A comparative study of' Bermuda Grass grown on soils amended with aerobic or anaerobically digeste d slud ge. Jnl Env Quality 12 (4): 508-513 Chaney, R L"(1990). Twenty years of land application research. Bi ocycle 31: 54-59 Parker, C F and Som mers, L E (1983 ) Mineralisation of nitrogen in sewage sludges. Jnl Env Quality 12(1): 150-156 In: Proc . Second Australian Co nference on Biological Nutrient Re moval from Wastewater. AWWA, Albury, October. Corb in, E J; Bamforth, I; Cooper, J and Osborne, G J . Beneficial Use of Nutrients in Sewage Sludge. Kanak A. Management of solids from bio. logical nutrient reduction process treatment plants- general observatins and experience in the Sydney region. Walsh, J and Rawlinson L There is More to a Successful Biosolids Application Program than Meeting the Regulatory Requirements.

Authors Anthony Kanak has been associated with Sydney Water's sludge management program since 1989, and was Manager of the Products Management business from 1992-4. He is currently a consultant in Aqua Re-use, Australian Water Technologies. Dr Gary Osborne is Manag er, Recycling Investigation;, at the Organic Waste Recycling Uni~ NSW Agriculture. He graduated in Agricultiiral Science from the University of Sydney in 1965, gained an MSc in 1975, then his PhD from the University of Reading, UK. WATER JULY/AUGUST 1995


BEST PRACTICES IN BIOSOLIDS LAND APPLICATION J Walsh*, L V Rawlinson** Abstract In most States in Australia regulations are being drafted to provide a framework in which to safely manage the beneficial use and disposal of a variety of biosolids products. They should encourage beneficial use based on the appropriate exploitation of the valuable characteristics of the products, while ensuring the minimisation of risk to the environment and human and animal health However, complying with the requirements of regulatory agencies is just one element in ensuring a successful biosolids beneficial use and disposal program. The promotion of 'best practice' in the biosolids industry, through the establishment of good operational management practices, particularly in the field, along with an open and continuous communications program, are also key elements of a successful program. The establishment of good operational management practices along with a comprehensive communications strategy will ensure the biosolids industry is recognised as a responsible and important contributor to waste recycling.

Keywords Biosolids, regulations, Code of Practice, beneficial use, good management practices

Introduction Along with the provision of clean, safe water for drinking, another indicator of a modern country concerned with the health of its citizens has been the isolation of sewage from communities and the construction of sewage treatment plants for its treatment, and disposal of waste products. It can therefore be difficult to convince people, who for many years have believed sludge to be not only a waste product to be disposed of, but also one that is smelly and unsafe, that it actually has valuable properties and is safe to use if managed correctly. Public perceptions about sewage sludge need to be changed. A first step in that direction has been to adopt the name 'bioso lid s' to describe sewage sludge that has the qualities to be used beneficially. WATER JULY/AUGUST 1995

If water authorities and other producers of biosolids products are to promote the beneficial use of biosolids they must continue to demonstrate to the community that these products can be used without harm to the environment and to human and animal health. Operators must be seen as credible and responsible ,employing good operational management practices to ensure their activities cause minimal impact on surrounding areas and are in line with total catchment management philosophies. State regulations coupled with good management practices, including a comprehensive communications program that involves the community and other stake holders including government agencies eg departments of agriculture, departments of water resources, catchment management committees, land care groups etc, should ensure the desired outcome of a successful biosolids beneficial use program, local, state and nation wide.

Why Regulate Biosolids? Biosolids are not toxic waste but neither are they mother's milk. Biosolids are waste products derived from sewage treatment and contain attributes of value such a nitrogen, phosphorus and other nutrients, as well as trace elements and organic matter. They can also contain a range of metals, organochlorines and human and animal pathogenic organisms which can be potentially harmful to the environment and human and animal health. The unwise and inappropriate use of biosolids products can turn beneficial characteristics, such as nutrients, into pollutants. For example, uncontrolled heavy rate applications can supply nitrogen in excess of plant needs. This could allow the remaining nitrogen to leach or runoff into nearby waterways contributing to the pollution of the waterways and groundwater. Biosolids are no different in this respect to other similar products, such as cow and chicken manure and inorganic fertilisers. Irresponsible and misinformed use and management of these products continues to contribute, along with other factors to pollution of our waterways.

Beneficial use implies the appropriate use of tlie valuable characteristic(s) of the biosolids products ie as a source of nitrogen, phosphorus and trace elements for plant growth or as a source of organic matter or as a liming agent for soil improvement, without compromising the environment. The regulations should provide minimum standards to help ensure the environment is not compromised by beneficial use and disposal activities.

What is Regulated in NSW? Most States are developing guidelines but this paper discusses those developed by NSW. The NSW EPA has developed a Draft Code of Practice for the Use and Disposal of Biosolids Products to Land. The Code has been developed by a committee consisting of representatives of the EPA, Agriculture, Health, State Forests, Sydney Water, Hunter Water, Public \Yorks ( who represent regional water authorities) and representatives of environmental groups and users, and has been open for public comment. The impact of the Code will have to be assessed by each sewage treatment authority. The Code sets out procedures for: Classification. Biosolids and biosolids products are classified by contaminant and stabilisation criteria (reduc- tion of odour and vector attractants). There are five contaminant grading criteria and three stabilisation criteria. The resultant classification determines the end use ie unrestricted, restricted (three categories - suitab le for urban landscaping, food production and non food production), and not suitab le for use. If a biosolids product is classified as Not Suitable for Use, either because of failure to comply with the contaminant (Grade E) or the stabilisation criteria (Grade C) or both, it can be reprocessed or blended and re-characterised at a higher grade. Otherwise it will need to be landfilled at a suitably EPA approved ' facility. Biosolids stabilisation is proving to * Sydney Water, 28 Burwood Road, Burwood 2134 ** L V Rawlinson and Associates, PO Box 255, Berry 2535


be an issue. It has become apparent that some BNR and IDAL plants do not generally comply with the required stabilisation criteria for Stabilisation Grade B. Sydney Water, after a preliminary study of a number of its STPs, found that many did not satisfy the criteria. This has led to serious consideration of changes in process at some of the se STPs, for example the recommissioning of digesters or longer sludge age coupled with more reliance on chemical dosing for nutrient removal to ensure required effluent standards are maintain ed as well as other processing options. Land application practices. Classification of the biosolids determines where and under what conditions the biosolids can be applied or disposed. For example, Re stricted Use applications, except in the urban landscaping market require, amongst others, • approval from the EPA, • the site to be selected against a set of criteria eg slope, site drainage etc. • determination of applications rates restricted by soil metal and organochlorine levels, biosolids contaminant concentration and nutrient loading; and • adherence to certain site management practices, such as withholding period s for s tock, buffer zone s from surface waters, residential areas, sensitive areas etc and the requirement for incorporation of the product into the soil (with the exception of forestry applications). Monitoring requirements for biosolids and biosolid products. A statistically validated sampling approach is incorporated in the Code, to measure quality on either a batch or continuous basis. Other approaches can be used if approved by the EPA. For land application sites, soils are assesses proir to each application. The sampling procedure in the Code has been developed by NSW Agriculture. Reporting and Reco rd k eep in g. Reporting and record keeping ensures information is maintained and provided to the EPA (and other government departments if requested) for each application site, or activity, on the quantity and the quality of the biosolids used, site characteristics, pre-application soil sampling, the nutrient and metal loading applied to the soil, distance of the site from surface waters, bores etc and crops grown. It is anticipated that t he Interim NSW EPA Code of Practice will be available for use in mid 1995. A draft code has already been through a public and industry review proce ss as well as through a number of training sessions to familiarise users, producers, regulator s and other interested agencies. It is expected that the research curr ently being undertaken by the Department of Agriculture, State Forests, CSIRO and others, will eventually be used to develop a set of contami14

nant thresholds based on risk assessment methodologies.

Good Management Practice Product quality. Biosolids are typically regulated on the basis of their quality with regard to heavy m etal a nd organochlorine content. However there are other quality issues which should be considered when utilising biosolids in a land application program. These include: a) Nutrient Content. The nutrie nt content of the product such as liquid or dewatered biosolids, particularly nitrogen, is often the component limiting the application rate of the biosolids. In excess of a particular rate, more nitrogen can be applied than will be taken up by plants, with the consequence that the excess nitrogen may leach or runoff. If the biosolids are to be used as a fertiliser they must be able to supply r equired nutrients, primarily nitrogen and phosphorus. If the biosolid s have been sundried or in storage for some time it is likely t he nitrogen level, at least, will have declined. This is particularly the case for alkali-treated products. Operators must be careful about how they are 'marketing' t heir biosolids. Operators need to be clear and informed about the value of the product when approaching potential users of biosolids. If farmers, for example, are promised a growth response for their crops that does not eventuate, they are unlikely to try the product again and this information is pa sse d on to other growers . Irresponsible 'marketing' of biosolids by an operator can have repercussions on other operators and the industry as a • whole. b) Solid8 content. The solids content of biosolids will affect the suitability and ease of different application technologies. If the solids content is highly variable then the application rates need to be adjusted accordingly. The solids content of the biosolids also has consequences for transport costs. For example, dewatered cake ideally should be in excess of 20% solids both for ease of spreading and for transport considerations. c) Lime equivalent. F or alkalin e bio solid s the lime equival ent of each batch needs to be determined to provide the farmer with a response which is comparable to agricultural lime. d) FOTeign Objects. Non degradable physical contaminants such as plastics should be excluded from the biosolids products. Care needs to be taken whilst storing biosolids to ensure that storage s ites are not use d as dump sites by sewage tr eatment plant employees and contractors. Th e presence of foreign objects such as rocks and building rubble etc, can result in contamination of the product as well as costly repairs to equipment and increased machinery downtime.

e) Odour. Operators should ensure the product they s'tipply is not offensively odourous. This should not be a problem if the sewage has been processed adequately and complies with the Biosolids Code stabilisation criteria. Any odour should be controlled by adequate treatment or sub-soil injection or incorporation as soon as possible following application. When choosing a site for biosolid s app lic ation consider the proximity of the site to residences, recreational areas, industrial sites etc. Also when operating on a site near residences and other occupied buildings, consider wind direction ahd other climatic conditions. Site selection and management. A major component of the costs associated with a beneficial use program is transport. For this reason sites closest to the biosolids source are most attractive. It is also desirable to find sites with sufficient suitable potential application areas to enable a number of applications to the same property, thereby minimising the costs associated with the initial site assessment. Care should be taken on sites which receive a number of annual applications. It is advisable to monitor the site for the build up of phosphorus and any increase in salinity. Typi cally bio solid s applications based on nitrogen may result in an excess application of phosphorus with respect to crop ph osp h orus requirements. This will depend on the biosolids product and how it has been processed, eg ferric chloride do sing can render phosphate• in the biosolids large ly unavailable for plant uptake. If applications are to repeated on an ongoing basis, for example on a dedicated site adjacent to a sewage treatment plant, phosphorus adsorption capacity of the soil prior to application and after five years of annual application should be determined and assessed. Transport requirements: ·a) Trucks. For dewatered and limeamended biosolid s which have a solids content of 15% or greater, the following requirements are recommended to minimise the risk of spillages. • all tr uck s mu st be li ce nse d to carry wastes • all trucks to have grain locks fitted prior to loading • all tr ucks must be covered and biosolids contained in water-tight tipper It is generally considered unsafe to carry biosolids of a solids content of less t han 15% in tr ucks, since they slump thixotropically. Such slurries should be carried in a tanker of a type suitable for the physical characteristics of the product, eg capacity and strength, suitable baffl e configuration, cleaning access, venting etc. b) Trucking routes. The transport route must minimise public nuisance in urban and rural areas. Access to land WATER JULY/AUGUST 1995

application sites should be chosen carefully in order to avoid creating a hazard . during the delivery period to the site. c) Incident management. An incident management plan should be developed for the trucking of biosolids. These procedures are needed to ensure rapid clean up of spillages both en route to the site and at the end use site. For biosolids products which are being transported to country areas it is important that local councils have input into the incident management plan for their area and that a contact person from the council is informed in the event of a spillage. It is important to note when spillages occur they should be contained and a dry clean up performed. d) Wash.down facilities. Washdown facilities should be provided at both the sewage treatment plant and the end use sites. Truck tailgates and tyres should be cleaned prior to leaving the site to ensure biosolids products are not spilt on roadways. Effluent from these washdown facilities should be dealt with appropriately, for example at application sites it should be irrigated on the biosolids applications area.

On site operations: a) Machinery operations and calibratwn. Prior to the application of biosolids, machinery should be calibrated to ensure biosolids are being applied correctly at the rate that has been calculated, based on the nitrogen and contaminant concentrations in the product. To avoid soil compaction, machinery should not be used during wet weather or immediately after extended rain. b) Storage. The use of stockpiling at some application sites is necessary to facilitate efficient operations and take advantage of cheaper backloading opportunities available from transport companies in some areas. These stockpiles are typically built by creating compacted earth bund walls of 0.8 - 1 metre height and with surface water diversion structures at the entrance to the bund. There should also be a drainage collection point located within the bund which is separate from the stored biosolids. The collected drainage water may be applied to the biosolids application area. However, storage of biosolids on application sites should be minimised. Longer term storage of biosolids on application sites would require construction of permanent storage facilities with an adequate hardstand base and drainage control to avoid any potential for transfer of nutrients and other potential pollutants to the environment. Public acceptance. The acceptance of a biosolids land application program by the community is integral to the success of the program. There are numerous case studies in the United States of America and some in the Sydney Water's program where public¡ WATER JULY/AUGUST 1995

opposition to projects has resulted in the ticular crops in the area, or alert operageneration of unfavourable media atten- tors to partlt:ular issues relating to soil tion and in some instances has stopped or water quality in the district. operations completely. There is a wide range of government Opposition has often arisen because departments which have an interest in affected people, such as nearby residents biosolids products either in a regulatory of a site, people on a trucking route etc, role or as land resource managers. In have not been adequately informed. NSW the government departments It is to the operators' advantage to which are involved in the biosolids reuse keep people informed. This can be time program include the EPA, NSW Agriculture, NSW Health, State Forests, consuming but well worth the effort. a) Farmers and other land ko'lders. Conservation and Land Management The farmers and other landholders (CaLM), Public Works, Water involved in the reuse program need to be Resources, Sydney Water, Hunter well informed of the regulatory condi- Water, Department of Planning and local tions under which the biosolids products councils. It is essential that these departments are being applied to their properties as well as understanding their own role and agree upon the appropriate regulations responsibilities. The role of the landhold- and management practices of the biosolids beneficial use industry. To er will depend on the operator but for example the Sydney Water program avoid potential conflict, it is advisable to requires the farmer to be responsible for inform all departments which might be incorporation of the biosolids following contacted by a concerned or interested application. This is a requirement of the member of the public regarding a particCode for application of biosolids to land ular application site. It is the practice in some programs in the USA to advertise to be used for agricultural activities, their operations in the local newspapers, including grazing. thereby avoiding the accusations of b) Neighbours. Application of biosolids products may impact on neigh- secretly dumping wastes. bouring properties due to truck moveConclusion ments during the delivery and potential Beneficial use of biosolids is a relaodours during application. Also neighbours, if not well informed, may become tively new concept in Australia. If it is to unduly concerned about environmental be successful, producers and their conand health consequences of an applica- tractors will have to continue to demontion. Therefore, informing neighbours strate to the community and the regulatory authorities that they are credible prior to delivery and application can and reliable operators by incorporating avoid potential conflict later. Farmers the requirements of the Biosolids Code and other land holders usually have an existing relationship with their neigh- of Praetice(in NSW) as well as good manbours and are therefore generally the agement practices into the running of best eeople to make the initial notifica- their biosolids business. tion of their intention to apply biosolids. References They can also keep the neighbours Interim Code of Practice for the Use informed about operational issues. and Disposal of Biosolids Products, c) Local community. To inform the Draft - June 1994, New South Wales general public about biosolids applications in their local area, displays may be Environment Protection Authority held at local field days and shows or static displays can be placed in the foyer of ¡ Authors Joanne Walsh has an Honours the local council. Making a range of brochures available on the program and Degree in Agricultural Science, and possible different market applications is worked in Sydney Water Residuals also useful. Presentations to interested Management Unit from 1991 to 1994, and concerned people through their local succeeding Lisa as Operations Manager clubs e.g. Rotary, environmental groups for the Land Application Program. She etc. can also been successful. A proactive attended the 1994 Residuals Conference approach is highly recommended i.e. in Washington DC and visited a number seeking people out to inform them rather of facilities. Since writing this paper she has moved to the NSW EPA. ¡ than waiting until an issue arises. Lisa Rawlinson gained her Masters d) Government agencies. The Code advises land appliers to inform relevant degree in Agricultural Science and government departments of their pro- worked in the Sydney Water Residuals posed application plans. This is good Management Unit from 1989 to 1994. In practice. Experience at Sydney Water 1993 she was appointed Operations has shown that keeping interested stake- Manager for biosolids land application. holders informed of the proposed appli- In 1991, as a Churchill Fellow, she visitcations can help short circuit potential ed schemes in USA; in 1992 and 1994 she presented papers at WEF problems on sites. Also personnel in these agencies, eg NSW Agriculture or Conferences, and visited schemes in UK. CaLM, can for example provide valuable She has recently started her own consuladvice on nutrient requirements for par- tancy in biosolids re"USe. 15


DESTRUCTION OF SLUDGE IN SUPERCRITICAL WATER A Shanableh * Keywords Sludge, supercritical water, deepwell treatment

Abstract The oxidation of hazardous organic wastes and sludges can proceed to completion under the conditions of temperature and pressure which define sup ercritical water, and this can be achieved in a totally enclosed treatment facility. Subsurface, deep-well application is safe, totally enclosed, and offers minimum exposure to the public, the zone of high temperature and pressure being deep underground. The organic component of sludge can be reduced to any level using supercritical water oxidation (SCWO) subject to temperature and residence conditions. This. paper describes an investigation of SCWO for destruction of a highly contaminated activated sludge. The destruction of the organic contaminants was virtually complete in relatively short residence times. Above 99 percent reduction of total chemical oxygen demand was achieved within 5 minutes at 450°C, 15 minutes at 425°C and 25 minute s at 400°C. The process produced a clear and odourless effluent and a disposable ash with good settling characteristics and nonleachable heavy metals. The process is applicable to a wide range of hazardous wastes and s lud ges and can become self sustaining at low concentrations of organic wastes.

Introduction As the complexity of environmental management continues to increase, environmental contaminants must be contained and destroyed. Otherwise, the destruction of toxic organic wastes and sludges becomes an overwhelming prob1em. The growing quantities of hazardous wastes and sludges require special attention and innovative treatment proces ses . The options for complete destruction of aqueous hazardous wastes and sludges are limited . Incineration, while potentially achieving complete combustion, does not provide total enclosure and the burning and gas cleaning 16

processes are expensive and difficult to centric tubes for separation of downflow control. Low temperature water oxida- and upflow. The weight of the liquid protion systems, such as wet air oxidation, vides some or all of the pressure necescannot achieve total destruction and gen- sary to achieve the desired reaction conerate, when applied for slud ge treat- ditions. The oxidant can be either oxyment, strong liquors that require signifi- gen or hydrogen peroxide or a combinacant treatment. On the other hand , tion of both, and can be injected as supercritical water oxidation (SCWO) desired in the lower half of the reactor can provide complete destruction of haz- based on heat tra n sfer, t hermal and ardous wastes and sludge s in totally kinetic considerations. The process can enclosed treatment facilities. become thermally self sustaining when Water is a supercritical fluid at tem- the chemical oxygen demand exceeds peratures and pressures above the criti- approximately 15,000 mg/L (Gloyna, cal point, 374°C and 22 MPa. Under 1988). these conditions, the boundaries between the phases disappear, and supercritical Equipment water, oxygen, and a wide variety of This project dealt with a highly contorganic compounds become completely aminated activated sludge obtained from miscible. The high diffusivity and high a plant which treated wastewaters from temperatures assist in destroying the a papermill, refinery and petrochemical organic solid s, and supercritical water so urce s. The sludge contained paper di ss olv es the organic compounds. fibres a nd so m e oil. Destruc tion of Intima te contact between reactants sludge wa; evaluated using laboratoryresults in a rapid and efficient destruc- scale batch and continuous-flow reactor s. tion of the organic component of the A schematic of the batch reactor vessel waste. • assembly is presented in Figure 1. The The effectiveness of SCWO in reaction vessel consisted of a horizontal destroying a variety of contaminants has coil-tube r eaction vessel (SS 316, 6.35 been demon strated (Gloyna, 19 88; mm O.D. x 4.57 mm I.D . x 1.22 m long), Lixion g et al, 1993; Shanableh and press ure transducer, a thermocouple, Gloyna, 1989, 1990, 1991). The applica- and a r eactor hold er. Temperature and bility of the process for treatment of a pressure variations during the course of variety of organic wastes from municipal th~ reaction were displayed and recordand industrial sources is summarised in ed. During a typical batch test, the reacTable 1 (Gloyna, 1988; Oxidyne, 1988). to r was charged with a homogen ised SCWO does not require sludge pre- sludge sample, mounted on the shaker, treatment and can be achieved in a total- pressurised with oxygen, checked for ly enclosed deep-well r eactor utili sing lea ks, imm er se d in a heated fluidized well-established oil-field technology. The sand bed for the desired r eaction time, deep-well vertical reactor technology was then removed and submerged in a water demonstrated to be an effective and cost- bath to terminate the reaction. On the competitive sludge management option average, 30 second s were r eq uired to in Longmont, Colorado, USA (Longmont, heat the r eactor vessel and contents to 1987). The Longmont reactor consisted the desired reaction temperature . of a 25 cm stainless steel subsurface A schematic of the continuous-flow, tubular reactor reachin g a depth of vertical reactor is presented in Figure 2. approximately 1600 m. A metallurgical • The reactor consisted of two concentric study after 5 years of operation showed stainless steel 316 (SS 316) tubes. The insignificant corrosion, consistent with outer tube dimension s were: 50.8 mm the 20 years design period (Longmont, outside diameter (O.D.) x 25.4 mm insid e 1987). The construction of a full-scale, diameter (I.D.) x 5.74 m long. The inner deep-well reactor in Houston, Texas, was r eactor tube dimensions were: 12.7 mm completed in 1994. Subsurface, deep-well, subcritical * Sc hool Of C ivil Engineering, Queensland and SCWO reactors may consist of con- University of Technology, Brisbane Qld 400 1 WATER JULY/AUGUST 199 5

O.D. x 10.9 mm I.D. x 5.74 m long. The reactor surface was initially heated using nine electric band heaters distributed along the reactor . Pressure was controlled by a back pressure regulator and was measured using a pressure transducer interfaced with a digital display. Temperatures were monitored at 16 different locations within the annular space and the core. The operator was protected behind a polycarbonate safety shield .

Materials and Methods Ammonia, pH, and TCOD were measured using standard analytical procedures (Standard Method, 1989). Acetic a nd propionic acids were mea sured using a Tracor 550 Gas Chromatograph equipped with a flame ionisation detector (FID) and recorder. A 122 cm long x 6.4 mm O.D. x 4 mm I.D . glass column packed with GP Carbowax 20M/0.1 percent H 3PO 4 was used. The column temperature was maintained at 100°c. The column inlet and outlet temperatures were maintained at 190°C. The detector temperature was maintained at 160°c.

The carrier gas was nitrogen and t he flow rate was 40 cm3/min. Samples and standards were acidified by the addition of one mL of H 3PO 4 to 10 mL sample and the sample injection volume was 0.4 uL. To test for toxicity, the toxicity characteristic leaching procedure (TCLP) was used. In the TCLP test, the supernatant was decanted and the solids were dried . The solids from the respective samples were added to individual extractor bottles and extracted with a weight of extraction fluid equal to 20 times the weight of the solids. The extraction fluid consisted of 5. 7 mL glacial acetic acid and 64.3 mL of 1.0 N NaOH diluted to a volume of one litre. The pH of the extraction fluid was adjusted to 4.93. The extraction bottle was tightly clo se d, placed in a rotary extractor and rotated at 30 rpm for 18 hours, then the contents of each bottle filter ed through a 0.6 m glass fibre filter and stored in a second bottle. The filtered extraction solution was analysed for metals using emission spectroscopy (inductively coupled plasma, ICP).

Table 1. Applicability of Subcritical and SCWO (Gloyna, 1988; Oxidyne, 1988). Wast.eStream

Subc.ritical Wat.er Oxidation


Biological Sludges Industrial Organic Chemicals Plastics Synthetics Drug Manufacturing Paints and Allied Products Industrial Organics Agricultural Chemicals Explosives Petroleum and Coal Products Rubber and Miscellaneous P lastic Products








Acrylonitrile Wastewaters Cyanide Wastewaters Polychlorinated Biphenyls (PCBs) Pesticide Wastewa ters Halogenated AJiphatics Halogenated Aromatics Aromatic Hydrocarbons Ketones (MEK) Organic Nitrogen Compounds





Table 2. Transformation of ammonia and acetic acid in the batch reactor (mg/L). Substance


10 minutes

16 minutes


SO minutes

Acetic Acid (350°C) Acetic Acid (400°C) Acetic Acid (425°C) Ammonia (350°C) Ammonia (400°C) Ammonia (425°C)

2800 1220 380 550 590 460

2590 310 20 550 590 270

2100 110 15 560 540 125

1660 40


550 470 25

450 260

Table 3. Sludge meta!,s (mg/kg) and TCLP results (mg/L). As Sludge Metals TCLP Limit Sludge TCLP Ash (33 0°C) Ash (350°C) Ash (396°C)

<1 5 <1

<1 <1 <1

Ag <2 5 <1 <1

<1 <1








22 100 1.8 <1 <1 <1

<1 1 <1 <1 <1 <1

63 5

<0.2 0.2 <0.2 0.2 <0.2 <0.2

7.5 5 <2



<1 < <1 <1


<1 <1

<1 <1 <1

Results Batch Reah ion. The data presented in Figure 3 illustrate the destruction of activated sludge subjected to subcritical and supercritical temperatures in the batch reactor. In this case, the temperatures varied from 300°c to 450°c and the density of supercritical water was maintained at approximately 0.25 g/mL. The initial total solids (TS) concentration was 3 percent. The initial TCOD of the liquid and solid fraction of the sludge was 30,300 mg/L. As the temperature was increa se d be twee n 300°C and 450°C, TCOD destruction increased at all residence times. However, it would seem that to achieve virtually complete destruction of TCOD, the temperature had to be above the supercritical point of 374°C. More t h an 80 percent of t he T COD of the raw slud ge was reduced during heatup to sup ercritical reaction temperatures. The heatup time, approximately 30 seconds, was not considered part of the residence time in Figure 3. For examp le, five minutes re sid enc e time was equivalent to five minutes and 30 seconds total reaction time, of which 30 se cond s were h eatup time . Th e remaining TCOD after heatup required longer r es idenc e times for improved destruction and was designated as the difficult-to-oxidise sludge component or r eaction transformation product. The diffic ult-to-oxidi se slud ge component was mo s tly (more than 60 to 80 perce nt) acetic acid . The destruction of this component of the sludge proceeded exponentially and a first order reaction mod el fitted the experimental data. Continuous Flow Reaction. The continuous-flow reactor _operated at constant flow rate and constant pressure, and re sidenc e time was dependent on the reaction temperature. As the reaction temperature increa sed, the fluid ex pa nd ed and t h e r es id e n ce t im e decreased. Nevertheless, the degree of slud ge de s truction incr ease d with increased temperatures. The sludge was destroyed in two regions of the continuous-flow reactor. The first region was at the top of the r eactor above the point where oxygen was introduced. In thi s region, sludge was subj ected to thermal decomposition. The sec ond r egion was below the point where oxygen was introduced . In this region, sludge destruction was due to both thermal decomposition and oxidation. The data prese nted in Figure 4 were based on an influent TS concentration of 3 percent, a pressure of 400 bar, and a sludge flow of 50 g/min. The amount of oxygen was based on stoichiometric requirements plus 100 percent excess. The ~es ulting TCOD destruction increased from approximately 75 percent at 30o 0 c to 97% at 450°C. Acetic acid was produced in large quantities at sub critical temperature s. Below 375°C, the concentration of acetic acid in




Oxygen Supply and Sample Recovery Tube

Pressure Transduce r

High Pressure, High Temp erature Valve











Figure 2 Simplified schematic of the continuous-flow, vertical reactor system Figure 1 Schematic of the batch reactor system


10000 --0

·c3 6



<ii > 0 E

• D

• 0


3oo•c 3so•c 400°C 425°C 4so•c




·a. 0


- ::J'





Influent TCOD = 30 ,300 mg /L

--0 · -


• • •



u E




0 I-







4000 0



0 0








• ••

2000 0




• • 0



80-+-~.......,_-r-~~-r-~~-r-~~-r-~~--.~~-1 40 60 50 10 20 30 0


• •



Reaction Time (minutes)

Figure 3 Destruction of sludge in the batch reactor using subcritical and SCWO

the effluent reached approximately 2,750 mg/L (Figure 4). Supercritical temperatures were required to oxidise acetic acid. The concentration of acetic acid dec;reased from 2,750 mg/L at 375°C to below 600 mg/L above 400°C. The short residence at supercritical temperatures in the continuous reactor limited TCOD removal to 97 percent and resulted in a residual acetic acid in the effluent. In the batch reactor, the destruction of acetic acid was virtually complete at SCWO temperatures (Table 2). The concentration of propionic acid in the effluent was low compared with the concentration of acetic acid. Below 325°c, propionic acid concentrations of 200 mg/L were produced. Above 325°C, the concentration of propionic acid decreased as the tern18

• •••• 325






4 75

Temperature (°C)

Figure 4 Transformation of the organic component of sludge in the continuous flow reactor

perature increase d from 200 mg/L at 325°C to 10 mg/Lat 450°C. Ammonia. The production and transformation of ammonia was an important aspect of sludge destruction. A comparison of t he production and transformation of ammonia at subcritical and supercritical temperatures in the batch reactor is presented in Table 2. The data indicate t hat ammonia was r emoved at supercritical temperatures, subject to temperature and residence conditions, while at subcritical temperatures, ammonia was not removed. Below 650°C, the products of organic nitrogen and ammonia SCWO are N 2 and N 20 (Gloyna, 1988). N20 decomposes to form N2. Settlability and Metals Leaching. While t he original sludge

containing 3 percent total solid s, paper fibres and oils, settled to a volume of 980 mL/L after two hours, the ashes, containing approximately one percent solid s, settled to a volume of approximately 110 mL/L in 30 minutes. Ash samples were analysed for leaching usi ng the tox icity characteristic leaching procedure, TCLP. The results are presented in Table 3. The sludge contained approximately 7.5 mg/kg Pb, 63 mg/kg Cr and 22 mg/kg Ba. The concentrations of the remaining regulated metals were low. Treatment using subcritical and SCWO did not in crease t h e extractability of metals and the concentrations of leachable metal s in the ash extract remained below the established TCLP maximum limits. WATER JULY/AUGUST 1995

Conclusions SCWO, including temperatures just below the critical point, offers an effective treatment concept that is applicable to a wide range of hazardous wastes and sludges. Using SCWO, the destruction of sludge, including associated industr ial contaminants, was virt ually complete within a relatively short r esidence time. The process produced a clear and odourless effluent and a settlable and disposable ash with nonleachable metals.

Acknowledgments Thi s s tudy was co nduc te d at t h e Univer sity of T exas at Au stin, sup ervise d by Professor E F Gloyna, with financial suppor t fro m the Univer sity, Gulf Coast Waste Di sposal Aut hori ty (US), Oxidyne Corporation (US), and the Texas Higher Education Coordinating Board (US).

Author Dr Abdullah Shanableh is a lecturer in environmenta l engineering at Queens land University of Techno logy. He was an assistant professor of environmental engineering at the University of Jordan, Amman-Jordan, and a senior engineer with Engineering-Science, Inc, USA. He receive d his PhD f ro m the University of Texas at Austin, USA. His research interests include sludge management and contaminated site remediation.

References Gl oy na, E F (1988) Sup e r crit ical Water Oxidation- Deep-Well Technology for Toxic Wastewaters an d S lu dges. Internal Resea r ch Doc um ent, Th e Uni vers ity of Texas at Austin, Austin, Texas. Lixiong, L, E F Gloyna, and J E Sawicki (1 993) Treatability of DNT Process Wastewater by S up erc ri t ica l Wate r Oxid ation . Water Environ Res , 66, 250 Long mon t, City of (1987) Aq u eo us-P hase Oxidation of Slu dge Usi ng t he Vertical Reaction Vesse l System . USEP A/600/287/022, Mar ch, 1987. Oxidyne Cor por ation (1988) In ternal Repor t, in Gl oy na (1988) S upe r cri t ical Water Oxidation- Deep-Well Technology for Toxic Wastewate r s a nd Slud ges. I ntern al Research Doc um ent, The Un iver sity of Texas at Austin, Austin, Texas. Sha nab le h, A, a nd E F Gloy na (1989) Super cri tical Wa ter Oxidation of Sludges. Water Envir n Fed 62nd An nual Conference, San Francisco, California, October 19 S han ab le h, A, a nd E F Gloy na (1990) Sup erc ri t ical Wate r Oxi datio nan d Slud ges . The Was t ewate r s In te rn at ional Assoc ia t ion on Water Pollution Research and Co ntrol (IAWPRC) 15th Bienn ia l In te rn ational Co nfere nce, Koyoto, Japan. Sha n ab le h, A, and E F Gloy na (1991) S up erc ri t ical Wate r Oxidatio nWastewater s and Sludges. Water Science and Technology, 23, Page 389-398 Standard Methods fo r the Examination of Water a nd Wastew a te r . Amer P u blic Hea lt h Assoc, Washington, DC, 17th Ed, (1989)


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ALGAL BLOOMS IN AUSTRALIAN COASTAL WATERS G Hallegraef* Keywords Algal blooms, marine eutrophication, dinoflagellates

Abstract Most algal blooms in Australian inshore (notably diatoms) and offshore waters (blue-green alga Trichodesmium) are completely natural phenomena, which have been recorded since historic times. Starting in the late 1980s , Australia's developing aquaculture industry has created a heightened public awareness of the possible harmful effects of algal blooms (e.g. fish kills caused by anoxia) and contamination of seafood products with algal toxins (paralytic, diarrhetic, amnesic, neurotoxic and bluegreen algal shellfish toxins). Furthermore, most coastal waters, estuaries and rivers adjacent to Australia's major population centres are now subject to eutrophication from increasing discharges of domestic and industrial wastes. The most serious impact of eutrophication is that it has the potential to cause shifts in phytoplankton species composition from wholesome diatoms to nuisance flagellate blooms, with farreaching implications for the structure of entire marine foodwebs . The toxic dinoflagellate Gymnodinium catenatum in Tasmanian waters is an example of a ship ballast water introduction which has successfully established itself in its new Australian environment.

Algal Blooms: The Good and the Bad The colour of the sea is ever changing. The open sea is blue while nearshore waters are more green, and the water is more transparent in winter than in spring. These differences are caused by the proliferation of microalgae, that is, microscopic floating plants which, just like land plants, use dissolved nutrients (nitrate, phosphate), carbon-dioxide and sunlight to grow and reproduce. In most cases algal blooms are beneficial for aquaculture and wild fisheries because they mean food for shellfish and larval fish. Sometimes these plankton blooms can become so dense (millions of cells per litre) that they obviously discolour the surface of the sea. It is believed that the first written reference to such a bloom ("red -tide") appears in the Bible: "... all the waters that were in the river


were turned to blood. And the fish that was in the river died; and the river stank, and the Egyptians could not drink of the water of the river" (Exodus 7: 2021). Algal blooms may also appear yellow, brown, green, blue or milky in colour, depending upon the organism involved. Most water discolourations are caused by motile or strongly buoyant species. Their high concentrations are achieved through a combination of high growth rates and vertical (behavioural) or horizontal (physical) aggregation. Dense algal concentrations are most strongly developed under stratified stable conditions, at high temperatures and following high organic input from land run-off after heavy rains. The majority of these algal blooms appear to be completely harmless events (Table 1), but under exceptional conditions, non-toxic bloom-formers may become so densely concentrated that they generate anoxic conditions that cause indiscriminate kills of fish and invertebrates in sheltered bays. Oxygen depletion can result from high respiration by the algae (at night or in dim light during the day) but is more commonly caused by bacterial respiration during decay ofi the algal bloom. An essentially different phenomenon is the production by certain species (especially dinoflagellates) of potent toxins that can find their way through fish or shellfish to humans. In this case, even low densities of the toxic algae in the water column may cause such illnesses in humans as paralytic shellfish poisoning (PSP), diarrhetic shellfish poisoning (DSP), amnesic s hellfi sh poisoning (ASP), neurotoxic shellfi sh poisoning (NSP) and ciguatera fish poisoning. PSP can result from eating either bivalve shellfish or planktivorous fish , while DSP , ASP and NSP are caused by eating shellfish, and ciguatera by eating tropical coral reef fish . The toxins involved evoke a variety of gastro-intestinal and neurological symptoms in humans (Table 2) but rarely affect the nervou s syste ms of fish or shellfish. Another group of toxins (ichthyotoxins) selectively kill fish by inhibiting their respiration . On a global scale, close to 2,000 cases of human poisoning through fish or shellfish consumption are reported each year, and, if not controlled, the economic damage through reduced local consumption and reduced export of seafood products can be considerable.

In Australian Waters Most algal blooms in Australian in shore and offshore waters are completely natural phenomena, which have been recorded since historic times. One example is the filamentous blue-green alga Tri chodesmium erythraeum observed as early as 1770 during Captain Cook's voyage through the Coral Sea ["The sea in many places is here covered with a kind of brown scu m, such as sailors generally call spawn"; Beaglehole, 1955]. This organism produces basically harmle ss water discolorations in the Coral Java Banda and Arafura Seas, and from there the East Australian Current and Leeuwin Current transport the algal masses (covering up to 40,000 square kilometres) as far south as Sydney (Jervis Bay) and Perth _(Albany). The alga is perceived as a nuisance to swimmers on Australian beaches and has significant impacts on recreation, but harmful effects on humans or marine life have seldom been reported. A hidd en danger, however, when dense algal blooms occur in sheltered embaymi!nts, is the generation of anoxic conditions. This phenomenon wa s already reported from Sydney Harbour by Whitelegge (1891): "Towards the latter end of last March (1890)", "The water in the harbour presented the appearance of blood"; "a large percentage of the oysters were seen wit~ the valves gaping widely and the ammals gone, or in a high state of decay". This event was associated with a dense bloom of the nontoxic dinoflagellate Glenodinium rubrum [now believed to have been the species Scrippsiella trochoidea; Hallegraeff, 1991]. Finally, a limited number of Australian algal species produce potent neurological toxins which can find their way through the foodchain via fish and shellfish, or sometimes also via drinking water to humans. The earliest documented example of a toxic Australian bloom comes from the brackish water Lake Alexandrina in South Australia from which Francis (1878) reported to the scientific journal Nature: "A conferva that is indigenous and confined to the lakes has been produced i'n excessive quantities so much as to render the water unw'holesome". "It is, I believe, [the blue• University of Tasmania, GPO Box 252C, HobartTas 7001


green alga] Nodularia spumigena". "It is swallowed by cattle when drinking". "This acts poisonously, and rapidly causes death", "Sheep, from one to six or eight hours; horses, eight to twenty-four hours; dogs, four to five hours; pigs, three or four hours". Most spectac ularly, in NovemberDecember 1991 a bloom of the freshwater blue-green alga Anabaena circinalis di sco loured 1000 km of t h e Darling River and thereby raised widespread public concern in Australia abo ut the environmental quality of most major rivers, estuaries and coastal waters near Australia's large population centres, where discharges of industrial, domestic and agricultural wastes are raising

nutrient levels in the water. Phytoplankton species that always have been present in low concentrations could respond to this increase by growing to bloom proportions. Furthermore, the considerable expansion of aquaculture production in Australia has started to focus attention on phytoplankton species, that can contaminate shellfish with neurotoxins or damage the sensitive gill tissues of finfish held in intensive cage culture systems.

Are Algal Blooms Increasing? The ¡question of whether some human activities may be involved in increasing the intensity and geographic distribution of harmful algal blooms has


a 1 111


e j


been a subject of considerable international debate (Hall egraeff 1993), and some consensus is now developing that what we are seeing is in fact a combination of (1) an increased scientific awareness of toxic species; (2) increased utilization of coastal waters for aquaculture; (3) translocation of species via ship's ballast water or associated with movement of she llfi sh stocks from one area to another; and stimulation of plankton blooms by (4) unusual climatological condition s (El Nino events, greenhouse warming, ozone depletion) and, last but not least, (5) eutrophication, ie the stimulation of algal growth by anthropogenic nutrient inputs via domestic and industrial wastes. Eutrophication problems and associated algal bloom problems are most pronounced in sheltered bays and estuaries with limited circulation. Thus blooms of Nodularia spumigena have increased in the Peel-Harvey estuary and Gippsland lakes in response to increased phosphorus loading from agricultural fertilisers. Changing patterns of land use (deforestation, agricultural fertilisers, hydro-electric power development) can also modify coastal algal blooms by altering organic nutrients and chelators in land runoff. The most serious impact of eutrophication is that it has the potential to cause shifts in phytoplankton species composition from wholesome diatoms to nui sanc e flagellate blooms, with farreaching implications for the structure of entire marine foodwebs. In the absence of carefully planned, long-term monitoring stations ,it will often be impossible to resolve whether observed increases in algal b14>oms represent a real increase or not. This problem is well illustrated in Table 3 , which summarises algal bloom phenomena recorded in Sydney coastal waters in t h e period 1890 to 1995 , including n atural phenomena (Trichodesmium), toxic species receiving increased scr u tiny (dinoflage ll ate Alexandrium, diatom Pseudonitzschia) and species that can be interpreted as an - early sign of coastal eutrophication (red water discolorations by the dinoflagellate Noctiluca). Fig 1 illustrates the diversity of organisms involved in harmful algal blooms.

Toxins in Australian Shellfish

Fig 1. Diversity of microalgal species responsible for algal bloom events in the Australian region. F'igs a, b. Species causing basically harmless water discolourations; a. Filamentous tropical bluegreen alga 'lrichodesmium erythraeum producing raft-like colonies, individual cells 7-12 mm wide, filaments 1-Smm long; b. Balloon-shaped red-water dinojlagellate Noctiluca scintillans, 1 mm diameter; F'igs c, d. Species non-toxic to humans but harmful to fish and marine invertebrates; c. Unarmoured dinojlagellate Gymnodinium mikimotot 25 mm diameter; d. Golden-brown flagellate Heterosigma carterae, 11-25 mm long; F'igs e, f, g, h, t j. Toxin-producing species; e. Chainforming unarmoured dinojlagellate Gymnodinium catenatum (PSP), individual cells 24-94 mm diameter; f Armoured dinoflagellate Alexandrium minutum (PSP), 15-22 mm diameter; g. Chainforming armoured dinojlagellate Alexandrium catenella (PSP), 37-49 mm diameter; h. Dinojlagellate Dinophysis acuminata (DSP), 25-47 mm long; i. Dinoflagellate Dinophysis fortii (DSP), 60-70 mm long; j. Chainforming diatom Pseudonitzschia multiseries (ASP), individual cells 68-140 mm long. WATER JULY/AUGUST 1995

Following a history of carefree harvesting of large quantities of wild shellfish by Aboriginal tribes (apparently without any traditions of shellfish poisoning), starting in the mid 1980 s the Australian shellfish industry has woken up to the potential dangers of contamination of cultured and wild shellfish with algal biotoxins (Fig 2). Positive test resu lts are now available from Australian shellfish for paralytic shellfish poisons (PSP) ' (from the dinoflagella tes Gymnodinium catenatum, Alexandrium catene lla, A. minutum), diarrhetic sh ellfi sh poison s (DSP)(dinoflagellates Dinophysis acuminata, D. fort.ii), amnesic shellfish poisons 21

(ASP )( pr es uma bly fr om t he di ato m

Pseudonitzschia pungens f multiseries) a nd blu e-gr ee n algal p e pt id e toxin s

(Nodu laria spumigena) (Hallegraeff 1995: Fig 3). While most of the causative algal species probably already existed in Australian coastal water s in Aboriginal times, faced with increased public awar eness of algal biotoxins in shellfish products, the shellfish industry is now forced to test shellfish products for an increasing diver sity of biotoxin s, using both mouse bioassays and chemical methods such as high-performance liquid chromatogr aphy (Hallegr aeff et al, 1995). Th e 19 93 out br eak of NSP in New Zealand when mor e than 180 human s hell fis h po iso nin gs wer e r epo r te d (J as pe r se et al 199 3), ca use d by a n organism similar (but not identical) to Gymnodinium breve , has highlighted how the economic costs of an unpredicted toxic algal bloom event could be devastating for Australian shellfish producer s. The aquaculture industry now has ini tiate d algal bloom moni to ring programs in Tasmania (since 1986), Victor ia (sin ce 1987) and mor e r ece ntly also So ut h Austr alia and West Austr ali a (Hosja & Deeley 1994) . These shellfish monitoring progr ammes ar e admini ster ed und er t h e a uspic es of t h e Australian Shellfish Sanitation Advisory Committee (ASSAC) whi ch was established by the Australian Quarantine and In spection Servic e (AQIS) to protect public health and facilitate the inter state and expor t trade of Australian shellfish.

Ballast Water Introduction of Toxic Dinoflagellates Bl oo ms of t he toxic dinofl agellate

Gymnodinium catenatum, a causative organism of paralytic shellfish poisoning, wer e fir st r ec ogni se d in sou t h ern Tasmanian waters in late 1985. Soon after , comm erci al shellfi sh fr om t he Derwent and Huon estuaries proved to be contaminated with hi gh concentr ations of paralytic shellfish poisons. This

led to the temporary closure in 1986 of 15 shellfish farr~s for up to 6 months. Since then, fur ther shellfis h fa rm closures have had to be enforced in 1987, 1990, 1991, 1992 and 1993. The question thus arose whether G. catenatum was a r ece nt in t r odu ction in to th e area or whether it had occurred there pr eviously in low concentrations without actually having been record ed. If it had always bee n presen t, its sudd en mass occ urr ence in the last twenty years could per-

Table 1 Different types of harmful algal blooms (1) Species which pr oduce basically harmless water discolourations; however, under exceptional cond itions

in sheltered bays, blooms can grow so dense that they cause indiscriminate kills of fis h and inver tebrates due to oxygen depletion . Examples: di noflagellates Noctiluca scintillans, Scr-ippsiella trochoidea, bluegree n alga Trichodesrniurn erythraeurn. (2) Species which produce potent toxins that can find t heil· way t hrough the foo d chain to huma ns, causing a variety of gastr ointestinal and new·ological illnesses, such as: • P aralytic Shell.fish Poisoning (PSP) (Examples: dinoflagellates Alexandrimn catenella, A. rninutum, A. tarnarense, G,Jmrwdinium catenaturn,

Pyrodinium bahamense var. cornpr·essum) • Di arrhetic Shellfish Poisoning (DSP) (Examples:dinoflagellates Dinophysis acuta, D. acmninata, D. Jortii, Pl'orocentri,m lima) • Am nesic Shellfish Poisoni ng (ASP) (Examples: diatoms Pseud<mitzschia pitngens f multiseries, P. australis ) • Ciguatera F ish Poisoning (Examples: dinoflagellate Garnbierdiscus toxiws • Neurotoxic Shellfish Poisoning (NSP) (Example: dinofl agellate Gymnodinimn cf. breve (New Zealand)) • Blue-green Algal Poisoning (Examples: blue-green algae Anabaena circinalis, Microcystis aeniginosa, Nodular'ia spmnigena) (3) Species, which ar e non-toxic to humans, but harmful to fis h and inver tebr ates (especially in inte nsive aquaculture systems) by damaging or clogging th eir gills. Examples : di atom Chaetoceros convolutus, dinofl agellate G,Jmnodiniurn rnikirnotoi, prym nesiophytes Chrysochrornulina polylepis, C. leadbeateri, Pl'yrnnesimn parvi,rn, P. patellffer~mi, r aphidophyte Heterosigrna car·terae


Table 2 Clinical symptoms of various types of fis h and shellfis h poisoning Paralytic Shellflah Polaonlng (PSP)

Dlarrhetic Shellflah Polaonlng (DSP)

Causative organism Awxarutr-iurn catenella,· Awxandriurn rninutum,· Awxandriurn tarnarense; Gymnodiniurn catenatum,· Pyrodiniurn baharnense

Dinophysis acurninata; Dinophysis acuta; Dinophysis Jo,tii,· Dinophysis no1-vegica Prorocentrurn lirna

Amnealc Shelltlah Polaonlng (ASP)

Neurotoxic Shellflah Poisoning (NSP)


Pseud011itzschia pungens

Gymmnodiniurn breve; G. cf b?·eve ( New Zealand)

Garnbierdiscus toxicus; ? Ostreopsis sianiensis; ? P,·orocentrurn li,na

f rnultiseries;

Pseud01,itzschia pseudodelicatissirna; Pseud011itzschia australis

Symptoma MildCa~e With in 30 min: tingling sensation or numbness around lips, gradually spreading to face and neck; prickly sensation in fingertips and toes; headache, dizziness, nausea, vomiting, diarrhoea.

After 30 min to a few hrs (seldom more than 12 hrs): diar rhoea, nausea, vomiting, abdominal pain.

After 3 - 5 hrs: nausea, vomiting, diarrhoea, abdominal cramps.

After 3-6 hrs: chills,headache, diarrhoea; muscle weakness, muscle and joint pain; nausea and vomiting

Symptoms develop within 12 - 24 hrs of eating fish. Gastro-intestinal symptoms: diarrhoea, abdominal pain, nausea, vomiting.

Chronic exposure may promote tumor formation in the digestive system.

Decreased reaction to deep pain; dizziness, hallucinations, confusion; short-ter m memory loss; seizures.

Paraesth esia; altered perception of hot and cold; difficulty in breath ing, double vision,trouble in talking and swallowing

Neurological symptoms: numbness and tingling of hands and feet; cold objects feel hot to to uch; difficulty in balance; low heart rate and blood pressure; rashes. In extreme cases, death through respiratory failure.

Extreme Ca~e Muscular paralysis; pronounced respiratory difficul ty; choking sensation; death through respiratory paralysis may occur within 2 - 24 hrs after ingestion.

Treatment Patient has stomach pumped and is given artificial respiration. No lasting effects.


Recovery after 3 days, irrespective of medical treatment.

No antitoxin or specific treatment is available. Neurological symptoms may last for mont hs and years. Calcium and mann itol may help relieve symptom s.


haps be related to a change in environmental conditions favourable for the growth of this dinoflagellate. G. catenatum is a conspicuous, large, .chain-forming dinoflagellate (up to 64 cells long), which is readily collected by plankton nets and can be preserved even by harsh fixatives such as formaldehyde. A survey of historic plankton samples suggested that the organism had been ab sent from Tasmanian waters in the period 1945-1950 and 1975-1978, and fir s t appeared in the Derwent River in 1980. A concomitant survey of local ho spital record s confirmed that human poisonings after shellfi sh consumption had occurred as early as 1980, but not before that date. Furthermore, there is no tradition of human poisonings among Aboriginal tribes that lived in the area prior to European colonisation . As part of its life cycle, the dinofla-

dinoflagellat e

gellate G. catenatum produces a r esistant, brown, spherical resting cyst with a distinctive fine, microreticulate surface ornamentation. A Tasmania-wide survey of coastal sediments found resting cysts to be mainly confined to the Huon and Derwent estu aries (Bolc h and Hallegraeff 1990). Furthermore, a dinoflagellate cyst survey in a marine sediment depth core showed the presence of Gymnodinium catenatum down to a depth of 9cm but not in sediments deposited before that time. 210Pb analyses dated the appearance of this toxic dinoflagellate at approximately 1971. This microfossil evidence, together with the absence of this cyst species from other Australian waters, strongly suggested that Gymnodinium catenatum is not endemic to Tasmania but has recently been introduced. The mo s t lik ely method of introduction appears to have


Human co nsumer

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"- -~-

': . .... - .:·, :· ~ -~ .·,- :~ -

.. ..'

res ting spore in sediment

· · · ;_ .-·: ; .• ·.·


;:_. · ·· ·

. ' ,



·. .' . .

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Figure 2 Transfer of dinoflagellate toxins via shellfish to humans

Table 3. Summa1-y of algal blooms in New South Wales waters Date



Mar 1890 Jul-Aug.1930-32 Feb.1945 Dec.1970 Oct. 1972 Dec.1972 Jan .1980 Oct.1980 Oct.1981 Aug.1982 Dec. 1983 April 1984 Nov.1984 Dec.1984 Aug-Sep. 1985 Feb.1986 Feb.1986 Jan . 1989 Mar.1991 Jun-Jul.1991 Nov.1991 Aug.1992 Sep.1992 Dec.1992 Jan. 1993 Feb.199 3 Jan-Feb.1993 Feb.1993 Oct.1993 Nov.1993 April 1994 Nov.1994 Feb.1 995

Sc,ippsiella trochoicka Gym:nodiniu1n sanguineu1n A uixandrium catenella Giffordia mitchelliae Trichodesmium Trichodesmium Spyridia Jilamentosa Gymnodinium sanguine-um Gymnodin,iu1n sanguineum, Noctiluca scintillans Trichocksmium Mesodin,iuni Mesodinium Trichodesniiun1, Thalassiosira parthe:neia Mesodinium Thalassiosira weissjlogii Trichocksmium Sc,ippsiella trochoicka Gymnodinium galatheanum Heterosigma carterae Noctiluca Noctiluca Gephyrocapsa oceanica Gonyaulax polygra,mna Gonyaulax polygramma Noctiluca Dictyocha octonaria A uixandr ium catenella Pseudanitzschia multiseries Noctiluca A uixandrimn catenella Noctiluca

Sydney Harbour Sydney Harbour Port Hacking Pt Macquarie-Diamond Hd Taree, Coffs Harbour Palm Beach- Cronulla Crescent Head Cooks River-Alexandra Canal Lane Cove River Lake Macquarie Newcastle, Narrabeen, Foster, Bondi Beach Lane Cove River Lane Cove River Sydney-Wollongong NSW coast Lane Cove River Alexandra Canal J ervis Bay- Ulladulla Hawkesbury Rive r Lake Illawara Berowra Creek Lake Macquarie Berowra Creek J ervis Bay Darling Harbour Bate Bay Sydney beaches,Pt.Kembla Newcastle Sydney Harbour Berowra Creek Ham & Chicken Bay Port Hacking Sydney


been via ballast water discharge from infected Jap~nese or Korean ports. In the period 1987-1993 the cyst stages of the toxic dinoflagellates Gymnodinium catenatum, Alexandrium catenella and A. tamarense were detected in 34 ships, originating from either Japan or Korea and entering 12 different Australi an ports (Hallegraeff & Bolch 1992). One ballast tank, filled during a toxic dinoflagellate bloom in the port of Muroran, Japan, and sampled in Eden, Australia, thus was estimated to contain more than 300 million A . tamarens e cy s t s . Fortunately, only a limi ted number of foreign introductions lead to succesful establishment' in Australian waters, and there is evidenc e that Japanese coldwater dinoflagellate s cannot survive when released in trop ica l Australian ports s uch a s Port Hedland and Hay Point. The problem of introduction of unwanted marine organisms by ballast water is discussed in detail by Rigby in this issue.

References Beag le hol e, J C (ed) 19 55 . Th e J ourn als of Captain James Cook on his voyages of discovery. Vol 1. Th e voyage of the Endeavor 176 8- 1771 , pp 404-40 5 . Cambrid ge University Press. Fra nci s, G 1878 . Poi so nou s Au str alian lak e. Nature 18, 11-12 Bo lch , C J and Hall egra eff, G M 19 90. Dinoflagellate cysts in r ecent marine sediments from Tasmania, Au stralia . Bot M eir 33, 173-192 Hallegraeff, G M 1991. Aquac ulturists' Guide to Harmful Au stralian Microalgae . CS IRO/Fi s hing Indu stry Tr a inin g Board of Tasmania, 111 pp. Hallegraeff, G M 1993. A revi ew of harm ful algal blooms and th eir apparent global in crease. Phycologia 32, 79-99 Hallegraeff, G M, Anderson, D M & Cembella, A D (ed s) 199 5. Manua l_on Harmful Marine Microalgae. IOC- UNE SCO. Paris (in press) . Hall eg ra eff, G M 199 5. Alga l t oxin s in Australian shellfish: Increased public awareness and impli cation s for indu stry . Proc First In t Conf Mollu scan Shellfish Safety, Sydney (in press) Hall eg ra eff, G M and Bolch , C J 199 2 . Transport of diatom and dinoflagellate resting spores in ships' ballast water: implication s for plankton biogeography and aquaculture. J Plankton R es 14, 1067-1084 Hosja, W an d D Dee ley 1994. Harmful phytoplankton surveillance in Western Australia. Wa terways Commi ss ion , report no 43, 61 pp. Jasperse, J A (ed) 1993. Marine toxins and New Zealand shellfi sh. Proc of a work shop on research issues, 10-11 Jun e 1993. The Royal Soc iety of N ew Zea land, Mi sce ll an eou s series 24, 68 p. Whitelegge, T 1891. On the recent discoloration of the waters of Port Jackson. R ec A ust Mus 1, 179-192

Author Dr Gustaaf Hallegraeff is a Senior L ecturer i n Aqu atic Botany at the Department of Plant Sci en ce of the University of Tasmania in Hobart. He has published more than 80 .iournal articles and produc ed or edited 3 books including a forthcoming JOG/UNESCO Manual on Harmful Marine Microalgae.



CONTROLLING MARINE INTRODUCTIONS: CRIMP RE Thresher *, R Martin Summary To prevent further introductions of exotic marine pest species and to control those already introduced to Australian waters , research mu st b e directed towards: (1) developing effective barriers, (2) determining which exotic species are already prese nt, (3) assessing the risks they pose for human health, marine industries and the marine environment and (4) controlling pest species, if not eradicating them . Australia has a long hi story and considerab le succe ss in applying these research needs to introduce d terrestrial pests, but effor ts to limit the impacts of marine introductions have focused largely on barrier controls. Th e d eve lopment of a co-ordinated , broadly-based r esearch effort has also been hampered by the lack of any central body with clear responsibility and adequate funding for addressing the problem. The recent initiative by the Federal Government to provide fund s to establish the CSIRO Centre for Research on Introduced Marine Pests (CRIMP) - represents a s ignificant move towards r edressing this situation. This paper outlines the aims and current activities of the Centre.

Introduction As a result of Australia's geographical isolation, its dependence on shipping for import and export, and world-wid e marine quarantine procedures that are poorly developed, Australia now hosts over 70 known exotic marine species of which around 20 are believed to have been introduced in ships' ballast water (Jones, 1991). The actual number of exotic sp ec ies in Au stralian ports is not known as no detailed surveys have been under taken in Au stralian waters. Overseas experience, however, suggests that the numbers of introduced species is likely to be higher than previou sly thought (Carlton, 1989). In most cases the threat these exotic species pose to the Australian marine ecosystems, to wild fisheries, the mariculture industry and human health is also not known . Three introductions, however , the toxic dinoflagellate Gymnodinium catenatum, the alga Undaria pinnatifida, and the Northern Pacific seas tar, Asterias amurensis, could cost the shipping, mariculture and fishing industries millions of 24

dollars annually . Both Undarias and Asterias have the potential to cause fundamental changes to the structure of temperate Australian coastal marine ecosystems. The potential impacts of other previously cryptic exotic species such as the fan worm Sabella spallanzanii and t h e European shore crab, Carcinus maenas, are only now being assessed.

Research Needs The Coastal Zone Inquiry (Resource Assessment Commission, 1993) noted that "there is an urgent need for further r esearch into th e potential effects of exotic pests a nd di seases introduced through ballast water discharges, into strategies for the management and possibl e er adication of such pests and di seases, and into ways of preventing the introduction of other pests and diseases" (p 301). The RAC statement highlights the need for research directed at two areas: (i) prevention of new introductions and (ii) assessing and minimi sing the impacts of existing introductions. Au stralia has taken a high profile internationally in an effort to minimise the risks .of ballast water introductions. Th e Austra li an Quar a ntine a nd Inspection Service (AQIS), through its chairmanship of the Marine Environment Protection Committee of the International Maritime Organisation, has been a strong and successful advocate for international controls on the discharge of ballast water . Within Australia, AQIS has been instrumental in the development of a Draft Australian National Ballast Water Mana ge ment Strategy and has taken the lead in developing draft domestic ballast water management guid elin es des igned to minimise risks of translocation of introduced pests within Australian coastal water s. Research in support of these regulatory initiatives has largely centred on efforts to develop ballast water treatment and management protocols. The r esults of this r esearch are described by Rigby in this issue. Efforts to assess the threat posed by exotic species in Australian waters and to control their abundance and spread have, to date, been largely ad hoc and ineffective. Research in support of remediation activities has suffered from an ~nwillingness by any government agency

to accept overall responsibility for the exotic species problem. The result of this has been a lack of adequate research funding and the consequent inability of any agency to mount an effective, broadly-based research program. In principle, the problem involves a trade-off between the costs of prevention (or risk minimisation) and control, and the costs to the environment and industry of an introduced pest. Eliminating the risk entirely may often not be possible, but controls can be sought to minimi se the costs of prevention and the costs resulting from environmental damage or direct effects on marine industries. To evaluate the problem and possible management options, one needs to: • Conduct a ba se lin e s urvey of the exte nt of the existing problem. Thi s would includ e determining its cau ses, the dynamics of the introduced populations, their effects on the environment, and the economic significance of their presence. • Predict future damage by both existin g and ;_e w introduction s, on the assumption that current shipping practices continue . An attempt should be made to predict dama ge in eco nomic terms, against which the benefits of a control program can be assessed. • Assess options for controlling specific introductions and their costs. Such costs may often extend beyond the normal direct or commercial costs to broad er social and environmental costs, such as impacts on biodiver sity. • Compare the costs of different control options with the reduction in the cost of damage that is predicte d to be achievable. The preferred option is then implemented, moni tor ed, and modifi ed, as required. • Undertake research into novel, more cost-effective techniques for increasing the effectiveness of the quarantine barrier and for control, if not eradication, of existing pests. As the overa ll probl em is characterised by high levels of unc er tain ty, both se nsitivi ty and scenario analysis will need to be used to explore possible bounds of control costs and environmental damage. Decision-analysis techniques will also be required to r esearch and for* CS IRO Division of Fisheries, GPO Box 1538, Hobart Tas 7001


mulate management strategies. Some aspects of the work, such as developing economic impact models and researching more effective barrier controls, have already been supported through AQIS initiatives. Others, such the ethics of releasing genetically enhanced biological control agents, are being examined both in Australia and overseas (eg Goodman, 1993), but have not yet been considered in the specific context of Australia's marine pests.

Implementation The evaluation and control of introduced marine pests clearly requires a multi-di sc iplinary approach involving areas as diverse as economics, environmental imp act assessment, taxonomy a nd en gi ne er in g. Recognition t h at CSIRO is the only Australian organisation capable of co-ordinating and conducting this research on a national scale led the Federal government to allocate funds in the 1994 Industry Statement for the estab li shment of a Centre for Research on Introduced Marine Pests (CRIMP) within CSIRO. The Centre draws on the diverse range of research skills within CSIRO and provides a core group to facilitate co-operative research involving the shipping, mariculture and fishing industrie s, and the Australian and international research community. The development of a research capacity in marine introductions is consistent with the high profile CSIRO has taken on research on introduced species in the terrestrial environment. The objectives of the Centre are to : • To develop and promote the application of techniques for earlier detection, more accurate prediction of impacts, and effective assessment of risks and costs associated with marine pest spec ies introduced into Australian waters. • To develop new methods or to improve existing measures for controllin g the spread and minimising the impacts of introduced marine pest species. Achievement of t hese objectives involves evaluating the environmental and economic threats posed by known introduced pest species; developing costeffective monitoring programs for early detection of these species in high-ri sk areas; providing the ecological basis for assessing the effectiveness of existing and new control measures; developing and promoting new control measure s nationally and internationally.

Staged Approach In practice, the cost of achieving all of these obj ectives sim ul taneo usly is daunting. Detailed ecological research on even one marine pest, such as the northern Pacific seastar, could easily absorb hundreds of thousands of dollars annually for many years, particularly when the real cost (including infrastructure) of WATER JULY/AUGUST 1995

research is taken into account. Consequently, CRIMP is taking a staged approach to the problem, focusing on key objectives and collaborating, wherever possible, with other research initiatives in order to maximise the dollar value of the research effort. Detailed discu ss ions with t h e Centre's primary clients - the fi shing indu stry, environm ental agencies and the shipping industry - led to the development of a preliminary research plan for the Centre that has four main components; assessing the magnitude, minimising translocation, biological control, international cooperation. Assessing the magnitude of the problem. This is in itself a daunt-

ing task. Initial plans for a comprehensive national survey to determine the numb er, id ent ity and distribution of exotic marine species ran immediately into two major difficulties: cost and taxonomy. Aside from the immediate and very high cost of surveying all likely infected habitats throughout Australia, the cost in developing and maintaining the taxonomic skills required to determine which species were introduced would be huge . The planktonic habitat, for examp le, is a prime candidate for invasion by ballast water introd uctions but the taxonomy of many planktonic groups is such that the positive identification of an exotic species, if present, would often not be possible. Similar, though perhaps less extreme problems, are typical of many marine groups. With the exception of fishes and a few of the larger invertebrates such as echinoderms and crustaceans, taxonomic coverage of Australia's marine biota is so limited th.at an attempt to identify even the mo st conspicuous of mari ne invaders would keep mar in e taxo nomi sts in Australia busy for many years. An alternative approach being develope d by CRIMP contains two components. First, at selected ports, a detailed assessment will made of those taxonomic groups for which identification of exotic species is feasible. The first port to be assessed will be Port Phillip Bay, on the basis that it is a major port for international shipping, is known to have a number of marine pests, has been well studied in the past, and is a site where we can draw on a great deal of local taxonomic expertise. The Port Phillip Bay project is planned to commence in mid1995, with the intent of having a report on the scale of infection in the Bay by the middle of 1996. The second component is to survey a series of Australian ports with the aim of determining the distribution of the pests we already know about and identifying unu sual species, which we can sub sequently examine in detail. A key element here is local knowledge. Overseas experience is that invading species are often not found by scientists, but rather by fishermen, school groups, dive clubs, etc,

- that is, members of the public with a detailed but often 'non-scientific' knowledge of their local coastline. For such individuals, the arrival of "something out of the ordinary" is quickly noted. CRIMP hopes to use this store of local knowledge to help develop a nati onal inventory of introduc ed spec ies. Discussions are currently underway with DEST to formally link CRIMP's activities with th e Coastcare initiative, in order to establish a national early warning network for the detection of marine introductions. Minimising the risk. The second major comp9mmt of CRIMP's research will be to seek ways of minimising the risk of domestic translocation. Several approaches are being taken towards this issue. These include studies, in progress, to determine the environmental tolerances of known pests, in order to determine their ultimate limits of distribution in Australian waters, field work looking at the likely mean s of transport (hull fouling versus domestic ballast water) and an assessment of the factors in ports that make them susceptible to invasion by exotic spec ies. Theoretical studi es indicate that biological invasions often occur following major environmental disturbances. The logic is that such disturbances create vacant habitat wh ich invaders can rapidly occupy. It is possible that in ports 'disturbances' such as dredging and pier construction provide major opportunities for exotic species to colonise new habitats. If this is tru e, minor modifications to port practices may well substantially reduce the likelihood ot'successful invasions. Biological control. The third, and largest, component of CRIMP's work will be in the area of biological control. Although local control of pests may be practical in some small, high-value areas (such as around marine farms), the 'open' nature of the marine environment means that once established, a marin e -pest will be virtually impossible to control or eradicate by physical removal alone. An alternative approach involves biological control using parasites, predators or pathogens. Biological control in the marine environment has never been attempted anywhere in the world . The principles are likely to be similar to terrestrial biological control, but the world's knowledge of marine parasites is poor. Nonetheless, we have indications that a number of parasites are found on the European shore crab and the northern Pacific seastar. How species-specific these parasites are and whether they can be use d as biological contro l agents remains to be seen. The difficulties in implementing such controls are formidable. Even rearing the parasites in captivity, for trials and ultimate release, will in itse lf require a major effort. Mo st marine species are extremely difficult to rear to maturity in captivity, and the marine parasites are likely to be no


exception. CRIMP is currently recruiting a small team of ~pecialists to investigate approaches to biological control in the marine environment and has commissioned field surveys in Europe, Japan and Russia to identify and assess the effects of native parasites on the source populations of pests introduced into Australian waters.

South Australian Water Corporation

International collaboration.


State Water Laboratory and Australian Centre for Water Quality Research For a complete service on sampling, analyses, advice and research of water, wastewater, sediments and sludges. This includes identification and enumeration of freshwater and marine phytoplankton and their toxins. Telephone (08) 259 0211 Facsimile (08) 259 0228

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CRIMP has already established contact with overseas researchers involved with the marine introductions problem. At CRIMP's expense, several overseas researchers have come to Australia to discuss and ass_ist with the development of the Centre's research plans; we have encouraged them to incorporate Australian species and problems in their own studies. CRIMP has also been approached regarding sabbatical studies by overseas workers and the Centre is providing support for post-graduate studies on diverse aspects of marine pest biology and control. CRIMP staff are active in ballast water issues at all levels of government, including the SCARM Coasta l Ballast Water Guidelines Working Group and the Interim Australian Ballast Water Management Advisory Council. Finally, CRIMP staff will be participants at a special symposium, sponsored jointly by the International Council for the Exploration of the Sea and the International Maritime Organisation, on the impacts of ballast water introductions. The symposi um is being held in Denmark, in September 1995, and will provide a major opportunity for the Centre to further devel6p its international research links.

References Carlton, J T (1989). Man 's role in changing the fac e of the ocean: biological invasions and implications for conservation of near-shore environments. Conserv. Biol. 3: 265-273. Goodman, B (1993). Debating the use of transgenic predators. Science 262: 1507. Jones, M (1991) Marine organisms transported in ballast water. Bur. Rural Res. Bull. (11) Resource As sess ment Commission (1993). Coastal Zone Inquiry Final Report. A.G.P.S. 519 p.

Authors I>r Ron Th:resher has a PhD from the University of Miami and joined the CSIRO Division of Fisheries in 1984. He is currently Program L eader for the Division's Temperate and Deepwater Fisheries Resources Program, Acting Head of the Cen tre for Res earc h on Introduced Marine Pests and a member of the Interim Australian Ballast Water Management , Advisory Council. Mr Richard Martin has a MSc from the University of Auckland, and joined the CSIRO Division of Fisheries in 1979. He is currently the Liaison Officer for the Centre for Research on Introduced Marine Pests in Hobart. WATER JULY/AUGUST 1995


TRANSLOCATION: THE BALLAST WATER PROBLEM G Rigby* cargo vessels, originating from either ment. Estuaries and bays with similar Japan or South Korea, and entering 9 temperatures and salinities are obviously Ships from over seas discharge baldifferent Australian ports). One ballast more prone o infection than offshore last water whic h may contain exotic ports. ¡ organisms . Some of these, if they tank, filled during a toxic dinoflagellate bloom in the port of Muroran, Japan, and become established in the receiving port, Current Status of Control can pose a serious threat to the natural sampled in Eden, New South Wales, was estimated to contain more than 300 milSince February 1990, the Australian environment, human health, fishing, lion Alexandrium cysts (Hallegraeff and . Quarantine and Inspection Service tourism and aquaculture industries. This Bolch, 199 la; Hallegraeff and Bolch, (AQIS) has adopted a set of voluntary paper outlines options for minimising 1992). guidelines which provide vessels with a such translocation. A National Strategy The dinoflagellate Gymnodinium number of options including: reballasting was announced in 1994 and research is catenatum is now well established in the at sea, an understanding not to release continuing Derwent and Huon estuaries of ballast water in Australian waters, enterTasmania, and has been responsible for ing into a "Compliance Agreement" to Keywords the closure of shellfish harvesting from maintain ballast tank contents in a clean Toxic marine organisms, transloca- this area for periods up to 6 months dur- condition, and implementation of an tion, quarantine, ballast water, treat- ing the years 1986, 1987 and 1991. As a approved treatment process. Random ment, cholera. result, Tasmanian health and fisheries sampling of ballast water for toxic authorities have had to implement a cost- dinoflagellate cysts has been practiced in Introduction ly shellfish toxin monitoring program to conjunction with compliance, at the time Ballast water has been an area of ensure the quality of commercial shell- of approval to enter an Australian port interest for many years as a possible fish products and protect public health. (Pratique) , by AQIS to monitor t h e cause of dispersal of marine organisms Current evidence suggests that this implementation of the guidelines. These species may have been introduced after Australian guidelines provided the basis around the world (Ostenfeld, 1908, through to Taylor, 1990). There is now 1973. The recently observed prolifera- for the adoption of a similar set of guideclear evidence that some hundred or so tion of the Japanese sea star (Asterias lines ("International Guidelines for amurensis) in the Derwent River in Preventing the Introduction of species have been translocated around the world with many establishing new Tasmania is of major concern, although Unwa ~te d Aquatic Organisms and population s in foreign waters there is not yet clear evidence that bal- Pathogens from Ships' Ballast Water (Hallegraeff and Bolch, 1991 a; last water has been the vector for this and Sediment Discharges") by IMO at Hallegraeff, 1993; Jones, 1991) introauction. the 31st Session of the Maritime At the international level some 40 Environmental Protection Committee However there are at least fourteen established species known with reason- recent invasions around the world have (MEPC). able certainty to have been introduced in probably been mediated by ballast water Following the National Symposium ballast water (Table 1). The actual num- (Carlton and Geller, 1993) although there on Ballast Water Management, organber of established non-indigenous species is still considerable debate amongst the ised by AQIS in May 1994, a National could be significantly higher than this, scientific community about the true ori- _ Strategy for Ballast Water Management since a very large proportion of the gin of some of these species. was developed and anno unc ed in The environmental and cost implica- December 1994. It will form the basis for Australian coastline (possibly 80-90%) has not been surveyed for possible intro- tions of these introductions have been an ongoing program of research and ductions. The seaweed Undaria pinnati- highlighted by the rapid spread of the development to address the many issues fida, from Japan, is now well established Zebra Mussel (Dreiss ena po lymorpha) involved. One important aspect of this on the Tasmanian east coast with an esti- through the Great Lakes of North program will be the involvement of a mated standing crop of 400 tonnes. This America . First observed in Lake St much wider group of participants who introduction is likely to have significant Claire in 1988, the Zebra Mussel had could be potentially affected by further long term ecological effects, since it has invaded almost 50% of all waterways in organism introductions. The strategy the ability to displace the native sea- the USA by March 1993 (Reigby 1994 b). will also address guidelines for manageweeds and is likely to affect the abalone This organism has such a prolific growth ment of domestic ballast water as well as habit, that it grows on almost any sub- international discharges. and sea urchin industry. Of more immediate concern has been strate and has been responsible for Australia, USA, Canada and New the potential dispersal of toxic dinoflagel- major blockages of intake cooling water Zealand have now applied the IMO la te species responsible for paralytic pipes in power stations. The cost of con- Guidelines. Australia, Japan and USA shellfish poisoning (PSP). In a recent trolling this invasion has been estimated also have in place management practices detailed survey of some 340 cargo ves- as US$5 billion up to the turn of the cen- for cholera detection, potentially a major sels entering 18 Australian ports the human health issue (AQIS 1993a). At its tury. The likelihood of an introduced March 1994 meeting (MEPC 35), a worktoxic dinoflagellates Alexandrium catenella, A. tamarense- - a:r.i..d..7 species creating a real problem depends ing group was establi shed to further Gymnodiniun catenatum were detected on it's survival in closed ballast tanks develop the Guidelines as a basis for a in 16 ships. Toxic dinoflagellate cysts during the voyage, and the similarity or were found in woodchip, gas and ore compatibility of the recieving environ- * BHP Research, PO Box 188, Wallsend NSW





new annex to MARPOL 73/78. Drafting of these guidelines will be further progressed at the MEPC 37 meeting in September 1995.

The Magnitude of the Problem It has been estimated that some 10 billion tonnes of ballast water is transferred around the world as ships' ballast. In Australia alone, in excess of 120 million tonnes/year of ballast water and sediments are discharged into some forty ports . Figure 1 illu strates t h e movement of this water represented by the number of international ship visits (Kerr, 1994). This water is transported to Australia in a variety of ship s, the majority being bulk carriers, mainly from Asia, with approximately half of this amount originating in Japan (Figure 2).

Ballast tanks are complicated.For examp le, the 141,475 ton n e ' Iron Whyalla', a typical example of a bulk carrier, carries 22 complicated tanks, total capacity 56,325 tonnes, with an option of a further 20, 000 tonnes in a cargo hold. Two ballast pumps each of 2000 m3/h capacity could deballast in 12 hours, but the operation must be coordinated with cargo loading and is controlled by computer to minimise bending stresses in the hull.

It is also recognised that these harmful exotic species are likely to be present in the ballast water of only around 6% of all ships entering Australian ports (Bolch and Hallegraeff, 1993). This observation means that unless solutions involve very minor cost or inconvenience, there is a good case to suggest that only ballast water known to have harmful toxic cysts present should be treated. If this strategy is accepted, then emphasis must be placed on the setting up of an effective monitoring program to identify the existence (or absence) of cysts in the water being ballasted in a particular port, so that a decision can be made whether or not to undertake a particular treatment.

Potential Solutions Research. A significant amount of interest and re search effort has been developed in recent years within Australia and in Japan, Korea, Canada, USA, Germany and New Zealand to quantify the local issues involved and to assess the various potential solutions to the ballast water problem. In Australia, a

research pro ( ram was insti gated by AQIS in 1991. This program has been developed and administered by a Ballast Water Scientific Working Group, consisting of repre sentative s from re search, shipping and regulatory organisations with a common interest in this area. Australian research has been at the forefront and has provided an impetus for the development of links and world-wide strategies to address the problem at an international leve l. Details of specific projects within the Australian research program have been summari sed elsewhere (Kerr, 1994; Rigby, 1994 a). The outcome of the work related to treatment options, together with other re levant studies related to potential solu tions which could minimise discharge of undesirable organisms is summarised below. It is reiterated t hat the focus of this work has concentrated on dinoflagellate cysts. Chemical/biocidal treatment. Many chemicals or biocidal treatments have been s uggested to inactivate dinoflagellate cysts. Whilst it is possible

Australian Focus The initial Australian focus has been to concentrate on practical means of minimising the transfer of toxic dinoflagellates, since this was the main area of initial concern, and it was considered that techniques which could manage these organisms would also be applicable to many other organisms of potential concern. This focus has been maintained t hrou ghout the research program to date, although some recent emphasis has been p laced on Vibrio cholerae (Cholera), Asterias amurensis (Japanese starfish) and Undaria pinnatifida (Japanese seaweed). An added complication has been that the toxic dinoflagellates of concern can produce resistant sexual cysts which can survive for long periods of time and subsequently germinate into the vegetative form und er favourable conditions . Recent work has shown that the vegetative forms of these dinoflagellates do not survive for many days in the closed ballast tank environment, and that the sexual resting cysts are not likely to form in the ballast tanks (Rigby and Hallegraeff, 1994). This has allowed interest therefore to be focussed on techniques which can minimise the transfer of ballast water containing permanent resting cysts. Based on the current knowledge of harmful dinoflagellates, the species considered to be mo st und esirab le are

Gymnodinium catenatum, Alexandrium catenella and A. tamarense.


22 'M,yalla 9Pcw1Bon-,,1ht.l\ 26Pet1Piri•


32Adelald• 12 Wallaroo S NdroUIW'I



5 p o,1 Qjoe




I 6P0<1La11

" """'

I ~


\_J,/_ 99 l~~·•911oba,,

Figure 1. Number of international ship visits recorded in Australian ports in 1991 (Kerr, 1994). Scale: eg Brisbane, 300 visits. Table 1. Introductions of marine organisms in Australia attributed to ballast

water or sediment discharge (Jones, 1991) Fish


Acanthogobius flaviinanus (yellowfin goby) Tridentiger trigonocephalus (striped goby) Lateolabrax .iaponicus (Japanese sea bass) Spai-identex hasta (sobaity sea bream)

Musciilista senhousia (Asian mussel) Theora lubi-ica (Asian semelid bivalve)# Aeolidiella inclica (sea slug)*#

Invertebrates Crustaceans Pyroinaia ti,berculata (crab) Eurylana arcuata (slater) Neomysis ,iaponica (mysid shrimp) Tanais dulongi (tanaid)

Polychaete worms Merc ierella eniginaticci * Boccardici probosciclea * Pseuclopolydora paucibranchiata *#


Toxic dinoflagellate

Undai-ia pinnatijida

Gymnoclinium catenatum

• Hull fo uling has been proposed as an alternative means of introduction # Natural distribution is uncertain and may include Australia.


to inactivate cysts of concern using various chemicals, the costs associated with such treatme n t are not likely to be acceptable in any application, other than for very small quantities of ballast water or in very special isolated cases. Table 2 summarises the indicative costs for treating t he ballast water handled by t he "Iron Whyalla" and includes the results of laboratory tests for a range of chemicals. Other biocide options, such as ultraviolet radiation, ozone and reduced oxygen concentrations may be effective for motile dinoflagellate cells, but have not been shown to be effective in inactivating dinoflagellate cysts. Physical/Mechanical treatment. Dinoflagellate cysts have a typical size of approximately 20-40 µm and could be removed by an appropriate filtration system, eit her on board ship s during ballasting or deballasting, or in a shore-based faci lity. Indicative overall treatment costs, using a sand filtration system and ultraviolet treatment of the discharged water, have been estimated as $300 - $700 per thousand cubic metres of ballast water (Table 2) (AQIS, 1993 b). Despite some refinements based on new knowledge of ballast water sediments, these costs are not likely to be acceptable to the shipping industry. Destruction of organi s m s due to mechanical damage in a high pressure pumping system has been suggested but would require the installation of special pumps and is not likely to be effective in destroying living organisms, let alone dinoflagellate cysts (Carlton, 1990). Mid-ocean exchange. Exchange of water at sea has frequently been cited as an inexpensive and effective quarantine procedure (and is currently the most recognised option) for minimising the likelihood of organism transfer. In this option, water from t h e deep ocean (which is considered to be free of the organisms of concern) is used to exchange the original water. The nearsurface dwelling (top 10-15 metres of the water column) organi sms of the deep ocean form a group quite distinct from

those organisms living in coastal waters, where ballast water is generally first taken on. Macroplanktonic organisms ar e generally in lower de n sities in the "plankton poor" open ocean, due to vastly reduced nutrient sources. Organisms taken on as part of t h e deep ocean exchange are likely to perish once discharged in coastal waters. In addition to exchanging all or part of the original water and organisms, this option can also be effective as a natural biocide by increasing salinity levels to a point where some fresh water species are not able to survive. This is the basis of the ballast exchange controls of zebra mussels in North America. The effectiveness of ballast exchange in eliminating organisms will depend on the efficiency of ballast exchange, together with the degree of exchange necessary to have t h e des ired effect. For example, an increase in salinity may not require complete exchange of the original water, whereas the elimination of all organisms would require total replacement of all of the original water. Three basic options exist for ocean exchange of water (Rigby and Taylor, 1994). • emptying of tanks followed by refilling (re ballasting) • continuous flu shing or flow-through (ballast-exchange) • a combination of the above. Reballasting is an effective way of replacing the original water with fresh ocean water. The efficiency of replacement will depend on the design of the ship's ballast tanks and pumping system, but will typically be as high as 99.5 to 99.9% (Rigby and Taylor, 1994). The potential hazard is that safe bending moments and stresses can be exceeded (Rigby. and Hallegr aeff, 1994). A sequential procedure where tanks are emptied and refilled in a defined sequence can assist in minimising excessive stresses and bending moments (AQIS, 1993 a). Ballast exchange avoids the problem of exceeding safe bending moments or stresses, since the tanks remain full at all t imes. Typically, an exchange of 3

Table 2 Summary of comparative costs for inactivation or removal of Gymnodinium cat,enatum cysts. Chemical

Concentration for inactivation

Treatment cost

for "Iron Whya)la• Hydrogen peroxide Chlorine Copper sulphate Microbiocide ("Kathan WT") Change in pH Change in salinity




5,000 - 10,000 500 - 1,000 minor effects at 200 no effect at 10,000

20-40 4-8

1M-2M 0.2M - 0.4M n.a. n. a.

no effect over range of 2 to 10 viability not effected when immersed in fresh water for 24 hours; no effect for salini ty levels in the range of 15 to 50 parts per thousand

n.a. n.a.

Othersyirtems Filtration and UV. Reballasting Ballast exchange

ship or shore-based (28 hours) (42 hours)


0.3-0.7 0.031 0.046

15-35 K 1.5 K 2.1 K

tank volumes will result in a replaceme of app r o»imate ly 95 % of the origin water and an even higher proportion organisms. Indicative times for exchange (actu pumping time) and costs for both reb: lasting and ballast exchange options e route for the "Iron Whyalla" are al summarised in Table 2. Exchange or replacement of balla water using one or more of these optio: is now in general use by many shippi1 companies. A draft set of guidelines f impl ementation of the various optio: has been prepared (Rigby and Taylc 199 4) an chwill assist shipp ers in t i more rigorous use and implementati< of this solution to the ballast water pro !em. Heat treatment. The potential inactivating toxic dinoflagellate cysts I heating the ballast water has attract, recent interest (Bolch and HallegraeJ 1993; Rigby, 1994 b; AQIS, 1993 c) as , environmentall y friendly solutio: Laboratory work undertaken by Bo!, and Hallegraeff (1993), indicated th. heating Gymnodinium catenatum cys to temperatures of 40-45°C for ve1 short periods of time (30 to 90 second can result in inactivation of the cyst Thermal treatment is used to kill zeb1 mussels. Temperatures in the vicinity of 36c for several minutes, or, alternative!: exposure to temperatures as low as 33° for 2 hours,• have been shown to be effe tive (Jenner et al 1993). Waste h eat from the ship 's mai engine can, in principle, be used to he: ball::tst water. Calculations utilising a se ond ary heat exchanger have indicate that insufficient heat would be availab to reach temperatures of 45°( However, a recent analysis of the variot options for the "Iron Whyalla" (Rigl: and Taylor, 1993) has concluded that tr most effective scenario for cost-effecth use of waste heat is to flush heated co< ing water through the ballast tanks. It possible that lower temperatures may l: effective for longer tr eatment times an further research work is in progress 1 assess the t ime-temperature regimE required to inactivate toxic dinoflagella1 cysts, so that this option can be furthE assessed and demonstrated on a ship, considered appropriate. Other options. In addition to th above options, a range of ballast watE management options are possible to pr vide effective solutions, or to minimi~ the uptake and subsequent discharge c und esirable organisms: Some of thet include; • avoiding, minimising or using elevate inlets when ballasting in shallow port: especially where'toxic cysts are known t exist. • confining contaminated ballast to sp, cific tanks (especially those which ar not normally designated as ballast tank1 and subsequently emptying these tanll


whilst filling the normal ballast tanks. • utilisation of an alternative source of water (for example, from a fresh shorebased supply). • incorporating facilities in new ship designs to make confinement of contaminated water possible to facilitate easy exchange. Effective use of these options will depend very much on ship designs and port ballasting requirements. Nevertheless they are worthy of consideration where possible, especially in ports where contamination is common or is likely to occur on a seasonal basis. Overall strategy. An overall strategy has been developed to a draft stage (Rigby, 1994 b). It requires an effective and manageable monitoring and/or analysis program. If it can be certified that the water taken on is free of the defined organisms, it can then proceed to the discharging port and deballast in accordance with normal AQIS procedures involving monitoring, radio pratique and other quarantine formalities . This step avoids the need to undertake any ballast water treatments en-route. If the water is found to be contaminated , then management practices involving the various options would need to be followed in accordance with established guidelines. One of the primary aims of the AQIS research program has been to develop some of these guidelines. The conditions existing in the port during ballasting can have a significant influence on the extent of contamination. For example, water taken on during an algal bloom (especially where cysts are present in the water column) means that more algae will be taken on during balla sting. The role of sediment is also important, since some dinoflagellate cysts can survive for many years in sediment and become re-established under appropriate conditions. It is noted that the IMO guidelines request member states to advise them of the presence of toxic organisms or algal blooms so that this information can be communicated to all member states. It is envisaged that IMO will provide a focus at the international level in the future for further development and implementation of an overall strategy. The strategy outlined above together with the other research and management initiatives developed by AQIS through the Scientific Working Group, will play an important role in international ballast water controls. A draft set of Australian domestic ballast water guidelines have also been prepared . These guidelines will be further developed as part of the National Strategy.

Conclusions A range of options and possible solutions have been proposed and investigated to minimise the impact of harmful marine organisms from overseas ports on Australian receiving ports. Chemical


or biocidal treatment and mechanical or physical option s are not attractive on cost, practicality, environmental or effectiveness grounds and are unlikely to be acceptable oth er than in very special cases. Ballast exchange or reballasting at sea under appropriate guidelines offers a cost effective solution to the problem and is currently being utilised by many shipping companies. Safety must at all times be an overriding consideration. The potential of utilising waste heat from the engine to inactivate dinoflagellate cysts is under investigation and may ultimately prove to be a satisfactory alternative. Various management options aimed at minimising the uptake of organisms in a contaminated port or isolating contaminated water in specific tanks for later disposal and replacement are worthy of consideration in some cases. Monitoring of ports to identify the presence, or ab sence, of unde sirable species is an important aspect of any overall management strategy which would minimise costs and inconvenience by requiring treatment only of ballast water known to be contaminated (as has been suggested by the working group on ballast water at MEPC's 35th session in March 1994). An effective monitoring program would require cooperation and collaboration at an international level.

Acknowledgements The author thanks BHP Transport and Alan Taylor for support in this work. The overall draft strategy outlined was developed in conjunction with Alan Taylor and Peter Mill s. Much of the experiwental work on ballast exchange and heat treatment was undertaken in collaboration with Dr Gustaaf Hallegraeff and hi s contribution is acknowledged with thanks.

References AQIS (1993 a) Report by Australi a International survey of the IMO member states r ealtin g to ships ' ballast water. MEPC 34th Session, 5-9 July, London. AQIS (1993 b). Ballast water treatment for the removal of marine organisms - report prepared by Gutherid ge Haskin s and Davey P ty Ltd, AQIS Ballast Water Research Series, Report No 1, June (59 pp). AQIS (1993 c). Shipping ballast water trials on th e bulk carrier M .V. "Iron Why alla " report prepare d by Rigby, G R a nd Hall egra eff , G M, AQIS Balla st Wate r Research Series, Report No. 2, September (123 pp). AQIS (199 3 d) . Ballast water management report pre pa red by Thompson Clark Shipping in assoc iation with Gutteridge Haskins and Davey and Lloyd's Register of Shippin g, AQIS Ballast Water Research Series, Report No 4, Septembe1·. Bolch , C J and Hall eg ra eff , G M (1993). Chemical and physical treatment options to kill dinofla ge lla te cysts in ship 's ballast water. J . Marine Env Eng. 1, pp. 23-29. Carlton, J T (1990). Preventative options for the management and co ntrol of accidental and interco ntinental transfers of exotic organ-

is ms. Notes pre pared for Work s hop on Exotic Speci s and the Shipping Industry Tor onto, March 1-3, Issued by Int. J oin t. Comm - Great Lakes Fish. Comm. Carlton, J T and Geller, J B (1993). Ecological Roulette: the global transport of non indigenous marine organisms, Science, 26 1, 78-82. Hall egra eff, G M and Bolch , C J (1991a). Transport of toxic dinoflagellate cysts via ships' ballast water. Mar. Poll. Bull. 22, 2730. Hall egraeff, G M and Bolch , C J (1992). Transport of diatom and dinoflagellate r esting s por es in s hip 's ballast water : Implications of plankton biogeography and aquaculture. J . Plankton Res, 14, 8, 10671084. Hallegraeff, G M (1993). A review of harmful alga l bloom s a nd their appare nt global increase. Phycologia, 32, 2, 79-99. Jenner, HA et al. (1993). Monitoring and control of Dreissena polymorpha and other microfou lin g bivalves in t he Netherl a nd s, in "Ze bra Mu ssels - Biology, Impa cts and Control ", edited by Na le pa, T F, and Sohloesser, D W, Lewis Publication. Jones, MM (1991). Marine organisms transported in ballast waters: A r ev iew of t he Australian scientific position. Bull No 22, Bureau of Rural Resources, Dept. Primary Industries and Energy, Aust. Govt. Pub. Service, Canberra, 48 pp. Kerr, S (1994). Ballast water - ports and shipping study. Bureau of Resources Sciences Report, May, 14 pp . Ostenfeld, C H (1908). Medd. Fra Komm. Fur Danmarks Fiskeri-og Hauund er sog. Se r. Plankton 1. 6, 44 pp. Rigby, G R, Steverson, I G and Hallegraeff, G M (1991). Environmental problems and treatment options associated with the international exchange of shipping ballast waters. Proc. 19th Aust. Chem. Eng. Conf. Chemeca 91, Newcastle 18-20 Sept. 22 1-230. Rigby, G R and Hallegraeff, G M (1994). The tra nsfer and co ntrol of harmful mar in e organisms in shipping ballast water: behaviour of marin e plankton and ballast water exchange trials on the MV "Iron Whyalla". J. Marine Env Eng, 1, 91-110. Rigby, G R (1994 a) . Status of Australian ballast water research program, in "Proceedings of Workshop on Non-Indigenous Estuarine and Marin e Orga nis ms" organ ised by the US Dept. Co mmerce Nat. Oceanog. and Atm . Admin. Seattle, 20-22 April 1993. In Press. .Rigby, G R (1994 b) Possible solutions to the ballast water problem. Proc. Natl. Symp. On Ballast Water, AQIS, Canberra. May 11-13 , pp 87-106. Rigby, GR and Taylor, AH (1994). Oc ea n exchange of ship' s ballast water to minimise the transfer of harmful marine organisms - a review of research work and recommendations for the use of different options. Report prepared for AQIS (M arch). T ay lor, F J R (1990 ). In: "Tox ic Marin e Phytoplankton", E . Gran eli et al, eds. (Elsevier , Amsterdam, 1990), p. 527-534.

Author I>r Ge-Off Rigby is a Senior Research Associate at the Newcastle laboratories of BHP R esearc h. He is a Chemical Engineer with over 25 years of experience in a wide rang(! of projects. He has been a member of the Ballast Wa ter Scientific Working Group set up by AQIS since its inception, and, sponsored by BHP Transp ort, has been activ ely involved for the past 5 years, both locally and internationally. WATER JULY/AUGUST 1995


ALGAL MANAGEMENT STRATEGY - DELIVERING THE VISION T J Verhoeven * Michael Flynn Award This paper won the Award for the best p/,a,tform presentation at the 16th. Federal Convention. This award is in m emory of Dr Flynn, a foundation member of A WWA.

to meet economic, social and environmental needs. The vision was clearly stated by the Premier of NSW on 28 September 1994 when he launched Rivercare 2000; a Vision of Clean, Healthy, Productive Rivers by the year 2000.

Algal Management Strategy Abstract The New South Wales Algal Management Strategy was developed to minimise the impact of toxic and nontoxic blue-green algal blooms. It integrates five key areas of contingency planning, improving water management, reducing nutrients in waterways, education and awareness raising, and research. Achievements after two years of implementation, and future targets are described. Its successful implementation will result in other improvements in land and water.

Keywords Water management, water supply, blue-green algae, toxins, contingency plans, nutrients, phosphorus, awareness raising, total catchment management.

Introduction The occurrence of major toxic bluegreen algae blooms in 1991, including the notorious 1000km long bloom in the Darling-Barwon River, created immediate water supply, social and environmental problems. These blooms also signalled to concerned governments and communities other water quality, flow management and land management problems in Australia's catchments. The NSW Blue-Green Algae Task Force was established as a direct response to these problems. The Task Force (1992) made 30 recommendations which represent the NSW Algal Management Strategy to minimise the occurrence and impact of algal blooms. Having successfully completed its objectives, the Task Force was replaced by the State Algal Coordinating Committee (SACC) in September 1992. SACC's role is to coordinate implementation of the Strategy; its annual reports (SACC, 1993; SACC, 1994b) highlight progress and achievements. The NSW Algal Management Strategy embodies the vision of water for the next century; sustainable management of the State's water resources WATER JULY/AUGUST 1995

The strategy. The Strategy's many measures can be grouped into five key areas as shown in Figure 1. It includes a State Algae Contingency Plan to minimise the effects of blue-green algal blooms, improved water management and other measures to control the factors affecting bloom development, short to longer term nutrient management measures targeting the causes of blooms, education and raising community awareness, and research . As discussed, AWWA and its members have an important role to play in many of these areas. Principles. As described by Verhoeven (1994), the Task Force developed the Strategy on five principles: (i) This is not a single issue water quality problem with a simple quick-fix solution. Blue-green algal blooms have a consid.erable complexity in their cause and effect; their growth is determined by many environmental factors, and they have a wide range of social, economic and environmental impacts (Figure 2). Water authorities both contribute to the causes, and are affected by the occurrence of algal blooms. (ii) The Strategy is statewide in coverage because the occurrence of bluegreen algae and their impacts are statewide. For example, in 1993-94 SACC reported 115 waterways throughout the State having major algal blooms, with 54 at high alert level. Blooms occurred in coastal and inland streams, in large and small storages. Farm dams were not included in the above statistics. Blooms also occurred in Queensland, Victoria, South Australia and South-west Western Australia. (iii) Everyone contributes to the problem, and all have a role to play in its solution. Implementation of the Strategy is by everyone in NSW, under the Total Catchment Management (TCM) umbrella; state government agencies working with catchment management committees, local government, communities, industries including AWWA, researchers and individuals.

(iv) Management measures must be implemented as part of an integrated catchment management approach which cuts across established agency and political boundaries. (v) Management measures should be implemented where the benefits (social, economic and environmental) of minimising blooms and their impacts outweigh or equal the costs of control works or activities. At times it may thus be appropriate to "live with the problem".

Minimising the Effects Contingency plan. As the Strategy is implemented and the vision of clean, healthy, productive rivers becomes reality, blue-green algae blooms should decrease in their impact and occurrence. However, because nutrients in waterway sediments will maintain algal blooms for many years, and because blooms will not disappear completely, the State Algae Contingency Plan was developed to minimise bloom impacts. The Plan is implemented by nine Regional Algal Coordinating Committees (RACCs), based on the State's major surface water catchment divisions. Each RACC is responsible for monitoring; field identification coupled with laboratory analyses; provision of rapid, accurate, concise information to communities and to the weekly State Algal Report; response plans for the provision of safe domestic water supplies. As with other water users, water supply operators should make themselves familiar with the operation of their RACC, and with the local algae contingency plan (the nearest office of the Department of Land and Water Conservation (DLWC) can assist). Councils and other members of AWWA can assist the operation of these plans by reporting their field identification of blue-green algae. These simple measures help the successful local management of algal bloom effects. Monitoring and testing algal blooms. All States in the Murray Darling Basin - New South Wales, Queensland, Victoria and South Australia - use the 1same water quality alert levels for blue-green algae, based on a model developed by Burch in South Australia. SACC (1993) has developed * Department of Land and Water Conservation, PO Box 3720, Parramatta 2124


an algal toxin data base; data from councils as well as State Government agencies and water boards will greatly improve our understanding of the occurrence of algal toxins. The Department of Land and Water Conservation has recently developed an Algal Watch Kit which can be used by councils and others to aid with the early detection of algal blooms. Safe water supplies. Major programs are well advanced by water boards, Department of Land and Water Conservation and councils to upgrade the use of water supply options such as treatment using activated carbon; dual water supplies; or alternative water supplies such as groundwater, as part of local contingency plans. Granulated or powdered activated carbon (GAC or PAC) is added as a treatment process to conventional water treatment to remove algal toxins, taste and odow·. Stocks of the expensive material are held by Hunter Water and some councils; DLWC maintains a register of all GAC stocks in NSW. SACC (1994a) has reviewed the viability, application and costs of water treatment processes for small communities, with the objective of providing a sustainable, safe domestic water supply assuming a toxic algal bloom in t he source water. There are a number of treatment processes available, with Slow Sand Filtration (with GAC) and Lagoon Settlement (with GAC or PAC) providing robust, straight-forward technologies suitable for operation by small communities. At the farm level, State Government is operating a fouyer ar Bore Subsidy Program to provide a safe groundwater alternative to landholders affected by blue-green algae in their surface water supplies, primarily alon g the DarlingBarwon and Hawkesbw-y Rivers.

Improving Water Management The Algal Management Strategy recognise s the need for a river flow regime to maintain the health and function of waterways and related environments, while meeting the needs of comm uni ties and other water users. The Department of . Land and Water Conservation is working with catchment management committees and other water users to develop an Environmental Flow Package for each major river valley. The first package was introduced in the Lachlan Valley in 1992, and is undergoing a five year trial. A draft package was completed for the Murrumbidgee in 1994, and those for other valleys will be ready by the end 1995. Each Environmental Flow Package contains a three part approach to introduce important features of natural variability in river flow: (i) Managing flow in the state's regulated waterways (those having a major dam controlling river flow) including a




Shon to medium term

Shon to long term

Algal issues

Bloom effects

Algal crop

Bloom causes

Management Strategies

State Algae Contingency Plan

Manage Blooms

Land and Water Ma na gement

. contingency plan

. water allocation and water

. nutrient control strategies

system management

l I

. monitoring and ac tion levels

. chemical methods

. safe water supplies

. biological methods

. waterway management

Education and Awareness Raising Research

Figure 1 The New South Wales Algal Management Strategy

review of abstraction licences. A portion of regulated supply in storages is re se rved as an Environmen ta! Contingency Allowance to meet urgent water quality and environmental needs. (ii) Managing unregulated flows, for example the Interim Unregulated Flow Manage men t Plan for the DarlingBarwon River, in operation since 1992 to preserve some river flow for algal suppression and fish movement. (iii) Managing releases from storages including flushing flows, minimum release rules and variables offtakes. Other, non-volumetric parts of the Package relate to operating procedures for dams and weirs: • Delivery rules to control the rate of change of dam discharge and temperature of discharge water. • Improved weir-pool management to influence water quality in the weir pool (Jones, 1993), fish passage, and varying flowrates downstream .

Chemical and Biological Measures to Manage Blooms Chemical measures include the use of algicides and algistats in off-river water ~upply storages and farm dams, but not m natural waterways. Biological controls are being re sea rched throughout Australi a; for examp le both the Department of Land and Water Conservation and CSIRO are researching the use of biomanipulation to control blue-green algae. The use of barley straw to help inhibit algal bloom development was trialled extensively for SACC. The first round of tests have shown that it has no noticeable effect (SACC, 1993), and reporting on the later trials is underway.

Nutrient Control to Manage Bloom Causes Nutrient control is central to the Strategy's range of short to longer term measures if the Vision is to be sustainable. Nutrient control is also an important area in which AWW A can assist. Nutrient management models and plans help catchment management committees prioritise control works and actions which are developed and implemented

for each catchment. Nutrient management plans.

Nutrient management models are being progressively developed for all major NSW catchments to identify and quantify all point and diffuse nutrient sources. Models have been completed or are being developed for the Murrumbidgee, Hawkesbury-Nepean, Hunter, Namoi, Lachlan, Macquarie, Gwydir and Murray Valleys . Each joint TCM-government project team is us ing CSIRO's Catchment Management Support System modelling tool to also prioritise nutrient control works and actions in a nu trient management plan for t heir catchment, as described by Long and Verhoeven (1995). A typical management plan will include recommendations for many of the works and activities described below. Reducing nutrients at source.

Nutrient&. particularly phosphorus, need to be reduced at source and intercepted at all points in the catchment to minimi se t heir e ntry in to waterways. Actions to reduce nutrients at so urce include: • The November 1993 detergent manufacturers' agreement with the NSW Government to limit to 5% by weight the amount of phosphorus in detergents, to introduce informative labelling on packaging, and to introduce a public education program. • Implementation of the NSW Local Government Phosphorus Action Plan which was launched Statewide in March 1994 following the Albury-Wodonga pilot. This campaign, with the support of the Department of Land and Water Conservation, aims to reduce phosphorus exports from urban and rm'al communities by raising awareness and changing behaviour of individual s. Thirty four counc il s are curr e ntly runnin g the Action Plan, with another 41 expected to join by mid 1995. • Current development of an awareness program by SACC to, provide the irrigation indust1-y and other primary producers with information on how to reduce their sources of phosphorus, particularly from soil erosion and the use of fertilisers. • Careful siting, design and operation of WATER JULY/AUGUST 1995


. / Toxins - - - - + Hu mans

Nutrients (P & N :P) /

Stock Domestic Animals Wild life (not to fish)

DIFFUS E SOURCES ( Light(+ Low Turbidity) -+

Oeoxygenatio n - (lnstream Effects


~~~::s~D / "'-.

tant behaviour changes being measured For exam~, phosphorus inflows to th1 Albury sewage treatment plant wen reduced by 20% within six months o commencing that city's campaign.

includin g Fish) Lack of Turbu le nce

.....__......_ Aesthetic --+-Scums





Od ou r Wate r Supplies -Taste and Odou r


Organic Load Affe ct Trea tmen t

Biolog ical (eg Predation)

Chemica l (eg high pH)


Environmental --+Water Chemistry Blologlca l



Figure 2 Blue-Green Algal Blooms - Ma_jor Causes and Effecf,S

septic tanks by improved administration of their design and maintenance, as described by SACC (1993). • Development by the NSW Urban Stormwater Task Force of Statewide strategies for reducing stormwater impacts, including nutrients, on the quality of receiving waters. Intercepting nutrients. Nutrients can also be intercepted, by measures including: • Improved sewage treatment and phosphorus removal by the Sydney Water Board, Hunter Water, and the Department of Land and Water Conservation working with councils. • Effluent reuse by communities and industry. A notable example is the 1994 agreement by Pacific Power's Eraring Power Station to reuse the total flow of treated effl u ent from Dora Creek sewage treatment plant. • Constructing a range of works such as wetlands, riparian buffer strips, grassed urban drainage systems. The cost and technical input to their design and construction are being met by major funding initiatives of the NSW Government, with some support from the Commonwealth, and working with catchment management committees, local government, irrigation and other industries, and landholders. Legislative and economic tools to reduce nutrients. State government already regulate s by the use of licences to reduce nutrient accessions to waterways. Studies of the use of economic tools, including tradeable property rights, to reduce nutrient discharges to waterways have been completed and are now being discussed with communities.

Community Education and Awareness Raising The succ ess of the NSW Algal Management Strategy depends on a state community which is aware and actively involved in deve loping and implementing solutions, from the early detection of blue-green algae blooms in contingency plans to implementing nutrient control measures. SACC (1994b) has already produced and disseminated a range of information items for general WATER JULY/AUGUST 1995

community use, for people having to deal with an algal bloom, and for specific iss ue s such as the Local Government Phosphorus Action Plan. SACC and its member agencies have also had considerable input into developing the Murray-Darling Basin Commission's Algal Management Strategy which complements the NSW Strategy, and to the Senate Standing Committee on the Environment, Recreation and the Arts Inquiry on Water Resources - Toxic Algae. As a result, many of the NSW Task Force finding s and recomm endation s were included in the MDBC and Senate reports.

Delivering the Vision Integration is the key. AWWA and its members have an important role to play in implementing the NSW Algal Management Strategy. Successful implementation entails: • Integrating immediate (bloom effects), sho t term (bloom development) and longer term (bloom causes) structural and non-structural measures; • Integrating nutrient and water management measures via TCM; • Integrating this Strategy with other water quality and natural resource man· agement strategies; • Integrating measures catchment-wide and basin-wide; • Integrating research and ideas to fast track 'best bet' solutions; and, • Importantly, integrating the efforts of the state community, industry (including AWW A), TCM, and the three levels of government. Early indicators of success. Significant progress has been made in the two years of Strategy implementation. Some indicators of its success are: • The adoption of the State Algae Contingency Plan and the operation of volunteer monitoring programs such as Riverwatch along the Darling River. • Acceptance by communities and water user s of flow management plans which now reserve a portion of river flow for the aquatic environment. • The adoption of the Local Government Phosphorus Action Plan, and the resul-


S ucc essful implementation of th1 NSW Algal Management Strategy wil aid achievement of the Vision for Clean Healthy, Productive Rivers by the yea 2000. This is because the benefits of min imising problems associated with blue green algae include not only: • Secure, reliable supplies of good quali ty drinking water for a range of uses and • Considerable savings in water treat ment and reservoir operation costs; bu also • Clean, h ea lthy waterways for th, enjoyment of present and future gener2 tions of Australians and overseas visi tors; • A healthy, balanced river ecology t, support our diverse native fauna an, flora, and the industries, which depenc on quality water; and, • Additional benefits and savings fron improved land and water managemen (reductions in soil erosion and loss o agricultural capital).


Jone s, G (1993) Toxic Blu e- Gre e n AlgaE Predicting and Contro llin g Toxic Bloom: CSIRO report. Long, G and Verhoeven, T J (1995) ' Nutri en management plannin g to improv e wate quality' , AWWA 16th Federal Conventio S¥dney 1995. NSW Blue-Green Algae Task Force (1992) Blu, Gre e n Algae. Final Re port of the Ta s Force, Department of Water Resources. NSW State Algal Coordinating Committe (1993) Implementing the New So uth Wale Algal Management Strategy . First Annu; Report, Department of Water Resources. NSW State Algal Coord ina ting Comm itte (1994a) Water Treatment Options for Sma Communities Affected by Blue-Green Alg: Blooms, Department of Water Resow·ces. NSW State Algal Coord ina ting Committe (1994b) Impl ementing the New South WalE Algal Management Strategy. Annual Repo1 1993/94, Department of Water Resources. Verhoeven , T J (1994) 'The New South WalE Algal Management Strategy: Integrating th professions and community', 25th Congrei of The Internat iona l Ass ociation c Hydrogeologists/ln tern a t ional Hydrolog and Water Resource s Sympos ium of th In stit ut ion of Engineers Australia, Th Institution of Engineers Australia, Vol. 1, p 73-77.

Author John Verhoeven is Manager of th Environment Branch, Department c Land and Water Conservation of NSl-1 Chairman of ~he NSW State Alge Coordinating Committee, and chaire the NSW Blue-Green Algae Task Force. He has an MEngSc with an extensi1 career in water resources manageme1 development and planning both in NSV Northem Te1·ritory and South-East Asia 3


FLOATING-MEDIUM DOWNFLOW FLOCCULATOR WITH COARSE SAND FILTER A SYSTEM FOR A SMALL COMMUNITY? H H Ngo, S Vigneswaran * Keywords Filtration, flocculation, floating medium, small community water supply.

Abstract This study aimed to evaluate a combined syste m of a downflow floatin g medium flocculator (DFF) and a coarse sand filter (CSF) to treat surface waters for small community water supplies. The downflow flo ating medium filter function s as a flocculator and as a prefilter whilst the coarse sand at the bottom of the filter column is a polishing filter. Semi-pilot scale filtration experiments conducted with s urfac e water from Moonee Creek Dam, Gosford indicated that: • the DFF unit not only provided uniform micro-floes but also retained more than 60 - 70 % of influ ent suspend ed so lid s (at filtration rates of 5 - 9.9 m'/m'.h); • the combined sy stem yi elded high quality effluent which met the drinking water standard with very low headloss development; • excellent removal of suspended solids, turbidity, colour, total iron was achieved, particularly at a low filtration rate (5 m'/m'.h), using polyaluminium chloride flocculant.

Introduction In small community water supplies, the floating medium filter can be used as a contact-flocculator and a prefilter in place of conventional processes for flocculation and se dimentation (Ngo and Vigneswaran, 1994). A number of buoyant media flocculation and filtration systems have been tried in water treatment and wastewater treatment as flocculators and filters (Vital et a l, 1990; Ishigaki , 1991; Ben Aim et al., 1993; Vigneswaran and Ngo, 1993; Wahshe et al, 1993; Sugaya, 1993; Ngo and Vigneswaran, 1994; Sahnoun et al, 1994 and Schulz et al, 1994). A detailed labo-


ratory-scale study with a static floccula- mixing problems, as in the typical dual tor packed with a bed of polypropylene media filter, and less energy for backbeads (d = 3.8 mm and p = 0.87 g/cm') washing. In this trial experiments wer e conshowed that it had a reasonable solid removal capacity with very low headloss ducted with varying filtration velocities, developmen t (Vi gn eswaran and Ngo, flocculants and flocculant doses. The pH, 1993). Johnson's filtration system (USA) suspended so lid s, turbidity, apparent colour, total organic carbon (TOC), total was used as prefilter at Bargo Water Treatment Plant (Australia) and gave iron floe size of efflu ent and headloss t urbidity and colour reduction from 8 dev~lopment were measured to evaluate NTU and 25-30 HU to 0.7-3 NTU and 7- the performance of this combined sys25 HU respectively (Walshe et al, 1993). tem. Sugaya's experiments with the Super Waki-Shimizu system (using a 0.6m deep Experimental b ed of 1.1 mm poly sty ren e bead s) The layout .of the experimental unit r educed th e suspend ed so lid s in raw used in this study is shown in Figure 1. water from 10-3 0 mg/ L to 5 mg/ L A well mixed raw surfa ce water was (Sugaya, 1993). A detailed experimental pump e d to the constant h ea d ta nk . study indicated that a two-stage buoyant Floccula-nt was inj ected continuously into coarse media flocculator provided effec- the influent fe ed line just ahead of the tive treatment at higher loading rates rapid mixing devic e usin g a chemical (30 m/ 1) and shorter residence times (2-3 dosing pump. The suspension was then min) than m ec h a nical floccul ato r s passed to the filter column . The rapid (Schulz et al, 1994). mixing device was fabricated by tightly In the combined DFF-CSF system, winding 3 - 6 mm internal diameter clear the first process involves the downflow PVC tube of pr edete rmin ed le ngth of destabilised water through a packed around a column to control the rapid bed of buoyant material. Flocculation is _mixing time to approximately 1 second caused by the turbulence in the inter- in all experiments. stices of the bed, followed by the separaA per spex fil ter column of 90 mm tion of particles and floes. Thus, it has a inside diameter (I.D.) and 1600 mm high dual function of flocculation and solid- was used in the combined system. The liquid separation. The subsequent polish- filtration was downflow mod e operating ing filter will then help to remove the at filtration rates of 5, 8, 9.9 m"/ m' .h. r emaining solids. Instead of two separate Polypropylene beads (d = 3.8 mm,p = units, a sand filter below the floatin g 0.87 g/cm") were used as floating fil ter medium can lead to a significant cost sav- medium . The floating beads wer e packed ing. This system also has several other in the column for a depth of 400 mm advantages such as no interfac e inter- with a porosity of approximate ly 0.36 and restrained by a coarse mesh stainless steel grid . Coarse sand (ES - 1. 7 mm, UC - 1.3) was placed at the bottom of filter column for a depth of 400 mm. Th er e was about of 400 mm s p ace between t he bo tto,m layer of fl oatin g medium and top layer of sand. The main flocculant (WAC HB) used in this study

Figure 1 E'J;J)erimental set-up

* School of Civil E ngin ee rin g, Univers ity of T ec hn ology, Sydney PO Box 123, Broadway, NSW 2007






[]WAC HB (75 mg/L) B21WAC HB (50 mg/L) . •WAC HB (25 mg/L)

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-~ u








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Parameter Figure 2 Effect of filration rate on pollutant removal efficiency (v - 5 m/h; depth of DFF - 40cm; depth of CSF - 40cm)



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120 l!liil W AC HB liZIFerric chloride •Alum

100 -


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80 60


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.... ~


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Parameter Figure 3 Effect of flocculant type at optimum dose on pollutant removal efficiency (v - 5 m/h; depth of DFF - 40 cm; depth of CSF - 40 cm)




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120 Dv = 5 m/h B8lv = 8 m/h •v = 9.9 m/h






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Parameter Figure 4 Effect of filration rate on pollutant removal efficiency (WAC HB 50mg/L; depth of DFF - 40cm; depth of CSF - 40cm)


was a commercial product (Poly alumin um chloriQ,I;) (Aln(OH)m(SO4)kCl3n·m-k; P 1.2 g/cm ' at 25 °C, produced b ATOCHEM, France). Commercial aim and ferric chloride were also compare1 The surface water used in the exper me n ts was obtained from th Sommersby Water Treatment Plant inl1 which draws water from Moonee Cree Dam, Gosford. The water quality of th source is summarized in Table 1. At the end of each experiment, tr filter was backwashed using compresse air at a pressure of 35- 70 kPa for 2 mi1 followed by backwash with water (at rate of 6 _Lfm'.s) for 5 min. It should t noted that this backwashing was done 1 clean the medium thoroughly betwee experiments, and was not the optimu1 backwash which would be determined i an operational s it uation . (On e mai advantage of using buoyant media is 1 s ig nifi can t ly r educe t h e backwa s requirement). The optimum flo ccula nt dose w~ estimated using the standard jar tei procedure. Filtrate quality was evaluate in terms of suspended solids, turbidi~ apparent colour, total iron and TO< Turbidity and colour was measured wil Hach turbidimeter 2100P and DR/20( Photometer respectively. Total iron w: measured by Perkin Elmer Atomic abs prtion Spectrometer. TOC was analysE using Dohrman DC 80 TO C analyse The size of aggregates (floes) from tl filter was determined by direct observ tion utilising a microscope. This syste uses a microscope (BH-2 Olympus) fittE witli a drawing attachment (BH2-D Olympus) to visually sup erimpo se t} image of floes over the surface image a drawing paper beside the microscop In each sample, more than 100 repr ese tative floes were considered and the fl, size (mean floe diameter) was calculate from the area of floes. Headloss throu~ the bed was directly recorded from tl manometer reading.

Results and Discussion Effect of flocculant dose. Tab 2 (hydraulic performance) and Figure (pollutant removal) summarize tr experimental results showing the inf! ence of dosage (75, 50 and 25 mg/1) Polyaluminum chloride (WAC HB) c the filter performance . Th e filtratic rate in this series of experiments was m'/m'/h, for runs of 6 h. The headlo: produced in the DFF component of ti unit was low and did not vary significar ly for different cases. In the combined f ter a flocculant dose of 75 mg/L led higher head loss development (22 .7 c compared to 15,5 cm and 12.8 cm wi· the lower doses of flocculant) . The hig er dose also led to the the larger expa sion of DFF depth and quicker detac ment of floes from DFF. The floes pr duced from DFF unit at 25 mg/L WA

HB (floe size of 20.5 µm) were significantly small er than the ones with 50 mg/L WAC HB (floe size of 34 µm ) and 75 mg/L WAC HB (floe size of 31.2 µm). The filter performanc e with WAC HB of 25 mg/L was the poorest, nevertheless, the effluent was satisfactory in all three cases. Pollutant removal was best at the optimum WAC HB do se determin ed from jar test (50 mg/ L) . Interestingly, the pH of effluent was in the range of 6.5 - 6.9 so pH correction was not needed. Effect of flocculant type. A series of experiments was carried out with three different flocculants: WAC HB, ferric chloride and alum. The optimum doses (from jar tests) were 50, 30 and 30 mg/L respectively. Figure 3 (pollutant removal) shows that all three flocculan ts were s uitabl e for use in this sytem since they all gave good effluent quality. The removal efficiency in terms of turbidity, SS and iron was superior with WAC HB (eg 94.6, 96.4 and 100 % respectively) whereas apparent colour and TOC r emoval were better with the other two flocculants (e.g 96 % apparent colour removal and 57-60 % TOC removal with alum and ferric chloride compared to 91 % and 53% with WAC HB) In general, headloss development was found to be low in all the three cases (Table 3), but lowest for WAC HB . (only 126 mm in a 6 h filter run) Th e SS r ete ntion capacity in the DFF was high with WAC HB (WAC HB (77.4 %) > alum (67 %) > ferric chloride (66.2 %)) (Table 3). The floe size and DFF bed expansion were similar in these three cases. It should be noted that the pH reduced only to 6.9 with WAC HB whilst it decrease d to as low as 5. 1 with the other two flocculant s (with no alkali added). Effect of filtration rate. Experiments were conducted with three differe nt filtration rate s of 5, 8 a nd 9.9 m'/m' .h; with the optimum WAC HB dose of 50 mg/L. Figure 4 shows the average removal efficiency in terms of turbidity, suspended solid s, a pparent colour, TOC and total iron. As expected, the removal effici ency of this system deteriorated with the increase of the filtration rate . The total iron r emoval was complete up to the filtration rate of 8 m3/m' .h. The highest removals of turbidity, SS, apparent colour, TOC and total iron over 6 h of filter run were 96.4, 94.9, 95.2, 59.5 and 100 % r espectively, Table 1 Charact,eristics of raw water used Parameter


pH Turbidity Suspended solids Apparent colour

6.9- 7.2 NTUl.8-4.4 mg/1 3.5 - 6.1 Pt/Co 53- 71 mg/L 3.9 - 5.8 mg/L 0.40 - 0.57

TOC Iron as Fe (total),



ac hiev ed at t h e filtration rate of 5 m'/ m' .h. The turbidity and suspend ed solids conce~tration in the effluent were consistently low (less than 1 NTU and 1 mg/L during 6 h of filtration time) . No breakthrough was observed for any of these parameter s. The size of the floe s form ed in the DFF unit decr ease d at higher filtration rates e.g .. 34, 28.4, 24. 7 µmat filtra tion rates of 5, 8 and 9.9 m'/ m' .h re spectively. Th e DFF itself retained up to 70 % of suspended solids. The headloss development of the combined system was very low (maximum headloss development was lower than 80 mm in 6 h of filter run).

During the ,filter run, the DFF medium expanded, oeing was higher at higher filtration rates. The flo es star ted to fall down from the DFF in an increasing manner with t h e ex pa nsion of filter depth. This may cause some negative effect on t h e efflu ent, h owever, t he experimental results indicated that its effect was not significant, at least up to 6 hours filter time. Headlosses through the combined filter at filtration rates of 5 and 8 m/ h were not significantly different (only 126 mm and 152 mm) while headlo ss development at the filtration rate of 9.9 m'/ 2 .h was found to be 310 mm. The headloss through the DFF unit

Table 2 Pe1formance of the DFF and combined filter system for different flocculant doses (WAC HB) (v - 5 m 3/m 2.h; depth of DFF - 400 mm: depth of CSF - 400 mm; filtration time - 6 h.). Dose of WAC HB-76 mg/L Average Max. headloss development floe size

Treatment unit

%SS retained (%)





45.1 75

49 227




70.3 94.9




40.3 59



DFFdepth expansion

Dose of WAC HB - 60 mg/L 51 155

Dose of WAC HB - 26 mg/L 63 128

Table 3 Performance of the DFF and the combined Jilter system with different types offlocculants (v - 5 m 3/m2.h; depth of DFF - 400 mm; depth of CSF - 400 mm; fi ltration time - 6 h). ... Treatment ., unit

%SS retained


70.3 94.9


66.2 92.8

WAC HB (60 mg /L) Max. headloss development 51 126

Average floe size (µm)

DFFdepth expansion (mm)







Ferric chloride (30 mg/L) 49 146

Alum (30 mg/L) (DFF) (DFF + CSF)

65 88.6

56 24 1

Table 4 Performance of the DFF and the combined Jilter system at different filtration rates (WAC HB dose - 50 mg/L; depth of DFF - 400 mm; depth of CSF - 400 mm; filtration time - 6 h). Treatment unit

Filtration rate v - 6 m3/m2 .h Max. headloss retained development (%)


70.3 94.9


Average floe size

DFFdepth expansion




51 126



Filtration rate v - 8 m3/m2.h % (DFF) (DFF + CSF)

62 83.2



(m m)

66 152



Filtration rate v - 9.9 m3/m2.h (DFF) (DFF + CSF)

54.2 80. 2




74 310




was nearly constant with filtration time (Figure 5) which proves that this system can successfully used as a static flocculator apart from it.s function as a prefilter.

Conclusions From this study, the following conclusions can be drawn: • The performance of a DFF unit with 40 cm bed of polypropylene beads was excellent, _particularly at filtration rates of 5 - 8 m0/m 2.h. As a flocculator, it was able to yield uniformly filterable floes (20 - 40 µm) throughout the filter run time of 6 h. It also provided reasonably high pol1utan t retention (e.g . 60 - 70 % SS removal) with very low headloss development. Thus it helps in improving the performance of the subsequent coarse sand filter, increasing significantly its filter run time . However, higher bed expansion of DFF and detachment of larger number of floes were noticed at high loading rate of 9.9 m3/m 2.h. • The removal of impurities by the combined system DFF-CSF was excellent (e.g . turbidity < 0.5 NTU (96.4 % removal), SS < 0.4 mg/1 (94.9 % removal), colour< 7 PCU (91 % removal) and Fe= 0 mg/L (100 % removal) at a filtration rate of 5 m"/m' .h with WAC HB as flocculant). Althou gh removal of organics was not as high as for the other parameters it was significant (50 - 60 % r emoval at filtration rate of 5 m"/m2 .h).

• Although all the three flocculant.s used (po lyalumini um chloride (WAC HB), alum and ferric chloride) yielded satisfactory performance, polyaluminum chloride (WAC HB) was the best in terms of turbidity, SS and total iron removal. In the case of WAC HB, there was no need for pH correction. The headloss development was also lower compared to the other two flocculants, which all ows longer filter runs. Overall, the DFF-CSF system can become a successful alternative in small community water supplies at reasonable loading rates of 5-8 m3/m2 .h. The system is very compact and requires less energy for backwashing. Further study on medium type, size and depth of DFF would be of interest.

Acknowledgment The authors acknowledge Mr Adam Barber's assistance in the experimental investigation.

References Ben Aim, R, Shanoun , A, Vi svanathan , C and Vigneswaran, S (1993) New Filtration Me dia and t he ir Use in Wa te r Tr eatmen t, Proceedings, World Filtration Congress, Nagoya, Japan, 273-276. Ishigaki Mechanical Industry Co.Ltd. (1990) Catalog no El5. Ngo, H H and Vignes waran, S ( 1994) Appli cation of floatin g medium filt er in water andwastewater treatment with con-

tact-floccula tion filtra t ion arran gement, J . Water Research (In commun ication). Sahnoun , A, Ben Aim, R and Vi svanathan , C (1993) Utilisation des lits fl ottants dans la fil. iere de potabilisation des eaux de surface. Recents Pro gr es en Geni e des Procedes, Lavoi s ier Te chnique et Docum enta tion , Paris. Schulz, C R, Singer, P C, Gandley, R and Nix J E (1994) Evaluating buoyant coarse media flocculation , J. Am. Wat. Wies Ass. 86, 51-62. Sugaya, K (1993) Filtration of Sewage Treated Water by th e Use of Floa t in g Media Proceed in gs, World Fil tration Con gress, Nagoya, Japan, 729-733. Vign eswaran, S and Ngo H H (1994) Floating Medium Filtration: Investigation of Particle Retention M(lchanism in Water Treatment, UTS - Projec 's Progress Report Vital, J L, Lemme!, H and Gaudin, M P (1990) Un nouvel appareil de filtra tion sur lit flottant. L 'eau, l 'indus trie et les nuisances, 135. Wal she, M, John ston , N, Craig, K, Nayl or , R, Brownin g, R a nd Rodd y, S (1 993) Tw o S ta ge Fil t ra t ion, Pr ocee din gs, AWWA Federal Conventi on, Gold Coast, 194-201.

Authors Both authors are in the School of Civil Engineering, University of Technology, Sydney. Dr. S. Vigneswaran i s an As sociate Professor, wi th inter ests in advanced water and wastewater treatment processes. H.H. Ngo, M.Sc, is a Researcher and Senior Technical Officer in water quality and treatment processes.

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