Australasian Biotechnology (backfiles) AusBiotech ISSN: 1036-7128 Vol. 7, Num. 6, 1997

Establishment of a Bioremediation Facility in South Australia - Research and Commercial Potential

Nick C. McClure, Cathy Dandie, Richard Bentham, Chris Franco and Ian Singleton*.

School of Biological Sciences, Flinders University of South Australia, GPO Box 2100, Adelaide 5001. (ph 61-8-82013930, fax 61-8-82013015, email nicholas.mcclure@cc.flind ers.edu.au) and
*Department of Soil Science, Waite Campus, University of Adelaide, Glen Osmond, SA 5064

Code Number: AU97047
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Centralised bioremediation facilities are relatively common in the U.S.A., Canada and some parts of Europe. Whilst there is a preference throughout most States in Australia for conducting soil remediations on-site, in some cases this is either technically difficult or hinders rapid development which would recoup remediation costs. Remediation of contaminated soil at a remote facility has a number of additional advantages; it allows increased timescales for achieving minimum residual pollutant levels, reduces individual site preparation costs and increases the potential for conducting longer term research projects. This paper discusses the establishment of a centralised commercial and research bioremediation facility in South Australia, describes ongoing bioremediation projects being undertaken and identifies research needs relevant to ex situ soil bioremediation in the Australasian region.

Keywords: Bioremediation, composting, biopiles, soil contamination.

Introduction

Bioremediation is becoming an accepted technology for the remediation of organic contaminants in polluted environments worldwide. The world market for bioremediation products and services has been estimated at approximately US $500 million in 1996 (Glass et al., 1997) with further growth predicted in expanding markets outside the US, including the Pacific Rim. The number of contaminated sites in New Zealand and Australia has been estimated at 8,000 and 80,000, respectively (Natusch, 1997). The size of the market in Australia has been estimated at US $194 million in 1994 with bioremediation representing between 5-10% of the total remediation activity by volume (Natusch, 1997). Despite this the Australasian region has lagged behind North America and Europe in developing and implementing novel bioremediation options for contaminated sites such as those being evaluated as part of the U.S.A. EPA's SITE programme.

There are a wide range of alternative technologies for the full scale remediation of contaminated soils (Martin and Bardos, 1996). Bioremediation processes being used extensively overseas include in-situ remediation of groundwater and soils, natural attenuation and the treatment of contaminated soils at centralised facilities. Disadvantages of bioremediation include the need for conducting pilot scale tests at sites, inconsistent results with recalcitrant pollutants and residual levels of pollutants which may restrict reuse options for remediated soils. Research efforts addressing these deficiencies are somewhat hampered by the gulf between laboratory scale investigations and those more relevant to full scale applications. The use of dedicated pilot scale research facilities may assist in investigating the factors which limit bioremediation processes in the field. A new pilot scale research and full scale bioremediation facility is being established in South Australia in a collaborative venture between Flinders University of South Australia and Lucas Waste. The facility will be used to undertake pilot scale tests and full scale remediation of pentachlorophenol-contaminated soil excavated from a local site. Current and future research programmes to be undertaken at the facility will be described. Discussion of bioremediation options will be limited to technologies for the remediation of contaminated soils, in particular biopile and composting processes being tested for the remediation of pentachlorophenol (PCP) contaminated soil.

Soil Bioremediation in Australia

Bioremediation processes have been used successfully for the remediation of contaminated soils throughout Australia. Successful clean-ups have included the remediation of 7,000m^3 of diesel contaminated soil at the Mile End Railway yards in Adelaide, numerous service station sites, (Natusch, 1997, Burns et al., 1996, Edgehill et al., 1991) creosote contamination at a wood treatment site in Gippsland, Victoria (McKinley and Rhodes, 1994) and hydrocarbon remediation at the Ampol refinery in Brisbane (Anon, 1997). In many cases detailed technical information about remediation rates is lacking and assessment of remediation efficiency limited to anecdotal reports. In the past the disposal of contaminated soils in licensed landfills or capping on-site have been common contamination management options which do not actually reduce pollutant levels. With increasing pressures on landfill space and heightened environmental awareness the implementation of genuine remediation options will become increasingly important.

Use of Centralised Bioremediation Facilities

Soil bioremediation will usually be carried out on-site in Australia, although there is a facility in Laverton, Victoria which is able to recycle soils contaminated with petroleum hydrocarbons in a joint venture between Alex Fraser Pty. Ltd. and ADI Ltd. At this facility the primary remediation technology is thermal desorption, although bioremediation of contaminated soils can also be conducted. Overseas the use of centralised bioremediation facilities is more common. For example WMX Technologies Inc. have developed and operate 25 fixed-location soil bioremediation facilities across the U.S.A and Europe. These facilities have treated over 3 million tons of petroleum-contaminated soils which can then be used in beneficial applications (Hamblin and Hater, 1997). At the facilities soils are treated using a vacuum heap bioremediation process with specific hydrocarbon-degrading inocula and inorganic nutrient supplementation. Single piles up to 60,000 tonnes have been treated successfully with typical treatment periods of 3 months.

There are advantages and disadvantages of using centralised facilities for soil remediation. There are concerns over the transportation of contaminated soils off-site and concentrating polluted materials in specific locations. These concerns are countered by the use of such facilities to achieve improved levels of remediation with reduced time constraints. Frequently sites undergoing remediation are destined for new uses and lengthy on-site remediation processes may limit site development. In addition the level of monitoring and control which can be set up at a central facility can be refined if the facility is being used over a longer time period for numerous remediation projects. New technologies can also be tested side by side with established methods. This may result in general improvements in remediation efficiencies for both on-site and off-site projects.

A new research and commercial bioremediation facility is currently being installed in South Australia in a collaborative venture between Flinders University and Lucas Earthmovers Pty. Ltd. The site will be utilised as a teaching, demonstration and research facility with pilot scale test systems (10-20 tonnes) being run alongside full scale bioremediation processes (1,000 tonnes +). A minor amendment to the management plan for the site was approved in December 1996 by the Development Assessment Commission to allow installation of a pilot and full scale bioremediation facility. As the site was already licensed to receive low level contaminated soil for landfill disposal, the site infrastructure (leachate control, monitoring etc.) was already appropriate for this new use.

The technologies being evaluated and developed include aerated biopiles and composting using forced aeration and in-vessel systems. Biopiles have been used successfully for the treatment of a variety of organic contaminants in soil (Rao et al., 1996, Morrison et al., 1997, Hamblin and Hater, 1997). Recent developments in biopile technologies include the use of on-line monitoring and control systems which can be used to optimise conditions for microbial activity and enhance bioremediation rates (Rao et al., 1996, Pollack et al., 1997).

Composting and PCP Remediation.

A major project being undertaken is the treatment of PCP-contaminated soil. More than 1500 tonnes of soil contaminated with PCP and turpentine have been excavated from the site of a disused timber yard. PCP concentrations ranging from 50 to >600 ppm have been detected in the soil. Turpentine concentrations of around 1000 ppm are also present. The project will involve laboratory, pilot and full scale studies comparing composting with amended biopile treatment of the contaminated soil. In particular the use of specific PCP-degrading bacteria will be investigated in a collaboration with colleagues in Massey University, New Zealand.

Composting has been used at bench scale to investigate its potential for hazardous waste treatment. A number of pollutants recalcitrant to conventional bioremediation have been successfully treated using composting including TNT and RDX compounds, petroleum hydrocarbons, polynuclear aromatic hydrocarbons and chlorophenols (Magelhaes et al. 1993, Stoner 1994, Kastner and Mahro 1996, Laine and Jorgensen 1997).

Laboratory based assessments of composting pollutants have been previously reported (Ashbolt and Line 1982, Magelhaes et al 1993, Tseng et al 1995). These systems have used water baths, incubators or modified ovens to reproduce the temperatures attained in natural compost. The advantages of these systems have been the reproducibility of the temperatures achieved in each system. The systems have been able to predict results of full scale composting systems under isothermal conditions. There are substantially fewer reports of composting as a pilot or full scale bioremediation strategy. Successful remediation of petrochemicals, TNT and sewage sludge, and chlorophenol contaminated soils have been demonstrated (Kuter et al 1985, Valo and Salikinoja-Salonen 1986, Breitung et al 1996).

There are some problems with interpreting laboratory models into natural systems. Firstly, the natural composting process is not isothermal, either throughout the compost material, or over the duration of the process. Secondly, the temperatures attained during the process are a function of the composition of the composting material. Depending upon composition the material may achieve higher or lower temperatures in vivo than those used at laboratory scale (Kuter et al 1985). Thirdly, the availability of oxygen is variable within natural systems and has a direct influence on the composting process. Though chiefly aerobic, composting involves both aerobic and anaerobic degradative processes.

To overcome these problems a laboratory scale system was devised which used small amounts of composting material in a controlled natural composting process. The aim of the system was to provide a microcosm which would be truly representative of the environmental conditions that would arise in a full scale composting process.

Bench scale studies using the self heating compost systems have been substantially completed. Results from these studies suggest that full scale remediation using composting is feasible. In laboratory microcosms concentrations of PCP have been reduced from >100 ppm to <10 ppm after six weeks (see figure 1). Controls using killed compost samples have demonstrated that PCP losses are due to biological processes rather than chemical binding of the contaminant to the compost matrix.

Figure 1: Mean PCP degradation and compost temperatures in laboratory composting microcosms

The degradation of PCP appears to commence after the thermophilic phase, during the cooling off and stabilisation of the compost. This is consistent with the expected behaviour of a biologically degraded complex organic compound in a compost system. Pilot scale composting of the soil will be conducted using 10-15 tonne batches incorporating amendments such as sewage sludge and manure and municipal green waste. The compost will be arranged in windrows on a sealed liner with vacuum aeration. Composting variables such as temperature, humidity, and oxygen concentration, will be monitored using dedicated probes and data loggers. PCP degradation will be monitored using GC and GC-MS. Soil toxicity will be assessed using seed germination, microbial toxicity tests and a human cell toxicity and genotoxicity assay. Once satisfactory pilot scale results are obtained a full scale bioremediation of the soil will commence.

Composting has been justifiably criticised as a remediation strategy because it involves the dilution of the contaminant. In this case the process targets a biocide at concentrations well above those used for microbial control. Any soil based strategy would require some dilution to avoid inhibition of microbial activity. This process has the advantage of the possible production of a useful product. Taking these factors into consideration composting is a suitable and attractive alternative to other land-farming based strategies. Comparison with conventional biopile processes at laboratory and pilot scale will enable these processes to be compared from an economic and practical perspective

Conclusions and Future Research Directions

There is a need for pilot scale testing of new remediation technologies to bridge the gap between laboratory tests and full scale implementation. In particular the remediation of recalcitrant pollutants such as polycyclic aromatic hydrocarbons (PAHs) and PCBs has given inconsistent results in the past. Problems arise through site-to-site variations, low bioavailability of pollutants due to low aqueous solubility or binding to soil, toxicity etc (Pollard et al., 1994). A number of technologies have been proposed to overcome some or all of these problems, including composting, fungal technologies, use of surfactants or specific microbial inoculants. There is a growing need to test these technologies at a scale more relevant to full application. This is the approach being taken at the new pilot scale facility and which is currently being used in ongoing studies on the bioremediation of PCP and DDT-contaminated soils. Another area which is of interest is the use of on-line monitoring and control systems which would facilitate optimisation of eg cycling aerobic/anaerobic processes for the remediation of highly chlorinated pollutants. The development of specific pollutant biosensors (Heitzer et al., 1994) is an exciting area of development which may be integrated into on-line monitoring systems once the robustness and consistency of such systems is proven.

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Copyright 1997 Australian Biotechnology Association Ltd.

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