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Australian population centres have low incidences of key helminth infections. Gibbs and Ho (1993) cited a reported incidence rate of Ascaris and Trichuris of 0.001 and 0.01 percent, respectively, in the Perth population in the early 1990s. T his was predominantly due to travellers and recent immigrants, rather than the resident population. In contrast, Barbier et al (1990) examined sludge from a French STP and estimated a helminth infection rate in the local population of 1. 5 to 2.7 percent, a figure considered to be similar to the national average. T he low incidence rate in Australia means chat it is difficult to demonstrate a 2 log reduction as per the US approach (without seeding studies) and further, an absence of helminth ova in a batch product test may provide no assurance that other pathogenic organisms have been removed (i.e. an absence of helminth may be due co no helminths in the raw sludge rather than removal by the treatment process) . Therefore, in Australia, greater emphasis may need to be on batch testing for viruses, bacteria and ocher organisms such as protozoa. The emerging approach within Europe for validating new technologies appears to be focused on demonstrating 6 log reductions of Salmonella seriftenberg or E. coli. However, it is not clear whether this is intended to apply o nly to already prescribed treatments, or whether it is an approach that can be automatically applied to new technologies. The former appears the most likely scenario, since the UK proposed legislative changes were underpinned by the demonstration that specified technologies achieved high log reductions against a wide range of key pathogen organisms, for example Campylobacter, Giardia and enteric viruses. If this is indeed the approach , it presents the challenge chat emerging technologies will have no fo rmal criteria against which to be assessed. It is interesting to note that for the previous treatment requirements in the UK, process efficiency is believed to have been based on evidence of90% reduction in Salmonella and Taenia saginata egg infectivity (although these biosolids had restricted uses) (UKWIR, 2002). In the proposed national Australian guideline, some specific direction is provided, with emerging technologies required to demonstrate 100% egg inactivation using a Taenia or Ascarid parasite egg- seeding assay and demonstrate < 1 enteric virus per 100 grams of final product. T he key challenge will be in ensuring the testing laborato ries are equipped to undertake these tests to the relevant standards. It therefore appears to be critical that some provision for batch
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testing of products is included in state guidance. T he difficulty, as highlighted with the low incidence rates for helminths, will be in selecting indicator organisms that provide assurance of broad pathogen removal. Process monitoring of an 'unrestricted ' grade product - Salmonella
As noted earlier, there are some significant differences in the international approaches to how Salmonella testing is used for assessing an 'unrestricted' grade biosolids product. T he US 503 rule includes an option of Salmonella testing, however, the testing is not recommended as a treatment verification tool (NRC, 2002). The draft EC requirements require treatment verification through a demonstrated 6 log reduction in Salmonella senftenberg W775, while a demonstration of non-detectable Salmonella is required in the draft UK (not detectable in 2 grams dw) and Australian (not detectable in 50 grams dw) approaches. A detailed examination of the basis for the Salmonella provisions is beyond the scope of this paper, other than to note the limits reflect con cerns regarding the importance of Salmonella as a pathogen (Carrington et al., 1991), its potential fo r regrowth and the difficulties some treatment processes have had in ac hieving adequate removals (Yanko, 1988; H ay, 1996; Gibbs et al., 1997) . While these reasons are clear, the justification for a highly sttingent Salmonella limit such as no detectable organisms per 50 grams dw, compared to the criteria proposed in the EC, is less clear.
Conclusions T here is a generi c level of consistency in the pathogen management approaches taken in the U S, E urop ean Commission (proposed approach) and the draft national Australian guideline, particularly with regard to the types of treatment processes required and the organisms that are used for process monitoring. There are also some important similarities in the end-use restrictions that apply to the specified products . From this perspective, there appear to be relatively stable framewo rks fo r the future management of biosolids application co land. Although the current management controls are believed to be appropriately conservative, there are some issues around the community acceptance of 'Class B' application programs. Therefore, there will need to be an increased focus on quanticati ve risk assessment approac hes to demonstrate the safety of the practice. There are co nsistencies and some issues around the regulatory limits established for
p rocess monitoring of defined treatments and the approaches used to ve1ify emerging technologies. It appears that future regulatory activities w ill need to focus on these latter areas.
The Authors Dr Hamish Reid (hamish.reid@ epa.vic.gov.au) is employed by the Victorian EPA as W ater Industry Program Leader, with an involvement in programs including biosolids and reclaimed water ma n agement. Amelia Savage is employed by the Victorian Department of H uman Servi ces and is involved in assessing the public health impacts of biosolids and reclaimed water management policy. References Barbier D, Perrine D,.Duhamel C, Doublet R, and Georges P (1990). Parasitic hazard with sewage sludge applied to land. Appl. E11viro11. Microbial. 56(5):1420-1422. Carrington E G, Pike EB, Auty D. and Morris R (1991) Destrnction of Faecal bacteria, enteroviruses and ova of parasites in wastewater sludge by aerobic thermophilic and anaerobic mesophilic digestion. Wat. Sci. Tech. 24(2): 377- 380. DEFRA (2002) Consultation paper - Proposals to amend the statuto,y controls for the agiicultu ral use of sludge. De partment for Environment, Food and Rural Affairs, Welsh Assembly Government. October, 2002. DEP (2002) West Australian guidelines for direct land application of biosolids and biosolids products. Department of Environmental Protection, Water and Rivers Commission, Department of Health. February 2002. DoE (1989) Code of Practice for Agriculture Use of Sewage Sludge. D epartment of Environment, United Kingdom. Dorn C R, Reddy C S, Lamphere D N, . Gaeuman G V and Lanese R (1985) Municipal sewage sludge application on Ohio farms: health effects. Ellviro11 . Res. 38(2): 332-359. DPIWE (1999) Tasmanian biosolids reuse guidelines. Department of Primary Industries, Water and Environment. EC (2000) Working Document on Sludge. 3rd Draft. Brussels, 27 April 2000. EC, (2001) Evaluation of Sludge T reatments for pathogen reduction. Report Number CO 5026/ 1. European Commission, DirectorateGeneral Environment. EPA Victoria (2002) Draft Guidelines for Environmental Management: Sustainable reuse of biosolids - land application. November 2002. G ibbs RA and GE Ho(l 993) Health risks from pathogens in uncreated ¡wastewater sludge implications for Australian Sludge Management Guidelines. Water 20 . February: 17-22. Gibbs R A, H u CJ, Ho G E and Unkovich I (1997) Regrowth of faecal colifonns and salmonella in stored biosolids and soil amended with biosolids. Water Sci Tech 35(11 / 12) 269275.
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