Water Journal : Water Journal August 2012
biosolids refereed paper technical features 76 AUGUST 2012 water harvested produce generally are much lower than the Codex Standards (Codex Alimentarius Commission Levels, 2006) or Food Standards Australia and New Zealand (FSANZ, 2010). These guidelines are derived to protect the chronic build- up of heavy metals in the crops that take up relatively high concentrations from contaminated soil. It is also interesting to note that the concentration of persistent organic chemicals (e.g., PCBs) and many heavy metals (e.g., Cd and Hg) have significantly reduced in biosolids since source control measures have been implemented (Harrison et al., 2006). Given these changes and the age of many biosolids guidelines, the contaminant 'limits' in relation to the risk and benefits associated with land application of biosolids should be reconsidered. Organic Chemical Rule (New Rule #10) With the increased knowledge now of organic chemicals found in biosolids, there may also be some logic for the one-in-five-year application to allow degradation of more persistent organic chemicals and minimisation of accumulation of organic chemicals in soils (Smith, 2009b). However, there appears to be no one regulatory document available that supports an 'organic chemical rule'. The half-life of organic chemicals of concern range considerably from days to years. With annual application of biosolids to land, organic chemicals will have an upper maximum soil concentration, driven primarily by application rate and degradation half-life. A precautionary approach to minimise the upper soil concentration, and minimise any potential risk, could be to apply once in every five years. Ideally, this should be supported with a risk assessment focused on the risk associated with organic chemicals found in biosolids produced in Australia. Conclusions To overcome the current complexity and inconsistency of guidelines in Australia and manage the concerns related to contaminants and emerging organic chemicals, we recommend a risk assessment approach be developed to manage land application of biosolids in Australia. Such an approach should consider nutrients as fertilisers, and base biosolids application on fertiliser rates while minimising any risks posed to the surrounding environment. It should provide a framework that will allow specific sites to be easily assessed for repeat applications within a local context for the key hazards associated with biosolids. The Australian Guidelines for Water Recycling (NRMMC and EPHC, 2006) have taken this approach for recycled water and the lessons learnt during this process may provide the ideal platform to attempt a similar approach for land application of biosolids. This paper was originally presented at the AWA Biosolids and Source Management Conference held from 18--20 June at the Gold Coast. Acknowledgements The authors would like to thank Mr Dominic Flanagan and Ms Pam Kerry for critical comments, and Dr Mirela Magyar for proof-reading the paper. The Authors Dr Daryl Stevens (email: email@example.com) has worked for NEPC from 2005--2010 developing the AGWR. He and his company (Atura Pty Ltd) consult across Australia in establishing and operating recycled water schemes and systems for land application of biosolids. Dr Aravind Surapaneni (email: aravind.surapaneni@ sew.com.au) is a Product Quality Scientist at South East Water Corporation and has been involved in managing a wide range of biosolids reuse activities. Nihal Albuquerque is a PhD student and Dr Barry Meehan is Associate Professor of Environmental Science (School of Applied Sciences), both at RMIT University. David Smith is Product Quality Manager, Peter Uren is Treatment Plants Manager and Paul Hansen is Treatment and Product Systems Branch Manager, all at South East Water Corporation. References Australian and New Zealand Biosolids Partnership (2009): Review of Biosolids Guidelines, Australian Water Association (AWA), Sydney, Australia. Bhogal A, Nicholson FA, Chambers BJ & Shepherd MA (2003): Effects of past sewage sludge additions on heavy metal availability in light textured soils: implications for crop yields and metal uptakes. Environmental Pollution, 121, pp 413--423. CEM (2004): Draft: Guide for the Beneficial Use of Non-Agricultural Source Materials on Agricultural Land, Toronto, Ontario, Canada, Environment Ministry. Chander K, Brookes PC & Harding SA (1995): Microbial biomass dynamics following addition of metal-enriched sewage sludges to a sandy loam. Soil Biology and Biochemistry, 27, pp 1409--1421. DOI: 10.1016/0038-0717(95)00074-o. 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