Effects of composting process on microbial indicators
Annual Conference
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Biosolids are a useful reusable and beneficial resource as they are rich in nutrients and some trace elements. However, their use can be limited by the presence of unacceptable levels of microbiological pathogens and organic pollutants.
In a recent study on the suitability of biosolids originating from a provincial wastewater treatment plant as a composting material, the presence and viability of several microbiological indicators was followed over the entire composting process and compared to the sludge before composting. The composting processes were found to be effective against the microbial indicator pathogens. If other pollutants are within the limits of the guidelines, the biosolids thus obtained, are safe for use by the general public for land application.
Free living nematodes are abundant in freshwater, saltwater and soils. These were found to be present despite undergoing the compositing process. This suggests that the latter had no impact on their survival. In contrast, microbial indicators were not detected at levels considered pathogenic according to the Guidelines for the Safe Application of Biosolids to Land in New Zealand indicating that the composting conditions used were effective in their elimination.