VERMICOMPOSTING ACHIEVES PATHOGEN STABILISATION OF BIOSOLIDS AT MESOPHILIC TEMPERATURES
Abstract:High temperatures, sometimes combined with alkaline pH, have traditionally been required to destroy pathogens effectively, i.e. achieve standards associated with PFRP, a process to further reduce pathogens in sewage sludge (biosolids). Previous research has indicated that vermicomposting has a potential ability to destroy pathogens. Now vermicomposting has been shown to effectively destroy pathogens in biosolids at mesophilic temperatures. Vermiculture is the process by which organic material is fed to earthworms in a controlled environment with the purpose of producing vermicast, and in some cases, more worms.
In April 1998, a vermiculture facility to process biosolids was opened in Redland, Queensland, Australia, near the city of Brisbane. The facility has processed over 50 000 tonnes of biosolids and green wastes to a consistent Grade A (New South Wales Environmental Protection Agency) Stabilisation. There have been no odour complaints at the facility. Dewatered biosolids are blended with shredded green waste and applied to open air, elevated vermiculture beds. The worms, principally Eisenia foetida, process the material in the bed for 60 days before it is harvested. The design and operation of the facility enables the vermicast to be harvested with few worms or capsules in the product.
Biosolids in general contain a range of bacterial, viral and parasitic organisms. For general distribution and use in home gardens, these pathogenic organisms must be destroyed. Vermicast sampled and tested according to a stringent testing regime prior to distribution confirmed that all of the product contained < 1000 cfu/g fecal coliform, < 100 cfu/g E. coli, salmonella not detectable, enteric viruses < 1 pfu/g, and helminth ova (Ascaris and Tichuris) < 1 ova/g.
Document Type: Research Article
Publication date: 2002-01-01
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