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Stabilisation and sanitisation of wastewater biosolids during composting

This work aimed at gaining an insight on the development of antibiotic
resistance in biosolids microbial population, as this may also pose risks to public health and soil ecosystems.

The factors influencing the stabilisation and sanitisation process of biosolids during composting are investigated, in order to identify mixtures and process control parameter values that optimise the overall process, maximise its efficiency and produce a high quality, well sanitised product. Process performance was assessed using both process parameters and compost stability indicators, while sanitisation was assessed both through counting pathogen indicators and detecting selected pathogens. Two mixtures of dewatered biosolids and green waste, at a ratio of 1:1 and 1:2 (v/v) respectively were composted in two Colombus reactors of 40 l capacity each, using temperature feedback controlled aeration and continuous on-line monitoring of CO2 production. Parameters analysed included: moisture content, volatile solids, pH, electrical conductivity, total carbon and nitrogen, and compost stability (determined as SOUR-Specific Oxygen Uptake Rate, OD20-Oxygen Demand, and the Solvita® test). The following microbial populations were measured: Total Mesophilic Aerobic Microflora (TMM), Total coliforms, E.coli, Faecal streptococci, Staphylococci, Clostridium perfringens, Salmonella spp. and Listeria spp. Escherichia coli and Enterococcus spp. strains were isolated and tested for antibiotic susceptibility, as antibiotic resistant microorganisms may constitute an important epidemiological risk if biosolids are
applied to agricultural land. Staphylococcus aureus and Listeria monocytogenes, two human pathogens transmitted with food and associated with serious epidemiological problems were absent in both the raw material and the composts. Clostridium perfringens constitutes a very important faecal indicator, as it is a member of human enteric flora but also an opportunistic human pathogen. It was considerably reduced from 2x104 - 3x104 cells/g dw in the raw mixtures to 8x102 and 6x102 cells/g dw in the final compost, in bioreactor 1 and 2, respectively. This bacterium can survive even in high temperatures because it transforms into endospore.

Copyright:	© European Compost Network ECN e.V.
Quelle:	Orbit 2008 (Oktober 2008)
Seiten:	9
Preis:	€ 0,00
Autor:	Dr. Katia Lasaridi Stamatis Stamatiadis A. Kyriacou
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