Control of Enteric Micro-Organisms by Aerobic–Thermophilic Co-Composting of Wastewater Sludge and Agro-Industry Wastes

Abstract

A field scale, pilot plant study of aerobic-thermophilic co-composting of digested) dewatered, wastewater sludge together with the agro-industry wastes, poplar bark and grape vine stalks was carried out by A.G.A.C in Reggio-Emilia, Province of Northern Italy. The compost piles reached a temperature of over 55°C for extended periods and concentration of the bacterial indicator organisms fecal coliforms, fecal streptococcus and Salmonella were reduced drastically to acceptable levels. The mean C/N ratio of the mixture was reduced during the composting period from 25 to 17. The final compost proved effective as a soil fertility additive in plant growth experiments. The special value of co-composting sludge with ligneous-cellulose residuals, which stimulate the biological interactions essential for effective composting were revealed in this study.