Physico-chemical aspects during the composting of municipal solid wastes and sewage sludge in a semi- industrial composting plant

Abstract

This study investigated at first the main physico-chemical and biochemical parameters during the co-composting process of municipal solid waste and sewage sludge under Tunisian pedo-climatic conditions, and secondly to assess potential toxic elements (PTEs) content of the finished compost and to evaluate its biological stability and maturity. Results show that the temperature revealed three classical steps, the mesophilic phase during the first 25 days, the thermophilic phase between 30 and 130 days and the cooling phase began after the 14th week in the two windrows W1 (100% of municipal solid wastes) and W2 (60% of municipal solid wastes and 40% of dried sewage sludge). Potential toxic heavy metal content appeared generally more important in W2 than W1, and both finished products of compost obtained in this study appeared to satisfy the most part of the recommended norm of agronomical use. The presence or absence of nitrifying activity allowed determining that the compost W1 is more matured than the compost W2. Key words: Compost, temperature, C/N ratio, potential toxic elements, compost maturity.