EVALUATION OF THE BIOSOLIDS COMPOST MATURITY IN SOUTHISFAHAN WASTEWATER TREATMENT PLANT

The composting process is a useful method of producing a stabilized material that can be used as a source ofnutrients and soil conditioner. Maturity of compost is essential for its optimal use as a soil amendment and asource of plant nutrients as well. Immature composts pose problems of malodors and flies and phytotoxicityand pollution during use. Stability and maturity both are required for compost quality control. Compostmaturity tests can be classified into physical, chemical, plant, and microbial activity assays. In this study,several methods of evaluating the stability and maturity of composted biosolids were compared based onchemical and biological properties. The sludge used of windrow cornposting was obtained from the dryingbeds of South Isfahan wastewater treatment plant. The results showed that , CIN ratio after 100 days ofcomposting reached to 15/1; NfL/N03 ratio decreased with increase ofthe time dewatered sludge compost,which this loss is 57.3%. The content of volatile solids, 28.8% decreased with composting time. The numberof fecal coliforms in the initial sewage sludge compost was 17.9xl06 and at the end of composting was898MPN/g of total solids and the compost process provided class A pathogen criteria . Use of chemicaland biological parameters exhibited three phases : rapid decomposition (day 40), stabilization (day 80) andmaturation (day (00) in biosolids compost. Thus, the biosolid compost was mature and ready for use as anagricultural substrate after about 100 days of composting.