Biosolids, sewage sludge, compost, wastewater, pathogenic agents, nutrients, soil conditioner, fertilizers.

Abstract

The composting process is a useful method of producing a stabilized material that can be used as a source of nutrients and soil conditioner. Maturity of compost is essential for its optimal use as a soil amendment and a source of plant nutrients as well. Immature composts pose problems of malodors and flies and phytotoxicity and pollution during use. Stability and maturity both are required for compost quality control. Compost maturity tests can be classified into physical, chemical, plant, and microbial activity assays. In this study, different methods of evaluating the stability and maturity of composted biosolids were compared based on physical, chemical and biological properties. The sludge used of composting was obtained from the windrow of Tobruk wastewater treatment plant. The results showed that, C/N ratio after 42 days of composting reached to 27/1 for the mixture ratio 90-10 (w/w) . The numbers of fecal coliforms and E. coli in the initial sewage sludge compost show high contents and at the end of composting were low contents, and the compost process provided class A pathogen criteria. Use of physical, chemical and biological parameters exhibited three phases: rapid decomposition (1st two weeks), stabilization and maturation (day 42-45) in biosolids compost. Thus, the biosolid compost was mature and ready for use as an agricultural substrate after about 45 days of composting.