Determining the Compost Maturity Time in Biosolids of Municipal Wastewater Treatment Plant

Background and There is no specific standard on the compost maturity time of biosolids of wastewater treatment plants in Ïran; therefore, the researchers made an attempt to employ different chemical and biological methods to assess the compost maturity time. Ïn this study, the sludge was obtained from the drying beds of South Ïsfahan Wastewater Treatment Plant and was then mixed with sawdust and windrow type of composting was performed to stabilize the sludge. The height, width and length of windrow were 1.2, 1.5, and 2.5 m, respectively. The windrow turning was done manually for 7-10 days. The results showed that, Ç/N ratio after 100 days of composting reached 15.1 and the NH4/NÔ3 ratio decreased with increase in the time of dewatered sludge compost. The content of volatile solids decreased up to 28.8 percent with composting time and the number of fecal coliforms reached 898 MPN/gram of total solids.Çonclusion: Thus, biosolids compost in this study was mature and ready for use as an agricultural substrate after 100 days of composting.