[Changes of chemical and biological properties during composting sewage sludge by using forced aerated static pile...

Municipal sewage sludge was composted for 53 days with Chinese medical herb residues as bulking agent through forced aerated static pile model. The temperature of the pile could quickly rise to more than 55 degrees C after the second day after composting. Furthermore, the temperature of more than 55 degrees C maintained as long as 8 days, which was helpful in inactivation of pathogens in compost. The cress seed germination index (GI) and the ratio of water-soluble organic carbon to organic nitrogen (soluble C/N-organic), used as indicators of phytotoxicity and maturation of compost, exhibited that the sludge compost was almost stabilized and matured near the 40th day of composting, when 80% of GI and 6.4 of soluble C/N-organic were obtained. The content of total N, P, Cu, Zn and Cd in compost increased as the composting time elapsed, while volatile solids, solid and water soluble organic carbons, pH, and NH4(+)-N decreased. F. coli, as a common indicator of pathogens in sludge, was reduced greatly from 1.41 x 10(5) to 2.32 x 10(1) in the final examination of the compost.