Study on biological method of heavy metal removal from urban sewage sludge

Abstract

The agricultural use of municipal sludge as fertilizer appears to be the most alternative owing to its abundant N, P, K, and organic matters from an economic perspective. The presence of the elevated concentration of heavy metals, represents a serious constraint to implementation of this practice. Chemical solubilization of heavy metals from sewage sludge has never been applied because of high cost, operation difficulties and large chemical agents. Bioleaching appears to be more practical and economically viable alternative for sludge decontamination and management. The major microorganisms responsible for bioleaching are a variety of acidophilic and chemoautolithotrophic bacteria such as Thiobacillus ferrooxidans and Thiobacillus thiooxidans, which can be isolated from sewage sludge. After aerobic incubation for a few days, the leached sludge can be dewatered using centrifuge of other solid-liquid separation methods. The leached sludge can be neutralized with lime, while precious metals can be recovered from the solution phase. This paper, on the basis of study of bioleaching for heavy metal removal from sewage sludge, represents the possibility of bioleaching and have an analyze on it's implementation of this practice.