Assessment of Biochemical Leaching of Domestic Sewage Sludge

Sewage sludge could be used as organic fertilizer and source for nutrients in soil. Sludge always contain toxic substances especially heavy metals. When applied to land heavy metals can accumulate in the soil and produce harmful effects in animal and vegetation. A safe use of sewage sludge as soil conditioner requires sewage sludge with low heavy metal content. The removal of the heavy metals from sludge reduces prospective health risk during its application to land and accumulation in the food chain as well as persistence in nature. Microbial and chemical leaching using Thiobacillus thiooxidans and H2SO4 was investigated to solubilize heavy metals (HMs) from domestic sludge at different concentrations. Result obtained showed that 100% Cr was solubilized at 50 ml sludge concentration when the bioleached sludge was digested with 50% (v/v) H2SO4, while 90% Cr was also solubilized at same sludge concentration when the bioleached sludge wasn't digested with H2SO4.The scientific community would benefit from this project since it has developed new methods for the removal and recovery of heavy metals from dilute solutions and their reduction to very low concentrations in sewage sludge.