Effect of Temperature on Bioleaching Heavy Metals from Sewage Sludge

Sewage sludge taken from Guilin Wastewater Treatment Plant (WWTP) and elemental sufur(S⁰) were used as the bioleaching medium and substrate respectively. Acidification effect of sewage sludge, activity of bioleaching microorganism and removal rate of heavy metals were investigated at various temperatures from 10°C to 40°C in the bioleaching process. Where Bioleaching experiments were process was operated at 3g·L^-1 S⁰ and 1.0L·min^-1 aeration rate. An indigenous Acidithiobacillus thiooxidans was the bioleaching dominant bacteria in the process. The results showed that acidification rate and bacterial activity increased with temperature rising in the temperature range of 10°C~30°C. The optimum temperature range for bioleaching bacteria growth was 20°C~30°C. The activity of bioleaching microorganism was the highest at 28.9°C and sulfate ions yield was 461.66(mg·L^-1)·d^-1, To achieve the treatment requirements and low operation energy consumption, the proper temperature for bioleaching engineering application should be controlled at 20°C. Under this condition, the removal rates of Cu, Zn and Cd were 47.45%, 77.07 and 80.57% respectively after 5-day bioleaching. The residual concentrations of Cu, Zn and Cd in the treated sludge met with the national standard for sludge agriculture use in China.