Feasibility of sewage sludge leached by Aspergillus niger in land utilization

Aspergillus niger is adopted in bioleaching to dispose of sludge from an urban wastewater treatment plant to determine the bioleaching influence of sludge on heavy metal fraction and nutritive material loss. The enrichment effect on wheat seedlings of Cu, Zn, Pb, and Cd in sludge is researched by a soil-cultivated experiment. Results indicate that the removal rates of Cu, Zn, Pb, and Cd are 74.1%, 87.6%, 82.1%, and 97.8% in the sludge after bioleaching, respectively. The remaining heavy metal in the sludge is mainly residual fraction followed by oxidizable fraction. The bioefficiency of the heavy metal decreases significantly. The loss rates of N, P, and K in the sludge are 29.8%, 13.3%, and 28.8%, respectively, with good fertility after bioleaching. The enrichment capacity order of heavy metals is Zn>Pb>Cu>Cd in wheat root and stem leaf, which is consistent with the order of unstable fraction content in the sludge after bioleaching.