Bioremediation of metal-contaminated soils by microbially-induced carbonate precipitation and its effects on ecotoxicity and long-term stability
Peng Liua, Yu Zhangb,c, Qiang Tangb, Shenjie Shib
School of Civil Engineering, Nanjing Forestry University, Nanjing 210037, China.
Bioremediation using microorganisms is a promising technique to remediate soil contaminated with heavy metals. In this study, Sporosarcina pasteurii (S. pasteurii) bioremediation by mixing method was used to remediate soils contaminated with lead (Pb), zinc (Zn) and cadmium (Cd). A significant reduction of heavy metal leaching concentrations was observed in S. pasteurii bio-treated samples. Furthermore, urease hydrolyzing bacteria have additional advantages of accelerating metal precipitation by increasing pH. The soluble-exchangeable Pb, Zn and Cd was reduced by 33.3 % ~ 85.9 %, 21.4 % ~ 66.0 %, 13.6 % ~ 29.9 % respectively after bioremediation. The primary objective of metal stabilization was achieved by reducing the bioavailability through immobilizing the Pb, Zn and Cd in the urease-driven carbonate precipitation. Luminescent bacteria toxicity experiments revealed that the metal toxicity of contaminated soil was reduced after bioremediation using S. pasteurii. When subjected to severe environmental conditions, S. pasteurii bioremediation was superior to chemical precipitation technology in terms of long-term stability.
Keywords: Microbial mineralization, Heavy metals, Carbonate precipitation.