About 45% of the contaminated sites are dealing with heavy metal problems. Metals are spread in the environment by mining activities, surface treatment and non ferrous processing. As heavy metals can not be degraded, removal or immobilization (leading to bioavailability reduction) are the only risk reducing measures that exist. Next to the often used but expensive pump an treat technologies, heavy metals can be immobilized by inducing sulfate reducing bacteria (SRB) to transform the sulfates, that are very often present in the same groundwater (due to the metal mining or processing activities), into sulfides. These sulfides will precipitate the metals as insoluble metal sulfides. At the moment several studies have demonstrated the feasibility of this In Situ Bioprecipitation Process (ISBP) for the removal of heavy metals from groundwater as well at lab scale (batch and column tests) as at field scale. However, some questions arise concerning the continuation of the process, the efficiency and the sustainability of the precipitates. The presented study will try to answer these questions. The study is based on more than 10 different studies, all done by the same authors, on different groundwaters and aquifer samples. The presentation will give an overview of the guidelines necessary for a correct and successful bioprecipitation process with stable metal sulfide precipitates. It will pay attention to the influence of the carbon source on the complexing of the metals and the efficiency of the induction of the bioprecipitation process, the possible negative influence of acetate inhibition, the influence on the competence between sulfate reducers and methanogenic bacteria and the influence of low pH on the ISBP. These results will allow the correct implementation of the ISBP with an eye on longevity and sustainability of the process and present the ISBP as a much more sustainable alternative to the pump and treat technology as measure for heavy metals contaminated groundwaters.
Diels, L.; Geets, J.; Dejonghe, W.; Van Roy, S.; Vanbroekhoven, K.; Szewczyk, A.; and Malina, G.
"Heavy Metal Immobilization In Groundwater By In Situ Bioprecipitation: Comments And Questions About Efficiency And Sustainability Of The Process,"
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy:
Vol. 11, Article 7.
Available at: http://scholarworks.umass.edu/soilsproceedings/vol11/iss1/7