Bioreduction and mineralization of Cr(VI) by Sporosarcina saromensis W5 induced carbonate precipitation

Abstract

The microbial reduction of Cr(VI) to Cr(III) is widely applied, but most studies ignored the stability of reduction products. In this study, the Cr(VI)-reducing bacterium of Sporosarcina saromensis combined with microbially induced carbonate precipitation (MICP) was used to explore the reduction and mineralization mechanisms of Cr(VI). The results indicated that the high concentration of Ca²⁺ could significantly enhance the reduction and mineralization of Cr(VI). The highest reduction and mineralization efficiencies of 99.5% and 55.9% were achieved at 4 g/L Ca²⁺. Moreover, the urease activity of S. saromensis in the experimental group was up to 13.28 U/mg NH₃-N. Besides, the characteristic results revealed that Cr(VI) and reduced Cr(III) were absorbed on the surface or got into the interspace of CaCO₃, which produced a new stable phase (Ca₁₀Cr₆O₂₄(CO₃)). Overall, the combination of S. saromensis and MICP technology might be a high-efficiency and environmentally friendly strategy for further application in the Cr(VI)-containing groundwater.

Keywords: Hexavalent chromium; Microbial remediation; Sporosarcina saromensis W5; Urease.