Low nitrogen MICP remediation of Pb contaminated water by multifunctional microbiome UN-1

Abstract

Microbial induced carbonate precipitation (MICP), is an efficient remediation method for Pb^2 + polluted water proposed in recent years. However, the NH₄⁺-N produced during MICP process is an important challenge for this method. To solve this problem, our study prepared a multifunctional microbiome UN-1 with both function of MICP and NH₄⁺-N degradation, revealed the Pb²⁺ removal and the NH₄⁺-N degradation rule of UN-1, characterized the morphology and composition of PbCO₃ from MICP, and clarified the influence factor on MICP reaction. Through this study, the following conclusions are drawn: UN-1 contains MICP model bacteria Sporosarcina (24.35 %) and NH₄⁺-N degrading model bacteria Nitrospira (11.09 %). UN-1-mediated MICP completely remove Pb²⁺ with c(Pb²⁺) < 200 mg/L, and the concentration of NH₄⁺-N decreased to less than 50 mg/L after 120 h. The degradation of NH₄⁺-N by UN-1 undergoes nitrification and denitrification and is regulated by a variety of nitrogen degrading enzymes. The MICP products are irregular cubes mineral with single crystal structure developed with a long axial length of 200–300 nm and short axial 100–150 nm. The crystal faces of (132), (112), (200), (202) and (313) of mineral are developed, and the XRD and XPS patterns are consistent with the mineral characteristics of PbCO₃. The optimal pH value and temperature range of UN-1-mediated MICP are 5.0–9.0 and 20–40℃. NH₄⁺-N concentration can maintain a low level under most pH and temperature conditions. Our study proposes a new method for resolving NH₄⁺-N generated during MICP, which will remove obstacles for the practical application of MICP technology.