Low nitrogen MICP remediation of Pb contaminated water by multifunctional microbiome UN-1
Hewei Song, Jia-Qi Sha, Shuhe Wei, Jing An
Abstract
Microbial induced carbonate precipitation (MICP), is an efficient remediation method for Pb 2 + polluted water proposed in recent years. However, the NH 4 + -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 NH 4 + -N degradation, revealed the Pb 2+ removal and the NH 4 + -N degradation rule of UN-1, characterized the morphology and composition of PbCO 3 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 NH 4 + -N degrading model bacteria Nitrospira (11.09 %). UN-1-mediated MICP completely remove Pb 2+ with c(Pb 2+ ) < 200 mg/L, and the concentration of NH 4 + -N decreased to less than 50 mg/L after 120 h. The degradation of NH 4 + -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 PbCO 3 . The optimal pH value and temperature range of UN-1-mediated MICP are 5.0–9.0 and 20–40℃. NH 4 + -N concentration can maintain a low level under most pH and temperature conditions. Our study proposes a new method for resolving NH 4 + -N generated during MICP, which will remove obstacles for the practical application of MICP technology. • UN-1 has both MICP function and NH 4 + -N degradation function. • UN-1-led MICP reaction can completely remove Pb 2+ (c< 200 mg/L). • UN-1 can reduce NH 4 + -N in MICP reaction system to less than 50 mg/L within 120 h. • UN-1-led MICP reaction can remove Pb 2+ to form PbCO 3 with good crystallization. • UN-1-led MICP reaction is affected by pH and temperature of water.