Study on the performance of carbonate-mineralized bacteria combined with eggshell for immobilizing Pb and Cd in water and soil

Abstract

Microbially induced carbonate precipitation (MICP) is an advanced bioremediation approach to remediate heavy metals (HMs) contaminated water and soil. In this study, metal tolerant urease-producing bacterial isolates, namely UR1, UR16, UR20 and UR21, were selected based on their urease activity. The e ciency of these isolates in water for Pb and Cd immobilization was explored. Our results revealed that UR21 had the highest removal rates of Pb (81.9%) and Cd (65.0%) in solution within 72 h through MICP. The scanning electron microscopy-energy dispersive x-ray and x-ray diffraction analysis con rmed the structure and the existence of PbCO 3 and CdCO 3 crystals in the precipitates. In addition, the strain UR21, in combination with urea/eggshell waste (EGS) or both, was further employed to investigate the effect of MICP on soil enzymatic activity, chemical fractions and bioavailability of Pb and Cd. The outcomes indicated that the applied treatments reduced the proportion of soluble-exchangeable Pb and Cd, resulted an increment in carbonated bound Pb and Cd in the soil. The DTPA extractable Pb and Cd was reduced by 29.2% and 25.2% with the treatment of UR21 + urea + EGS as compared to the control. Besides, the application of UR21 and EGS signi cantly increased the soil pH, cation exchange capacity, and enzyme activities. Our ndings may provide a novel perceptive for an eco-friendly and sustainable approach to remediate heavy metal contaminated environment through a combination of metal-resistant ureolytic bacterial strain and EGS.

Experimental Study on the Preparation of a Highly Active Bacterial Suspension for MICP in the South China Sea

“…In recent years, MICP technology has emerged as a research hotspot in civil engineering at home and abroad, and is widely used for sand reinforcement [3][4][5][6], restoration of ancient sites [7][8][9][10], and remediation of contaminated soils [11][12][13][14]. The advantages of this type of construction are its ease of construction, low cost, and environmental friendliness.…”