Abstract
Microbially induced carbonate precipitation (MICP) is an advanced bioremediation approach to remediate heavy metal (HM)-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 efficiency of these isolates in water for Pb and Cd immobilizations 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 confirmed the structure and the existence of PbCO3 and CdCO3 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, which resulted in an increment in carbonate-bound Pb and Cd in the soil. The DTPA-extractable Pb and Cd were 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 significantly increased the soil pH, cation exchange capacity, and enzyme activities. Our findings 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.
Highlights
Contamination of natural surroundings by heavy metals (HMs) through industrialization, smelting, mining activities, excessive use of fertilizers and pesticides in farming areas and combustion of hazardous waste materials has become a widespread environmental problem (Guo et al 2020; Hua et al 2021; Wei et al 2021)
The aims of the current study were to: (1) isolate and identify Pb and Cd tolerant bacteria that secret urease; (2) estimate the capability of bacteria for Pb and Cd removal in water through Microbially induced carbonate precipitation (MICP) and to confirm the mechanism involved through scanning electron microscopy-energy dispersive x-ray spectrometry (SEM-EDS) and x-Ray diffraction; (3) compare the Pb and Cd immobilization effect of urease-producing bacteria supplemented with urea and eggshell waste (EGS) in soil; (4) assess the influence of urease-producing bacteria supplemented with urea and EGS on soil physicochemical properties
The results revealed that the isolates UR1, UR16, and UR21 are closely related to one another and correspond to the genus of Bacillus sp. and the isolate UR20 belongs to the genus Citrobacter sp. (Fig. S1)
Summary
Contamination of natural surroundings by heavy metals (HMs) through industrialization, smelting, mining activities, excessive use of fertilizers and pesticides in farming areas and combustion of hazardous waste materials has become a widespread environmental problem (Guo et al 2020; Hua et al 2021; Wei et al 2021). The adsorption, chemical precipitation, membrane separation, and biological methods have been purposed for the remediation of HMs contaminated water and soil (Muhammad et al 2021; Zhai et al 2018). Among these suggested approaches, biological methods that incorporate the use of biological microorganisms called microbial remediation is well-accepted due to their low economical costs, environment-friendly and the reduced amount of remaining contaminants (Fang et al 2018; Hamid et al 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Environmental science and pollution research international
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
