Cleanup of Cr(VI)-polluted groundwater using immobilized bacterial consortia via bioreduction mechanisms

Wei-Han Lin; Chih-Ching Chien; Jiun-Hau Ou; Ying-Liang Yu; Ssu-Ching Chen; Chih-Ming Kao

doi:10.1016/j.jenvman.2023.117947

Cleanup of Cr(VI)-polluted groundwater using immobilized bacterial consortia via bioreduction mechanisms

J Environ Manage. 2023 Aug 1:339:117947. doi: 10.1016/j.jenvman.2023.117947. Epub 2023 Apr 17.

Authors

Wei-Han Lin¹, Chih-Ching Chien², Jiun-Hau Ou³, Ying-Liang Yu³, Ssu-Ching Chen⁴, Chih-Ming Kao⁵

Affiliations

¹ College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China; Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan.
² Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Chung-Li City, Taoyuan, Taiwan.
³ Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan.
⁴ Department of Life Sciences, National Central University, Taoyuan, Taiwan. Electronic address: osycchna@ksts.seed.net.tw.
⁵ Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan; Center for Emerging Contaminants Research, National Sun Yat-Sen University, Kaohsiung, Taiwan. Electronic address: jkao@mail.nsysu.edu.tw.

PMID: 37075632
DOI: 10.1016/j.jenvman.2023.117947

Abstract

Cr(VI) bioreduction has become a remedial alternative for Cr(VI)-polluted site cleanup. However, lack of appropriate Cr(VI)-bioreducing bacteria limit the field application of the in situ bioremediation process. In this study, two different immobilized Cr(VI)-bioreducing bacterial consortia using novel immobilization agents have been developed for Cr(VI)-polluted groundwater remediation: (1) granular activated carbon (GAC) + silica gel + Cr(VI)-bioreducing bacterial consortia (GSIB), and (2) GAC + sodium alginate (SA) + polyvinyl alcohol (PVA) + Cr(VI)-bioreducing bacterial consortia (GSPB). Moreover, two unique substrates [carbon-based agent (CBA) and emulsified polycolloid substrate (EPS)] were developed and used as the carbon sources for Cr(VI) bioreduction enhancement. The microbial diversity, dominant Cr-bioreducing bacteria, and changes of Cr(VI)-reducing genes (nsfA, yieF, and chrR) were analyzed to assess the effectiveness of Cr(VI) bioreduction. Approximately 99% of Cr(VI) could be bioreduced in microcosms with GSIB and CBA addition after 70 days of operation, which caused increased populations of total bacteria, nsfA, yieF, and chrR from 2.9 × 10⁸ to 2.1 × 10¹², 4.2 × 10⁴ to 6.3 × 10¹¹, 4.8 × 10⁴ to 2 × 10¹¹, and 6.9 × 10⁴ to 3.7 × 10⁷ gene copies/L. In microcosms with CBA and suspended bacteria addition (without bacterial immobilization), the Cr(VI) reduction efficiency dropped to 60.3%, indicating that immobilized Cr-bioreducing bacteria supplement could enhance Cr(VI) bioreduction. Supplement of GSPB led to a declined bacterial growth due to the cracking of the materials. The addition of GSIB and CBA could establish a reduced condition, which favored the growth of Cr(VI)-reducing bacteria. The Cr(VI) bioreduction efficiency could be significantly improved through adsorption and bioreduction mechanisms, and production of Cr(OH)₃ precipitates confirmed the occurrence of Cr(VI) reduction. The main Cr-bioreducing bacteria included Trichococcus, Escherichia-Shigella, and Lactobacillus. Results suggest that the developed GSIB bioremedial system could be applied to cleanup Cr(VI)-polluted groundwater effectively.

Keywords: Bioremediation; Cr(VI) bioreduction; Cr-reducing bacteria (CRB); Groundwater; Immobilized bacteria.

MeSH terms

Bacteria / genetics
Biodegradation, Environmental
Chromium* / analysis
Groundwater*
Oxidation-Reduction

Substances

chromium hexavalent ion
Chromium