Bioremediation of trichloroethylene-contaminated groundwater using green carbon-releasing substrate with pH control capability

Hsin-Chia Lee; Ssu-Ching Chen; Yih-Terng Sheu; Chao-Ling Yao; Kai-Hung Lo; Chih-Ming Kao

doi:10.1016/j.envpol.2024.123768

Bioremediation of trichloroethylene-contaminated groundwater using green carbon-releasing substrate with pH control capability

Environ Pollut. 2024 May 1:348:123768. doi: 10.1016/j.envpol.2024.123768. Epub 2024 Mar 15.

Authors

Hsin-Chia Lee¹, Ssu-Ching Chen², Yih-Terng Sheu³, Chao-Ling Yao⁴, Kai-Hung Lo¹, Chih-Ming Kao⁵

Affiliations

¹ Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan.
² Department of Life Sciences, National Central University, Chung-Li City, Taoyuan, Taiwan.
³ General Education Center, National University of Kaohsiung, Kaohsiung, Taiwan.
⁴ Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan.
⁵ Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan. Electronic address: jkao@mail.nsysu.edu.tw.

PMID: 38493868
DOI: 10.1016/j.envpol.2024.123768

Abstract

In this research, a sustainable substrate, termed green and long-lasting substrate (GLS), featuring a blend of emulsified substrate (ES) and modified rice husk ash (m-RHA) was devised. The primary objective was to facilitate the bioremediation of groundwater contaminated with trichloroethylene (TCE) using innovative GLS for slow carbon release and pH control. The GLS was concocted by homogenizing a mixture of soybean oil, surfactants (Simple Green™ and soya lecithin), and m-RHA, ensuring a gradual release of carbon sources. The hydrothermal synthesis was applied for the production of m-RHA production. The analyses demonstrate that m-RHA were uniform sphere-shape granules with diameters in micro-scale ranges. Results from the microcosm study show that approximately 83% of TCE could be removed (initial TCE concentration = 7.6 mg/L) with GLS supplement after 60 days of operation. Compared to other substrates without RHA addition, higher TCE removal efficiency was obtained, and higher Dehalococcoides sp. (DHC) population and hydA gene (hydrogen-producing gene) copy number were also detected in microcosms with GLS addition. Higher hydrogen concentrations enhanced the DHC growth, which corresponded to the increased DHC populations. The addition of the GLS could provide alkalinity at the initial stage to neutralize the acidified groundwater caused by the produced organic acids after substrate biodegradation, which was advantageous to DHC growth and TCE dechlorination. The addition of m-RHA reached an increased TCE removal efficiency, which was due to the fact that the m-RHA had the zeolite-like structure with a higher surface area and lower granular diameter, and thus, it resulted in a more effective initial adsorption effect. Therefore, a significant amount of TCE could be adsorbed onto the surface of m-RHA, which caused a rapid TCE removal through adsorption. The carbon substrates released from m-RHA could then enhance the subsequent dechlorination. The developed GLS is an environmentally-friendly and green substrate.

Keywords: Dechlorination; Emulsified oil; Green and long-lasting substrate; Rice husk ash; Trichloroethylene.

MeSH terms

Biodegradation, Environmental
Carbon
Groundwater* / chemistry
Hydrogen
Hydrogen-Ion Concentration
Trichloroethylene* / metabolism
Water Pollutants, Chemical* / analysis

Substances

Trichloroethylene
Carbon
Water Pollutants, Chemical
Hydrogen