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

• Published in: Environmental pollution (1987) Vol. 348; p. 123768
• Main Authors: Lee, Hsin-Chia, Chen, Ssu-Ching, Sheu, Yih-Terng, Yao, Chao-Ling, Lo, Kai-Hung, Kao, Chih-Ming
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.05.2024
• Subjects: Biodegradation, Environmental; Carbon; Dechlorination; Emulsified oil; Green and long-lasting substrate; Groundwater - chemistry; Hydrogen; Hydrogen-Ion Concentration; Rice husk ash; Trichloroethylene; Trichloroethylene - metabolism; Water Pollutants, Chemical - analysis; Rice husk ash; Trichloroethylene; Dechlorination; Emulsified oil; Green and long-lasting substrate
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2024.123768

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. [Display omitted] •Green/long-lasting substrate (GLS) was developed to enhance TCE dechlorination.•GLS containing emulsified oil/modified rice husk ash (m-RHA) releases TOC slowly.•m-RHA (a plant-based zeolite with alkali ions) has a high adsorption capacity.•GLS addition improves hydA and DHC populations and reduces sulfide toxicity.•GLS is a green and environmentally-friendly substrate with pH control ability.