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Long-Term Capacity of Plant Mulch to Remediate Trichloroethylene in Groundwater
Citation:
Shen, H., C. J. ADAIR, AND J. T. WILSON. Long-Term Capacity of Plant Mulch to Remediate Trichloroethylene in Groundwater. JOURNAL OF ENVIRONMENTAL ENGINEERING. American Society of Civil Engineers (ASCE), Reston, VA, 136(10):1054-1062, (2010).
Impact/Purpose:
Kinetic analysis of methane production in batch tests provides supporting evidence that plant mulch is able to sustain long term biological activity in a typical barrier contructed with plant tissues.
Description:
Passive reactive barriers are commonly used to treat groundwater that is contaminated with chlorinated solvents such as trichloroethylene (TCE). A number of passive reactive barriers have been constructed with plant mulch as the reactive medium. The TCE is removed in these barriers through adsorption, biological reductive dechlorination, and abiotic reactions with reduced iron minerals that are formed in the barrier. The long term performance of these barriers will be controlled by their capacity to support biological activity. Laboratory batch experiments were inoculated with an enrichment culture of dechlorinating microorganisms. Dechlorination of TCE to ethylene was achieved using plant mulch; however, neither a water extract nor organic solvent extract of the mulch could sustain dechlorination of TCE. This indicates that biodegradation of the structural fibers in the plant cell wall provide the substrate for dechlorination of TCE. Kinetic analysis of the methane production in the batch tests provides supporting evidence that the plant mulch is able to sustain long-term biological activity in a typical barrier constructed with plant tissues. The recognition of the intact plant tissues as a long-term carbon and energy source expands the knowledge about the microbial dechlorination under natural conditions. In addition, the production of dissolved inorganic carbon observed in a column study was used to estimate the lifecycle of a full-scale biowall installed at Altus AFB, Oklahoma. With a steady-state production rate measured at 10 mg per liter per day, the mulch in the biowall could be expected to support microbial activity for twenty six years.
