Anaerobic dechlorination of trichloroethylene (TCE) to ethylene using complex organic materials

Reductive dechlorination of trichloroethylene (TCE) to ethylene was supported by complex organic matter such as cane molasses and ligno-cellulosic materials as a substrate and electron donor under methanogenic conditions. The studies were performed with an anaerobic dechlorinating, methanogenic microbial consortium at 20–22°C. A high molar ratio between methane and ethylene (158 mol/mol) was observed during rapid dechlorination of TCE with cane molasses as a substrate. Three ligno-cellulosic materials (corn cobs, hard wood chips and newsprint) supported dechlorination of TCE to ethylene. After 140 days of incubation, the molar ratio between methane and ethylene was 36, 29 and 22 mmol/mmol for corn cobs, wood chips and newsprint, respectively. The rates of dechlorination and methanogenes were relatively rapid during the first 60 days. The efficiency of COD and electrons used for dechlorination ranged from 0.3–0.5% for cane molasses to 2.0–3.5% for ligno-cellulosic materials. Methanogenesis was more prevalent reaction than dechlorination during the studies, but the fraction of electron donors and chemical oxygen demand (COD) used for dechlorination was increased when biodegradability of the ligno-cellulosic materials slowed. The complex organic matter can be used as a cost-effective substrate for anaerobic biotreatment of chlorinated ethylenes.