influence of ethylene dichloride concentration on the methanogenic activity of anaerobic biomass

background : in this study, the inhibitory effect of ethylene dichloride (edc) on biodegradation was investigated using the specific methanogenic activity (sma) test of anaerobic biomass. methods: in the present study, 40 sma tests were performed using 120-ml vials in batch mode. substrate, biomass, and biogas occupied 66%, 17%, and 17% (v/v) of the volume of each vial, respectively. the duration of each batch was 10 days. produced methane was measured through gas replacement with 2n koh solution as co 2 absorbent. the chemical oxygen demand (cod) test was performed on samples before and after each test. the variation in temperature and ph were retained at 35 ± 2ºc and 7, respectively. the input cod was measured for each vial at the beginning and end of the experiment. edc was analyzed through gas chromatography-mass spectrometry (gc-ms) at the beginning and end of the experiment. findings: in this study, at the concentrations of 500, 1000, 5000, and 20000 mg/l of edc, 12.6, 9.9, 2.98, and 0.86 ml ch4/g vss decrease in the production in methane was observed, respectively. a decline in the efficiency of cod removal was also observed in the mentioned concentrations. the efficiency of cod removal at the mentioned concentrations was 68.9, 70.5, 54.4, and 33.8%, respectively. the inhibitory effects of edc on methanogenic activity of anaerobic biomass started at edc concentrations of higher than 750 mg/l. the amount of cumulative methane at edc concentrations of 750, 5000, and 20000 mg/l was 30.7, 9.86, and 1.9 ml, respectively. edc removal efficacy at concentrations of 500, 2000, and 3000 mg/l was obtained using gc-ms and was equal to 95.2%, 94.7%, and 93.8%, respectively. conclusion: the results of this study indicated that edc concentrations of higher than 750 mg/l caused a reduction in methane production and bacterial activity.