Removal Of Tetrachloroethylene And2-Chlorophenol And Their Toxical Effects On Bacterial Community In Activated Sludge

As a cleaning solvent in manufacturing plants, Tetrachloroethylene (PCE, C2Cl4) is widespread soil and groundwater contaminants due to its extensive use and inappropriate disposal practices environment. PCE often co-exists with chlorophenol solvents (CPs) in the industrial wastewaters. Anaerobic biological technique was a widely-used process to remove such co-contaminated compounds, but the bio-treatment performance was affected by many factors, including pollutant type and concentration due to their toxic effects on the activated sludge. This study investigated the dechlorination of PCE and2-CP in a Fe0-amanded upflow anaerobic sludge blanket (Fe0-UASB) and the effect of PCE and2-Chlorophenol (2-CP) on the microbial community in anaerobic sludge based on enzymatic activity and the microbial diversity. Result showed that the addition of Fe0to UASB reactor favored the participation of the degradation of PCE and2-CP. After94d, COD, PCE and2-CP removal rates were observed to be97%,86%and72%respectively. And anaerobic granular sludge was successfully constructed in the reactor with a bigger size for TSS/VSS rising from75.6%to87.5%. The co-contamination of PCE and2-CP significantly affected the activated sludge performance. The activities of three enzymes (dehydrogenase, phosphatase and urease) were significantly decreased (p<0.05) in exposure with PCE and2-CP, especially dehydrogenase was more sensitive than others. The dehydrogenase activity was inhibited by93.2%in the mix-treated samples with PCE and2-CP both at150mg/L. PCR-DGGE analysis revealed that PCE and2-CP contamination decreased the microbial diversity during short-term exposure, and significantly changed the microbial community structure after long-term exposure. Alphaproteobacteria, Gamaproteobacteria and Actinobacteria were the major bacterial groups during the short-term exposure. In contrast, they nearly disappeared after long-term exposure. Firmicutes (42.71%), Bacteroidetes (31.25%), Proteobacteria (12.5%) became the dominated groups and many dechlorinating bacteria were enriched such as KB-13, Smithella sp., Clostridium sp.06-1235251-43and bacterium DCE25.