Enhanced 4-chlorophenol biodegradation by integrating Fe_(2)O_(3)nanoparticles into an anaerobic reactor:Long-term performance and underlying mechanism

Fe_(2)O_(3)nanoparticles have been reported to enhance the dechlorination performance of anaerobic systems,but the underlying mechanism has not been clarified.This study evaluated the technical feasibility,system stability,microbial biodiversity and the underlying mechanism involved in a Fe_(2)O_(3)nanoparticle-coupled anaerobic system treating 4-chlorophenol(4-CP)wastewater.The results demonstrated that the 4-CP and total organic carbon(TOC)removal efficiencies in the Fe_(2)O_(3)-coupled up-flow anaerobic sludge blanket(UASB)were always higher than 97%and 90%during long-term operation,verifying the long-term stability of the Fe_(2)O_(3)-coupled UASB.The 4-CP and TOC removal efficiencies in the coupled UASB increased by 42.90.4%and 27.50.7%compared to the control UASB system.Adding Fe_(2)O_(3)nanoparticles promoted the enrichment of species involved in dechlorination,fermentation,electron transfer and acetoclastic methanogenesis,and significantly enhanced the extracellular electron transfer ability,electron transport activity and conductivity of anaerobic sludge,leading to enhanced 4-CP biodegradation performance.A possible synergistic mechanism involved in enhanced anaerobic 4-CP biodegradation by Fe_(2)O_(3)nanoparticles was proposed.