| Pentachlorophenol(PCP) is a stable,hardly biodegradable and toxic substances in the environment,and seriously threats the ecological environment. and the anaerobic biodegradation is a more satisfactory way to dispose it.In this paper,a USAB reactor and a batch reactor were used for studying the anaerobic degradation characteristics of PCP and the feedback effects of PCP for biological systems,and the effects of PCP for different biology were investigated.This research had a certain guidance value for the biodegradation of the chlorophenols sewage.An experimental study that simulates continuous-flow,PCP contained sewage water was carried out using a UASB reactor.The experimental results indicate that during the three stages of PCP addition(initial PCP addition,PCP concentration increase,and PCP load increase) the degradation rates of PCP and COD show the trend of initial quick drop followed by a slow raise.After the anaerobic degradation system was stabilized,the degradation rates of PCP and COD reached to 91.2%and 83.5%,In the process,PCP influenced the microorganism of the anaerobic system,gradually transforming the acidogenic bacteria from butyric acid bacteria dominated to propionic acid bacteria dominated.PCP significantly inhibited the activity of methane bacteria.The volume of methane production was reduced from 12.1L/d before the PCP addition to 2.5L/d after the PCP addition.The acid floor in UASB reactor was extending with the increasing of PCP concentration.The sludge in different floors had different degradation capability of PCP,while the bottom sludge had the higher degradation capability of PCP.The removal efficiency of PCP in the bottom of UASB was above 87%,which used glucose as co-substrate,while it was only 37.7%at the top. The intermittent experiment results indicated that PCP affected the type of anaerobic fermentation system,gradually transforming from butyric acid bacteria dominated to propionic acid bacteria dominated.After the impact of PCP,acid bacteria and methanogenic bacteria become revived their activity gradually,while acid bacteria activity revived ahead of the methanogenic bacteria.The experiment also investigated some factors of anaerobic system(the different initial concentration of PCP,temperature,alkalinity and sludge concentration),the result showed that the higher pcp concentration was,the more seriously PCP restrained microorganism.The degradation capability of PCP controlled temperature at 35℃was higher than that at 25℃,the PCP removal at 35℃was 10%higher than that at 25℃..The high concentration of sludge could degradate PCP better,adjusting alkalinity was propitious to degradate PCP.At the same time,the anaerobic degradation capibility of PCP was different when different co-substrates.The PCP removal was 98.2%using glucose as co-substrate,while the PCP removal was 42.2%using acetic acid as co-substrate.the sequence of different co-substrates is: glucose＞propionic acid＞butyric acid＞ethanol＞acetic acid.The anaerobic degradation of PCP accorded with first-class dynamic equation,the velocity degradation of sludges was distinctness in different floors of UASB reactor,and the velocity were gradually advanced from top to bottom in reactor,the sequence of different co-substrates:propionic acid＞butyric acid＞ethanol＞acetic acid.,the K was 0.0118h-1,0.0069 h-1,0.0067 h-1 respectively. Analysis of degradated intermediate products of PCP by HPLC showed that the the sequence of PCPdegradated was:PCP→2,3,4,6-TCP→2,4,6-TCP→2,4-DCP→2-CP or 4-CP.
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