Studies On Characteristics And Mechanism Of Anaerobic Degradation Of Pentachlorophenol

A batch anaerobic test was conducted to examine the biodegradability and metha- ne formation toxicity, influential factor, and dynamics of PCP anaerobic biodegradati- on. Furthermore, the biodegradation mechanism and pathway of PCP was discussed. T- he test conditions was as follows: glucose was used as co-substrate and the temperature was 35±1℃. The results indicated that PCP was a recalcitrant organic compound (the removing rate of PCP dropped off significantly when PCP concentration increased to above 10mg/L); The inhibition (or toxicity ) to methanogenic bacteria of PCP had dose response to its effect. Middle inhibition was caused when concentration of PCP was 5～40 mg/L. And the activity was strongly inhibited when PCP concentration increase- d to 60mg/L; The inhibition level was PCP>2,4,6-TCP>2,3,4,6-TeCP>2,4-DCP. The methanogenic activity recovery level was 2,4-DCP>2,3,4,6-TeCP>2,4,6-TCP>PCP. The recovery of methanogenic activity became more difficult as the toxicity of chloro- phenol increased, and decreased as chlorophenol concentration increased; The rank of biodegradability was PCP>2,3,4,6-TeCP>2,4,6-TCP>2,4-DCP, the relation between the chlorophenol removing rate and its toxicity wasn't obviously under the conditions of glucose was used as co-substrate. But the toxicity had obvious influence to COD re- moving rate, COD removing rate decreased when the toxicity of chlorophenol increas- ed; The suitable conditions for PCP anaerobic biodegradation with co-substrate were as follows: the pH was 7～8, the saturated sludge concentration was about 9.28gVSS/L, the COD concentration of co-substrate glucose was 1800～1900mg/L; The anaerobic biodegradation of PCP was followed by pseudo first-order kinetics with glucose as co- substrate (the COD concentration of glucose was 1800～1900mg/L). The degradation rate would be decreased when increased the initial PCP concentration. The more highly chlorinated, the more easily reductive dechlorinated, resulted in more rapid of PCP de- gradation rate; PCP could be reductive dechlorinated sequentially through the pathway of PCP→2,3,4,6-TeCP→3,4-DCP→3-CP, and was mineralized to CH4 and CO2 event- ually. The change of Gibbs free energy value could be used as one way to predict the pathway of PCP anaerobic biodegradation.