Anaerobic Degradation Of PCP In Wastewater By Continuous Stirred Tank Reactor

Pentachlorophenol (PCP) is a toxic and hardly biodegradable xenobiotic,and it has been placed on the Priority List of Pollutants by the U.S. Environmental Protection Agency and our country. In recent years, a large number of foreign studies show that pentachlorophenol was degradated well under the anaerobic conditions, but the research in this area in our country is still in its beginning stage. In this paper, degradation of Pentachlorophenol (PCP) in the wastewater was investigated in the continuous stirred tank reactor(CSTR). Emphasis was placed on assessing the operational controlling strategy on the domestication operation of CSTR with high efficiency.It was in order to provide the basis theoretic data for the development and application of anaerobic treatment of wastewater containing PCP.In the paper, the accurate, rapid and sensitive method of detecting PCP were determined firstly. UV spectrophotometer and HPLC were studied: the average relative standard deviation of UV spectrophotometer is 6.0%, the detection limits of PCP is 0.92mg/L and the average recoveries of the standard addition tests for PCP is 96.97%, while the average relative standard deviation of HPLC is less than 1%, the detection limits of PCP is 8.25mg/L and the average recoveries of the standard addition tests for PCP is 98.71%. By comparing UV spectrophotometer with HPLC, UV spectrophotometer was used to determine PCP at high concentration, while HPLC was used at low concentration.In the running of CSTR reactor, effect rules pH, concentration of glucose and PCP loading rate on the system were studied, and effects of hydraulic retention time and stirring speed of reactor on performances of the reactor were also discussed. Experimental results show, the reactor was operated well when pH was at 6.3⁷.1. When the reactor at low pH, NaHCO3 can be added to adjust pH and its suitable concentration is 0.3g/L.Appropriate increase of glucose concentration favored degradation of PCP and COD, and in the study appropriate concentration of glucose was 2.2g/L. PCP and COD removal rate will increase when the stirring speed of reactor was at 150r/min¹80r/min and hydraulic retention time was 6⁸h.The reactor was started-up and continuous operated secondly at the suitable conditions which were mentioned above. In the second time start-up, the beginning COD volume loading rate was 2.73kg·m^-3·d^-1. The reactor achieved steady operating station after 21 days. PCP volume loading rate rate stepped up from 1.0×10-3kg·m^-3·d^-1 to 48×10-3 kg·m^-3·d^-1, and the removal rate of PCP could achieved about 90%. PCP and COD removal rate will descend to a certain extent when PCP loading rate was increased.