Isolation,Identification And Degradation Characteristics Of Triclocarban Degrading Bacteria From Activated Sludge

Triclocarban(TCC),as common medicines and personal care products,was frequently detected in the environment,which has attracted more and more concerns of people.In this paper,the presence of TCC in four wastewater treatment plants in Xiamen was examined.The effect of TCC degradation by aerobic and anoxic activated sludge was studied.The strains that could degrade TCC effectively were separated from activated sludge and identified.Experiments were performed to study TCC degradation effect of strains.Moreover,the study detected the intermediate products produced during TCC degradation and inferred the biodegradation pathway of TCC.The main conclusions of this study were as follows:1.The TCC concentrations of incoming and outgoing wastewater in the four sewage treatment plants of Xiamen were dectected.Results showed that the conventional sewage treatment process could remove TCC,while the remove effect was low,even appeared higher TCC concentrations of effluent than influent.There was no obvious change of TCC concentration with diffenrent times and places.TCC degradation by aerobic and anoxic activated sludge experiments showed that with the condiction of the temperature of 20°C and TCC initial concentration of 1000 ?g/L,TCC concentrations in the aqueous phase decreased rapidly while the TCC concentration in the sludge phase increased rapidly during the initial stage of TCC degradation,which indicated TCC could quickly adsorbed on the activated sludge.The adsorption rate was greater than 90% and the biodegradation rate was less than10%.There was no significant biodegradation.After 3 days of reaction,the apparent removal rate of aerobic and anoxic activated sludge to TCC was high(over 99%).The biodegradation rate of aerobic activated sludge was 40.57% and the adsorption rate was 59.25%.The biodegradation rate of anoxic activated sludge is 29.45% and the adsorption rate is 70.11%.The biodegradation effect of activated sludge under aerobic conditions is better than that under anoxic conditions.Anoxic activated sludgeremoved TCC mainly through adsorption.2.Seven strains that can degrade TCC were isolated from activated sludge using TCC as the carbon source.Compared with other strains,strain JZ-1 with significant degradation effect was adopted for further study.TCC degradation rates were 75.09%and 66.55% at the TCC initial concentration of 1 and 10 mg/L,respectively.The strain JZ-1 was observed for morphological characteristics,physiological and biochemical characteristics and molecular biological identification.The strain JZ-1was identified as Pseudomonas.3.The effect of different conditions on TCC degradation by the isolated strain JZ-1 was tested.Results showed that with the strain growth,initial concentration of TCC,pH,temperature increased,the degradation rate of TCC increased and then decreased.The degradation rate of TCC increased with the increase of inoculum size.In the logarithmic growth phase of the strain,the TCC initial concentration of 1 mg/L,the pH value of 7 and the temperature of 30°C,the inoculum size of 5%,the TCC degradation rate reached the maximum and were the optimal degradation conditions.The LC-MS method was used to detect the intermediate products produced during the TCC degradation process.The four products of DCC,MCC,NCC,and 3,4-DCA were found.Two TCC degradation path were inferred: the TCC dechlorination and TCC hydrolysis.