Study On The Membrane Bioreactor For Treating Surfactant Wastewater

Surfactant is common in chemical,machinery,petroleum,metallurgy and other fields,whose main component is linear alkylbenzene sulfonate(LAS).LAS which is toxic to the ecological environment and human can cause serious harm.Bio-degradation is an important method to remove LAS.However,traditional sewage land treatment efficiency has been unable to treat the growing demand for wastewater discharge and treatment.In this study,the effect of membrane bioreactor(MBR)on the treatment of surfactant wastewater and its operation characteristics were studied,and the technical support was provided.In order to investigate the effect of degratation of LAS,some activated sludge is taken from the aerobic tank and the anaerobic tank of a sewage treatment plant in Shenzhen,then it is cultivated and domesticated in a membrane bioreactor(MBR)with artificial surfactant wastewater.The first is the start-up phase,in which the influent contains no LAS but glucose as the sole carbon source.When the removal rate of COD remains stable and efficient,the start-up can be considered finished.The start-up phase lasts 20 days.The next is the domestication phase.LAS is begun to be added in the influent and the concentration increases gradually.In the early phase of domestication,the removal rates of COD and LAS were respectively 85.49% ~93.31% and abOTU 80%,at relatively stable levels.It showed that LAS could be degraded by co-metabolism in the presence of growth medium.When the concentration of LAS reaches 175mg/L,the removal rate of COD and LAS decreased obviously,which showed that there was a limit to the adaptation of microorganisms to LAS toxicity.By adjusting different operating parameters,the influence of hydraulic retention time,aeration intensity,carbon and nitrogen ratio,temperature on the removal efficiency of COD and LAS was studied.The results showed that the treatment effect of MBR system is the best,when the hydraulic retention time is 10 h,the carbon and nitrogen ratio is 2/1~6/1,the aeration rate intensity is 1~4 L/min,the temperature is20~30 ?.Moreover,the effects of aeration inrensity,intermittent water OTUlet mode and back washing intensity on membrane fouling were also discussed.The results showed that the slowest development of membrane fouling is realized when the aeration inrensity is 3 L/min,the intermittent mode is on time for 8 min and off time for 2 min,the back washing intensity is 20 LMH.In this case it takes abOTU 15 days for the TMP to reach beyond 60 KPa.The substrate degradation kinetics model of COD and LAS and microbial increment dynamics model are also established,and the relevant parameters are obtained under the experimental conditions.