Study On The Characterisrics Of Electroplating Wastewater Treatment By MBR Process Integrated With Suspended Carrier

Electroplating wastewater has become a major problem in the field of industrial wastewater treatment,with the characteristics of large amount of water,large variation of water quality,complex composition,high toxicity and difficult to be degraded.Electroplating synthetical wastewater contains a variety of pollutants,including COD,ammonia nitrogen,heavy metals and large molecular organics such as surface active agent,brightener,etc.Conventional biological treatment technology is difficult to achieve ideal treatment effect.In view of the situation,the exploration of better effect and less cost of sewage treatment process need to be carried out.The Hybrid Membrane Bioreactor(HMBR)system was built with the addition of suspended biological carrier.In contrast to the common MBR process,the test mainly performed the optimization of the operation parameters of the reactor,removal efficiency of pollutants under the condition of stable operation,the effects on pollutants removal efficiency,sludge mixed liquor properties and membrane fouling of four stages shock load with different concentrations of three heavy metals(Cu,Ni,Cr),the analysis of heavy metals enrichment in the sludge,and research of changes in microbial community under the effect of heavy metals.The inoculated sludge was from a secondary sedimentation tank of Harbin city sewage treatment plant.Simulated electroplating wastewater was used in sludge acclimation,membrane forming of the packing materials and start-up of the reactor.By operating parameters optimization,the optimal operation parameters of reactor:hydraulic retention time is 16h,aeration is 0.4L/min,mixed liquid reflux ratio is 250 percent.Under the optimal parameter conditions,average treatment efficiency by HMBR system of COD,ammonia nitrogen,TN were 94.4%,74.8%,52.9%,better than the control group.In the shock load test,the removal efficacy of pollutant decreased gradually with the increase of the concentration gradient of heavy metal,nevertheless the COD?NH4+-N and TN removal rate of the HMBR system were still superior to that of the common MBR system,and the effluent quality was more stable as well.The heavy metals negatively impacted the total biomass concentration of the system,and it had a relative less effect when it turned to the HMBR system;what's more,when the sludge activity was reduced,the SOUR inhibition of the HMBR system was less than that of the control.To protect themselves from the heavy metals,the microorganisms produced more EPS which could bond the heavy metals and therefore reduce their toxicity.However,the accumulation of EPS led to the increase of the viscosity and sludge specific resistance of the system,which deteriorated the filtration performance and further speeded up the membrane fouling.The effect on the HMBR system was less compared with the control one,which was mainly showed in the growth rate of the transmembrane pressure(TMP),resistance in membrane filtration and membrane pore blockage degree.The enrichment ability of the system to heavy metals was Cu?Ni and Cr in descending order.The shock load of heavy metals could destroy the sludge aggregates in a common MBR system,it could also result in a loose structure and the sludge aging problem,while the HMBR system can keep high activity under this situation.High throughput sequencing analysis showed that the microbial diversity in the HMBR system was more abundant than the common MBR system.