Design And Debugging Of A~2/O+MBR Process For Electroplating Wastewater

Electroplating wastewater contains a very complex composition with largequantities of heavy metals, cyanides, acids, alkalis andvarious organic additives.General method for the removal of heavy metal ions is chemical precipitation method.But the treatment effect of traditional chemical treatment to the removal of COD,ammonia nitrogen and total phosphorus in electroplating wastewater isn’t verygood.New treatment process of electroplating wastewater is needed badly.This wastewater treatment project is for a large electroplating industrial park inShenzhen,which has fully investigated and researched the types and characteristics ofwastewater discharged by the workshop. Well pre-treatment is made to make sure thatthe treated water reached the biochemical system feed water requirement.This article is for the amount of the wastewater COD and NH3-N and TPpollution index， propose the wastewater treatment process for the engineeringcharacteristics: CASS process and A2/O+MBR process. Through the technical schemedemonstration and technical and economic comparison, A2/O+MBR process waschosen as the implementation of this project. The A2/O+MBR process arrangment isanaerobic tank, flowing to sedimentation tank, anoxic tank, contact oxidation tank,membrance bioreactor(MBR), flowing out. Ensure that organic matter removalefficiency,strengthen the denitrification and phosphorus removal to ensure that theeffluent standards.In the biochemical treatment system, anaerobic sludge reflux alone,nitrifying liquid back into anoxic period at the end by the membrane area.Study on running of the A2/O+MBR process showed that the microbial flora wasstability and highly active in the follow conditions: reflux ratio=80%, DO(aerobicpool)=2.5mg/L, SV%=20%, MLSS=2000mg/L.After the treatment above, the effluentCOD was less then40mg/L, more than88%removal efficiency; the effluent NH3-Nwas less then5mg/L, more than92%removal efficiency, better than the dischargestandard, realized the discharging standard. But the sludge concentration was lowwhile the sludge retention time was long, the effect of Sludge discharge was no good,TP removal efficiency was low.The capacity of process is1500000m3/a，the total investment is11,570,000yuan，The total operation cost is1074.717yuan per year, biochemical systemprocessing costs is3yuan/m3. The project net income is5,902,430yuan per year. The Engineering static payback period is1.96year. This project has great economicenvironmental benefits and social benefits.