Research On Application Of MBR On Advanced Treatment Of Petrochemical Wastewater In One Ningbo Petrochemical Company

Water pollution and water scarcity is one of the biggest concerns of the world's environment and resources.Petrochemical wastewater is a main source of water pollution.Petrochemical wastewater advanced treatment by MBR can reduce environmental pollution and regenerate water for future production.Therefore,it is well worth doing this research and popularizing it.This thesis,based on one petrochemical project case,with MBR as its core technology and unoil-CAF-DAF-A/O-MBR as its process,developed a 300t/h wastewater treatment system that could treat petrochemical wastewater to the point of meeting the standard of recyclable water.In May 2015,According to the pilot test,this paper set the MBR system operation parameters as follows.Sludge was cleared by tank bottom scraper once a week.1mg/L of PAM and 50mg/L of PAC were put in flotation.Sludge concentrations in the A pool,O pool and membrane pool were kept at 3000mg/L,5000mg/L and 6000mg/L respectively.Activated sludge reflux ratio was set at 200%.The MBR System backwashed every 12 minutes for 30 seconds and did maintenance washes three times a week.This could remove oil,COD and NH3-N in wastewater while didn't contaminate the membrane.The result of MBR application in one petrochemical company shown that the average oil,CODcr and NH3-N contents of MBR treated water were as low as 0.18mg/L,15.26mg/L and 0.2mg/L respectively in November 2015,making high removal rates of 98.88%,97.63% and 99.87% respectively.This indicated that the MBR process could effectively remove the oil,COD and NH3-N in petrochemical wastewater and that treated water could meet the requirements of recycle water.From October to November 2015,MBR membrane maintained a flux of 14.3LMH.A degreasing pretreatment measure was taken.Proper MLSS and aeration intensity was kept.In addition,a combination of backwash and chemical cleaning was employed.The average pressures of the two MBR membranes were kept at-3.44 kPa and-4.78 kPa.After 6 months of running,the MBR system still demonstrated a good filtration performance.No seious membrane pollution was seen,therefore,restorative cleaning was not needed.According to the result of MBR application,this petrochemical wastewater advanced treatment brought a profit of 4.4 million yuan/year after excluding depreciation of investment and operating costs.Petrochemical enterprises MBR projects could significantly reduce pollutant emissions to the surrounding environment and improve the regional environment.It had significant environmental and social benefits.