Study on Treatment of Preserved Wastewater by Combined Ultrafiltration-Nanofiltration

The treatment process of preserving soaking waste water by combined ultrafiltration-nanofiltration process was investigated. In the nanofiltration experiment,measuring the effects of different enrichment times on the flux, COD, total phosphorus and ammonia nitrogen to analyze the characteristics of the nanofiltration process and membrane fouling problems during nanofiltration.The results indicated that when the enrichment multiple was 4 times,the removal rate of COD was up to 87%, the removal efficiency of total phosphorus was above 90% and the removal rate of ammonia nitrogen was up to 63%, besides the membrane flux could be maintained at a better level. With prolonged operation, membrane flux decreased by 71%. After being soaked and cleaned with sodium hydroxide solution, membrane flux can be restored to more than 73% of the original. The concentrated waste water soaked by nanofiltration can be treated with advanced oxidation process,and the filtrate can reach the standard for reuse water.