Experimental Study On Nanofiltration And Reverse Osmosis In Advanced Treatment Of Municipal Sewage

With the rapid population growth and development of social economy, water pollution and water resource shortage are aggravating. It has to look for a water resource instead of clean water to alleviate the condition of water resource shortage. However, the reclamation of municipal domestic sewage after advanced treatment, undoubtedly, is the best approach for resolving water resource shortage.In this paper, MF-AC-MF-RO and MF-AC-NF two processes were used to treat secondary effluent of municipal wastewater plant. The cut-off, recycle direction and influencing factors during membrane separation of two processes were studied and the results showed that in RO process, the removal rates of organics, heavy metals, PAEs that were residual in secondary effluent are 79.7%～97.8%, 91%～99%, 82%～84.4% respectively and in NF process, the removal rates of organics, heavy metals, PAEs are 40%～82%, 52%～92%, 70%～75.49% respectively. The removal rates of total bacterial are both 100% in two processes. The effluent of two processes can reach the standards of urban miscellaneous water, circulating cooling water and so on.The effects of operation pressure and operation time on nanofiltration performance were studied. The results showed that membrane flux increases, the rejection increases first and then decreases with increasing operation pressure. With the prolongation of time, the membrane flux and rejection both decrease because membrane fouling for polarization concentration difference.Through experiment, the cleaning effect of 0.5% NaOH and 0.5% C₆H₈O₇ washed RO/NF membranes were studied and the results showed that the two cleaning methods are both effective for membranes flux recovery.