Study On The Treatment Of The Concentrated Brine Solution Of Seawater Desalination By Nanofiltration And Vacuum Membrane Distillation

The direct drain of the concentrated brine produced in the desalination will ruin the ecological environment seriously. Facing with the problems such as the scarcity of land resources of Chinese coastal areas, it is necessary to treat brine. The treatment of the concentrated brine solution of seawater desalination by nanofiltration and vacuum membrane distillation was studied. The treatment pilot-plant for the concentrated brine solution of seawater desalination with10ton/day was designed. The detail results are as follows:First, the treatment of the concentrated brine solution of seawater desalination by nanofiltration was studied. The influence of pressure and feed concentration on separation performance of nanofiltration were discussed. The result showed that under constant temperature permeate flux, rejection, recovery and divalent ion rejection all increased as the pressure raising but decreased as the feed concentration raising. When the feed concentration was6wt.%, the permeate flux of NF system was up to47.9L/(m2h) and the rejection of Ca2+、 Mg2+、SO42-was37.8%,57.8%,82.9%. The recovery of NF system was57.6%which was higher than general recovery.Then, the treatment of the concentrated brine solution of seawater desalination by vacuum membrane distillation was studied. The influence of feed temperature, feed concentration, permeate pressure and feed flow rate on separation performance of vacuum membrane distillation were discussed. The experimental results showed that the flux increased as the feed temperature and feed flow increasing, decreased as the feed concentration and permeate pressure increasing. Besides, vacuum membrane distillation crystallization of NaCl and Na2SO4were discussed. The permeate flux of VMD system was up to33.0L/(m2-h) and the rejection was nearly100%.Finally, the treatment pilot-plant for the concentrated brine solution of seawater desalination with10ton/day was designed according to the results of ultrafiltration, nanofiltration and vacuum membrane distillation (UF-NF-VMD) system was adopted to treat brain. The study showed that the treatment pilot-plant was able to treat10ton/day concentrated brine solution efficiently.