Research On The Effectiveness Of Thesewage Concentration By Forward Osmosis With Seawater As A Draw Solution

As a promising green technology in the membrane process treatment,Forward Osmosis have advantages just as energy conservation and the protection of water environment to keep away from pollution as well as highly pollution resistance and high quality water outlet.Owe to the very low hydraulic pressure input,FO delivers lower fouling tendency,eaiser fouling removal and lower cost,which makes a widespread concern in the scope of waste water treatment.The traditional process easily give risk to offshore pollution and the enrichment of nitrogen and phosphorus in the ocean.And the FO process requires higher osmotic potential and non-toxic,easily recoverable in the reconcentration system.Seawater is considerd as a abundant sources to draw solution,which can directly emission after filtration,for further lower the energy and cost,improve the simplicity of the process.As a result of the high efficiency rejection of pollutants in the FO process to optimize the water quality of the effluent, has a important significance to the water environment protection and utilization.This study aim to investigate the performance of processing municipal wastewater by forward osmosis with seawater as a draw solition.This study assesses the efficiency of a FO process concentrate wastewater,and the influenc of operating conditions to the performance of seawater as a draw solution,just like cross-flow rate and temperature which have a affect on water flux and solute reverse osmosis,and the ability to concentrate.The results shows a highly increase in high temperature and flow rate to both water flux and reverse solute flux.The PRO mode has been observed a greater increase than FO mode.In the case to membrane fouling test,sewage from residence community was used in the experimental which has a process in 10 hours.Measure the concentrate of pollutants before and after the reaction such as COD、ammonia nitrogen、TP,to observe the rejection of FO membrane to the pollutants in the wastewater.Observe the effect to the water flux in the long-time running test,and the change of reverse solute flux with the intensification of membrane fouling.Combined with the membrane surface characterization of contamination after the pollution experiment,analysis the effect of membrane fouling on the performance of the process.The result show that the cake layer which on the active layer can be reduced to recover flux by hydraulic cleaning,but the pollution in the support layer hardly be removed.The rejection of the pollutant over the 90% in the long time running process in both FO and PRO mode. The K+ in the monovalent ions were observed higher level than the Na+ for the solute reverse,while the two valence ion such as Ca2+ and Mg2+ easily attached to membrane surface which formed the compound to reduce the flux,so almost no solute reverse were found.The water flux reduce by the increase the degree of membrane pore plugging in the FO process.And the solute reverse flux decline by the increased membrane fouling in the FO mode while in the PRO mode which increased in the polluted membrane.Due to the irreversible affect,the concentration polarization caused the most of the decline of the water flux.This study use a simulate municipal sewage which contain the main components in sewage,to discuss the effect of different membrane orientation and different contaminants on concentration polarization.The experiment show that organic compound is the main factors that affect the CP,and in the mixed solution the influence of inorganic salts can be ignored.For the same consistance feed solution,the draw solution with high concentration caused a lower concentration polarization.For the same consistance draw solution,the feed solution with lower concentration caused a lower CP.Due to the electrostatic repulsion on the surface of structure,the ability of concentrated high concentration BSA solution in a short-term running in the FO process is very suitable.But for the complex inlet water BSA enhanced concentration polarization layer which make the mass transfer effort of organic matters reduce.