Study On The Efficiency Of The Osmosis Membrane Bioreactor In The Treatment Of Domestic Sewage

The osmosis membrane bioreactor(Osmosis Membrane Bioreactor,OMBR)has attracted more and more researchers' attention because of its low energy consumption,less membrane pollution trend and higher water quality than the traditional membrane bioreactor(Membrane Bioreactor,MBR),because it only relies on the osmotic pressure difference on both sides of the FO membrane to drive the operation and the high retention performance of the FO membrane without external pressure.However,the problems such as reverse salt permeation of the draw solutions,membrane flux attenuation caused by membrane fouling and recovery and separation of the draw solutions are the key to the application of OMBR.In this paper,based on the separated OMBR for the treatment of simulated urban domestic sewage,with the help of two different solutes,the operation effect,salinity accumulation and FO membrane pollution were investigated.In addition,in order to recover the concentrated draw solutions and clean water,OMBR and RO were combined to form a combined process to explore the impact of RO on the recovery of the two kinds of draw solutionsThe main research results are as follows:(1)Using ths inorganic ion sodium chloride as the draw solution,and using two kinds of FO membrane of triacetate(CTA)and polyamide composite film(TFC)to run OMBR.The results show that the flux of the two kinds of FO membrane is basically the same,but the reverse osmosis of TFC-FO membrane is lower,and the high reverse osmosis of CTA-FO membrane is not conducive to the growth of microorganisms in the reactor.(2)0.5 M NaCl and 0.3 M EDTA-2Na were used as the draw solution,respectively.Under the same conditions,separate OMBR was used to treat simulated urban domestic sewage.TFC-FO membrane was adopted,with cross flow rate of 200 L/min and SRT of 30 d.The effects of two different draw solutions on the performance and membrane fouling of OMBR were investigated.The results showed that EDTA-2Na had higher water flux and lower reverse salt permeation,which effectively alleviated the problem of salinity accumulation in the reactor;at the same time,it slowed down the reduction of activated sludge concentration in the reactor,reduced the EPS content of microbial secretion,and reduced the FO membrane fouling.In addition,the removal rates of TOC,TN,ammonia nitrogen and TP were 94.6%,96.5%,64.7%and 99.2%respectively when OMBR was used in the two kinds of draw solutions,which only depended on the retention performance of FO membrane and had nothing to do with the kinds of draw solutions(3)The OMBR,which is operated separately by the two draw solutions,was used to recover the draw solutions and separate the clean water by RO.The removal rates of TOC and TN in domestic sewage by OMBR-RO combined system were over 98.1%,and the removal rates of ammonia nitrogen and TP were 100%respectively.The RO recovery rate of EDTA-2Na is 97.1%,which is much higher than that of NaCl(69.6%)At the same time,the draw solutes attached to the surface of FO membrane polluted the supporting layer of FO membrane,and the pollutants enriched in the draw solution pool have not been found to affect the pollution of FO membrane.