Characteristics Of Simultaneous Wastewater Reuse And Seawater Desalination By Forward Osmosis-Reverse Osmosis Process

Reuse of urban sewage and seawater desalination is an important way to solve the global water shortage. The traditional urban wastewater treatment technology and seawater desalination technology has high energy consumption and high processing cost and other issues. Therefore, it is necessary to establish a new technology to reduce energy consumption and achieve urban sewage regeneration and seawater desalination. Forward osmosis(FO), a new emerging membrane process, has become increasingly attractive for its low or no hydraulic pressures, low energy cost and high fouling resistance property. This experiment in the optimization basis of operating conditions, and combined with reverse osmosis(RO). Investigate the system of water flux, desalination rate and pollutant retention characteristics.Finally analyses the economic and energy consumption, for synchronous sewage regeneration and seawater desalination to provide technical support.Under different pressure on TFC-ES, CTA-ES and CTA-NW membrane water permeability(A) and salt permeability(B), and different draw solution concentration, different velocity and different draw solute of three kinds of FO membrane water flux and salt back mixing effect and membrane fouling conditions, the optimal performance best FO membranes. The results showed that: the A value and B value of FO membrane are increased with the increase of pressure, during the test of performance of the membrane structure while using spacer support. and increased along with the increase of pressure, the largest increase in the TFC-ES film. When the concentration of the solution was increased from 0.1mol/L to 0.6mol/L, three kinds of FO membrane water flux and salt reflux increased, but the nonlinear growth, the order of Jw and Js of the three kinds of FO membrane were TFC-ES>CTA-ES>CTA-NW. When the flow rate of the feed solution increased from 8 cm/s to 32 cm/s, Jwof TFC-ES and CTA-ES increase the magnitude of the equivalent,while CTA-NW increased less.Then the preferred TFC-ES membrane collaborative osmotic Pressure assited osmosis(PAO)performance test, observe RO operating characteristics, and the optimized parameters of PAO-RO combined process simultaneous wastewater regeneration and seawater desalination were analyzed,the analysis of the distribution of organic matter and molecular process of using excitation-emission matrix spectroscopy and gel permeation chromatography. The results showed that: in a single PAO process, Jw is positively related to the pressure, and the JS is decreased, the rejection of TOC decreased slightly. In RO test, with the increase of the influent concentration, the yield and the desalination rate decreased. The secondary effluent was feed solution, seawater was draw solution, the combined process of PAO-RO, after running 12 h, the system of water rate increase by about 150% than RO, seawater desalination rate of 94.8%, the whole system of precipitated water TN, TP and TOC removal rate reached 98.1%, 98.4% and 99.6% respectively,the protein and humic acids have been well removed, water molecules are mainly distributed between the 80~500Da, produced water reach to The reuse of urban recycling water-Water quality standard for industrial uses.(GBT19923-2005). After 10 days of continuous operation,PAO initial water flux decreased by about 25.6%, RO water initial water flux decreased by 19%after 95.2% PAO recovery after backwashing flux, RO flux recovery 99.1%.Finally, the wastewater as feed solution, the Hangzhou Bay seawater as the draw solution, the study of PAO-RO process operating characteristics, and analysis economic and energy consumption of system. The results show that: after running 12 h, the water yield of the system is increased by about 45%, and the sea water desalination rate reaches 97.8%. The removal rate of TOC, TP and TN in the system is 98.2%, 97.5% and 99.8%, respectively, and the water is clear and transparent, produced water reach to The reuse of urban recycling water-Water quality standard for industrial uses.(GBT19923-2005). The molecular weight of water production is mainly distributed between 40~400Da. After 10 days of continuous operation, the initial water flux of PAO decreased by about 23%, and the initial water flux of RO was decreased by 9%. After the reverse irrigation, the PAO flux recovered to 98%, and the RO flux recovered to 98.4%.FO-RO technology compared with SWRO technology can save 30% of the cost of energy consumption, increase the Capital expenditure(CAPEX) of 20%~25%, and save the operational expenditur(OPEX) of 15%%~25%. When the FO membrane flux is above 25L/m2 h, FO-RO hybrid system may be economically feasible.Compared with the results of simulated seawater, the RO membrane fouling was heavy, which showed that the RO membrane fouling was increased in the actual seawater.