Research On Optimization And Application Of Double-layer Filter Material Filter-nanofiltration Combined Process

The test was carried out in a water plant in Taicang.In order to explore the feasibility of using a double-layer filter instead of an ultrafilter in the double-membrane method,the coal sand double-layer filter was introduced.Optimize the selection of filter parameters through the comparison test of the construction parameters of the filter,and explore the effect of reducing turbidity,removing organic matter,and removing aluminum and the feasibility of replacing ultrafiltration as the pretreatment of nanofiltration through the comparison test of the effect of ultrafiltration.Subsequently,the double-layer filter and nanofiltration are used as a combined process to continuously analyze the interception of each pollutant,and the combined process is optimized by adding scale inhibitors and biological inhibitors through the nanofiltration process.During the test,it was found that the residual aluminum in the water body was difficult to remove and would aggravate the membrane pollution.In order to effectively alleviate the membrane pollution problem and increase the operating cycle of the nanofiltration system,the coagulation process test was optimized to reduce the production of residual aluminum.The research content mainly includes the following aspects:(1)Optimization of the construction parameters of the double-layer filter media and comparative analysis with the treatment effect of the ultrafiltration process: adjust the construction parameters of the filter,by adjusting the coal sand double-layer filter media filter anthracite/quartz sand thickness ratio,quartz sand quartz sand The effective particle size d10 can effectively improve the retention effect of the double-layer filter material filter,which plays an important role in improving the treatment effect of the filter and improving the quality of the filtered water.(2)Comparative analysis of the operation effect of double-layer filter media and ultrafiltration: compare the processing effect and stability of the double-layer filter media pilot test and ultrafiltration pilot test running simultaneously,and explore the double-layer filter media filter.The feasibility of replacing ultrafiltration as the pretreatment of nanofiltration process.Through experiments,it is found that the turbidity removal efficiency of the doublelayer filter is basically the same as that of ultrafiltration.Both processes have high turbidity removal efficiency and good stability;for the removal of electrical conductivity and silicon,two The two filtration processes have no obvious effect;for the removal of residual aluminum,the removal rate of aluminum in the double-layer filter is slightly higher than that of ultrafiltration,and the stability is relatively better;for the removal of TOC,the double-layer filter The filter is slightly better than ultrafiltration,and the stability of the two processes is very good.Therefore,double-layer filter media can be used as the pretreatment process of nanofiltration.(3)Double-layer filter media filter-nanofiltration combined process operation interception situation: without adding scale inhibitors and biological inhibitors,the double-layer filter media filter-nanofiltration combined process has effects on aluminum,silicon,and electrical conductivity.The interception rates of,TOC can be 60.7%,7.7%,18.6%,and 90.4% respectively.The effluent quality of the combined process meets expectations,and the combination of doublelayer filter media and nanofiltration can ensure the quality of the produced water.(4)Adding scale inhibitors and biological inhibitors to optimize the combined process and membrane fouling: the addition of scale inhibitors and biological inhibitors can effectively reduce the membrane fouling caused by aluminum and TOC in the nanofiltration process.In the case of a decrease in flux,the running time of the membrane is approximately doubled.Especially for organic pollution,the inhibitory effect is very obvious,which is the main factor to slow down the rate of membrane pollution.In terms of inorganic pollution,it can effectively reduce membrane pollution caused by aluminum.The increase of nanofiltration membrane pollution also has an impact on the water yield and FCP.When the membrane flux drops by30%,the system water yield will drop by about 12% to 15%,and the FCP will greatly increase,which is an important manifestation of membrane pollution..(5)Experimental study on the control of residual aluminum produced in the coagulation process: In the experiment on the Yangtze River water treatment process,by comparing the coagulation effects of different coagulants,it is found that PAC is better than Al2(SO4)3 as a coagulant.The coagulation performance of high basicity PAC is better than that of low basicity PAC.The best coagulation effect is when the dosage is 30mg/L.By comparing the coagulation effect of raw water with different initial p H,it is found that the coagulation effect is the best under the initial p H 6.5 and the dosage of 30 mg/L.By comparing the coagulation effect of raw water at different temperatures,it is found that the coagulation effect of the coagulant at 23°C is significantly better than that at the low water temperature of 16°C.Therefore,reasonable control of the coagulant type,dosage,coagulation p H,coagulation temperature and other parameters in the coagulation process plays an important role in the generation of residual aluminum,and also greatly affects the membrane fouling in the subsequent advanced treatment process.ease.