Removal Performance And Membrane Fouling Control Of Wastewater Reuse Based On Double Membrane Method(Ultrafiltration-Nanofiltration)

With the development of science and technology and the progress of society,the contradiction between urbanization,modernization process and water shortage and water pollution has become increasingly prominent.Sewage reuse is an effective waste resource utilization method that removes waste water into recyclable clean water through secondary treatment and advanced treatment.However,at present,the cost of returning water treatment is high,and the existing facilities and technology development are not matched,which limits the development of water reuse research·It is imperative to explore high-quality,low-cost water reuse processes.The membrane treatment process has the advantages of small footprint,no pollution,high treatment efficiency,etc.It is technically feasible to apply the membrane treatment process to the reuse of water.This study will treat the secondary effluent from the wastewater treatment plant by double membrane method(ultrafiltration-nanofiltration),and design different pretreatment schemes to optimize the treatment effect of the double membrane method,explore the water quality optimization effect and membrane fouling of the double membrane method,and analyze the pollutant removal characteristics and membrane fouling models.Firstly,a small test was conducted to investigate the decontamination efficiency and membrane fouling,and then through the long-term operation of the pilot plant,the treatment effect and process stability of the dual membrane method applied to the actual domestic sewage treatment were investigated.Systematic evaluation of the feasibility of the dual membrane method applied to actual wastewater treatment.The results of small-scale experimental water treatment show that the removal rate of turbidity and microbial indicators was higher by ultrafiltration,but the removal rate of conventional indicators and metal ions was poor.Adding industrial aluminum sulfate for coagulation strengthening can optimize TP removal,but the concentration of metal ions in the effluent increases;adding powdered act ivated carbon for adsorption strengthening can effectively optimize COD removal.Nanofiltration has a significant effect on the removal of organic matter,TP and metal ions,and can effectively remove hardness ions such as calcium and magnesium in water.The results of small-scale experimental membrane fouling analysis show that the pretreatment with coagulant and adsorbent has a controlling effect on membrane fouling.The ultrafiltration membrane resistance curve actually approaches the logarithmic curve of 1/J-e~t,and the filter cake layer.Pollution dominates.The nanofiltration membrane pollution has a correlation with the influent organic matter and metal ion content.It is speculated that the metal ion acts as a bridge between the nanofiltration membrane and the organic matter to adsorb the organic matter on the surface of the nanofiltration membrane.Nanofiltration membrane contamination is actually based on metal ion-organic complexation.The results of pilot-scale operation show that the double membrane method has good adaptability to the fluctuation of water quality under the condition of long-term treatment of actual domestic sewage.Ultrafiltration treatment effluent meets the standard of landscape water use,and nanofiltration effluent meets the standard of groundwater recharge(well irrigation).Follow-up energy consumption analysis and the electricity and pharmaceutical cost calculation show that the cost of wastewater treatment in blank operation is about 0.478 yuan/t,the cost of coagulation pretreatment is 0.486 yuan/t,and the cost of adsorption pretreatment is about 0.728 yuan/t(including secondary treatment).It is technically feasible to reuse high quality wastewater by using double membrane method,which has great ecological and social benefits.