Research On Change Characteristics Of NOM And Membrane Chemical Enhanaced Backwash In Hybrid Process Of Ultrafiltration

Ultrafiltration membrane,as the core of short water purification process,has caused widespread concern in the water-supply industry since 2008.Some experts even mention the height of “the third generation of water purification process”.Various kinds of the combination of ultrafiltration membrane water purification process are springing up constantly,but the water quality problems caused by the membrane fouling and membrane cleaning also challenge for their survival.Therefore,based on the latest technology of chemical enhanced backwash?CEB?,the study of CEB has positive significance for protecting the water quality of membrane effluent and promoting the water purification process.In this paper,different combination of ultrafiltration membrane device was used to process actual raw water and study the changing rule of the membrane surface material.By regulating the backwash duration,reagent concentration,backwash interval,backwash flux,the study determined the types and variation characteristics of chemically enhanced backwash by products?CEBBPs?.The relationship between CEB control parameters and membrane cleaning effect was studied,and the best parameters of chemical cleaning was determined by the single factor and response surface test,meanwhile,the CEB optimization control model was established.The membrane water health risk assessment method was put forward to evaluate the effects of typical CEBBPs on human health.The Al/UF and PAC/UF NOM content in membrane outside pollutants was higher than the UF and O₃/UF.Three kinds of pretreatment?coagulation,adsorption and oxidation?reduced the accumulation of large molecular weight of organic matter in membrane pore,but for small molecular weight organic matter had no effect.The kinds of CEBBPs in The effluent of Al/UF,PAC/UF and O₃/UF after CEB were 21,18 and 22 respectively.By the response surface quadratic model,the Al/UF optimization membrane cleaning solution was obtained as follows: backwash duration was 4min,reagent concentration was 29mg/L,backwash interval was 60 min,backwash flux was 23L/?m²·h?.The optimization membrane cleaning solutions of PAC/UF and O₃/UF were obtained as the same method.The health risk appraisal was used to assess the membrane effluent after CEB.The results showed that the membrane effluent of Al/UF and PAC/UF after CEB did not cause non-carcinogenic hazard and carcinogenic risk;the membrane effluent of O₃/UF process did not cause the non-carcinogenic hazard,but would cause carcinogenic risk.By the O₃/Al/UF and O₃/PAC/UF operation efficiency,the O₃ process could improve the Al/UF and PAC/UF process treatment efficiency and further reduce the membrane fouling.The cleaning parameters showed that at the same time period the amount of cleaning agent into O₃/PAC/UF was higher than O₃/Al/UF,thus the CEBBPs concentration in O₃/PAC/UF reactor was high.The effluent of O₃/Al/UF and O₃/PAC/UF after CEB did not cause non-carcinogenic hazard and carcinogenic risk.