Effect Of Enhanced Coagulation On Operating Condition Of Ultrafiltration Membrane And Removal Efficiency

In this study, humic acid (HA)-kaolin and fulvic acid (FA)-kaolin were treated by inorganic polymer coagulant and inorganic-organic composite flocculant in enhanced coagulation and enhanced coagulation-ultrafiltration process. And a series of coagulation process conditions were determined which had high natural organic matter (NOM) removal efficiency.The floc size and fractal dimension were obtained by on-line monitor of coagulation process using Mastersizer2000. Membrane fouling was determined by floc characteristic. Moreover, the relationship between enhanced coagulation process and membrane fouling was investigated. According to the concentration of disinfection byproducts (DBPs) after enhanced coagulation and enhanced coagulation-ultrafiltration process, inbibitional effect of DBPs was estimated under enhanced coagulation process. The main conclusions are:(1) NOM removal efficiency, floc characteristic and inbitional effect of DBPs were direct affected by enhanced coagulation parameter, and membrane fouling was indirect affected by enhanced coagulation parameter. In enhanced coagulation and ehanced coagulation-ultrafiltration, NOM removal efficiency was increased by the process of increasing coagulant dose effectively. Meanwhile, the formation of DBPs was restrained and the membrane fouling was relieved. In enhanced coagulation and ehanced coagulation-ultrafiltration, NOM removal efficiency was increased by the process of regulating pH condition effectively. Meanwhile, the fratal dimension was reduced and the formation of DBPs was restrained. Membrane fouling was relieved by the process of adopting new coagulant. Meanwhile, the floc size was increased remarkably.(2) In HA-kaoling teat water, the dosage of82mg/L of poly ferric chloride (PFC) was the most optimal dosage control condition in restraining the formation of DBPs. It was also achieved high dissolved organic carbon (DOC) removal efficiency in enhanced coagulation-ultrafiltration. For high DOC removal efficiency in enhanced coagulation, the most optimal dosage and pH control condition was dosage=82mg/L of PFC and pH=7. The least serious membrane fouling was obtained at the dosage of73mg/L of poly aluminium chloride (PAC).(3) In FA-kaolin test water, the dosage of72mg/L of PFC was the most optimal dosage control condition in removing DOC. It was also restrained the formation of DBPs in enhanced coagulation-ultrafiltration process effectually. The dosage of50mg/L of PAC was the most optimal dosage control condition in restraining the formation of DBPs in enhanced coagulation. The least serious membrane fouling was obtained at the dosage of41mg/L of polyferric chloride-polydimethyldiallyammonium chloride (PFC-PDMDAAC).