Analysis of membrane fouling genesis in nanofiltration process for advanced treatment of dyeing and finishing wastewater

In order to investigate the types and genesis of membrane fouling of nanofiltration desalination system treating dyeing and finishing wastewater of cotton knit textile,comprehensive analysis,using ICP-AES,SEM-EDX,FTIR,TGA,high optical microscope and XRF,was carried out based on tests of influent water quality,and tests of the membrane fouling states of different processes and tests of membrane cleaning.The results showed that the types of membrane fouling included inorganic fouling,organic fouling and microbial fouling.The mass percents of bound water,organic substance and inorganic substance of dry foulants,dried at 105℃,were 8.2%,41.0% and 50.8% respectively.Ferric salt was the most serious inorganic fouling salt,and the main functional groups,found from organic foulants,were —OH,—CH and —CC.Several kinds of protozoa were found from the membrane foulants as well as metazoan.The analysis of short-term and long-term membrane fouling indicated that it need a long time cumulative effect for the formation of organic fouling and microbial fouling.The results of NF cleaning tests showed that the mainly reason lead to the decline of membrane flux were organic fouling and microbial fouling,which took 53.3%.