Analyses of molecular weight distribution of organic matters with pre-oxidation and PAC–UF pretreatment before seawater reverse osmosis

Abstract The water source of Shanghai, China is located in the lower Yantze River close to the estuary of East Sea. Due to the decreasing of upriver water in recent years, the water supply is facing with the challenge of salt tide from East Sea. Before reverse osmosis, powdered activated carbon–ultrafiltration (PAC–UF) pretreatment is employed to remove organic matters and turbidity to prevent the rapid fouling of reverse osmosis membrane. The purpose of this study was to analyze molecular weight (MW) distribution and conversion in oxidation and PAC–UF pretreatment processes and to find out the relationship between dissolved organic carbon (DOC) removal, oxidant dosage and PAC–UF treatment. The results showed that by conventional water treatment, chlorination (Cl2) and potassium permanganate (KMnO4), pre-ozonation can reduce DOC concentration for larger MW fractions (>30 k, 10–30 k, and 3 k–10kDalton (Da.)), however, at the same time, increased smaller MW fraction. PAC adsorption was regarded as the effec...