Removal of Membrane Fouling and Control of Halogenated By-Products by a Combined Cleaning Process with Peroxides and Sodium Hypochlorite

Sodium hypochlorite (NaClO) solution is wildly used to remove membrane fouling-derived organic materials and restore membrane flux, which can result in the formation of halogenated by-products. To reduce the halogenated by-products, a combined cleaning process with NaClO and peroxides including hydrogen peroxide (H2O2), peroxydisulfate (PDS), and peroxymonosulfate (PMS) were applied in offline mode to remove the organic fouling. It was found that all the combined cleaning processes could effectively restore the membrane flux. Compared with the process of NaClO cleaning followed by peroxide cleaning (NaClO–peroxide), fewer halogenated by-products were generated in the NaClO post-combined cleaning process (peroxide–NaClO), and the PDS–NaClO cleaning process exhibited the best performance in controlling by-products. Overall, most by-product generation showed a positive correlation with reaction time and temperature.Keywords:membrane fouling;chemical cleaning;halogenated by-products;sodium hypochlorite (NaClO);peroxide