Pre-ozonation for dead-end microfiltration of the secondary effluent: suspended particles and membrane fouling

Laboratory bench-scale experiments were conducted to elucidate the effect of ozone on the microfiltration membrane fouling through reaction with particulates in the secondary effluent from BeiXiaoHe WWTP. Membrane resistance (R) was recorded during the filtration course of source water and that after ozone treated. Also, the particle size distribution and other water quality parameters such as zeta potential, TOC, UV254 were analyzed. The results of the experiments revealed that the addition of ozone can: (1) break large particles into smaller ones and make the particle size distribution into a narrower and smaller range obviously at the dosage of 4.915 mgO3/mgSS, 15 min contact time; (2) reduce the filtration resistance in filtration of secondary effluent and the longer the ozone contact time, the smaller the R was. Ozone may affect the fouling performance through three ways: to reduce the loading of fouling materials such as SS and organic foulant, to change the PSD to a narrow range, to change the particulates zeta potential.