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.

• The addition of ozone can reduce the filtration resistance in filtration of the secondary effluent. The longer the ozone contact time, the smaller the R value. • Ozone can 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. However, it has an effect of aid-coagulation at small dosage of 0.548 mgO3/mgSS, 2 min contact time. Total SS did not change very much with the ozone dosages of 0.548– 1.338 mgO3/mgSS; on the contrary, SS changed to a notable extent with the ozone dosages of 2.296–4.915 mgO3/mgSS. • 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.