Synergistic Characteristics Of Ozonation Combined With Ceramic Membrane In Water Treatment Processes

The combined processes of ceramic membrane with ozonation have been considered as a well-established technology for the water/wastewater treatment in terms of effective fouling alleviation,ozone dosage reduction and low energy consumption.However,the understanding of ozonation characteristics within membrane porous channels on the basis of catalytic oxidation is still unclear,and this may restrict the application of this technology.In this study,the combination of ozonation with flat-ceramic membrane were studied for their synergistic effect.The ozone decomposition kinetics within membrane layer and support layer were investigated.Four kinds of trace pharmaceutical and personal care products?PPCPs?,including sulpiride,bezafibrate,atenolol,and2-quinoxalinecarboxylic acid?2-QCA?were tested to explore their degradation characteristics within ceramic membrane pores.Ceramic membrane fouling and alleviation effectiveness for three representative organic matters including alginate?representing the polysaccharide?,bovine serum albumin?BSA,representing the protein?and humic acid?representing the humus?were studied for the combined processes of ceramic membrane filtration and ozonation processes.Four kinds of ceramic membranes with different thickness of membrane layer?20-25?m,35-40?m,70-75?m,95-100?m?were compared for ozone decomposition kinetics,as well as the influences of pH and electrolytes.Results showed that the membranes layer can ozone decomposition was accelerated both within the membrane layer and support layer,and the efficiency was higher within the membrane layer.And some active hydroxyl radical were identified using molecular probe within the ceramic membrane porous during ozone decomposition.pH condition,the addition of NaCl?CaCl₂ and Na₂SO₄ could affect the ozone decomposition percentage within membrane porous channels with different extents,respectively.The integrated processes of in-situ ozonation with ceramic membrane can significantly increase the degradation efficiency of the selected four PPCPs.The degradation efficiency of sulpiride,bezafibrate,atenolol and 2-QCA were 99%,96%,99%and 64%,respectively.With the initial dissolved ozone concentration of 3 mg/L,the degradation efficiency of sulpiride,atenolol and bezafibrate increased to almost100%for the former three PPCPs,and to 97%for 2-QCA.Such degradation efficiencies were all higher than that with ozonation alone.The addition of tert-butyl alcohol as radical quenching agent demonstrated that the membrane porous channel may promote higher production of hydroxyl radical thus enhance the degradation efficiency of the selected four PPCPs.Both pre-ozonation process and in-situ ozonation processes were effective in controling the membrane fouling rested from the alginate,BSA and humic acid.The ozone dosage should be carefully selecetd to control the membrane fouling.The fouling mitigation by in-situ ozonation was mainly ascribed to the results that ozonation can efficiently broke down the high molecular weight?MW?fractions of alginate into the lower MW fractions,thus alleviating the hydraulically reversible fouling resistance.For the BSA-based fouling,the formation of BSA crosslinks and aggregates progressively accumulating on the membrane surface and within the membrane pores during filtration,thus remarkably deteriorated the membrane fouling,resulting in the increase of hydraulically irreversible resistance.For the humic acid-based fouling,the increased hydrophility of humic acid may result in the gradually accumulation of foulants on membrane surface and within pores.This study revealed the synergistic characteristics of ozonation with ceramic membrane from a fundamental viewpoint and is of guiding significance in the development of new functional ceramic membranes and in the optimization of integrated treatment processes.