Controlling Of Ceramic Membrane Fouling Using Ozone And Hydrogen Peroxide In Wastewater Treatment

Ceramic membrane has been attracting more and more attentions in wastewater treatment for its robust mechanical and chemical stability.However,membrane fouling is still a big issue for the wide application of ceramic membrane in wastewater treatment.In this study,the mixed liquor was sampled from the aerobic tank of Luofang Wastewater Treatment Plant.The effects of both pre-ozonation and in-situ ozonation on the mitigation of ceramic UF membrane fouling and the corresponding mechanism were systematically and quantitatively studied.The combination of hydrogen peroxide with ferrous ion on cleaning of ceramic membrane fouling was also explored.The results showed that intermediate blocking resulted in the main membrane fouling during the mixed liquor filtration process,main fouling substances ranged from10 to 200 kDa in terms of molecular weight,mostly are protein and polysaccharide.In the combined processes of pre-ozonation and ceramic membrane,when ozone dosage reached 5 mg/L,there were better settleability of sludge and remarkable reductions of DOC,SMP and EPS happened,the ceramic membrane fouling can be mitigated.TheΔTMP was reduced by 44.9%at ozone dosage of 5 mg/L（1.7 mg-O₃/g-MLSS）,and hydraulically reversible fouling resistance was reduced by 45.7%.When the ozone dosage was above 10 mg/L,however,cell lysis occurred seriously which led to the significant release of dissolved organics in the mixed liquor and worse settleability of sluge,which in turn resulted in the membrane fouling deteriorated.In the integrated process of in-situ ozonation with ceramic membrane,intermediate blocking can be effectively alleviated,probably due to the direct oxidation of ozone on fouling matters.TheΔTMP was reduced by 55.6%at ozone dosage of 5 mg/L（1.3 mg-O₃/g-MLSS）,meanwhile,cake layer resistance and gel layer resistance were reduced by61.5%and 32.3%respectively.In-situ ozonation had trade-off effects on the filterability of mixed liquor.On one hand,the filterability of mixed liquor was improved as a result of the remarkable reduction of MLSS,MLVSS,SV₃₀,SVI₃₀,and EPS.On the other hand,the filterability of mixed liquor deteriorated as a result of the obvious increase of DOC and SMP.Additionally,the contributions of sludge index and supernatant index to the improvement of mixed liquor filterability were 62.1%and 33.2%respectively.Thus,the filterability of mixed liquor was effectively improved by 160%at the ozone dosage of 5mg/L.It was found that when using 1.5%hydrogen peroxide solution for cleaning,socking the fouled membrane for 2 hours,more than 92.5%of?TMP and 97.2%of the residual resistance can be recovered.The concentrations of DOC,EEM and VSS in the reversible fouling layer decreased.Ferrous ion can efficiently catalyze the hydrogen peroxide to remove ceramic membrane fouling,more than 93.6%of?TMP and 76.4%of the residual resistance can be recovered after socking 4 hours at 62 mg Fe²⁺/L(the mole ratio of Fe²⁺and H₂O₂ was 1:400).This paper provided a new method to control ceramic membrane fouling in wastewater treatment,and it is of significant values in both theory and application.