Characteristics Of Membrane Dissolved Ozone Flotation In Wastewater Reclamation

In recent years,decentralized sewage treatment process has aroused widespread attention.Membrane dissolved ozone flotation process was built for wastewater reclamation from effluent of wastewater treatment plant.Coagulation,ozone oxidation,air floatation and membrane filtration were combined in one reactor,and flocculation,oxidation,particle separation,deodorization and de-coloring can realize in one single operation unit.The results of the study have important application value for the rich sewage treatment process.This study analyzed the operation characteristics of dissolved ozone flotation(DOF)and membrane dissolved ozone flotation(MDOF).The results show that when the dosage of coagulant was 80mg/L,the ozone flotation process can achieve good removal performance for color,organic matter and microorganism.With the increase of ozone dosage,removal efficiency of the pollutants can be significantly improved except total phosphorus(TP)and turbidity.The MDOF not only further enhance the color,organic matter and microbial removal efficiency,but also significantly enhance the TP,turbidity removal performance.In addition,the recycled water quality can achieve "urban sewage reuse city miscellaneous water quality"(GB/T18920-2002)standard.The reason is that the MDOF not only has the advantage of ozone flotation to remove the color,organic matter and microorganisms,but also increase suspended solids and insoluble phosphorus efficiency by the membrane filter for the stability of the effluent quality.The results of membrane fouling analysis showed that with the increase of the ozone dosage,the amount of polysaccharides and microorganisms on the membrane surface decreases and the d50 of the pollutant particle size increases.The membrane fouling was slowed down.By analyzing the extracellular polymeric substances(EPS)extract of the cake layer,it was found that the fluorescent materials of soluble EPS(SEPS)were mainly fulvic acid substances.The fluorescent substances of bound EPS(BEPS)were protein-like,fulvic acid and tryptophan.The appropriate ozone dosage can effectively reduce the fluorescence intensity in BEPS.The molecular weight distribution of SEPS did not change significantly,but with the increase of ozone dosage,the intensity decreased slightly,while the small molecules of BEPS disappeared with the increase of ozone dosage.The content of protein,polysaccharide and humic acid in the SEPS decreased slightly with the increase of the ozone dosage,while the content of protein,polysaccharide and humic acid in BEPS decreased significantly.The increase of ozone retards the membrane contamination due to the fact that proteins and polysaccharides are the main cause of membrane fouling,and ozone can reduce the membrane surface protein and polysaccharide content.