Study On The Efficiency Of Oxidation Based Pretreatment On Nanofiltration Membrane For Treating Organic Pollutants In Water

Now some unsolved problems still exist in the yield of water treatment,including the removal of the dissolved organic matter and micro organic matter.In this study,nanofiltration is used to improve the removal efficiency of the substances mentioned.However,when the nanofiltration was put to large-scale applyment,membrane fouling is always a obstacle.Therefore,peroxymonosulfate?PMS?is chosen as the oxidizing agent.And Fe???/PMS,as a pre-treatment technology,is used to mitigate a portion of fouling on the membrane.We will investigate the changes in physicochemical nature and the permeate water quality of natural organics?NOM?after PMS catalyzed by Fe???,mechanism and degradation path of micro organic matter and the mitigation caused by all the substances mentioned.First,humic acid?HA?,sodium alginate?SA?and bovine serum albumin?BSA?are selected to represent the different components in NOM.We investigate the changes in physicochemical properties and the permeate water quality of natural organics after PMS catalyzed by Fe???treatment.And we verify the conclusion by the surface water from the Songhua River?SHR?.The experimental results indicate large molecules can be almost completely oxidized to small molecules and even mineralized.And most of the NOM become more easily to be removed by the coagulation of Fe??I?,which is converted from Fe???.Thus,a high removal efficiency of the dissolved organic carbon?DOC?is acquired.The permeate water quality remains unchanged and even improved,which has a distinct advantage compared with the combination of the pre-oxidation technology and ultrafiltration.Then,we choose sulfamethoxazole?SMX?as the representative of the micro organic matter.The degradation of SMX by PMS catalyzed by Fe???treatment under different conditions and the mechanisms and paths of this process are investigated.The results indicate that the proportion of the concentration of Fe???and PMS has significant influence on the degradation of SMX.And when the ratio is 1:1,the oxidation system present the highest degradation efficiency of SMX.The results also show that sulfate radical(SO₄^?-)and hydroxyl radical??OH?was the main reactive oxygen species in this process,in addition,minute quantity of singlet oxygen?¹O₂?also exist.And degradation products and metabolic pathways of SMX are analyzed in detail.Finally,the fouling on the membrane is always a problem can not ignored.Theeffect of Fe???/PMS on the alleviation of the membrane fouling is investigated.We still choose natural organics,SMX and SHR as the target contaminants.The results shows that Fe???/PMS is able to mitigate the membrane fouling to a great extent,especially for the fouling caused by humic acid and the Songhua River water.Furthermore,we can draw the conclusion that Fe???/PMS has obvious advantages on alleviating the nanofiltration membrane fouling by the comparison with other pre-treatment technology.