| In order to solve the problems of trace organic pollutants in reclaimed water and membrane fouling in the process of double membrane treatment,it studied the concentration and variation of seven characteristic trace organic pollutants（sulpiride,caffeine,metoprolol,roxithromycin,liguron,diclofenac and carbamazepine）in the existing reclaimed water treatment process of a sewage plant in Tianjin,and carried out environmental risk assessment.A pilot process of coagulation-activated carbon adsorption-ultrafiltration-reverse osmosis for reclaimed water treatment was constructed,and parameter optimization research was carried out.The membrane fouling characteristics of the pilot treatment processand existing process were analyzed,and measures to slow down membrane fouling were put forward.In spring,the average concentration of trace organic contaminant in the influent of the factory was the highest,464.7 ng/l.With season changes the average concentration of trace organic contaminant gradually decreasing to a minimum of 78.0ng/L in winter.There was almost no obvious difference in the removal effect of trace organic contaminant by reclaimed water process in different seasons.Except the removal rate of liguron being about 80%,the removal rate of other trace organic contaminants was kept above 94%.In summer,air flotation had the best removal effect on trace organic contaminants,with removal rates above 50%.Autumn air flotation had the worst removal effect on trace organic contaminants,and the removal rate does not exceed 20%.Ultrafiltration in spring had the best removal effect on trace organic contaminants,with removal rates being above 43%.Ultrafiltration had the worst removal effect on trace organic contaminants in summer,and the removal rate did not exceed 30%.In summer,reverse osmosis had the best removal effect on trace organic contaminants,with removal rates exceeding 82%.Reverse osmosis had the worst removal effect on trace organic contaminants in spring,and the removal rate did not exceed 81%.A pilot-scale treatment process of coagulation,activated carbon adsorption,ultrafiltration and reverse osmosis was established.The parameters of each treatment unit were determined as follows:coagulant dosage was 30 mg/L,the dosage of coagulant aid was 1 mg/L,mixing time was 1 min,flocculation reaction time was 9 min,sedimentation time was 10 min,the hydraulic retention time of activated carbon adsorption tower is 20 min,the membrane flux of ultrafiltration membrane was50 L m-2·h-1,the membrane flux of reverse osmosis membrane was 35 L m-2·h-1.Compared with the existing process,the pilot-scale system strengthened the removal effect of the original process on trace organic contaminants in the plant area.The removal rate of liguron in the whole process rose from 79.1%to 87.5%,while the removal rate of other trace organic matters remained above 97%.XRD,XPS and three-dimensional fluorescence spectra were used to characterize the ultrafiltration membrane scaling in the existing process of the sewage plant and the ultrafiltration membrane scaling,and the reverse osmosis membrane scaling in the pilot test respectively.Molecular weight distribution of effluent from each unit of the existing process and the pilot test was analyzed.It was found that coagulation and activated carbon adsorption processes have a strong removal effect on macromolecular substances>10 k Da,and can also enhanced the removal effect of double membrane system on trace organic substances.Coagulation and activated carbon adsorption processes,as pretreatment processes of double membrane systems,can effectively slow down membrane fouling. |
