Experimental Research On The Treatment Of Micro-polluted Water With Pretreatment-microfiltration Membrane Process

In this paper,we use a combination of pretreatment-microfiltration membrane to deal with micro-polluted water, we study the removal of micro-polluted water by different pretreatment methods(coagu-lation, oxidation coagulation,adsorption) and Pretreatment-Microfiltration Membranes,and the same time investigate microfiltra-tion membrane flux recovery by different ways of membrane cleaning.The conclu tions were obtained as follows:1. Use Different pretreatments Deal with micro-polluted water, The conclutions were obtained as follows:(1) From coagulation pretreatment experimental we can get that:Comparing the Removal of UV254, ammonia, turbidity by use of polyaluminum chloride andaluminum sulfate in in the different dosages, PAC's removal is better,and dosage of PAC is25mg/l, and the removal rate of UV254, ammonia, turbidity are68%,47%,98%.(2) From the pre-oxidation and coagulation tests we can get that:oxidating Potassium permanganate can play a coagulant effect to coagulation and improve the removal rate of the UV254, ammonia, and turbidity effectively. When the dosage of Potassium permanganate is0.5mg/l, the removal rate of the UV254, ammonia, and turbidity are increased by7%,5.4%,4%compared to PAC that is added at the Concentration of25mg/l.(3) From the static experiments of powdered activated carbon we can get that:When the dosage of powdered activated carbon is70mg/l,and the pretreatment time is30minutes,the removal rate of UV254can reach55%.2. This article used different pretreatment methods to deal with micro-polluted water by PVA microspheres, the results showed that:(1) Three pretreatment can effectively improve the removal rate of turbidity, the removal rate of directly membrane filtration is78%, Adsorption pretreatment is93.8%, coagulation pretreatment is98%and oxidation ofcoagulation pretreatment is98.5%when operated Stablely. Coagulation and oxidation coagulation pretreatment are best ways of turbidity removal, and coagulation pretreatment is the better choose for the micro-polluted source water in high turbidity.(2) The experimental results show that the removal rate of UV254is low by directly filtering the membrane and the removal rate has a larger increase after pretreatment. The removal of UV254is Smaller with time by adsorption pretreatment and the result of removal is Stable.coagulation and coagulation oxidation treatment efficiency are best when operated Stablely, and the removal rate of UV254has reached89%after60minutes by coagulation oxidation.(3) The removal rate of ammonia nitrogen is only10%by directly filtering the membrane and the removal rate has increase after pretreatment in some ways, but the removal rate still just common. The removal rate of ammonia nitrogen by powdered activated carbon adsorption pretreatment is just38%when operated Stablely, and this proved that powdered activated carbon's capacity to ammonia nitrogen was limited. The removal rate of ammonia nitrogen by coagulation pretreatment and oxidation coagulation pretreatment are close, about66%, indicated that pre-oxidation ammonia nitrogen is limited to improve the removal rate of ammonia nitrogen removal rate.(4) Three pretreatment have effects on membrane flux.Adsorption pretreatment did not play a significant role in mitigation Compared with directly filtering the membrane, and sometime even affect the membrane fluxe. Coagulation, oxidation coagulation pretreatment have play a role in mitigation of membrane fouling, can mitigate membrane flux in decreasing.3. Cleaning PVA microspheres membrane in several different ways has showed that:Only use mechanical scraping membrane to clean the Cake layer on surface of membrane, And membrane flux decreased by9%after three cycles. The effect of washing only by using water backwash is better, and membrane flux decreased by4.5%after three cycles. Using the combination of air-water backwash, and membrane flux decreased by6%after three cycles; Using water and mechanical scraping membrane combined process has the best effect, and membrane flux decreased only by3%after three cycles. Considering easier to Promote, backwashing costs nd membrane flux recovery, Using the combination of air-water backwash as the way of washing PVA microspheres membrane.