The Research Of The Ultrafiltration Combined Processes In Drinking Water Treatment With Micro-Polluted Source Water

PVC alloy ultrafiltration membrane was used to treate micro-polluted source water of Jinan southern mountain region and Yellow River.It was studied systematically the influencing factors of water pollutant removal effect and operation parameter by direct ultrafiltration. Direct ultrafiltration was improved basing on existed problems, which pretreatment process -floatation and chlorine dioxide/coagulation addition for improving operation and removal pollutants performance.Research results as follows:(1)The direct ultrafiltration has better removal ability to polluter ,such as turbidity, alga, bacterium in water, the removing rate is more than 97%. Holding back of ultrafiltration membrane make that effluent water turbidity is lower than 0.1 NTU, coliform bacteria was not detected. It is obvious ultrafiltration has better removal results of the macromolecule polluter in water. It is limitied for the direct ultrafiltration removal ability of water organic pollution index UV254 and CODMn, removal rate was 15% and 30% respectively. TOC removal rate is only 30%. Organic pollutes can not is improved effectively in effluent water. Taste and odor and geosmin removal rate were 38% and 24% respectively. The chloroform and tetrachloride in disinfection by-products from precursors were 42% and 67%, CHBrCl2 and CHBr2Cl has not been removed nearly in the process.The experiment discovered that the raw water quality influence greatly membrane flux and the membrane pressure. Membrane flux is higher 30% while raw water of TOC equalling 2.0 mg/L compared to average TOC 3.8 mg/L, the membrane pressure is approximately lower 38%.Therefore the direct ultrafiltration completely guarantee in removing the turbidity, algae, bacterium, coliform bacteria in water.But it is limited for the organic matter and disinfection by-product elimination to membrane serious pollution.(2) Floation and ClO2/ coagulation before ultrafiltration is conducted according to existed problems of direct ultrafiltration.The result shows that the best chlorine dioxide dosage is 8 mg/L with floatation-UF combined process,0.1 mg/L with ClO2/ coagulation-UF. Removal rate of CODMn increase 30 % and 10.1%, UV254 increase 35 % and 42.9% for direct ultrafiltration comparing to the other two processes under the best dosage .the data shows that pretreatment ultrafiltration processes greatly improve removal rate of organic matter .Although direct ultrafiltration elimination rate of chlorophyll a and the algae are closed 100%, filter membrane burden is overweight. The floation and chlorine dioxide strengthening coagulation pretreatment processes remove chlorophyll a 60% and 35% respectively, removal rate of algae are 54 % and 70 % respectively ,which the two pretreatment processes alleviate effectively membrane fouling. Chlorine dioxide strengthening coagulation pretreatment processes is superior to floation for algae. Geosmin removal rate is 24% with direct ultrafiltration, 50% with floatation-UF, 58% with ClO2/PAFC- UF combined process. Removal rate of two pretreatment processes to geosmin is raiser 26% and 32% respectively than direct ultrafiltration. The chloroform and tetrachloride in disinfection by-products from precursors are 61% and 97% in the process, is raiser 19 % and 30% respectively than direct ultrafiltration. Two process has not been removed nearly with CHBrCl2 and CHBr2Cl.So removal efficiency of some by-products from precursors is promoted in floation-ultrafiltration.ClO2/ chlorate and chlorite is not limit exceeding in coagulation -ultrafiltration process. It can satisfy the request even if the chlorine dioxide dosage is 0.5 mg/L.The two combine processes compared to the direct ultrafiltration processes, ultra filter membrane pressure drop 25% and 18% respectively, the membrane flux rises 10% and 8%.Therefore two kind of pretreatment processes effectively alleviate membrane contamination concern.