Study On The Control Of Ultrafiltration Membrane Fouling By Chlorine Water Backwashing

Into the 21 st century, ultrafiltration membrane technology in the field of drinking water treatment is widely used all over the world. Ultrafiltration pretreatment technology,maintenance cleaning and chemical cleaning technology is currently the most widely used to ultrafiltration pollution control technology, which plays a crucial role in mitigating the ultrafiltration membrane pollution, but the pollution control technology of ultrafiltration membrane is still essential elements to promote the application of UF, although conventional pretreatment greatly ease the pollution of ultrafiltration membrane, but the membrane fouling is still inevitable, frequent maintenance cleaning and chemical cleaning chemicals in high concentrations impact the ultrafiltration membrane life in certain degree,and bring high concentration pharmaceutical wastewater treatment problems. It has been the pursuit of efficiency, energy saving, environmental protection, the pace of technological innovation never stop. So exploring new UF pollution control technology has important scientific and practical significance.On the basia of the pre-oxidation, backwash technology and maintenance cleaning technology, we propose a low concentration of chlorine water line cleaning technology for the timely removal of the membrane surface organic pollutants, and then controlling pollution. The main topic of low concentrations of chlorine water backwash on membrane technology is to remove organic pollution and control effectiveness, and explore the group its removal mechanisms of organic pollution and its effects on membrane fouling engineering applications, the main purpose is to analyze the chlorine water backwash technology engineering feasibility, provide theoretical and technical support for the promotion and application of technology.Low concentrations of chlorinated water backwash technology for humic acid organic pollution of ultrafiltration membrane has effectively remove and control effectiveness, and with the increased dosage of chlorine, the effect of control and removal of organic contamination of ultrafiltration is better; the growth trend of Transmembrane Pressure(TMP) more slowly. When the pollutants include colloidal particles, the dosage of chlorine in backwash water is not as high as possible, overdose can cause excessive damage colloid,increase the fine particulate matter, these tends to increase the likelihood of membrane pores clogging. The effect of low concentrations of chlorinated backwash on Bovine serum albumin pollutant of UF membrane caused weak, difficult to achieve pollution controlaction, and therefore minimize the content of protein substances in water before ultrafiltration membrane should be applied in order to reduce the ultrafiltration membrane irreversible contamination; when UF is used to treat surface water due to poor resistance to pollution impact,the raw water quality requirements is higher,so UF is not suitable for handling eutrophic water. Therefore, to increase the capacity of the resistance to pollution load of ultrafiltration process, ultrafiltration system is applied after flocculation process.In chlorine water backwash test of surface water, on flocculation + ultrafiltration,precipitation/ultrafiltration process, the chlorinated water backwash show good results on ultrafiltration membrane pollution control; the increment of flocculation /ultrafiltration chlorinated water backwash Unified fouling coefficient(defined UMFI ? Q unified ultrafiltration membrane fouling factor, Unfied Membrane Fouling Coefficient, UMFC) is0.0003 lower than the backwash without chlorine; precipitation/ultrafiltration process,when the increment of chlorinated water backwash UMFC is 0.0016 lower than increment of UMFC of the backwash without chlorine. The backwash with chlorinated water reflects a clear advantage in the production of effluent water treatment pilot test trials, due to the relatively small particles, organic pollution is mainly factor on ultrafiltration membrane fouling, and it has effective control of the ultrafiltration membrane fouling by 10mg/L chlorinated water backwash so that long-term stable operation of the ultrafiltration membrane.To further exploring the removal mechanism of membrane fouling by chlorine water backwash, this paper analysis the organics molecular weight of the backwash eluent of polluent membrane with and without chlorination and organics molecular weight of humic acid with and without chlorination; when dealing with natural water, the particle size distribution and Zeta potential was analyzed. Found humic organic contamination on the membrane surface caused by mainly organics relative molecular weight greater than 5K,and organics characteristics which enables membrane fouling are changed by chlorinated water backwash, high molecular weight organic substances are oxidized and decomposed into small molecular substances, organic matter under the influence of chlorine oxidation becomes more hydrophilic, which the organic matter can be removed by water backwash.In the treatment of surface water flocculation stage hypochlorite dosing did not make increase the proportion of small particles, but reduced; the oxidation of sodium hypochlorite reduces the electrostatic interaction between organic matter and improve the flocculation conditions, the hydrolysis of aluminum and sodium hypochlorite can contribute to promote flocculation to increase the proportion of large particles. Theprecipitation water and sand filtration in adding sodium hypochlorite result in big proportion of particles increasing, small particles reduced at this concentration oxidizing conditions, particulate matter does not disintegration phenomenon; After flocculation,sedimentation, and sand filtration in adding sodium hypochlorite, all of them, Zeta absolute value decreased. These phenomena can be explained by two aspects, first, the interaction of metal ions and sodium hypochlorite, sodium hypochlorite dosing has a role in promoting the formation of colloids on flocculant process wate containing residual metal ions, the small particles in the water under the metal hydroxide colloids regroup and settle, thereby reducing the metal ion contamination of ultrafiltration membrane; the second, the oxidation of sodium hypochlorite also provide more organic oxidation groups, promoting binding of colloidal and organic matter, so that the dispersed small particulate matters produce large alum again by adsorption, so that most of the particles as well as some organic matter get removal by precipitation, reducing the ultrafiltration membrane inorganic and organic contamination.