| Natural organic matter is the main precursor of the disinfection by-products(DBPs)and mutagenic substances in the water,the humic acid in the natural drinking water sources brings about a series of effects on human beings,plants and animals.In the sewage treatment and recycling,natural organic matter is an important separation composition by ultrafiltration membrane,but the natural organic macromolecules form will create and exacerbate membrane fouling and thus greatly reduce the ability of the membrane separation,and affect the productivity,product quality,and process costs.So one of the critical issues for the successful application of ultrafiltration in water treatment is membrane fouling caused by soluble organic.The research issues for the application of ultrafiltration and membrane fouling is NOM contaminated properties,the prevention of NOM pollution and the removal of NOM pollution.The natural organic humic acid is tested for the study,and is removed by flat ultrafiltration membrane which is low molecular weight(MWCO10kDa).We study that the humic acid which is in the different environments has the impact on membrane fouling trend.And we preliminary study with membrane fouling phenomenon and trends in the UF separate system and PAC leading-in UF system.At the same time we research relatively effective cleaning method and the method of flux recovery against this kind of fouling.Pilot study showed that,in the higher metal cation concentration environment,the chelate reaction between humic acid and calcium played a key role,and membrane fouling was effectively mitigated.At the same time,the removal rate of humic acid could be increased to 89.5%,strengthening the humic acid removal,and to a certain extent,helping to remove calcium ions in water.In acidic solution,humic acid acidified and condensed into precipitation of colloidal,mitigating membrane fouling,and helping to intercept by ultrafiltration membrane which has small aperture and low molecular weight.But in the isoelectric point of pH=6.00,the film seriously polluted.By comparing the separate UF systems and the PAC leading-in UF system,we found that after adding PAC flux decline slowed down somewhat.But it was not very significantly alleviate membrane fouling to acquire high flux.So the small molecular of dissolved organic which was adsorbed by PAC was not a major factor which caused membrane fouling.Increased PAC dosage had not increased membrane fouling,that the small molecular of dissolved organic which was adsorbed by PAC formed a "secondary membrane" in the membrane surface.The test found that PAC into the UF system helped to remove humic acid effectively.The same states of the fouled UF membranes were cleaned by ultrasonic cleaning method and the traditional chemical cleaning method.It showed that ultrasonic cleaning can significantly enhance cleaning,and greatly shorten the cleaning time.
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