Factors Affecting The Removal Of Disinfection By-products By Multi-stage Reverse Osmosis

Drinking water disinfection is a common method of inactivating pathogenic microorganisms in water environment.Its aim is to cut off the route of transmission,and prevent the occurrence and spreading of infectious diseases.However,the residual disinfectant can inevitable react with most organic matter in water,generating a series of carcinogenic,teratogenic and mutagenic organic pollutants,namely disinfection by-products(DBP).Because of their toxicity and wide distribution in the pipe network,it is particularly important to carry out the study of the DBP removal technology.RO method is currently the terminals of the most widely used and effective removal of DBPs technology on the market.However,the traditional single stage RO process of pure water recovery rate was only about30~50%,this phenomenon has caused the waste of water resources and limit the further breakthrough in RO technology in the field.This paper by using multistage RO technology and achieving the efficient recycling water and water efficient removal of DBP.In this paper,by examining including halogenated methane(HM)and halogenated acetic acid(HAA),halogenated acetonitrile(HAN),halogenated acetaldehyde(HAL),halogenated nitromethane(HNM),halogenated acetamide(HAcam)and halogenated phenol(HP),seven classes,more than 30 kinds of DBPs in the process of multistage RO change trend,illustrates the ionic and nonionic states the method of water removal efficiency of organic DBPs.Results show that the ion DBPs(HAAs)in water,with the increase of RO series,HAA removal rate showed a trend of decreasing step by step as a whole.When the water recovery rate reaches 90% with the 5-RO,the absolute removal rate of HAAs is75~95%.By investigating the aquatic environment,pressure,p H and other factors affecting removal of HAAs on the multistage RO,the effect of alkaline environment(p H 7.5)or higher,the water pressure of 0.6 MPa and the actual water body environment more conducive to HAA s in multistage RO process implementation.In order to further reveal the mechanism of multistage RO with HAAs removal of water,in this paper,based on the structure of the material characteristic parameters and its removal efficiency in RO at all levels,build the five quantitative structure-activity relationship model.Results show that the main reason for the HAAs dissociation is strength and the space steric in multistage RO process.State of non-ionic DBPs(HM,HAN,HAL,HNM,HAcam and HP)in terms of its overall trends compared with ion state in the multistage RO of HAAs removal,namely with the increase of RO series,its removal ra te decreasing step by step.When pure water recovery more than 90%(4-RO),molecular radius is larger than 0.220 nm non-ionic state DBPs(11 species)the average absolute removal rate was 85%,the molecular radius between 0.220 and 0.20 0 nm non-ionic state DBPs(8 species)is 70%,the removal rate of the absolute and molecular radius is less than 0.200 nm non-ionic state DBPs(4 species)the absolute removal rate is about 45%.Multistage RO technology of 5 kinds of DBPs with non-ionic state,the mean absolute order removal efficiency is HAN < HM < HAL < HNM < HAcam < HP.By investigating the factors of aquatic environment,such as p H and methanol solvent for multistage RO with ion state of DBPs,in addition to the TCM and TCAN,the above factors on the state in this paper,the six kinds of non-ionic DBPs had no significant effect.And when the p H is alkaline,THMs removal efficiency will decrease.Also in alkaline environment,due to the increase of the hydrolysis of high-intensity acetonitrile was hydrolyzed to remove.Stress of a multistage RO remove non-ionic state is the important factors of DBPs in water,when pressure is 0.4 MPa(low pressure),pure water recovery rate reaches 90% of energy consumption is about comparing with pressure with 0.6 MPa(medium voltage)2 times.When the pressure is 0.8 MPa(high voltage),the water pressure close to the critical pressure of RO membrane,membrane performance is decreased obviously.So when the water pressure of 0.6 MPa is more advantageous to nonionic state of DBPs in water to remove.In order to further reveal the multistage RO water non-ionic state of DBPs in water removal mechanism,this article is based on the structure of the material characteristic parameters and its removal efficiency in RO at all levels,build the quantitative structure-activity relationship model of three kinds of DBPs.Results indicate that the electric induction effect,octyl alcohol water distribution coefficient,molecular radius is the main cause of ion state organic DBPs in multistage implementation to remove in RO process.