Study On The Degradation And Transformation Of Free Cyanobacteria Extracellular Polymer By Traditional Disinfection Technology

At present,the generalization and seriousness of the cyanobacterial pollution situation in the water source cause cyanobacteria extracellular polymer(EPS)pollution control is imminent.First of all,cyanobacteria EPS is an essential source of organic pollution in the origin of the water.It is released in large amounts during the growth and reproduction of cyanobacteria and is free in the surrounding water environment.Because of the characteristics that free cyanobacterial EPS is not easy to be trapped in the conventional physical and chemical treatment process,it is easy to remain in the effluent of the process and become a precursor of disinfection by-products.This study focuses on the degradation and conversion effect of traditional sterilization process on free cyanobacterial EPS,comparative analysis The degradation and conversion efficiency of different contents of free cyanobacteria EPS with varying treatments of disinfection and process conditions such as sodium hypochlorite,liquid chlorine,ultraviolet light,ozone,etc.,and the generation of disinfection by-products of free cyanobacteria EPS after different disinfection processes was explored,and the free cyanobacteria were clarified The removal rule,and conversion mechanism of EPS in the traditional water treatment and disinfection process is based on the removal of free cyanobacteria EPS organic pollution and the analysis of the safety limits of by-product disinfection of drinking water quality.The method of drinking water disinfection treatment is compared and preferred.The research contents and conclusions of this paper are as follows:(1)The degradation and transformation of cyanobacterial EPS in the process of sodium hypochlorite and liquid chlorine disinfection and the production of disinfection by-products during different chlorination disinfection processes were studied.In other words,under the same disinfection dosage,sodium hypochlorite disinfection degrades polysaccharides,proteins,and humic acids in cyanobacterial EPS more than liquid chlorine.After disinfection with sodium hypochlorite,the degradation efficiency of protein in water sample is almost 100%,and the degradation efficiency of polysaccharide is also 41.6%-74.6%,which is much higher than that of 21.4%-41%after disinfection with liquid chlorine.Sodium hypochlorite disinfection promotes the degradation of macromolecular chain substances to a greater extent.It tends to be transformed entirely into small molecular chain substances.However,at the same time,after using sodium hypochlorite to disinfect the water bodies of the same concentration of cyanobacteria EPS,the amount of disinfection by-products produced is far more than that of liquid chlorine disinfection,among which the production of trihalomethane and haloacetic acid is particularly obvious.After disinfection with sodium hypochlorite,the content of trihalomethane and haloacetic acid in the high-content EPS water sample was 492?g/L-592?g/L and 368?g/L-586?g/L respectively,and the content of trihalomethane and haloacetic acid in the low-content EPS water sample was 266?g/L-294? g/L and 212?g/L-324?g/L respectively;while the content of trihalomethane and haloacetic acid in the high-content EPS water sample after disinfection with liquid chlorine was 59?g/L-145?g/L respectively The contents of trihalomethane and haloacetic acid in low content EPS water samples were 37?g/L-60?g/L and 60?g/L-103?g/L,respectively.A large amount of organic matter in cyanobacterial EPS is an essential precursor for the production of disinfection by-products.The degradation of cyanobacterial EPS organic components and the production of disinfection by-products in the chlorination disinfection process follow specific transformation rules:the degradation efficiency increases with the increase in disinfection dose,Decreases with increasing cyanobacterial EPS content;by-product generation increases with increasing disinfectant dose and increases with increasing cyanobacterial EPS content.Therefore,the increase in the treatment of chlorinated disinfection and the increase in the concentration of cyanobacterial EPS are the main factors that lead to unsafe disinfection water quality Compared with liquid chlorine,sodium hypochlorite has a higher contribution value to disinfection by-products,and its water quality is less safe.Therefore,if considering the safety hazards generated by disinfection by-products,the use of liquid chlorine disinfection maybe more reliable than sodium hypochlorite disinfection.However,in the process of water treatment,the addition of cyanobacteria EPS removal process to the cyanobacteria-containing EPS water disinfection treatment can more effectively reduce the generation of disinfection by-products.(2)Comparative analysis of different non-chlorinated disinfection processes,the degradation,and transformation of cyanobacterial EPS in the process of ultraviolet and ozone disinfection and the generation of disinfection by-products.More details,because of the destructive effect of ultraviolet radiation and the strong oxidation of ozone Macromolecular organic substances such as polysaccharides and proteins in cyanobacterial EPS can achieve a higher degree of oxidative degradation.As the disinfectant dose increases,macromolecules tend to be more The tendency of degradation of small molecular weight substances is more prominent.The degradation and transformation of cyanobacterial EPS macromolecular organic components by ultraviolet light is more efficient than that of ozone,which is related to the breakage and destruction of polysaccharide macromolecular chain material structure by ultraviolet light.Compared with chlorinated disinfection methods,both invisible and ozone non-chlorinated disinfection methods will not cause a large number of disinfection by-products such as trihalomethane,haloacetic acid,and total organic halogen.Even ozone disinfection can destroy trihalomethane and halogen.The material structure of acetic acid,total organic halogen,etc.has a certain degree of degradation control effect on the content of halogenated natural disinfection by-products.Therefore,non-chlorinated disinfection is more suitable for the safe treatment of cyanobacteria-containing EPS water sources than chlorinated disinfection.Meanwhile,ozone disinfection is more preferably a synergistic disinfection process of free cyanobacterial EPS degradation and disinfection by-product control.