Anion-exchange Resin Adsorption Followed By Electrolysis:A New Disinfection Approach To Control Halogenated Disinfection Byproducts In Drinking Water

Disinfection is an important part of drinking water treatment,which can prevent human from waterborne disease,and is essential to protect public health.Chlorination is the most commonly used disinfection method for drinking water.However,chlorine can react with natural organic matter(NOM)and halides in source water to produce numerous halogenated disinfection byproducts(DBPs).Previous studies have proved that DBPs were cytotoxic,genotoxic,mutagenic,and positively related to human risks such as miscarriage,and birth defects.A common strategy for DBP control is to decrease precursor levels prior to disinfection.Anion-exchange resin adsorption has been applied in contaminant removal from water with relatively low cost and high regeneration ability.The application of chloride-form anion-exchange resins to remove NOM,bromide and iodide can result in releasing of chloride,which may affect drinking water quality aesthetically.However,if the released chloride could be oxidized,it can achieve turning waste into treasure to generate reactive chlorine species(RCS)for disinfection.In this study,we developed a new approach using chloride-form anionexchange resin adsorption followed by electrolysis to control halogenated DBPs.Control efficiency of the new approach on halogenated DBPs was evaluated based on analyses of total organic halide(TOX),four trihalomethanes(THM4),five haloacetic acids(HAA5)and 23 new phenolic DBPs.Disinfection efficiency of the new approach was evaluated with three seeded microorganisms(Escherichia coli,Pseudomonas aeruginosa,and Staphylococcus aureus).Results showed that pretreatment of resin using sequential base/acid wash,methanol extraction,and five-times deionized water wash could avoid resin leaching and decrease influence of chloride and methanol.Up to 93.7%of NOM and 91.2%of bromide were removed at a resin dose of 20 mL per 2 L of simulated source water sample at a contact time of 1 h.Meanwhile,49.5 mg/L of chloride was released from the resin to the water sample via anion-exchange,which was further oxidized by electrolysis(current intensity of 0.40 A,Ti/RuO2-IrO2 anode,and graphite cathode)to generate RCS(5.0 mg/L as Cl2)within 192 s.With this new approach,formation of TOX,THM4,and HAA5 was reduced by 86.4%,98.5%and 93.2%,respectively,while the formation of 23 new phenolic DBPs increased,compared with chemical chlorination alone.The comparative experiments clearly demonstrated the advantage of the new disinfection approach for microorganism inactivation.The disinfection efficiency of new disinfection approach achieved 99.99%of all the three seeded microorganisms in 38 s,suggesting that the new approach was not only effective to Escherichia coli but also the chlorine-resistant bacteria including Pseudomonas aeruginosa and Staphylococcus aureus.