Efficiency Research Of Chlorite Removal In Drinking Water Pretreatment By Granular Activated Carbon

With the widely use of chlorine dioxide as disinfector in water treatment,the potential problem of inorganic disinfection by-products chlorite?ClO₂^-?are gradually exposed.Due to its good adsorption,activated carbon can be applied to remove the ClO₂^-in the water treatment.The research scholars abroad has different conclusion on study of activated carbon to remove ClO₂^-.Domestic research has carried out some research on the powder activated carbon,but it is still less.Three parts of research for granular activated carbon?GAC?to remove chlorite are studied,including the comparison and choice of GAC,the influence factors of GAC removal of ClO₂^-in the static adsorption conditions,GAC adsorption column to remove chlorite technology and its comprehensive effect evaluation.In this paper,the differences in the removal of ClO₂^-by varied properties of GAC were studied.The coal-based and columnar GAC was selected as the experimental GAC because of its largest chlorite adsorption capacity in all of the GAC materials,the saturated adsorption amount of chlorite is 111.61 mg/g The adsorption of ClO₂^-on GAC was more consistent with the Freundlich model,and its adsorption process was preferential adsorption.The internal particle diffusion model was more suitable than pseudo first order kinetics model and pseudo second order kinetics model to describe the progress of ClO₂^-adsorption by GAC.The experiments of influencing factors showed that GAC dosing quantity,the initial concentration of ClO₂^-,and p H would greatly influenced the removal efficiency of chlorite by GAC.Nevertheless,the temperature,stirring intensity and particle size had a little impact.When the initial concentration of ClO₂^-increased from 1 mg/L to 5 mg/L,the removal rate also increased from 41.9% to 87.1%.While when the p H increased from 3 to 13,the removal rate decreased from 100% to less than 10%.Both anions and organic matter?humic acids?had influence on ClO₂^-removal and the influence of the organic compound was less than the anion,besides,monovalent anion > bivalent cation > trivalent anion.ClO₂^-is partial convert to Cl-,after being adsorption by GAC,while some exists in the form of ClO₂^-,there is no Cl O3-formedThe technology study of GAC-column adsorption on ClO₂^-removal showed that empty bed contact time?EBCT?and carbon layer thickness had a great influence on chlorite removal.Filtering direction and backwash basic didn't affect the removing ability of chlorite.The removal rate of ClO₂^-increased by nearly 60% once the EBCT increased from 1 to 15 min.And carbon layer thickness is proportional to the ClO₂^-removal rate.The exist of chlorite had slight influence on the removal of organic matter,p H,turbidity and chromaticity.It would move the microbial growth area down,while the total number of microbial remained unchanged basically.Referenced the waterworks' operating conditions and "drinking water health standards"?GB 5749-2006?,we estimates that coal columnar activated carbon filter could effectively control ClO₂^-concentration for more than 1 700 d.