Detection Optimization Of Peracetic Acid And Its Application For Removal Of Earthy And Musty Compounds In Water

Chlorine is used as disinfectant in drinking water treatment plant for a long time because of its excellent sterilization efficiency and economics feasibility,but the formation of disinfection by-products in the chlorination disinfection can’t be ignored.Chlorine can’t also control taste and odor problems caused by typical earthy and musty matters halogenated anisoles(HAs),geosmin(GSM)and dimethylisoborneo(2-MIB)which attracted more attention of researchers with the improvement of customers’drinking water quality requirements.Therefore,the rapid detection method of residual PAA in water,the decay of PAA in drinking water and raw water,and the control of taste and odor problems by PAA with HAs as target matter was studied in this paper to reach the target of disinfection and control taste and odor problems by PAA used to be drinking water treatment disinfectant.A systematic evaluation of the dection of residual PAA in water by spectrophotometry-total chlorine pillow bag method with minimum detection of 0.28 mg/L determined that the linearity of this method is acceptable in residual PAA of 0-10 mg/L(the regression coefficient R2=0.994).Infection factors such as pH,temperature,and coloration time have little effect on this method when residual PAA of samples is in the range of 1-10 mg/L.The accuracy and stability of spectrophotometric-total chlorine pillow bag method are better than titration method and DPD(N,N-diethyl-p-phenylenediamine)method,and the advantages such as fast and stable coloration,high reproducibility and simple operation determined it’s feasible to be used for rapid detection in the field.The first order kinetic model can describe the decay of PAA well ascribed to the rapidly PAA consumption at initial time caused by natural organic matter(NOM)in water.A key factor affecting PAA decay is pH which can obviously promote the decay of PAA in alkaline conditions because of the different forms of PAA in acidic and alkaline conditions.In addition,the content of organic matter(calculated by total organnc carbon,TOC),conductivity and initial concentration of PAA also affect PAA decay with the order:TOC>conductivity>initial concentration.The promotion and acceleration of PAA decay in high initial concentration of PAA condition was mainly attributed to high consumption of PAA in fast reaction stage.The low removal efficiency of HAs by PAA alone was demonstrated in pre-experimental study,but the removal rate of HAs by PAA/UV system was more than 92%.The degradation rate fitted by the second-order kinetic model followed the order:2,4,6-TBA>2-MCA>2,4-DCA>2,4,6-TCA.PAA can improve the efficiency of PAA/UV system with the contribution rate of 24%and 36%to the degradation rate of HAs.The effect of pH on PAA/UV system is little because of small affection for the degradation of HAs by PAA alone.Direct photolysis contributed more to bromoanisoles than chloroanisoles and oxidation,direct photolysis,hydroxyl radicals(·OH)and other free radicals have similar contribution to removal of chloroanisoles.The inhibition of TBA on degradation proved the existence of ·OH in the removal of HAs by PAA/UV.As for other free radicals,the possibilities of CH3CO2·、CH3CO· and CH3CO3·were greater than HO2·、CH3·and CH3O2·.The active sites of HAs molecule predicted by density functional theory(DFT)were consistent with the experimental data which determined main products were anisole and chlorophenols in PAA/UV system and another toxic chlorinated guaiacols were only excited in in H2O2/UV system.Because of the resistance to oxidation of tertiary alcohols,PAA/UV has low removal efficiency to GSM and 2-MIB.