Comparative Study On The Effects Of Different Disinfectants On The Effluent Quality Of Raw Water In Taihu

As we all know,disinfection methods have a great impact on tap water quality.This paper was carried out for Taihu raw water following p re-ozonation – conventional treatment – ozone biological activated carbon process,on the influence of the quality of water after O3-BAC with different disinfectants(free chlorine disinfection,chloramine disinfection,UV disinfection,UV and free chlorine disinfection,UV and chloramine disinfection).The conclusions of this study are obtained as follows:(1)The greater the dosage of chlorine,the higher the decay rate of residual chlorine under chlorine disinfection.The dosages of free chlorine were 0.5mg/L,1.0mg/L,1.5mg/L,2.0mg/L,3.0mg/L respectively.The decay rate of residual chlorine was the highest when the reaction time was 30 min(when the dosage was 3 mg/L,the decay rate of residual chlorine was 1.64mg/(L?h)).The dosages of chloramine were same with free chlorine.When the reaction time was in 2~9h,the dosage was 3 mg/L,the decay rate of residual chlorine was highest,0.18 mg/(L?h).When the reaction time reached 9h,the concentration of residual chlorine became stable.When 24 h,the concentration of residual chlorine became 0 under the free chlorine dosage of 0.5mg/L,1.0 mg/L,1.5mg/L,became 0.2mg/L,0.88mg/L respectively under 2.0mg/L,3.0mg/L,the concentration of residual chlorine was about half of the initial concentration under chloramine.(2)Put different disinfectants in ascending order on the effects of biostability: UV disinfection(radiation dose: 40mJ/cm2,AOC: 89.793μg/L,increased 2.00% than initial value),chloramine disinfection(dosage: 1.5mg/L,reaction time: 9h,AOC : 139.342μg/L,increased 28.61% than initial value),free chlorine disinfection(dosage: 1.5mg/L,reaction time: 5h,AOC: 132.953μg/L,increased 42.08% than initial value).(3)Put different disinfectants in ascending order on the effects of DBPs: UV disinfection(radiation dose: 40mJ/cm2,THMs: 2.20056μg/L,increased 62.37% than initial value),chloramine disinfection(dosage: 3.0mg/L,reaction time: 5h,THMs: 7.01572μg/L,increased 642.94% than initial value),free chlorine disinfection(dosage: 3.0mg/L,reaction time: 24 h,THMs: 13.80239μg/L,increased 849.20% than initial value).(4)The combined applications of UV and free chlorine could increase the decay rate of residual chlorine slightly,as well as the combined applications of UV and chloramine.They have the smilar little influence on DOC,the different influence on AOC and THMs.When the reactime reached 5 h,the concentration of AOC was 128.542μg/L,THMs was 4.66293μg/L after the combined applications of UV and free chlorine.They were higher than the combined applications of UV and chloramine,increased by 57.65%,220.75% respectively.From the view of experimental point,UV disinfection is the best,chloramine is the second,the combined applications of UV and chloramine is the third,free chlorine disinfection is the fourth,the combined applications of UV and free chlorine is the last,under the consideration of AOC and THMs.On the cosideration of the practical application and the advantages and disadvantages of disinfectants,the combined application of UV and chloramine is the best.