Evaluation of sequential inactivation of Bacillis subtilis spores in drinking water with ozone and chlorine
臭氧-氯联合灭活饮用水中枯草芽孢杆菌芽孢的研究

The inactivation effect of Bacillis subtilis (B. subtilis) spores with individual chlorine disinfection, individual zone disinfection and sequential disinfection with ozone followed by free chlorine, was examined in natural water samples. Results show that B. subtilis spores were highly resistant to free chlorine disinfection. Only 0.84 log reduction was achieved by chlorine when initial chlorine concentration was 6 mg/L and contact time was 240 min. Ozone disinfection is more effective than chlorination. At contact time of 5 min, ozone disinfection results in 4.68 log reduction. Up to 7.1 log reduction was achieved with 2 min ozone pretreatment followed by 6 mg/L chlorine, which is much higher than the sum of inactivation rate of zone and chlorine disinfection individual. The effect of the combined applications of ozone and chlorine in inactivating B. subtilis spores is a kind of synergistic effect, which is enhanced with the increase of the level of ozone pretreatment.