Experimental study on cryptosporidium inactivation in drinking water by chlorine-based disinfectants

In order to find chlorine-based disinfectants' inactivation effect on cryptosporidium in drinking water,factors influencing inactivation efficiency such as the dosage of chlorine and chlorine dioxide,contact time,turbidity,pH value and temperature were investigated. It was found that optimal cryptosporidim inactivation efficacy of chlorine-based disinfectants was obtained at 360 min with chlorine dosage of 6. 5 mg / L and at 120 min with chlorine dioxide dosage of 3. 0 mg / L,respectively. Cryptosporidium inactivation ratio of chlorine reduced with higher turbidity; cryptosporidium inactivation ratio of chlorine dioxide was almost stable when turbidity increased to 5. 0 and 10. 0 ntu. The fluctuating of pH value had little influence on inactivation by chlorine; optimal inactivation efficiency of chlorine dioxide was obtained at pH value of 6 ～ 7. In the temperature range of 5 ～ 35 ℃,inactivation ratio was enhanced with the increase of water temperature.