Inactivation of Cryptosporidium parvum oocysts by sequential disinfection with chlorine following ozone

自由氯胺和臭氧对Cryptosporidium Parvum Oxysts感染率的影响已被评估。自由氯林CT （集中和接触时间的产品）对减少感染率的要求在1至100毫克/升的暴露氯林浓度范围内高度依赖.在感染率中n对数减少的CT值（CTn毫克min/升）和暴露的平均游离氯林浓度（C毫克/升）在20 C， pH值7.0时的CTn = n·（21.3 C +793）。对于臭氧， CT要求没有显示臭氧浓度在测试范围内的0.1至1.0毫克/升的任何依赖性，并发现臭氧CT值在2至3毫克/升的狭窄范围内减少2个对数的感染率。已测试的臭氧和氯丁结合感染的有效性。Oocysts were exposed to ozone with the CT of 0.75， 2.0和3.0 mg min/L，然后暴露到游离chlorine of 1，400 mg min/L. Achieved reductions in infectivity by combined disinfection with chlorine following ozone were 2.17， 1.68， 1.43 log for 0.75， 2.0， 3.0 mg min/L of ozone， respectively。按氯胺减少1，400毫克分钟/升的感染率为1.74 log，按比例减少混合感染率为0.97 log、-0.06 log、-0.31 log，分别为0.75、2.0、3.0毫克分钟/升。因此，在感染率中减少的综合性增加可以观察到0.75毫克分钟/升的臭氧，但通过综合性效应的额外减少是有限的，只有1 log。在附加情况下，任何显著的同步效应都不能在另外两个案例中观察到。从这些结果中可以看出，通过顺序模式的染色跟随臭氧扩散并不是一个实际的方法来期望在综合效应的感染中减少过度的有机体。

The effects of free chlorine and ozone on infectivity of Cryptosporidium parvum oocysts were evaluated. Free chlorine CT (the product of concentration and contact time) requirement for reduction in infectivity was highly dependent on exposed chlorine concentration at the range of 1 to 100 mg/L.Obtained relationship between CT values for n log reduction in infectivity (CTn mg min/L) and exposed mean free chlorine concentration (C mg/L) was CTn = n・(21.3C+793) at 20 C, pH 7.0. As for ozone, CT requirement did not show any dependency on ozone concentration at the tested range of 0.1 to 1.0 mg/L and obtained ozone CT values for 2 log reduction in infectivity were in narrow range of 2 to 3 mg min/L.The efficacy of combined disinfection with ozone and chlorine was tested. Oocysts were exposed to ozone with the CT of 0.75, 2.0 and 3.0 mg min/L and then exposed to free chlorine of 1,400 mg min/L.Achieved reductions in infectivity by combined disinfection with chlorine following ozone were 2.17, 1.68, 1.43 log for 0.75, 2.0, 3.0 mg min/L of ozone, respectively. As reduction in infectivity by chlorine of 1,400 mg min/L was 1.74 log, excess reductions by combined disinfection were as small as 0.97 log, -0.06 log, -0.31 log for 0.75, 2.0, 3.0 mg min/L, respectively. Thus, synergistic increase in reduction in infectivity was observed in case of 0.75 mg min/L of ozone, but additional reduction by synergistic effect was limited only 1 log. In addition, any significant synergistic effect was not observed in other two cases. From these results, combined disinfection by sequential mode of chlorination following ozonation is not a practical method for expecting excess reduction in infectivity of oocysts by synergistic effect.