为了满足过滤避免测定的要求，并收集未来决策所需的数据，纽约市环境保护局（DEP）对卡茨基尔和特拉华水系统进行了消毒研究。本文介绍了在不进行后续过滤的情况下进行初步消毒的消毒研究结果，以满足当前地表水处理规则（SWTR）规定，并提高隐孢子虫的灭活水平。研究了几种消毒剂（臭氧、氯和二氧化氯）和消毒剂的顺序应用（臭氧后氯），以满足不同温度条件下的三种灭活水平。 这些灭活水平被定义为2对数隐孢子虫灭活的高CT目标，1对数隐孢子虫灭活的中CT目标，以及3对数贾第鞭毛虫或4对数病毒灭活的低CT目标。在合理的二氧化氯和臭氧剂量和接触时间下，所有三种确定的条件（低CT、中CT和高CT）均满足CT目标。氯气消毒和顺序消毒（先用臭氧，再用氯气）不能有效地满足选定初始剂量和接触时间的既定CT目标。

To satisfy the requirements of the Filtration Avoidance Determination and to collect data needed to make future decisions, the New York City Department of Environmental Protection (DEP) conducted a disinfection study for the Catskill and Delaware water systems. This paper presents the results of the disinfection study conducted to investigate primary disinfection without subsequent filtration to satisfy current Surface Water Treatment Rule (SWTR) regulations and to achieve increased inactivation levels for Cryptosporidium. Several disinfectants (ozone, chlorine, and chlorine dioxide) and sequential application of disinfectants (ozone followed by chlorine) were studied to meet three inactivation levels at various temperature conditions. These inactivation levels were defined as a high CT goal of 2-log Cryptosporidium inactivation, a mid CT goal of 1-log Cryptosporidium inactivation, and a low CT goal of 3-log Giardia or 4-log virus inactivation. The CT goals were satisfied for all three conditions established (low CT, mid CT, and high CT) with reasonable chlorine dioxide and ozone doses and contact times. Chlorine disinfection and sequential disinfection (ozone followed by chlorine) were not effective in meeting the established CT goals for the initial doses and contact times selected.