地表水处理规则（SWTR）规定了实现致病微生物不同程度失活的C x T值，C是任何反应器出水中消毒剂的浓度，T是取决于反应器水力的特征接触时间。将使用SWTR规定的C x T方法计算的反应器消毒信用与基于公认消毒动力学和基本反应器行为的预测进行比较。该分析表明，C x T方法缺乏可靠的概念基础，往往有些保守，对许多水处理厂来说成本不必要。无量纲参数k CO是消毒速率常数、出水消毒剂浓度和理论滞留时间的乘积，为评估消毒条件和工厂改造提供了一种系统方法。 考虑了反应器中氯的衰变，纠正了AWWA杂志上一篇文章中的错误。包括8个参考文献、表格、图表。

The Surface Water Treatment Rule (SWTR) specifies C x T values for achieving various degrees of inactivation of pathogenic microorganisms, with C being the concentration of the disinfectant in the effluent from any reactor and T being a characteristic contact time dependent on reactor hydraulics. The disinfection credit calculated for reactors using the SWTR-prescribed C x T approach is compared with predictions based on accepted disinfection kinetics and fundamental reactor behavior. This analysis demonstrates that the C x T approach lacks a sound conceptual basis, tends to be somewhat conservative, and is unnecessarily costly for many water treatment plants. A dimensionless parameter, k CO, the product of a disinfection rate constant, the effluent disinfectant concentration, and the theoretical detention time, provides a systematic approach for evaluating disinfection conditions and plant modifications. The decay of chlorine in the reactor is considered, and an error in a previous Journal AWWA article is corrected. Includes 8 references, tables, figures.