EPA CT was developed to assess the performance of disinfection systems mostly related to drinking water biological quality. EPA CT Tables provide CT values for the major drinking water disinfectants such as: chlorine (free chlorine), chloramines, ozone, and chlorine dioxide. The CT for chloramines was developed based on disinfection data collected from preformed chloramine (which means chloramine solution was prepared and the chloramines were already formed in the solution before being used for the disinfection). However, in the field, current chloramine application uses the sequential method where free chlorine is applied first for certain period and then ammonia is introduced in the system to produce the chloramines. This method of chloramine production is different from the method that EPA used (preformed method of chloramine production) to prepare the CT tables. MIOX (a mixed oxidant system) operates a mixed oxidant solution including free chlorine, hydrogen peroxide, and others that are simultaneously produced in the disinfection solution. MIOX uses EPA CT tables to assess its disinfection performance, although the disinfectants are simultaneously produced in their systems. Here multiple disinfectants are systematically formed in the process, while EPA CT tables are based on single disinfectant systems. From the above two cases, it can be observed that the method of disinfectant production seems to be irrelevant to the use of EPA CT tables.
I do not think that your wish of an "universal" assessment methods of disinfection systems can come true. As you clealy pointed it out, even in a rather simple system as drinking water, there can be some differences in the way the methods are implemented.
For more complex system such as swimming pools or food industry surfaces, the problem is much more complex due to the permanent flow of organic matters likely to react with free chlorine which leads to the fromation of very complex chloramines which themselves go on reacting with free chlorine.
Some examples below:
Article Occupational exposure during cleaning and disinfection in th...
Article Exposure to chloramines in the atmosphere of indoor swimming pools
Article Exposure to Chloraminies in a Green Salad Processing Plant
Thank you for your response. The question is about the practicality of disinfection effectiveness assessment. No matter how complex the system can be, there is always a need to know that the swimming pool or the drinking water is disinfected and the best way to measure the performance (during the process) of whatever disinfectant used (beside taking some samples for biological testing). This leads us to the CT concept. As I indicated, we all know that the CT concept can be applied to different methods of disinfection. By “universal” I am looking at the generalization of the concept. I guess the question is to know if the CT concept can be generalized to address the performance of any disinfection system.
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