AOAC Method 965.13 Disinfectant (Water) for Swimming Pools
Purpose of Test
The AOAC Disinfectant (Water) for Swimming Pools test method is a suspension-based method used to evaluate the efficacy of disinfectants intended for use in swimming pools, spas and hot tubs. Numerous factors influence the necessary concentration of a product to be effective for disinfection of swimming pool water. Some factors include: the number of swimmers/bathers in the pool; frequency of use; frequency with which water is changed; general weather conditions; and types and degree of organic contamination of the water by the swimmers/bathers themselves (e.g., suntan lotion and oils) and by various debris. Therefore, a two-phased study, consisting of a laboratory test and confirmatory field test, is recommended by the U.S. EPA. This method is used to fulfill the laboratory portion of testing.
Summary of Test
In this method, a sample of test substance is inoculated with the test organism, commonly Escherichia coli and Enterococcus faecium. Over a series of time points, samples are removed, the test active is neutralized and the sample is quantitatively assayed for surviving test organism. In a similar fashion, a known concentration of a sodium hypochlorite reference standard is inoculated, exposed, neutralized and assayed for survivors. The resulting subcultures are incubated and subsequently evaluated for survivors. The test subcultures are then compared to the sodium hypochlorite control subcultures. The lowest concentration of test substance providing results equivalent to the sodium hypochlorite control solution is considered the lowest effective for disinfection.