OCDE 170-4: 2012. Activity of disinfectants for pools and SPA disinfectants in laboratory.

Test accredited by ENAC (Spanish National Accreditation Entity), for standard mandatory microorganisms and viruses and additionals (except  for protozoa cysts).

For many years the disinfection of swimming pools and SPAs has been based on chemical disinfection with products with chlorine or bromine, whose efficacy is well known for several classes of pathogenic microorganisms. The effectiveness of the new disinfectants must be known in the conditions existing in swimming pools and SPAs before being approved for their use. Furthermore, for new disinfectants, their safety must be checked both for human health and for the environment, before performing the efficacy tests, and the tests in the laboratory or field tests.

Efficacy criteria: the activity of the new products should be established against several pathogenic human pathogen indicators (bacteria, protozoa and viruses), which can often be found in swimming pool or SPA waters and should have an activity equivalent to that obtained with chlorine derivatives. In addition, the new products must have the following characteristics: 1) Maintain a residual effective concentration in the pools that provides a continuous disinfection in the water. 2) In the case of public toilets they must be able to be dispensed by means of an automatic dosing system; 3) The efficacy must be maintained in a pH range, chosen by the manufacturer, compatible with human safety and comfort, which can be maintained in the presence of ions and other concentrations of solutes usually found in swimming pool water; 4) They must have a practical method to measure their concentration, which can even be determined by particular users; 5) Supplemental doses should be able to be added when the concentrations fall below the recommended effective concentration, or if microbial contamination is detected; 6) A margin of effectiveness should be established for normal concentrations of use; 7) For disinfectants containing more than one active substance, the relative contribution of each component to overall efficacy must be known; 8) The disinfectant must have algaecide properties that have been proven, or that its use is compatible with other algaecide products.

Phase of evaluation in laboratory: in this phase the activity is evaluated against some microorganisms indicating the main groups (bacteria, viruses and protozoa) associated with swimming pools and SPAs, in defined laboratory conditions. In the event that subrogated microorganisms should be used for any reason, they should be accepted by the corresponding regulatory institution in charge of product registration. In the performance of the tests, a chlorine control must be included, including the determination of free chlorine at the beginning and at the end of the test. The tests must be carried out at a temperature between 25 and 30ºC for swimming pools and between 34 and 36ºC for SPA pools and under pH conditions that allow the effectiveness of the disinfectant and are acceptable for the comfort and safety of the users. For chlorine controls the pH should be from 7.2 to 7.3. It is recommended to perform the test including interfering substances representative of clean conditions (such as 0.3 g/L bovine albumin) to simulate the organic load of a well maintained swimming pool. However, it is not mandatory and interfering substance may not be added. The disinfectant must be effective at 50% of the recommended concentration to allow a margin that covers the periods of decrease in concentrations during use due to dosing errors or automatic dosing systems. This margin can be calculated with a single strain such as Pseudomonas aeruginosa. In the case of products with more than one active component (e.g., metals and oxidants) the activity of each of them must be demonstrated. The contact times will be as indicated below for each microorganism. The volume of the test with respect to the inoculum volume will be 199: 1. A control with neutralizer must be included with its corresponding validation in the tests. The determination of the concentration of the product at the beginning and at the end of the tests, as well as the controls with chlorine, must be carried out. The density of the inoculum must be 100 times higher than the logarithm of the required reduction. All tests must be done at least in duplicate. The microorganisms used will be: Escherichia coli, Enterococcus faecium, Pseudomonas aeruginosa, Legionella pneumophila, Staphylococcus aureus, Adenovirus, Rotavirus, Naegleria fowleri cysts and Giardia intestinalis or Giardia muris. Contact times will be 30 seconds for all bacteria, except for Enterococcus faecium 2 minutes; Adenoviruses (10 minutes); Rotavirus (2 minutes); Naegleria fowleri (30 minutes); and Giardia spp. (45 minutes). The reduction of microorganisms obtained should be 4 log10 for the five bacteria species, 3 log10 for the two viruses, and 4 and 3 log10 for the cysts of Naegleria fowleri and Giardia intestinalis, respectively.

Phase of evaluation of field in real swimming pools: before being approved for its use, the product must be evaluated in the real conditions of use, preferably a pool and / or SPAs very concurred. In these cases, no microorganisms are added, but samples should be taken from the areas where they can usually be found. To perform the field tests, you must first have passed the safety tests for human and environmental health. The field tests must be designed for a minimum period of 3 months and must be accepted by the regulatory institution in charge of their registration. The tests must be carried out following the ISO 6222 standards for aerobic microorganism counting, showing that there are less than 100 CFU / mL; for thermotolerant coliforms following the ISO 9308-1 standard for the detection of E. coli and coliforms, showing that they are not detected in 100 mL; and for Pseudomonas aeruginosa following ISO 16266, demonstrating that they are not detected in 100 mL. The design of the field study will include the specifications of the pool in terms of dimensions, volume and location; the distribution of water and its circulation; the replacement rate; dosing methods of the disinfectant; filtration, flocculation; presence of rains for outdoor pools; the methodology for the microorganisms tested; the location of the samples for microorganisms and disinfectants; the conditions of transport of samples; the design of the sampling; water temperature and transparency measures; the number of bathers; the relation of the samplings with the presence of bathers; the concentration of disinfectant at the time of sampling; the pH measurement at the time of sampling; the measurement of the total alkaline reserve; the concentration of any other relevant chemical product; etc.