Recreational waters are those in which primary contact occurs. Primary contact recreation activities are those that could be expected to result in the ingestion of, or immersion in, water (e.g., swimming, water skiing, and kayaking). There are two general types of recreational waters. The first type includes natural sources of water, such as lakes, streams, and coastal waters, where the water source cannot be disinfected and where these sources are at risk for contamination via point sources, such as sewage and industrial waste, and nonpoint sources, such as streams, storm drains, and animals (e.g., birds and bathers). Natural sources of water are used primarily for swimming, wading, and surfing. The second type of recreational water is found in facilities using municipally treated water; it should be disinfected continuously. The designated uses of this type of water may be recreation, such as swimming pools, or therapy, such as whirlpools. Ideally, the quality of recreational water is suitable for its designated use.
Historically, concentrations of selected microorganisms have been used to determine the suitability of recreational water for its designated use. Recreational water quality indicators are microorganisms for which densities in the water can be related quantitatively to the degree of potential contamination with pathogens and thus health hazards resulting from recreational use, particularly where upper body orifices are exposed to water. These indicators are used to determine whether recreating in the water may be detrimental to human health. The ideal indicator has the best correlation between density and the health hazards associated with a given type of pollution. It also is consistently and exclusively present when the contaminant is present, occurs in higher densities than the contaminant, cannot proliferate more than the contaminant, is more resistant to environmental stresses and more persistent than the contaminant, and has characteristic, simple reactions for easy, simple identification.1
Correlations between microbial density in water and predictable disease have been established for exposure to natural sources of recreational water but not for recreational waters that are routinely disinfected. Epidemiological research shows a correlation between gastroenteritis and concentrations of Escherichia coli and enterococci in natural fresh water sources used for swimming. Further, results showed that gastroenteritis positively correlated with concentrations of enterococci in fresh and marine waters used for swimming. This research involved water from beaches contaminated by known point sources.1 Water quality standards have been established using these indicators of fecal contamination. National Pollutant Discharge Elimination system (NPDEs) permits and state permits authorized by the NPDEs program require dischargers to monitor such waters for the parameters included in their permits. For discharges into coastal recreational waters, any permits including fecal indicators likely require monitoring for enterococci or E. coli. For continuously disinfected water, such as water in swimming pools and whirlpools, concentrations of disinfectant (e.g., free and total chlorine, bromine) are frequently monitored. In many US communities, suitability of such waters is based primarily on hourly (pH, temperature, and disinfectant) or daily (hardness and alkalinity) water-chemistry measurements rather than frequent monitoring for microorganisms or correlation with predictable health effects. The frequency and type of parameters measured depend on the individual state, county, or municipal swimming pool codes. Although most swimming pools are disinfected with chlorine, bromine or a nonhalogen-based system may be used. If chlorine is used, free chlorine typically is monitored hourly (occasionally total chlorine also is monitored).