User:NMS Bill/Swimming pool santitation proposed changes/Prevention of diseases in swimming pools and spas

Prevention of diseases in swimming pools and spas

Disease prevention should be a priority for every water quality management program for pool and spa operators. Disinfection is critical to protect against pathogens, and is best managed through routine monitoring and maintenance of chemical feed equipment to ensure optimum chemical levels in accordance with state and local regulations. Ideal chemical parameters include disinfectant levels according to regulated pesticide label directions, pH between 7.2-7.8, total alkalinity of 80-120 ppm and calcium hardness between 200 – 400 ppm.

The education of parents of small children and other people with regard to good hygienic behavior at swimming pools is also important for improving health safety at swimming pools and spas. Showering before swimming can reduce introduction of contaminants. Those with diarrhea or other gastroenteritis illnesses should not swim, especially children. To minimize exposure to pathogens, swimmers should avoid getting water into their mouths and never swallow pool or spa water.

Chlorine and bromine as primary methods of disinfection

Conventional halogen-based oxidizers such as chlorine and bromine are convenient and economical primary sanitizers for swimming pools and provide a residual level of sanitizer that remains in the water. Chlorine-releasing compounds are the most popular and frequently used in swimming pools whereas bromine-releasing compounds have found heightened popularity in spas and hot tubs. Both are members of the halogen family with demonstrated ability to destroy and deactivate a wide range of potentially dangerous bacteria and viruses in swimming pools and spas. Both exhibit three essential elements as ideal first-line-of-defense sanitizers for swimming pools and spas: they are fast-acting and enduring; they are effective algaecides; and exhibit strong oxidizer action of undesired contaminants.

Swimming pools can be disinfected with a variety of chlorine-releasing compounds. The most basic of these compounds is elemental chlorine gas (Cl₂); however, its application is primarily in large commercial public swimming pools. Inorganic forms of chlorine-releasing compounds frequently used in residential and public swimming pools include sodium hypochlorite commonly known as liquid bleach or simply bleach, calcium hypochlorite and lithium hypochlorite. Chlorine residuals from elemental chlorine and inorganic chlorine-releaseing compounds break down rapidly in sunlight. To extend their disinfectant usefulness and persistence in outdoor settings, swimming pools treated with one or more of the inorganic forms of chlorine-releasing compounds can be supplemented with cyanuric acid -- a granular stabilizing agent capable of extending the active chlorine residual half-life (t_½) by four to six fold. Chlorinated isocyanurates, a family of organic chlorine-releasing compounds, are stabilized to prevent UV degradation due to the presence of cyanurate as part of their chemical backbone.

Maintaining an effective concentration of disinfectant is critically important in assuring the safety and health of swimming pool and spa users. When any of these pool chemicals are used, it is very important to keep the pH of the pool in the range 7.2 to 7.8; higher pH drastically reduces the sanitizing power of the chlorine due to reduced oxidation-reduction potential (ORP), while lower pH causes bather discomfort, especially to the eyes.

Chlorine reacting with urea in urine and other nitrogen-containing wastes from bathers can produce chloramines. Chloramines typically occur when an insufficient amount of chlorine is used to disinfect a contaminated pool. Chloramines are generally responsible for the noxious, irritating smell prominently occurring in indoor pool settings. A common way to remove chloramines is to "super-chlorinate" (commonly called "shocking") the pool with a high dose of inorganic chlorine sufficient to deliver 10 ppm chlorine. Regular superchlorination (every two weeks in summer) helps to eliminate these unpleasant odors in the pool. Levels of chloramines and other volatile compounds in water can be minimized by reducing contaminants that lead to their formation (e.g., urea, creatinine, amino acids and personal care products) as well as by use of non-chlorine "shock oxidizers."

To help ensure the health of bathers and protect pool equipment, it is essential to perform routine monitoring of water quality factors (or "parameters") on a regular basis. This process becomes the essence of an optimum water quality management program.

Other methods of sanitization

Conditions sometimes exist in heavily-used commercial and/or public swimming pools whereby supplemental oxidation is warranted. In these instances Advanced Oxidation Processes (AOPs) can be employed whereby water contaminants are oxidized by one or more of four different precursors: ozone, hydrogen peroxide, oxygen, and air in combination with UV radiation and in some instances a catalyst such as titanium dioxide (TiO₂). These AOPs react with water (H₂O) to produce powerful oxidants such as hydroxyl radical (OH·), singlet oxygen (O) and molecular oxygen (O₂).