An article by Bonnie B. Sandel from Aquatics International, a magazine devoted to the commercial and public swimming pool industries; posted with permission from Aquatics International

Otitisexterna, Pseudomonas folliculitis, Pontiac fever, Legionnaires' disease, gastroenteritis, cryptosporidiosis, Giardiaisis, candida, athlete's foot, bacteria, viruses, fungi and protozoans.

The last thing you want the public worrying about is how good their immune systems are, but with the list of possible waterborne diseases, it could be a valid question. How well you maintain your pool and spa can make the difference between a healthy, refreshing dip and a bath in a microbial soup.

Every two years the Centers for Disease Control and Prevention (CDC) publishes a summary of waterborne disease outbreaks they have investigated. Included is a listing of outbreaks associated with recreational water: waterparks, swimming pools, spas, whirlpools, lakes, rivers and beaches. The CDC records show that inadequate disinfection of swimming pools and spas can lead to serious consequences.

A shipboard outbreak of Legionnaires' disease was linked to a heavily used spa where buildup of oils and other organic matter on the filter had turned the sand black and created a haven for microbes. When air jets were used, the bacteria in the aerosol infected people who merely sat on deck near the operating spa.

The most frequently reported outbreak in recreational water is dermatitis -- itchy, sore, infected skin brought on by the use of a whirlpool or spa which is loaded with Pseudomonas aeruginosa bacteria.

Ironically, this disease, which is readily prevented by the use of an adequate residual from a chlorine-based sanitizer, is often blamed by patrons on too much chlorine, citing the odor around the facility. Both the odor—from chloramines—and the itching—from bacteria—could be reduced by using more chlorine, but too often misguided operators cut back still further on their use of the very sanitizer that could solve the problem.

The CDC admits that reported outbreaks are only a fraction of the total. They do not pick up residential pool problems and it's a rare public health department that has enough staff to track cases of mild gastrointestinal infections or swimmer's ear. Nevertheless, their reports are good motivation for ensuring that swimming pool and spa sanitation is adequate.

Wise sanitation practices will help limit the public's exposure to microbial risk. These practices include a combination of careful cleaning and sanitation, properly handled water treatment and management of bathers through rules and recordkeeping. Disinfection is the primary weapon against microbial risk, but attention to bather and surface cleanliness will pay off in more efficient disinfection.

Restrict The Microbe's Diets

While bathing, adults will typically shed a layer of dead skin cells, a pint or more of perspiration, a small amount of urine, and a few grams of oils and cosmetics. This organic matter may build up to become both a haven and a food source for microbes unless it is physically or chemically removed.

Some precautions can reduce the amount of organic material that could build up in the water, filters and circulation systems. For example, the amount of organic material that makes it into the water can be reduced if users are required to take a quick shower before entering the pool or spa.

The amount of buildup can also be limited if attention is paid to the number of bathers. Tracking the number of simultaneous users and restricting it to that appropriate for the size of the spa is especially important in maintaining a healthy spa environment.

A sudden influx of users in excess of safety or health codes may overwhelm the system's ability to provide sanitizer residuals. In addition, the warm water and relatively low volume of water per bather combine to buildup organic matter in a spa much more rapidly than in pool water. A program of thoroughly draining and cleaning spas after a calculated number of uses will help prevent the spa from becoming a haven for bacteria.

To limit the buildup of organic matter in pools, a similar program where a set amount of water (for example, 8 to 15 gallons) per bather is replaced daily, has been included in some public health codes. In others, the buildup of total dissolved solids (TDS) is monitored. Because each user leaves behind some salts as well as organic matter, TDS buildup is related to the age of the water and the number of users. Some health codes recommend partial water replacement when levels have risen by 2,000 or 3,000 parts per million (ppm) above the source water.

Keeping the pool water clean through regular destruction of dissolved organic material is another aspect of good sanitation. Chlorine-based sanitizers are effective at oxidizing bather and bacterial waste. In some outdoor pools, maintaining a constant adequate residual of available chlorine of 1 to 3 ppm suffices to keep organics from building up if a properly calibrated controller is combined with adequate feed and circulation designs that ensure distribution throughout the system.

However, most other pools and all spas will require periodic shock treatment (superchlorination). This requires that free chlorine levels be raised to between 5 and 10 ppm, or 10 times the combined chlorine level, whichever is greater. The time between shock treatments will depend on the rate of organic matter entering the pool. Heavily used spas may require daily shocks; lightly used pools may only need it every other week.

Clean pool surfaces also help to reduce the number of places where microbes can breed and feed. Scrubbing visible surfaces, cleaning skimmers and traps, and attending to filter cleaning on a regular basis will result in a more efficient use of sanitizing chemicals.

Residuals Ensure Health

The most important thing the operator can do to ensure the health of people using pools and spas is to maintain the proper residual of sanitizer in the water at all times. In most states, the required residual of available chlorine is between 1 and 3 ppm in pools and between 1 and 5 ppm in spas. Some states allow a residual of bromine or another sanitizer provided it can be shown to keep the microbial risk low.

Chemicals which provide available chlorine include chlorine gas, liquid bleach (sodium hypochlorite solution), calcium hypochlorite, lithium hypochlorite and the chlorinated isocyanurates, usually called dichlor and trichlor.

Because bacteria are constantly being added to the water from the environment and from bathers, a disinfectant must be present at all times. Chlorine gas and the hypochlorites are universally accepted for use in pools and spas because the chlorine supplied by chlorine-based sanitizers is the strongest oxidizer that persists in a pool. Most of the billions of bacteria that enter the pool with each dive are killed within 30 seconds, preventing bather-to-bather infections.

Residual chlorine also kills pseudomonads entering from the environment, making dermatitis and ear infections unlikely.

Disinfectants must be effective against a wide variety of organisms. Chlorine deactivates a variety of microorganisms at rates dependent on the species. Bacteria and viruses are destroyed within seconds, while the slower destruction times of Cryptosporidium and Giardia require special care in avoiding and taking care of fecal accidents.

In addition to rapid kill and persistence in water, an effective pool or spa disinfectant should destroy pathogens, not merely injure them, and should not allow resistant bacteria strains to grow up. Chlorine-based sanitizers are effective disinfectants that retain their ability to maintain water purity over weeks, months and years of use, demonstrating that resistant strains of bacteria don't readily develop. This means that the bacteria which infect ears and open pores will not grow up in the pool this season—or next.


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