Recreational water illnesses are a major concern for facility operators, with outbreaks up significantly last year. In the fight against these stealthy germs, industry professionals use several approaches based on research, health department regulations and recommendations from the Centers for Disease Control and Prevention.
Here’s a look at some of the traditional methods for fighting these pathogens — and some newer methods that show promise.
One of the most effective tools to prevent the threat of swimmer sickness is still good, old-fashioned chlorine sanitizer. But when chlorine is used against contaminants in pool water, it’s very important to understand that there are varying contact time values to which you need to pay attention. These values depend on the type of pathogenic (disease-causing) microorganism.
For example, giardia has a CT value of 45 minutes at 1 ppm of chlorine. This means that a giardia protozoa is inactivated in 45 minutes of contact with pool water carrying a 1 ppm residual of chlorine.
The problem child of pathogenic microorganisms is cryptosporidium (crypto), which has a CT value of 9,600 minutes or 6.7 days. Consequently, it remains active for at least a week in normally chlorinated pools. Recent studies conducted by the EPA have shown that the average adult swallows up to an ounce of water when swimming. Children usually swallow twice as much as adults. With the possibility of billions of chlorine-resistant crypto cysts present in pool water, it’s easy to see how swimmers can become infected. This is especially true in pools with a high bather load.
Because crypto is so chlorine- resistant and has a size of 4-6 microns, it is very difficult to deal with. The majority of public facilities still use sand filters that only filter down to 25 microns. DE filters can pick up under 4 microns. This may appear to be a solution. However, studies have shown that crypto cysts actually have the ability to elongate and press through filtration media in a viable state.
Existing preventive measures for crypto hardly seem effective, currently ranging from ensuring that swimmers shower, to keeping sick swimmers out of the water.
Hyperchlorination (aka superchlorination) methods are recommended by health departments to deal with the suspicion of possible crypto in pools. The hyperchlorination method is typically 20 to 30 ppm of chlorine for eight to 12 hours. This method may vary depending on local health regulations. The CDC reported in 2004 that there was no conclusive evidence to prove complete eradication of crypto even using this recommended method. Fortunately, there are some alternative methods for dealing with crypto as well as other RWIs.
Ozone is becoming popular as a possible backup means for eradicating crypto. Ozone kills bacteria and crypto cysts 3,125 times faster than chlorine.
Ultraviolet light is another system quickly gaining in popularity. However, note that high turbidity can be a problem that could cause UV systems to become less effective in the fight against crypto. For this reason, health departments also regulate turbidity levels in public pools.
The biggest problem with many public facilities is that they rely on chlorine alone and use sand filtration. Thus, to effectively deal with crypto, expensive upgrades such as ozonators and UV units need to be installed. Many private and publicly funded aquatics facilities simply don’t have the budgets to make such vast improvements.
Regular dilution of water is another means of reducing the risk of illness. This is already practiced on public pools in Europe, where there are requirements of an entire pool being diluted with fresh water over a month’s time. Some other standards suggest adding approximately 8 gallons of fresh water daily for every swimmer in the pool.
Another viable method is enhanced filtration. The CDC and many aquatics experts have long considered filter enhancement with the use of specialty clarifiers such as polymers. The technology in question here uses two opposing biopolymers that quickly and effectively entrap microorganisms such as algae, e.coli and cryptosporidium. This method has been soundly proven through an independent study conducted at Auburn University.
The study showed that when using this method, stable “flocs” of crypto were able to form and thus be able to be held in simulated sand filters. According to further research, there was a 99.99 percent removal of crypto from pool water using sand filtration treated with the two-stage polymer.
Even with these tools, multiple technology layers most likely will be the key to providing safe and disease-free swimming pools. These layers will include a residual of chlorine sanitizer, ozone or UV, regular dilution of pool water and enhanced filtration of microorganisms using a polymer system that is approved for this use.