Recent studies conducted by the Environmental Protection Agency (EPA) have shown the average adult bather swallows up to 29.5 mL (1 oz) of water when swimming. Children typically ingest twice as much. With the possibility of billions of chlorine-resistant Crypto cysts present in pool water, it is easy to see how swimmers can become infected. This is especially true in pools with high bather loads.
Due to the fact Crypto is extremely chlorine-resistant and ranges between four and six microns, it is difficult to deal with. The majority of aquatic facilities still use sand filters, which are only capable of filtering down to 25 microns. Many residential pools, however, have filters that use diatomaceous earth (DE) media, which can pick up particles under four microns. This may appear to be the solution, and some service professionals may think Crypto would not be a problem in a pool with a DE filtration system; however, studies have shown Crypto cysts have the ability to elongate and press through filtration media in a viable state. (see Figure 1)
Current preventative measures for Crypto currently range from ensuring swimmers shower, to keeping sick bathers out of the water. However, these measures alone are not enough to keep an outbreak from happening.
Other methods for dealing with RWIs
Ozone is becoming popular as a possible backup means for eradicating waterborne pathogens. In fact, ozone kills bacteria and Crypto cysts 3125 times faster than chlorine.
Ultraviolet light (UV) is another sanitizing system that is quickly gaining in popularity. In fact, after an outbreak at a splash park in New York in 2005, the State of New York has mandated the use of UV on all public splash park facilities. However, high turbidity of the water can be a problem that could cause UV systems to become ineffective against Crypto. For this reason, health departments also regulate turbidity levels in public pools.
The biggest problem with many public facilities is they rely only on chlorine, and use sand filtration. Thus, to effectively deal with Crypto, expensive upgrades such as ozonators and UV units need to be installed, and many private and publicly funded aquatic facilities do not have the budget to make these upgrades.
Some health departments also recommend hyper-chlorination methods when dealing with the suspicion of Crypto in pools. This typically entails raising chlorine levels between 20 and 30 ppm for eight to 12 hours. This method may vary depending on local health regulations. In 2004, however, the CDC reported there was no conclusive evidence to prove complete eradication of Crypto using this recommended method.
In North America, the standard protocol for water quality maintenance (WQM) is premised on the assumption appropriate filtration and residual halogen disinfection will inactivate all pathogens. Experts agree that moving beyond the basics will require revising the two-pillar approach that includes filtration and halogen, and adopting supplemental disinfection for water quality management in pools and spas/hot tubs.
The costs involved in preventing RWIs using ozone, UV, and regenerative filters can create sticker shock for those aquatic facility managers who have budget constraints. As a result, it may prevent some smaller facilities from taking these additional measures.
Inline UV disinfection is recognized as an extremely effective and reliable method for deactivating pathogens in pool water and reducing the bather’s exposure to disinfection byproducts. Some public health authorities are already beginning to mandate supplemental inline UV disinfection. In addition to New York State, several other states and provinces, such as Florida and Ontario, amongst others, now mandate supplemental inline UV disinfection.
