Risks associated with recirculating splash pad design
From a water feature design perspective, major concerns have been associated with splash pads that are operated with recycled water and/or with holding tanks, as standard pool filtration and chlorination are not effective against Crypto. Chlorine is ineffective in the inactivation of this parasitic disease, with kill times ranging from more than a week at 100 parts per million (ppm).
Some microbiological organisms (e.g. parasites) can bioaccumulate in holding tanks and be difficult to remove and kill off in some spray park designs, such as recirculating splash pads. These facilities present a more significant health risk, as water is recirculated and recycled rather than using a continuous flow of treated potable drinking water, whereby used water is discharged directly to waste.
Additional risks are presented when toddlers, who are not toilet trained, bathe in training pants and/or diapers, as this can lead to fecal accidents. Children and toddlers often carry a number of micro-organisms picked up throughout their daily routine, from person-to-person contact (e.g. family members and playmates) and their surroundings (e.g. institutions, schools and daycare facilities). These micro-organisms can include bacteria like E. coli and pathogenic parasites, such as Crypto and Giardia (cyst and oocyst), which can be very persistent in recreational waters and have a low effective dose rate.
In the occurrence of a human fecal accident at a splash pad, used water is collected and discharged by gravity directly into the deck floor drains around the splash pad. If the system is designed using a reservoir, these liquids are then concentrated in a holding tank along with other suspended dirt, debris, organic materials and other fecal matter from domestic pets and wildlife.
Reducing micro-organisms through filtration
While chlorine is not effective against Crypto in both public pools and splash pads, the latter are more prone to these outbreaks. This is likely because filtration systems at public pools normally operate 24-7, which results in a larger turnover rate; undesirable micro-organisms are continuously filtered out. Public pools also have a much larger water volume, and are by law required to add a certain amount of fresh water—depending on the daily bather load—and subsequently send the equivalent amount of ‘old’ water to waste. This process decreases the micro-organism count per volume of water. (Based on the simple toxicological thinking, “Dilution is part of the solution.”) On the other hand, the relatively smaller water volume contained in a recirculating splash pad facility’s holding tank, which may not be continually filtered 24 hours a day, allows micro-organisms to bioaccumulate, thus increasing the micro-organism count per volume of water and bather risk.
Cryptosporidiosis occurs due to exposure from contaminated water and food. When dealing with parasite transmission risks, multi-barrier removal and inactivation techniques should be in place to protect bathers from contracting such diseases. This includes the use of a high-rate filtration system, such as micro-filtration, slow sand and/or ultra filtration (to remove Crypto, a filtration pore size less than one micron is desirable). Inactivation and suitable disinfection techniques, which deal with pathogenic micro-organisms and parasites, are required. One popular example is the use of an ultraviolet treatment (UVT) device. UVT devices use specifically targeted UV radiation to inactivate microbial contaminants such as chlorine-resistant parasites. If using such a device, it should also be equipped with self-cleaning capabilities and a built-in, fail-safe device, such as a sensor/alarm for turbidity and UV light transmittance monitoring.
