Avoiding recreational water illnesses

by Sally Bouorm | October 1, 2013 3:23 pm

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By Dave Callahan

Recreational water illnesses (RWIs) are always a hot topic of discussion at the end of summer when higher bather loads at commercial aquatic facilities force filtration systems to work overtime to keep pool water clean and clear. Unfortunately, there are always outbreaks—some bigger than others, which everyone hears about via mainstream media. This article is not going to discuss the graphic descriptors of these microscopic invaders, but rather look at the methods for destroying and keeping these bugs out of pools.

Cryptosporidium (Crypto) outbreaks happen every year. Usually by mid-July and early August, news media have reported outbreaks that originate in commercial aquatic facilities. Unfortunately, traditional chlorine disinfection systems are not enough to battle Crypto, which are highly resistant to chlorine (Cl) and can linger in a pool for up to a week. When bather loads are high and users are swallowing pool water while swimming and playing in pools, facility managers need to have systems in place to help prevent the introduction of Crypto cysts along with methods of removing them from pool water.

A two-pronged approach to avoiding an outbreak should first involve physical steps to preventing the introduction of cysts into the pool water by bathers, followed by implementing secondary systems to trap, remove, and/or deactivate the pathogen cysts so they are rendered inert and harmless should they be ingested by bathers.

Aquatic facilities can avoid a Crypto outbreak by putting a prevention plan in place to try to prevent pool water contamination and by incorporating a secondary sanitation system to remove dangerous Crypto spores from the water, assuming they will likely enter the pool at some point.

Fighting the good fight

In the fight against these stealthy germs, industry professionals use several approaches based on research, health department regulations, and current Centers for Disease Control (CDC) recommendations. One of the most effective tools to prevent the threat of swimmer illnesses is still good old-fashioned chlorine sanitizer.

Due to its proven ability to disinfect, chlorine became popular for swimming pool use in the 1920s. In 2000, Life magazine called the use of chlorine as a disinfectant in water “one of the most important inventions of the last thousand years.”

When chlorine sanitizer is used against contaminants in pool water there are varying contact time (CT) values that exist depending on the type of pathogenic (disease causing) micro-organism. For example, Giardia has a CT value of 45 minutes at 1 parts per million (ppm) of chlorine, i.e. a Giardia protozoa is inactivated in 45 minutes of contact with pool water carrying a 1 ppm residual of chlorine. Norovirus can take approximately 30 to 60 minutes to become inactivated[2].

The problem child of pathogenic micro-organisms is Crypto as it has a CT value of 160 hours or 6.7 days; therefore, this pathogen remains active for a week (or longer) in traditional chlorinated pools. Recent studies conducted by the U.S. Environmental Protection Agency (EPA) have shown the average adult swimmer swallows up to 29.5 ml (1 oz) 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 is easy to see how swimmers can become infected. This is especially true in pools with high bather loads. Because Crypto is extremely chlorine resistant and is only four to six microns in size, it is very difficult to deal with should an outbreak occur.

Further, the majority of public facilities still use sand filters, which only filter down to 25 microns. On the other hand, many residential pools use diatomaceous earth (D.E.) filtration media, which is capable of picking up micro-organisms under four microns; however, studies have shown Crypto cysts actually have the ability to elongate and press through filtration media in a viable state.

Have a good backup plan

Unfortunately, not only are RWIs dramatically increasing, but research has also shown halogen disinfection creates hazardous byproducts. These disinfection byproducts (DBPs) include chloramines, trihalomethanes (THMs), haloacetic acids (HAAs), and other contaminates that are recognized to have serious negative health effects. It is also established that certain pathogens are resistant to chlorine and ozone, thus leading to various diseases including respiratory, skin, and gastrointestinal problems.

Awareness and concern about exposure to DBPs in pools and spas is increasing at an alarming rate. As a result, health officials have acknowledged the increase of RWIs and negative health effects associated to DBPs necessitates a paradigm shift in how pool and hot tub water is treated.

Experts agree, moving beyond the basics will require revising the two-pillar approach, which includes filtration and halogen, followed by adopting supplemental disinfection for water quality management (WQM).

Today’s three known and popular measures for the prevention of Crypto (and other RWIs for that matter) include the use of ultraviolet (UV) light, ozone, and enhanced filtration.

UV light

Inline UV disinfection is recognized as an extremely effective and reliable method for deactivating pathogens in the water and reducing the bathers’ exposure to DBPs. Many public health authorities are already beginning to mandate supplemental inline UV disinfection. For example, after the Crypto outbreaks in upstate New York a few years back, New York State now mandates this equipment on all public splash parks as do several other states and provinces, such as Ontario.

Ozone

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Using ozone as a secondary oxidizer destroys ammonia and nitrogen, preventing the formation of chloramines. As a disinfectant, this technique requires a large unit to disinfect by injecting the ozone into a side stream (between 10 and 25 per cent of the water) and then returns it into the full flow. Ozone is capable of killing bacteria and Crypto cysts 3,125 times faster than chlorine.

Enhanced filtration

One viable and more affordable method that any facility or pool can begin using immediately is enhanced filtration. This technology uses two opposing biopolymers that quickly and effectively trap micro-organisms such as algae, Escherichia coli (E. coli), and Crypto.

This method of enhanced filtration has been soundly proven through an independent study conducted at Auburn University, which was presented at the World Aquatic Health Conference (WAHC) in 2005. The study showed very stable flocs of Crypto were able to form and be held in simulated sand filters. According to another presentation at the 2006 WAHC, there was a 99.9 per cent removal of Crypto from pool water using sand filtration treated using the two-stage polymer.

Giving swimming pool filters the ability to trap more debris is the idea behind enhanced filtration products. Using characteristics of naturally occurring biopolymers, which are widely used for clarification of pools as they showed a superior capacity to flocculate (or form larger clumps) and sediment suspensions of particles in water.

The pore paths in sand beds are typically 50 microns and up; therefore, the enhanced filtration products must generate clumps this large to be successful. Enabling filter media to remove particles that are in the submicron size allows for the removal of microbial organisms. The most troublesome RWIs measure a few microns (or smaller), and therefore, they typically pass through most filters with the flow of water.

How does enhanced filtration work?

First, it is important to understand the complicated inner workings of a depth filter (e.g. sand bed), as it traps particulates suspended in the incoming water. For example, there are lots of influences on surface charge, particle size, conformation, rigidity, density, etc., on the nature of the path taken by the particles, and the frequency of their collisions and interactions with the filter medium.

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The outcome is simple to understand; smaller particles tend to make it through the filter bed and come out in the effluent, whereas larger particles stand a greater chance of getting trapped en route. All of the retained particles alter the total amount of tortuous path available within the filter bed for the next influx of water. The pathway is restored for future entrapment after periodical backwashing of the filter medium. Properly maintained depth filters do a fine job of keeping swimming pool water free of debris, which become suspended in the water during normal use of the pool.

In terms of enhanced filtration, molecular weight, shape, charge, and absolute and relative concentrations of the biopolymers, plus timing of exposure, are all critical factors. In fact, data from laboratory experiments showed with the proper polymer treatment, inert particles (bentonite clay was used for the purpose of the study) could be flocculated into larger clumps, enabling many of the resulting aggregates to be removed in a single filter bed pass. Later experiments involving biological as well as other inert particle types showed similar success, even to the extent that suspensions of live Crypto cysts could be taken out at a rate of 99.9 per cent in a single pass through sand.

Accomplishing this required sequential treatment of pool water with two differently acting biopolymers—one charged positively, the other negatively. In the right proportions and concentrations, these results could be achieved reliably and repeatedly.

Positively charged polymer molecules (stage one) alter surface charges on small particles in water, destabilizing the normal tendency they have to repel one another (and therefore, keep separate and fully suspended, indefinitely). The particles aggregate and become enmeshed in the lattice of long, cross-linked polymer molecules to form much bigger clumps. If the concentration of the cationic (positively charged) polymer is too low or high, this does not happen.

Negatively charged polymers (stage two) then entangle the complexes, firming them up so they can withstand being trapped in the filter bed until the filter is backwashed, taking them into the waste stream. The net effect is Crypto cysts, which are normally capable of passing through sand bed and other particulate filter media, become trapped as cyst-polymer complexes and get removed from the circulating water.

Crypto is not the only biological agent that can be trapped in this manner; other waterborne microbes (e.g. Giardia and E. coli), as well as algae, are similarly affected. Polymer additions for large pools can be accomplished by controlled metering, but a manual process, properly timed, also is entirely practical for smaller scale operations.

Stage one and two polymers are completely biodegradable and safe for bather exposure. The concentrations required are also extremely low (in the parts per billion [ppb] range). With particle removal possible at the submicron level, overall water clarity also improves. Thus, giving sand filters the ability to trap such small particles offers operators a new way to fight RWIs and improve water quality.

 

 

Dave Callahan is the commericial aquatics manager for Halosource Inc., the parent company of the SeaKlear® brand of water treatment products based in Bothell, Wash. He has several years’ experience in the commercial sector, and previously managed the company’s sales in the mid-west U.S. He can be reached via e-mail at dcallahan@seaklear.com[5].

Source URL: https://www.poolspamarketing.com/trade/avoiding-recreational-water-illnesses/

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