Putting Water-Borne Pathogens to Rest
Some Misconceptions and Facts
By Christopher Kareis, Ph.D.
Construction of a new or renovation of a current aquatic facility is a daunting task. From ensuring the safety of staff and patrons to compliance with local, state and federal codes and regulations, there are many issues an aquatics manager will have to tackle. One of the most important decisions that will be made is selecting a sanitizing system. Choice of a sanitizing system should not be made on the basis of cost or past experience alone; rather the selection should be tailored to the specific venue. Aside from keeping the appearance of the water pristine, the sanitizing system is also responsible for helping keep the patrons from exposure to waterborne health risks by killing pathogens and oxidizing contaminants. After all, safe and happy patrons are a vital part of an aquatic facility's reputation.
This article will address a few basic aspects of sanitizing systems that aquatics directors and managers should take into consideration when identifying the system best suited for their facility. It is not a comprehensive review of primary and secondary systems. One should always refer to applicable code (e.g., state or local code), standards (such as APSP-11), pool certification training materials (such as CPO or AFO) and manufacturers' directions.
Sodium Hypochlorite or Bleach ('Liquid Chlorine')
Industrial-strength liquid bleach is the most common form of chlorine used in commercial pools. Since the active ingredient, sodium hypochlorite, is already dissolved in water, it is able to quickly increase chlorination levels to adapt to sudden increases in chlorine demand or bather load, assuming appropriate sizing of the bleach pump. Whether pumped from 55-gallon drums, which are well-suited for smaller bodies of water like those found in a health club, or larger polyethylene tanks refilled from a tank truck for large swimming pool venues, secondary containment and adequate safety protocols are needed in case of an accidental release as liquid bleach is highly corrosive.
Misconception: Sodium hypochlorite bleach offers a low-cost method for sanitizing water at aquatics facilities.
Fact: Though the cost of the product itself my appear low, operators need to take into consideration additional costs, such as the acid required for pH balance, secondary containment investment and operator time for maintaining peristaltic or diaphragm pumps.
Misconception: At the time of delivery, the product contains 12 percent strength.
Fact: The strength that is presented typically represents the strength at the time of manufacture. Environmental factors can affect the strength as the product ages in inventory, during delivery and while in storage at the aquatic facility. The only way an operator can verify product strength is to have a chlorine assay kit on-hand and be proficient in its use.
Chlorine Generators (Salt Systems)
Though salt systems have gained in popularity among residential pool owners, they have received limited commercial pool acceptance due to the need to consistently generate enough chlorine to maintain an acceptable residual chlorine level (1- 4 ppm). Also, since the water needs to have a high concentration of salt (typically around 3,500 ppm), big bodies of water such as those found at a municipal pool, university pool or waterpark require larger amounts of salt to be purchased and maintained at the facility to replenish what is lost through dilution. Also, due to high upfront investment costs for the cells and power supplies, on-site chlorine generators may easily be undersized, meaning these systems will not be able to handle a sudden increase in bather loads.
Misconception: Saltwater pools are chlorine-free.
Fact: The term "salt system" is a misnomer. These systems use electrolytic cells to convert saltwater to sodium hypochlorite by use of an electric current. "Saltwater systems" are just another way of chlorinating a pool.
Misconception: Salt systems are "green."
Fact: The cells within the salt systems are inefficient generators of chlorine. The amount of electricity required to generate a pound of chlorine in one of these cells is far greater than in a typical chlor-alkali manufacturing facility.
Calcium Hypochlorite Tablet Systems
Calcium hypochlorite tablet systems are the second-most-prevalent sanitizing system in commercial pools and spas. Increased bather loads are handled by simply increasing water flow into the feeder to erode the tablets more rapidly.
Misconception: All tablets are the same.
Fact: Calcium hypochlorite tablets from one manufacturer have unique dissolve rate and performance characteristics that distinguish them from other tablets. NSF/ANSI 50 certification of a feeder is dependent on the exact tablet specified by the feeder manufacturer. Use of any other tablet will void the NSF 50 certification, which may put the pool out of compliance with applicable code.
Misconception: Calcium hypochlorite tablets will cause scale formation on pool and heater surfaces.
Fact: While calcium hypochlorite does contain calcium, the formation of calcium scale can be controlled with proper water balance. Moreover, calcium buildup in the pool water is usually far less than one might expect. Calcium solids typically are captured in filters and removed during routine backwashing. Normal water replacement also reduces calcium levels in pool water.
Ultraviolet (UV) Systems
Interest in UV systems has been on the rise due to an increased focus on preventing recreational water illnesses. These systems have been proven effective at inactivating chlorine-resistant pathogens like Cryptosporidium. Water clarity plays a huge role in the effectiveness of UV systems, as cloudy or colored water will prevent the UV rays from penetrating through the water.
Misconception: UV systems fully protect against recreational water illnesses.
Fact: While UV systems inactivate bacteria, viruses and other waterborne pathogens, this activity is restricted to the UV contact housing. This UV action does not extend to the pool itself; rather, disinfected water from the UV unit returns to the pool to gradually dilute the germs in the pool. Diluting the germs to zero concentration would take forever. UV provides no residual to protect against bather-to-bather transmission. For this reason, UV systems should only be used for secondary protection. They are not EPA-registered or NSF-certified as primary disinfectants.
The views expressed in this article are those of the author and should not be attributed to Axiall Corporation. Axiall assumes no liability, obligation, or responsibility, express or implied, in connection with the information the author has presented or the use thereof.
The information and recommendations the author has provided herein are based on the best available information, data and practices currently known to the author and are provided for informational purposes only. The author does not guarantee, represent, or warrant the performance or results to be obtained by using the information or by following the guidance and recommendations presented. The author assumes no liability, obligation, or responsibility, express or implied, in connection with the information and recommendations presented or the use thereof.
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