Strategies for chloramine removal: Best practices for maintaining proper air and water quality at indoor pools

by Samantha Ashenhurst | March 27, 2019 3:18 pm

By Frank H. Goldstein and Michael Lowry

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Indoor recreational water facilities across North America see millions of visitors a year enjoying swimming, soaking, and just plain fun during the colder seasons. Whether it is at a pool, spa, or hot tub at a ski resort, waterpark, hotel, YMCA, or municipal facility, there are plenty of opportunities for family aquatic fun. However, all this activity can put a strain on the water and air quality within the aquatic venue. Dealing with these issues, particularly at an indoor facility, can be a daunting task. These issues can affect the comfort of bathers/swimmers, as well as the health of the staff that are there for longer periods.

Chloramines are formed when free chlorine reacts with perspiration, urine, and other nitrogen-containing contaminants that are introduced into the water which create a demand on the free chlorine. Free chlorine reacts with these contaminants to produce chloramines, also known as combined chlorine, that created a demand for free chlorine. When this reaction is allowed to progress, some of the chloramines produced are volatile and gas-off creating poor air quality, which leads to bathers/swimmers complaining about stinging eyes, nasal irritation, or difficulty breathing within the aquatic facility.

Many people think this odour is a result of too much chlorine; however, what it really means is too much combined chlorine. Some volatile chloramines, along with high humidity, also contribute to the corrosion of metal components within the aquatic venue. Chloramines can also be introduced into the aquatic environment via the domestic fill water added to the pool, as some municipalities use chloramination for disinfection.

Chloramines can exist either as monochloramine (NH₂Cl), dichloramine (NHCl₂), or trichloramine (nitrogen trichloride [NCl₃]). The NCl₃, according to White’s Handbook of Chlorination and Alternative Disinfectants, “is easily aerated because of its low solubility in water.” NCl₃ is the volatile substance that is irritating to the eyes and nose of bathers/swimmers and corrosive to structural metallic components of the venue. The effects of trichloramine are even more pronounced in a confined, humid room where little or no air is circulated.

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When free chlorine reacts with organic substances it creates organic chloramines which are much more difficult to remove from the water than inorganic, ammoniated, or nitrogen-based chloramines. Any chlorine-based compound resulting from this reaction is called a disinfection byproduct (DBP). DBPs include organic compounds found in body lotions (e.g. deodorants and sunscreens), bathing garments, various body fluids, and fecal matter on the bather. DBPs also form when free chlorine reacts with fecal coliform bacteria, creatine, L-histamine, chloroform, and excess medication found in urine, along with the urea found in urine itself. While it is known these compounds exist at this point in time, it is not known at what levels they become toxic in an aquatic venue. Competitive swimmers and pool personnel may be at greater risk for inhalation of volatile substances as they remain in the aquatic environment for longer periods of time than the average bather/swimmer.

While there are many strategies for dealing with this problem they fall into several distinct groups; chemical treatments, supplemental sanitizers, filter additives, and, lastly, heating, ventilation, and air conditioning (HVAC) systems.

In Germany and in other European countries, the chlorine used to deal with bather demand is kept low, usually below 0.5 parts per million (ppm). This low chlorine residual is maintained because of the use of supplemental sanitizing systems that can achieve the same or better oxidative or disinfectant results. With a low free chlorine level, combined chlorines simply cannot form in concentrations higher than the available chlorine despite the concentration of ammonia. Ozone and chlorine dioxide are examples and are strong oxidizers and sanitizers that can be used to supplement the chlorine. In North America, the use of ozone, ultraviolet (UV)-C light, and advanced oxidation process (AOP) are examples of strong oxidizers that can be used to supplement the chlorine in the pool.

Chemical treatments

Dilution

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‘Dilution is the solution to pollution.’ In most cases, this method can work to reduce chloramines, total dissolved solids (TDS), and other contaminants in pool/spa water. If the source fill water contains chloramines they should be removed before they enter the recreational environment to prevent any problems. Therefore, it is important to know what is in the source water.

As of July 1, 2018, the Ontario Health Protection and Promotion Act Regulation 565 Section 7, subsection 13 (R.R.O.1990, Reg. 565, s. 7 [13]) states:

(13) Every operator shall add make-up water to the pool during each operating day in a minimum amount of 15 L (3.96 gal) per bather as determined by a water meter installed for the purpose.

For those pools not under the authority of Ontario Regulation 565, another method to achieve dilution of these contaminants is to purposefully drain 51 to 102 mm (2 to 4 in.) of water out of the pool each week after closing to the public and replacing it with fresh fill water. This 51 to 102 mm (2 to 4 in.) of water is in addition to normal water loss from bather splash-out/run-off, evaporation, and backwashing tasks.

Once the water has been added, the pool water needs to be tested and the chemical balance should be adjusted accordingly. Depending on how many bathers/swimmers have been in the water during that last week determines whether to use the lower or higher level of this dilution range. By performing this task at closing it allows the fresh fill water to be heated overnight so water in the pool/spa reaches the appropriate temperature when opened the next morning.

Due to the higher bather-to-water ratios in spas/hot tubs, water replacement is a more effective and economical strategy then continually adding more chemicals to try and maintain healthy water. Completely draining and filling the water in spas/hot tubs is the standard strategy rather than partial replacement as these vessels typically contain a much smaller volume of water than a pool.

The suggested method of determining when to drain a spa/hot tub may be different based on where the facility is located and may not be specified in the local regulations. The most common formula to determine when to change the water in a spa/hot tub is:

Water replacement interval (WRI) (days) = (¹/₃) x (water volume in U.S. gallons) ÷ (number of bathers per day).

In Ontario, the regulation guiding draining for spas/hot tubs under 4000 L (1056 gal) is:

WRI (days) = Total volume in litres ÷ (10 x Total estimated number of bathers uses per operating day).

Essentially, what this formula says is the number of days between water replacements, or draining the spa/hot tub, is when the number of bathers who have used the spa/hot tub equals one-third the gallons of water in the vessel.

If the spa/hot tub holds 1514 L (600 gal) of water, then one third of that is 757 L (200 gal). When approximately 200 bathers have used the spa/hot tub, it should be drained, flushed, and refilled with fresh water. Then, the system should be restarted and the water chemistry adjusted back to proper levels.

Keep in mind, in spas/hot tubs chemicals are typically added in measurements of teaspoons and tablespoons, making it a fairly inexpensive way of handling bather waste, TDS, and chlorine demand issues.

Aeriation

In France, one solution to this problem is to aerate the water outside to confines of the pool enclosure forcing the volatile combined chlorine into the atmosphere. Air is forced into a chamber, such as an exterior surge tank, and the combined chlorine goes from an aqueous form to a gaseous form, allowing the bad air to be discharged where bathers are not present.

Breakpoint chlorination

When combined chlorine concentrations exceed 0.2 ppm in the water it may start to produce eye and nasal irritation as it is gassing off into the pool atmosphere. One of the simplest and least expensive ways to deal with this is called breakpoint chlorination.

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If the concentration of combined inorganic chlorine in the water is known, it can be burned off chemically by adding 10 times the concentration in new, free chlorine to the pool water. For example, if the combined chlorine concentration is 0.3 ppm, it would take 3 ppm of new free chlorine to burn off the combined inorganic chlorine present in the water. How much product this would entail depends on the form and concentration of the chlorine product being used.

This process will remove the odour of the ammoniated combined chlorine which is what most people are worried about. However, it will not be sufficient to remove the organic chloramines that may buildup over time. A dilution program or one of the following strategies must be employed to remove these.

How often is breakpoint chlorination needed? It depends mostly on bather load, gallons of water the bather load is impacting, and how quickly the chloramines build up. In a busy facility this might need to be performed daily as part of the closing procedure. On the other hand, in a small, rarely used venue, this might have to be done only once a week or even every two weeks.

When volatile chloramines go into the venue environment the air handling system (HVAC) is tasked with removing these gasses and discharging them outside.

In some cases, there are insufficient fresh air exchanges in the venue and these gasses remain in the environment. When inhaled by bathers/swimmers and staff, they can potentially create breathing problems. In some pools this insufficient fresh air is such a great problem that when the venue is being breakpoint chlorinated the fire doors need to be opened and exhaust fans set up to force the malodorous air out of the building.

If these volatile chloramines are not removed from the air and are allowed to sit above the pool surface, these gasses go back into water thereby increasing the concentration.

As for pool and spa/hot tub regulations in Canada, some provincial codes put limits on the combined chlorine concentration in the pool water, but due to the complexity of testing chloramines in the air, the limits are not regulated. The regulations in Ontario (R.R.O.1990, Reg. 565, s. 11 [1]) state:

(1) Every owner and every operator of a public pool or public spa shall ensure that the pool or spa, the deck and, where provided, the dressing and locker rooms, water closets, showers and connecting corridors appurtenant to the pool or spa are,

        (a) Kept clean, free from slipperiness and disinfected;

        (b) Free of hazardous obstructions; and

        (c) Ventilated so as to remove odours.

Non-chlorine oxidizers

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Non-chlorine oxidizers are oxygen-based oxidizers that will remove bather waste by destroying organic and inorganic pool contaminants. The active ingredient in these products is potassium monopersulfate (KMPS). They are odourless, fast acting, and completely dissolve in the water.

KMPS oxidizes chloramines as well as urea, the active ingredient in urine, according to John Wojtowicz, a well-known water chemist in the industry. It reacts very slowly with ammonia. KMPS’s lifetime in pool water depends on the quantity of oxidizable material. All things being equal, however, it is not nearly as sensitive to sunlight as chlorine. According to Wojtowicz, unstabilized chlorine is more than 90 per cent decomposed within a few hours, while KMPS is approximately 23 per cent decomposed per hour.

In Canada, these products are not regulated by the Pest Management Regulatory Agency (PMRA) as they are not disinfectants, which mean they do not kill disease organisms. They are purely oxidizers and have a place in maintaining a healthy pool water environment. As they are not chlorine-based they cannot create additional free or combined chlorine residuals nor can they increase the DBPs.

If using non-chlorine oxidizers, test kits require an additional reagent to remove the KMPS from the test sample. Facility managers/operators should contact their test kit manufacturer/provider for the proper reagent.

Superchlorination

Superchlorination is a strategy which involves adding sufficient amounts of chlorinating product to increase the free chlorine to a level in excess of 10 ppm, and maybe as high as 30 ppm in an attempt to burn out any and all contaminants that may exist in the water. However, in this process there may also be other compounds created from incomplete oxidation of microscopic cellular components. These DBPs can be removed using non-chlorine oxidizers or dilution.

Supplemental sanitizers

Ozone

Ozone is one of the strongest oxidizers a pool operator has in their arsenal. It is a supplemental sanitizer that will oxidize water contaminants in a chlorinated or brominated pool or spa/hot tub. With bromine it will regenerate the bromide ions back to active free bromine without the need to add additional chemical products.

In addition to its oxidative attribute, ozone is a micro-flocculent which means it polarizes the small suspended particles in the water so they are attracted to each other. This forms larger particles which are easier for the filter to remove.

Like most treatments, ozone has some drawbacks that need to be taken into account when considering this strategy. First, it is impossible to maintain an ozone residual as it quickly reverts back to oxygen in a few minutes. Second, it has a low solubility in water which means a lot of it gasses off into the air; therefore, a lot of ozone needs to be produced constantly to achieve the desired effect. Third, ozone production is dependent on temperature, humidity, wattage of the bulbs, and the configuration of the chamber. This means all units of the same size may not produce similar results.

When ozone is used in an indoor facility, the air within the complex should be monitored to be sure the ozone in the air does not exceed the regulated short-term exposure limit.

UV-C light

UV-C light supplemental sanitizing units can destroy chloramines and the ammoniated compounds that create chloramines and DBPs. It can also deactivate micro-organisms by destroying its DNA.

Medium pressure UV-C light units produce a wider spectrum of UV light which covers the necessary range for deactivating the micro-organisms and breaking the bond of amines from the chlorine molecule.

Advanced oxidation process (AOP)

This process works by combining ozone and UV disinfection. This system has the highest oxidative level of all the options currently available to pool operators. As with ozone and UV, this system is effective as a secondary or supplemental sanitizer and should be used in conjunction with a chlorine or bromine primary sanitizer. The benefit of this system, as with all supplemental sanitizers, is it allows free chlorine residuals to be maintained at or near the minimum levels required by regulation.

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In AOP systems ozone is created using a corona discharge ozonator and a UV-C light is introduced to the ozonated water, which results in the creation of unstable (reactive) hydroxyl radicals (OH). These OH radicals only last for fractions of a second. The highly unstable radicals react with dissolved waterborne contaminants to oxidize them. Organic and inorganic chloramines, as well as micro-organisms, human waste, and other contaminants, are oxidized and chlorine demand is reduced.

Filter additives

In addition to destroying and preventing the off-gasses of chloramines by using different chemical and supplemental sanitizing systems, it is also important for pool operators to look at removing the ammoniated bather wastes before they have a chance to combine or early on in their transition from monochloramine through trichloramine.

Zeolites

Zeolites are a naturally occurring material. Their structure is irregularly shaped and courser than typical filter sand. This irregular shape gives it a surface area thousands of times greater than that of typical filter sand, making it capable of filtering finer particulate matter from the water.

Zeolites are negatively charged which gives them the ability to exchange ions with many different products including sodium and ammonia. When charged with sodium ions they have the capacity to exchange the sodium ions with ammonia ions to remove human contaminants from the water, eliminating the development of chloramines.

On a regular basis, based on the amount of bather load the water receives, the zeolites need to be soaked for 24 hours, with the filter system turned off, in a sodium solution to reverse the process. The ammonia ions are exchanged for new sodium ions and the ammonia ions are then backwashed to waste before turning the system back to filter mode.

Zeolites, like filter sand, need to be replaced on a regular basis (typically every one to four years of actual usage). The frequency is dependent of the amount of bather load the system is forced to work with rather than being based on the pool volume or its turnover rate.

Granular activated carbon (GAC) filter

This off-line filter system is installed as an effluent and will remove the chloramine water as it passes through. The effluent side of the GAC filter is attached to the main system prior to the clean filtered water going back to the pool.

While this is a simple system to install, the GAC will need to be replaced on a systematic basis as it will be used up by its collection of chloramines and the process is not reversible like the ion exchange with Zeolites.

HVAC systems or modifications

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One of the most important aspects in designing an indoor aquatic venue is the HVAC and dehumidification systems. These issues need to be considered from the design phase of any construction as they are more expensive to correct once the facility is operational.

Water chemistry, bather loads, water and air temperature, air velocity (including where it is being drawn out of and returned into the aquatic environment), and relative humidity all play a significant factor in designing a great aquatic environment that can be enjoyed by all. After all, these facilities are designed for the health and comfort of bathers, facility staff, and spectators.

Where the incoming fresh air is directed, where the exhaust air is collected and discharged, to the ratio of fresh air to recycled air within the facility, all of these factors must be calculated pre-construction. As soon as the first bather/swimmer enters the water, combined chlorine (in the venue’s water and air) starts to become an issue for the operator. All of these factors should be considered prior to the facility being built or renovated.

During the winter, many indoor facilities reduce the amount of fresh air drawn inside. This is due to the cost of heating the cold air before it is returned to the pool area and discharging all of the heated, humid air. Other concerns include condensation on building surfaces and bather discomfort.

Without enough air exchanges, the removal of the volatile combined chlorines from the air within the facility becomes more difficult as it sits just above the pool’s water surface. The location of the supply and the return openings have to allow for this air removal without creating an excessive amount of evaporation from the water’s surface.

To minimize evaporation and aid in keeping the humidity down, the air temperature should be one to two degrees warmer than the water temperature. However, when the water temperature is increased for special use, such as instructional or therapeutic needs, the warmer air temperature may not be comfortable or practical for bather comfort. Therefore, this has to be considered when designing the system.

Dehumidification units

One important aspect of designing an indoor aquatic facility is the use of dehumidification units. Sizing this equipment requires a fair amount of planning during the facility’s design phase.

Items that need to be considered include:

• size of venue;
• the outdoor temperature at the coldest time of the year;
• the materials that constitute the indoor building surfaces;
• the type of usage the facility will see; and
• the air and water temperatures that will be maintained.

All these items are critical to determining the right size unit.

Dealing with bather discomfort

Despite best efforts, in some cases, facility operators may have difficulty getting rid of the lingering odour associated with combined chlorines. This odour can be a significant issue at hotels, spa facilities, and other ‘class B’ pools in Canada and the U.S., where the air handling system may not be adequately able to handle this problem.

There are new products on the market that eliminate the odour of combined chlorines, without correcting the underlying chemistry of bad air. For example, deodorizer products do not remove the actual chloramine problem from the pool water chemistry, they only mask the odours associated with the problem.

These products do not absolve the operator and facility engineer from properly maintaining the pool’s water chemistry. They need to perform the required water tests and record the results to maintain the free and combined chlorine within regulatory requirements, as well as make appropriate dilutions to ensure healthy and safe recreational water. That said, these products may have a place in some facility operator’s arsenal of strategies for dealing with the combined chlorine issue.

Every aquatic facility operator wants an environment that is not only healthy for patrons and staff, but also enjoyable for spectators. Accomplishing this requires a lot of work to maintain the water chemistry and air quality. A quality test kit capable of reading combined and free chlorine levels is a necessity.

This article presents several strategies to aid a facility operator’s thinking on this topic. Some might not be applicable in all cases; however, by reviewing these aquatic facility maintenance strategies operators can determine which one might work for them in their current situation. It is important to keep in mind, however, there is no substitution for good water quality maintenance.

[8]Frank Goldstein, president and CEO of Chesapeake Aquatic Consultants LLC, is a pool and spa industry veteran with more than 50 years of experience. Along with being the author/editor of many of the Association of Pool & Spa Professional’s (APSP’s) technical training manuals and training programs, he recently finished writing his fifth edition of the APSP Service Tech Manual and was the technical editor of the publication. Goldstein also provides expert witness testimony for many segments of the industry in Canada and the U.S., and teaches at several community colleges as adjunct faculty. He has also conducted several of the Lowry School of Pool & Spa Chemistry courses in Toronto, where he taught an advanced water chemistry and commercial pool and spa operations program developed by the late R. Neil Lowry, Ph.D. Goldstein, who became an APSP Fellow in 2015, has served on the national board of directors and was one of the founding members of the National Service Council. He can be reached via e-mail at chesaqua@msn.com[9].

[10]Michael Lowry is an instructor with, and promoter of, the Lowry School of Pool & Spa Chemistry. His 25 years of experience range from servicing pools to selling commercial, industrial, and residential pool chemicals. In 2012, Lowry was recognized by the National Swimming Pool Foundation (NSPF) for exceptional performance at the group’s annual instructor meeting earning two distinguished instructor awards—one for the highest increase in certified pool operator (CPO) certifications in 2011 over 2010, and the second for the highest number of certifications outside the U.S. He can be reached via e-mail at mlowry@lowryassociates.ca[11].

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