Archive for April, 2013

Pathways of trihalomethane uptake in swimming pools

Article: Pathways of trihalomethane uptake in swimming pools.
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ABSTRACT: Chlorination of pool water leads to the formation of numerous disinfection by-products (DBPs), chloroform usually being most abundant. Bathers and pool guardians take up various amounts of DBPs by different pathways. Identification of different uptake paths is important in order to develop a technical strategy for swimming pool water treatment and to develop focussed technical solutions to minimize THM uptake. Basically, trihalomethanes (THMs) can be taken up by inhalation, by dermal absorption, or orally (swallowing of water). In our experimental study involving up to 17 participants we quantified the body burden resulting from exposure to three different concentrations of chloroform in water and air of an indoor swimming pool, during a 60 min exercising period. Chloroform concentration of the water was 20.7, 7.1, and 24.8 microg/l and was not influenced artificially. Corresponding air CHCl3 concentrations were measured at two different levels (20 cm and 150 cm) and ranged from to 85 to 235 microg/m3. To dissociate the dermal exposure route from that of inhalation, THM concentrations were measured in the blood of subjects practicing in an indoor pool with and without scuba tanks, as well as in the blood of subjects walking around the pool without swimming. Chloroform concentrations were measured in blood samples before and after each exercise period. Blood chloroform concentration of participants with scuba tanks was 0.32 +/- 0.26 microg/l, without scuba tanks 0.99 +/- 0.47 micro/l, and for persons walking around the pool 0.31 +/- 0.25 microg/l. Our results indicate that THMs are mainly taken up over the respiratory pathway. Only about one third of the total burden is taken up over the skin. We examined the relationship between blood concentration and environmental chloroform concentrations by using linear regression models. Blood concentrations are correlated to air chloroform concentrations; correlation to water concentrations is less obvious.

International Journal of Hygiene and Environmental Health 01/2005;

Optimizing Chloramine Treatment

Optimizing Chloramine Treatment

Nitrate Removal from Water

Treatment: Anion Exchange Water Softener (Countercurrent Regenerating)

image004A specialized type of Anion exchange water softener is used to remove nitrates. A water softener uses the principle of ion-exchange – in this case, anions – to remove nitrates from raw water. The equipment contains a “bed” of softening material known as ‘resin’ through which the untreated water flows. Although the anion softener looks the same on the outside, this unit is very different from a standard water softener. As water passes through the resin, the nitrates in the water attach themselves to this material. This ion-exchange process occurs literally billions of times during the softening process. Weekly automatic regeneration, or recharging, is necessary. The unit is set to automatically perform this regeneration as needed, based on water usage. To recharge the resin, it must be rinsed with a rich brine solution (Sodium Chloride – salt). This washes the nitrates out of the resin and replaces them with chloride, so the resin is once again ready to exchange ions to remove more nitrates. During the recharging cycle, the unit is also backwashed. Reversing the normal flow of water also serves to remove any turbidity and sediment, which may have accumulated during the softening process due to the filtering action of the ion exchange material.  Backwashing also loosens and fluffs up the bed of resin. Countercurrent regenerating water softeners add the salt against the service flow, and use significantly less salt than traditional water softeners. Our softeners are controlled using Clack® WS-1 control heads, which offer the option of either metered “demand initiated regeneration” or the more traditional “timed” regeneration.

Chloramine toxicity

Chloramine toxicity.

“Chlorine is an oxidizer, which burns a fishes’ gills. Chloramines, on the other hand, pass across the gills of a fish and into its blood, where the molecule attaches to the hemoglobin, acting like nitrite to induce methemoglobinemia. The toxicity of chloramines is affected by pH, I’m reading at FishDoc, with Chloramine-T more toxic at lower pH. Fish stricken by chloramine poisoning are sluggish and respire heavily.”

And we thought it was from over-training!?

Chloramine & Chloramine Removal for Ferments & Cultures

Problems Reaching Breakpoint

Although rarely a problem in outdoor pools, since sunlight destroys chloramines, and the objectionable odors blow away, many pools operators have a great deal of difficulty ridding their indoor pools of chloramines. Unfortunately, HOCl also reacts with UV light (sunlight) and becomes an inactive chloride ion or salt (Cl–).

Some pools have enormously high bather load to water volume ratios, resulting in heavy organic loading, and high levels of ammoniated impurities in the water. Spray features at amusement parks, health club spas, therapy pools, swim school pools, and children’s wading depth pools with interactive play features, for example, often have chlorine levels unfathomable to operators of more traditional swimming pools. It is not surprising to find that an 18,000 gallon swim school pool maintained at 94° Fahrenheit having a bather load of 300 pre–school aged children per day, will have a continuing problem with chloramines. Ten thousand gallon children’s wading pools at successful commercial waterparks may have bather loads exceeding 2,000 children per day. It is not unusual to find amusement park water spray features with interactive fountains that have more users coming into contact with the water than number of gallons of water in the water feature. These same pools often have problems reaching breakpoint or keeping chloramines within acceptable levels.

If a chloramine residual persists in a pool in spite of the operator following proper breakpoint chlorination techniques, and continues to be a chronic nuisance, some of the following suggestions should be tried.

Regular Dilution

Drain and replace with 30 liters (approximately 8 gallons) of fresh water per user per day, as recommended in the German DIN (Deutsch Industrie Normen) Standard 19,643: “Treatment & Disinfection of Swimming & Bathing Pool Water”. The DIN Standard has been adopted by the European Community, and FINA requires water standards compatible with the DIN standard during international swimming competition.

Increase Exposure Time and Chlorine Concentration

You may be successful in reaching breakpoint by superchlorinating for longer periods of time with higher levels of chlorine.

Draw Water from the Pool Surface

Chloramines are concentrated near the surface of the water, as are most organic contaminants. During breakpoint chlorination, turn off the valve which draws water from the main drains and direct all the water through the perimeter overflow system. By circulating only through the skimmers or gutters, you will speed up the process by removing the water where chloramines are concentrated first.

GAC Filtration

Install secondary granulated activated carbon (GAC) filters and remove ammonia through filtration. GAC filters can be used to treat a slip–stream of water continually drawn off the main effluent line, or to treat source water prior to its being added to the pool. Many pools in areas of the country where municipal water utilities are adding ammonia to the source water to prevent trihalomethane formation in drinking water are installing GAC filters to pre–treat fill water to keep ammonia levels below 0.02 ppm. Chloramination has become a common practice by water utilities in order to comply with U.S. EPA water quality standards for drinking water to prevent formation of chloroform, a known carcinogen. Since chloramines do not react with raw water organic precursors which form when vegetation decays, monochloramines are commonly being used to treat water which has been stored in reservoirs. This practice is causing havoc in swimming pools.Non Chlorine OxidizersPotassium peroxymonosulfate (AKA: monopersulfate), can be used instead of chlorine to shock , or oxidize chloramines and other organic contaminants from the water. The product is a buffered chemical compound which utilizes oxygen to prevent or destroy the eye irritation and odor qualities of pool water by reacting with ammonia to produce chloride and nitrogen. Sold under various trade or brand names, the product has be successfully marketed to homeowners, and is beginning to make inroads into the commercial pool market.

Unlike chlorine which must reach a “breakpoint”, any amount of potassium peroxymonosulfate added to water will oxidize some material. Normally though, between 5 ounces and one pound per ten thousand gallons of water is added on a weekly basis to pools, and daily basis to spas. Non chlorine oxidizers will not raise chlorine levels, are totally soluble, do not cause bleaching, and they don’t affect water balance or pH. Monopersulfates are especially recommended for pools or spas with high bather load to water volume ratios where total dissolved solids and ammonia normally build–up at a rapid pace.

The pool owner should be cautioned however, that regular use of non chlorine oxidizers may irritate bathers causing them to itch. Also, potassium peroxymonosulfate is known to have an effect on DPD reagents in both liquid and tablet form, causing water samples to turn dark red, and may cause a false high free available chlorine reading. DPD reagent #3 is oxidized by monopersulfate so the test actually reads the monopersulfate residual preventing an accurate reading which distinguished between free and total chlorine. Some test kit manufacturers sell FAS–DPD reagents that eliminate monopersulfate interference.

Some pools maintain a residual of monopersulfate to help eliminate bather waste and the build–up of organic contaminants, as a preventative rather than corrective treatment. One manufacturer (U.S. Filter) has patented a continuous breakpoint halogenation and peroxygenation system. Potassium peroxymonosulfate doesn’t react with chlorine, but rather oxidizes contaminants and reduces the demand on the sanitizer. It should be noted though that not all products sold as non chlorine oxidizers contain the active ingredient potassium monopersulfate. For example, sodium percarbonate (AKA: sodium carbonate peroxyhydrate) releases or produced hydrogen peroxide, and reacts with chlorine.

Eliminate the Chlorine to Eliminate the Chloramines

Hydrogen peroxide or sodium thiosulfate can be added to the pool to drop the chlorine level to zero. This eliminates the free chlorine residual by converting chlorine back to chlorine salt. When chlorine is eliminated from the water, chloramines will also be eliminated. However, when chlorine is reintroduced, it will start combining with the ammonia which is still present in the water and form chloramines, but hopefully in a gradual manner and as a less objectionable monochloramine rather than nitrogen trichloride.

A word or two of caution – don’t overdo the amount of hydrogen peroxide or sodium thiosulfate you add to the water or you will create a chlorine demand and have a difficult time reestablishing a chlorine residual. Also, do not add products containing hydrogen peroxide to a pool which utilizes diatomaceous earth filters, since hydrogen peroxide reacts with and dissolves D.E.


Zeolites with a high (at least 80%) percentage of clinoptilolite can be used as a filter media instead of #20 silica sand in sand filters. Zeolites are a family of granular, extremely porous volcanic minerals capable of removing ammonia from the water as well as particles down to 5 microns in size, equivalent to the filtering capabilities of a diatomaceous earth filter. Zeolites for swimming pool filtration are marketed under various trade names by Neptune Benson (Clinopure 80), British Zeolite Co. (Zeoclere–30), Innovative Water Science (Zeo–Pure 90), Eco Smarte (Hydroxite #2), and others.

When a layer of 10% sodium chloride (table salt) is added to the filter bed an ionic reaction occurs which causes the absorption and removal of ammonia as the water passes through the filter, thereby reducing chloramine formation. The pool operator must regenerate filter media every 6 months by backwashing, shocking with a salt solution, allowing the bed to reactivate for 24 hours, agitating the media, then backwashing. Zeolites supplied by a reputable distributor should have a life expectancy 5 to 7 years.

Corona Discharge Ozone Systems

Organic contaminants are slightly reactive with ozone, but after being partially oxidized, microflocculation allows their removal by filtration. Inorganic contaminants such as ammonia react significantly with ozone when the pH is maintained below 9.0. Ozone constantly oxidizes monochloramines to form chloride and nitrate ions. Unfortunately, ozone also destroys high free chlorine residuals in the process of destroying chloramines, so chlorine lost in the process must be constantly replaced.

Ultraviolet LightUV light whether from natural sunlight or from UV light sanitation systems can be used to destroy chloramines and aerosolized chlorine compounds. If natural sunlight cannot be brought into the natatorium, UV light sanitation systems can be installed to provide supplemental sanitation and destroy chloramines.

UV light systems are installed in–line and are used in combination with either hydrogen peroxide or chlorine which provides a residual sanitizer and oxidizer in the pool water. The system consists of a treatment chamber installed on the filter effluent line, control box and power supply. Photolytic liners are permanently attached to the internal surfaces of the treatment chamber. Water flows through clear, quartz glass or Teflon tubes through the treatment chamber, passes the UV lamps (arc tubes) and pathogens are destroyed. UV kills microorganisms by destroying the DNA in the cells. There is no change in water color, temperature, taste, pH or chemical composition, however, turbid water will absorb UV light and make UV less effective as a disinfectant.

Disinfectant level is related to light intensity and exposure time. UV dosage is measured in either microwatt seconds per square centimeter (MWS/cm2). You may also see intensity and exposure time expressed in millijoules per square centimeter (mJ/cm2) instead. Six thousand to 10,000 MWS/cm2 or a minimum of 60 mJ/cm2are needed to destroy pathogenic organisms.

There are two types of UV lamps: low pressure (with an electromagnetic spectrum between 185 and 254 nanometers); and more commonly used today, medium pressure high intensity (with a wider electromagnetic spectrum between 180 and 400 nanometers, and not affected by water temperature). UV is most germicidal in wavelengths between 240 and 280 nanometers. Organic compounds are best photo oxidized by hydroxyl radicals in wavelengths below 230 nanometers. The bond between chlorine and nitrogen is broken, and chloramine destruction is most effective in the range of 245 and 340 nanometers, making low pressure bulbs a poor choice for chloramine destruction.

Increase Airflow Over the Water SurfaceIt is not possible to superchlorinate below a pool blanket or inside an enclosed pipe. By definition, oxygen is needed for oxidation to occur and off gassing into the air must take place. If there isn’t enough oxygen over the pool, breakpoint will not be achieved. Think of a fire. If the fuel is present but oxygen is lacking, combustion will not occur. Do whatever you can to get more air moving over the pool. So open the windows and doors, turn on the exhaust fans to move large volumes of air.

Unfortunately, as you speed up the removal of chloramines from the water, you release them into the air in the natatorium. Since like an outdoor pool, you do not have the ever present wind to blow away the odors and irritants, the air handling system must be designed to take the place of nature.

Chloramines are very volatile and easily vaporized into the air surrounding the pool. You can reduce the chloramine concentration in the air, by increasing the percentage of outside air brought into the natatorium and diluting the objectionable chloramine odors and irritants with fresh air. There should be at least 8 complete air exchanges per hour. Open air dampers to permit 100% fresh air to be brought in especially during breakpoint chlorination. During regular operation, as little as 15% fresh air may be permitted by code, but a minimum of 40% is recommended (up to 100%) depending on usage patterns, natatorium design, and equipment installed. For instance, pools that have water features installed that agitate water or aerosolize water vapor, particulates, or pathogenic organisms should exchange more air.

The location and placement of supply registers and return/exhaust ducts should be such that air is supplied low, moved across the water surface at a velocity less than 25 feet per minute to move the heavier than air gasses concentrated and settled directly over the pool, and exhausted high near ceiling level. Pollutants travel from positive to negative pressure areas, so natatoriums should be positively pressured in relation to the out of doors, and negatively pressured in relation to surrounding occupied spaces.

The air handling system installed should be capable of providing thermal environmental temperatures acceptable to 80% or more of the primary/priority facility users, averting sick building syndrome problems, and preventing discernible odors, without evident drafts, stratification of air, thermoclines or temperature gradients.

Air-stratification Leads to “Sick Pool Syndrome”

“Sick Pool Syndrome” is a phrase that is relatively unfamiliar to the HVAC community. However, if there is a high school or college in your area with an indoor pool where swimmers train, there is a good chance that some of those swimmers suffer from Sick Pool Syndrome’s consequences: extreme shortness of breath or asthma events.

Correcting the problem holds opportunities for contractors interested in natatorium work. From the HVAC perspective, the problem is not just excessive humidity and corrosion from chlorine (although those considerations could be helpful in obtaining the necessary funding for the work).

The IAQ problem is caused by air stratification, which creates dead air at the water’s surface, where swimmers inhale what is essentially chlorinated air.


Swimming has been considered a healthy sports alternative for young people with asthma. In addition to easier breathing than higher-impact land sports, the deep breathing of swimming has even been considered beneficial to asthmatics. So it was not surprising that after a swim meet or during rigorous workouts, some members of the swim team would use their inhalers — there were just more asthmatics on the swim team, right?

According to Paul Richards, aquatics director at Dickinson College, Carlisle, PA, asthmatic members of his swim team routinely use their inhalers before swimming laps to prevent asthma events. The situation in Dickinson’s natatorium became alarming when those swimmers had to stop in the middle of exercising and use “rescue inhalers” because they couldn’t breathe.

Depending on how the pool water is cleaned, dead air at the water’s surface could be carrying chlorine gases. Richards explained that pool chlorine breaks down into hypochloric and hydrochloric acids and other compounds broadly called “chloramine,” which become trapped in that dead space 10 to 12 inches over the water’s surface. Swimmers inhale just above the water’s surface, where the chemicals are concentrated.

Even though the amount of chlorine measured at the water’s surface is relatively low, over the course of a workout, a swimmer breathes in much more of the chemicals, resulting in exercise-related asthma (bronchospasm), according to Drobnic, Freixa, Casan, Sanchis, and Guardino in their paper, “Exercising Increases the Toxicity of a ‘Safe’ Chlorinated Pool Atmosphere” (Medicine and Science in Sports and Exercise, 1996).

Still more alarming: In 2000, Dr. Stephen J. McGeady from Thomas Jefferson University, Wilmington, DE, measured the lung function of competitive swimmers in swimming pool and lab settings. He and his colleagues heard that many non-asthmatic university team swimmers had to use inhalers. This proved to be true. Richards said he was not surprised to hear it.

Richards said that ideally, air return intakes should be positioned to direct airflow so as to eliminate dead areas. However, he noted, “Ventilation [of natatoriums] was not a design issue for a long time.”

Dickinson College’s poor natatorium IAQ was remedied with an overhead trunk fabric duct design (above) and a heat recovery dehumidifier (below).


Coach Richards joined Dickinson College in 1994. In addition to his coaching and teaching duties, Richards oversees the operations of Dickinson’s year-round aquatics facility. His background includes the study of natatorium mechanics.

There was no doubt in his mind that his natatorium suffered from Sick Pool Syndrome. In fact, he recounted that when he first arrived, the ventilation system was completely shut off because as he was told, “The chlorine odor was too strong in the parking lot.” He got that situation changed immediately, but the problems continued.

Swim practice was periodically interrupted by team members with breathing problems caused by stagnant, chloramine-laden air near the pool surface. While all of these team members were already known to have asthma, he agreed that “anyone with restricted airway disease” is susceptible to Sick Pool Syndrome. He was not surprised to hear of the reports of non-asthmatics suffering bronchospasms while swimming.

The 23-year-old Dickinson natatorium was built in the 1980s. It was originally designed with a commercial air conditioner. Its air distribution consisted of two 4- by 4-foot wall grille returns in one location, and a series of five 3- by 1-foot wall diffuser air supplies in only one wall. Consequently, air stratification was significant in more than 50% of the pool area. Air movement was particularly dead at the pool’s surface level, where heavy chloramine gases became trapped.

In addition, 80% humidity levels had taken a toll on many parts of the 10,000-square-foot natatorium structure, as well as the roof and metal amenities of Kline Athletic Center, a 78,000-square-foot field house.

Ongoing roof problems in the adjacent field house eventually led school officials to appropriate $248,000 for repairs. These included a complete retrofit for Dickinson’s eight-lane, 25-yard-long pool natatorium. Richards, who has a masters degree in sports sciences with a specialization in aquatics maintenance, management, and design, researched natatorium technology with the help of Durwin Ellerman, supervisor of mechanical and electrical trades at Dickinson.

Natatorium environments are most effective with a combination of under-deck and overhead air supplies, according to the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).

However, this was not feasible with the school’s budget.

Rich Munkittrick, vice president of manufacturers representative H&H Sales, Mechanicsburg, PA, provided drafting and engineering assistance. Since under-deck ductwork was not economically feasible, Richards and Ellerman conceived of a main, 52-inch-diameter trunk line spanning 120 feet down the center of the natatorium. Their design incorporated a heat recovery dehumidifier from Dectron Internationale (Roswell, GA) and fabric duct from DuctSox (Dubuque, IA), which could improve the pool’s indoor air quality (IAQ) while staying within budget.


The trunk line delivers approximately 15% of the airflow through the fabric’s natural porosity, according to its manufacturer. The remaining air is delivered through a linear diffuser and four 20-inch-diameter, perpendicular branches that spray the windows and the spectator section with 82 degree F air.

Air distribution at the pool’s surface level, which was a major concern of Richards because of swimmers’ health issues, now relies on new returns at the shallow end to draw the conditioned air down from the supply duct to mix with evaporating chemicals and then return them to the dehumidifier.

For the best air distribution and aesthetics, Richards said he wanted the trunk line at the center of the roof’s peak; however, existing lighting fixtures would have been blocked by the duct.

Ellerman conceived of a fixture retrofit that would allow both the trunk and the lighting to hang at the center. He lowered the lighting below the trunk line by extending the ceiling-mounted conduit pendants into an “O” shape that encircles the duct and connects to the fixture below the duct.

Another important factor is the temperature differential between the air and water (which now measure 82 degrees and 80 degrees, respectively). Previously, the differential between the 75 degree air and the 80 degree water caused additional humidity problems. The current relative humidity is maintained at 50%, thanks to the improved air-to-water temperature differential and the addition of the heat recovery dehumidifier.

Richards said that the conditions now are ideal. And the dehumidifier recaptures condensate, “a complete pool fill per year,” said Richards.

“I guess the jury is still out,” on how well the fabric ducts will stand up to the corrosive environment, he said. “I think it will last a lot longer than metal.” He also pointed out that it was “very easy to install,” hence, very easy to replace. And it can be taken down by hand and washed.


The most important consideration, of course, is the swimmers’ health. These days, inhaler use is minimal at practices, according to Richards.

Visiting spectators and opposing teams regularly make positive comments on humidity levels and IAQ during swim meets held at Dickinson, he said. “We did a survey in our regional conference. Based on chemical evidence and anecdotally, we were certainly not the exception” for Sick Pool Syndrome.

He suspects a significant number of natatoriums nationwide may need complete retrofits or serious fine-tuning to their air-handling and chemical systems, as well as their operating procedures.

However, knowledge of poor IAQ in natatoriums may be lacking among high school and college administrators. Even in his own school’s case, it was the roof deterioration that finally got funding approval for the field house.

HVAC contractors may need to educate aquatics directors on humidity control, air stratification, and the role they play in Sick Pool Syndrome.

“Colleges and universities tend to hire swim coaches and then name them aquatics directors,” Richards said. “Unfortunately, a large percentage of swim coaches have little or no training in facilities management and know very little about water chemistry. So then those responsibilities are left to physical plant engineers, who many times don’t have aquatics facility training either.”

Sidebar: It All Starts With Good Design

When mechanical contractors design an enclosed swimming pool, they have to keep in mind how to correctly distribute the air throughout the space and how to remove air from the room efficiently, in order to avoid air stagnation or stratification in the natatorium.

Controlling humidity in a natatorium presents many challenges. Special attention and careful consideration must be given to the location of supply air ducts, the location of the air return grille, the use of moisture barriers, and door and window insulation values, according to Pat Reynolds, president of PoolPak Inc.

Obviously, a well-designed dehumidifier is only one step toward effective climate control in a pool space.

According to Reynolds, “Efficient dehumidification of a pool enclosure requires well-balanced and properly placed ducting systems. Ducts should never be positioned in a manner such as would result in the short cycling of the supply air. Short cycling is caused when the location of the return duct is too close to, or directly in line with, the supply duct causing warm, dry air to recycle prematurely.”

The return intake(s) should be positioned so that all of the moist, warm air flows efficiently back to the dehumidification system, eliminating dead areas where air stagnation can occur, Reynolds stated. “In most instances, a single return duct is ideal in the pool area. The desirable location for the return is at a point high enough to capture the warm, humid air that naturally rises.” Normally, this is about 10 to 15 feet above the floor, or the surface of the pool.

“Airflow should never be directed over a pool surface or over any concentration of water,” Reynolds said. “Should air flow over or too close to the water, it will speed evaporation and limit the effectiveness of the dehumidification system. The greater the velocity of the air currents, the greater the evaporation process.”

Typically, an indoor pool requires space air heating 70% to 90% of the year. Therefore, the most effective air distribution system is one that takes advantage of hot air’s natural tendency to rise. This type of system will supply the air “low” and return it “high,” Reynolds pointed out. “When this is not possible, a ceiling supply arrangement is necessary.”

The supply air grille should be located close to the windows, preferable within 12 inches from the surface to sufficiently bathe the cold glass with a blanket of warm, dry air. The majority of the supply air (80%) should be directed down the walls. The remaining 20% should be directed along the ceiling to break up any stratification and stagnation that might occur there.

Where skylights are present, it is best to utilize supply ductwork to flood the glass with warm, dry air. Another method to deal with skylights is to install ceiling fans, running in reverse, to draw up the warm air against the glass surface. This, however, is not as reliable as a direct flow of air from ducts.

Reynolds points out another important factor: “You can correctly build the enclosure and have a very good dehumidification system, but if you do not maintain your equipment, you cannot control the humidification adequately.”

Publication date: 08/12/2002