Darla M. Goeres1, Philippe Hartemann2 and John V. Dadswell3
1 Center for Biofilm Engineering, Montana State University, Bozeman, MT, USA2 Department of Environment and Public Health, Nancy School of Medicine, Lorraine University, Vandoeuvre-Nancy, France3 Reading, UK
19.5
Introduction
Swimming is an activity enjoyed by people of all ages and abilities in all parts of the world. Swimming promotes known health benefits. The water provides support for the body, making it an ideal activity for people with joint pain or who are recovering from an injury. In addition to exercise, soaking in hot tubs or hot springs promotes relaxation and soothes sore muscles. With the notable health benefits and enjoyment associated with swim-ming, it is important that the water and facility do not become a source of disease and/or injury. Swimming may be thought of as communal bathing. Bathers introduce varying amounts of organ-ics into the water including sweat, urine, dead skin, hair, oils, lotions and microorganisms every time they enter. The type and concentration of organics introduced by the bather is a function of the individual and the facility they are using. A small child in swim diapers in a splash pool is very different to an adult com-petitive swimmer practicing in a lap pool. Regardless, it is the responsibility of the facility operator to maintain healthy water quality.
Four factors contribute to maintaining a healthy water quality in a recreational water facility: engineering design, water chem-istry, disinfection and facility management. All factors must be operating properly for a facility to maintain a healthy bathing environment. For instance, if a facility operator does not adhere
to their policies in remediating a fecal accident in the pool water, then even if the facility has a disinfectant residual when the event occurred, they have still placed the other bathers at risk. This chapter will present a holistic approach for the main-tenance of recreational water. This includes a discussion on the engineering aspects that define the different facilities, a general discussion on maintaining balanced water chemistry, the use and evaluation of disinfectants and a general discussion at the end on the importance of well-trained facility managers. An overview of the various illnesses that are associated with recrea-tional water which is not maintained correctly are presented as a cautionary note. Finally, like any industry, recreational water is subject to trends, which will be addressed in the appropriate sections.
Engineering design considerations
People have enjoyed built communal swimming pools for centu-ries. The original design for these pools was simple. Hot water, typically from a spring, was piped into an enclosed structure and the spent water flowed out. Over time, this simple design evolved to include recycle, filtration and heat exchangers so that a cold source water could be used. At some point, disinfectants were added and the water chemistry was balanced. In recent history, recreational water facilities have evolved well beyond a simple
Russell, Hugo & Ayliffe’s: Principles and Practice of Disinfection, Preservation and Sterilization, Fifth Edition. Edited by Adam P. Fraise, Jean-Yves Maillard,
Health effects, 481Management and reporting, 483References, 483
Special Problems in Hospital Environments19
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filter is no longer operating according to design specifications. To keep the filters operating properly, it is important that they are cleaned regularly using a backwashing procedure, and replaced when backwashing does not decrease the pressure drop to an acceptable level.
A more recent trend in swimming pool filtration technology is the use of coagulants and flocculants to reduce turbidity and improve water quality by the removal of particles smaller than 20 µm. For instance, researchers are investigating the use of floc-culation for the improved removal of Cryptosporidium oocysts [1]. Another research area is the use of filters filled with granular activated carbon (GAC) which would filter out both microbial contaminants and organics, thereby reducing the formation of disinfection by-products [2].
Swimming pools are found both indoors and outdoors. Both locations pose their own set of challenges. For outdoor swim-ming pools, increased exposure to the elements will lead to increased levels of contamination from dust, dirt, pollen, leaves, insects, etc. that find their way into the pool water from the envi-ronment. An intense rainfall will impact the water’s chemistry and sunlight will cause both evaporation and chlorine degrada-tion. Air quality is a concern for swimming pools located indoors, including the accumulation of disinfection by-products and increased humidity, which can lead to higher microbial contami-nation rates of items located next to the swimming pool, such as carpets and painted walls.
In recent years, the complexity of swimming pools has grown dramatically with the popularity of water theme-parks that include features to encourage play and a fun swimming experience. These may include slides, wave pools, features that spray water, collect and dump water or toys anchored in water, all of which may pose a challenge for maintaining healthy water quality [3]. Many of these features are designed specifi-cally for small children that are not yet potty trained. It is not uncommon to find these water parks inside, especially in colder climates. This enables the water park to operate year-round to maximize profits. The new designs, although fun, have resulted in new challenges for maintaining the water quality. The aero-solized water may spread contaminants [4], increase the rate of chlorine degradation and make it more challenging to maintain balanced water chemistry. Features such as slides have a large surface area and intimate contact with people yet little treated water flowing over them. Often all the water from the various features will be piped to one filter system. Therefore, in case of a fecal accident, the quick spread of the contaminate to the other features could put the health of many bathers at risk.
As energy becomes more expensive, the costs associated with operating a swimming pool will also increase. The energy required to heat a pool is significant, but the costs of pumping water through the system cannot be overlooked. There are multiple avenues that may be pursued for a more environmentally-friendly and affordable means of energy (e.g. the use of solar power is a viable option given that many pools and water parks are located
swimming pool to include complex water parks with specialized pools. The engineer who designs the facility must balance funda-mental concepts, such as filtration, recycle rates, material choices and safety with energy costs, ease of maintenance and, of course, bather enjoyment. A poorly designed facility is virtually impos-sible to maintain, whether it is new or old. An old facility, though, poses special engineering challenges including high maintenance costs and the challenge of retrofitting new technology in an old system. This section will discuss a selection of recreational water facilities and the engineering design parameters that set them apart from each other.
Swimming pools and water parksHistorically, swimming pools were simple geometric shapes con-structed out of concrete, tile or vinyl. The swimming pool was filled with water that was continuously recycled through skim-mers to remove gross contamination, a filter to remove smaller particles and a heat exchanger to warm the water before going back into the pool. Although the water is recycled, a small percent of freshwater is routinely added to public pools. The turnover rate, also known as recycle rate, is the time required for the entire volume of water in the swimming pool to make it through the entire process. A typical turnover rate for swimming pools is 6 h, which means that the entire pool volume passes through the filter four times every day. The actual turnover rate is set by the design guidelines under which the pool is operating. A well-designed pool has no dead spaces, where water is allowed to stagnate and avoid going through the filter. Dead spaces occur when the placement of the inlets from the filter and outlets to the filter create a flow channel. In addition to preventing chan-neling, inlets and outlets are designed with swimmer safety in mind. It is important that the inlets and outlets are designed to prevent reasonably small items from entering the filter, “trap-ping” swimmers under water or causing injury from exposed rusty or sharp edges.
One of the most important engineering parameters in swim-ming pool design is the filter. Swimming pool filters are gener-ally constructed from diatomaceous earth, sand or compressed synthetic fibers housed inside a cartridge. The goal of filtration is to remove very small particles, on the order of magnitude of 20–100 µm. The filter loading rate is defined as volume per time per area. Filter loading rates are specified in swimming pool design guidelines. Filters are sized based upon the requirements for the filter loading and turnover rates and the volume of water in the pool. The actual surface area available in a swim-ming pool filter is much greater than the calculated cross-sectional surface area. This large surface area provides an ideal location for bacteria and other charged particles to attach, which means over time the filter will start to foul. Fouling is indicated by an increase in the pressure drop across the filter. In practical terms, more power is required to push water through a plugged filter at the same rate as an unplugged filter. As a filter becomes plugged, the water will begin to find a preferred path or channel through which to flow. Once this happens, the
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Water chemistry
Balanced water chemistry is the second of the four factors that contribute to maintaining healthy water quality in a recreational water facility. The term “balanced” refers to the water’s satura-tion or Langelier index. The five parameters that are used to calculate the saturation index are: temperature, pH, total alkalin-ity, calcium hardness and total dissolved solids. The first four parameters are easily measured and adjusted. If the total dis-solved solids measurement becomes too high, then either some of the pool water must be drained and make-up water added, or a flocculent added and the solids filtered out of the water. A discussion on how to calculate the Langelier index is beyond the scope of this chapter, and may be found in water chemistry texts [9, 10].
Unsaturated water is corrosive and attacks the equipment and pool surfaces; conversely, overly saturated water results in scale deposits and cloudy water. In addition to the negative impacts unbalanced water has upon the facility’s equipment, it may also result in bather discomfort by irritating the skin or eyes. Finally, many disinfectants, particularly the halogens, depend upon bal-anced water chemistry to achieve the desired levels of water decontamination.
Disinfection
The need for proper disinfection of swimming pool water has been known for a long time [11]. The primary function of a disinfectant is to make the water microbiologically safe for swim-mers, and this is accomplished by bringing to an acceptable level the number of viable organisms found both in the pool water and as biofilms on all the exposed surfaces. While an “acceptable level” remains difficult to define, the goal is to minimize the risk of illness to those using the recreational facility.
Chorine is the most common chemical used to disinfect water in recreational facilities. Although chlorine is used in various forms and under different trade names, the mechanism of its microbicidal action remains the same. In water, chlorine forms hypochlorous acid and hypochlorite ions, and the total concen-tration of these two compounds is known as the free available chlorine (FAC) level in the treated water. The relative propor-tions of the hypochlorous acid and hypochlorite depend upon the pH of the water. Under acidic conditions the proportion of hypochlorous acid is higher but under alkaline conditions hypochlorite ions predominate. Whether the pH of treated water increases or decreases depends upon the chemical formulation of the product used. The pH of the water is, therefore, critical because hypochlorous acid is a stronger microbicide than hypochlorite ions. Another challenge with chlorine disinfection in swimming pools is that inorganic chlorine compounds are degraded by direct sunlight. Cyanuric acid is combined with chlorine to form a more stabilized compound; two examples
in warmer climates [5]), better insulation, wind breaks and the use of pool blankets. It is important to consider the impact an engineering cost-saving design “improvement” has on the entire system, though. For instance, even though fewer turnovers per day would save money, the impact on the sanitary condition of the water and therefore increased risk of infection would not balance the cost savings.
Hot tubs and spasHot tubs (also known as spas) are smaller tubs of water that are used recreationally for relaxation or for therapy. Hot tubs contain a separate circulation system with air blowers and hydrotherapy jets, which help soothe sore muscles, increase blood flow to the central organs, provide respiratory exercise and provide a relaxing effect [6]. As with the increase in popularity of water parks, hot tubs have also become more common. Like swimming pools, the water quality in a hot tub is maintained through the use of filtra-tion and addition of chemicals. These common features resulted in hot tubs being regulated and maintained as small swimming pools, although there are numerous design and operational pa -rameters that distinguish them from swimming pools, including high operational temperatures, heavy bather loads, aeration, large surface area to volume ratios and different water turnover rates. These particular features elucidate the difficulty in maintaining balanced water quality in a hot tub, which may allow for the formation of biofilm within the piping and filter [7], resulting in an increased risk of exposure to microorganisms.
Hot springs and natural poolsHot springs or natural pools are filled with water from thermal features that usually contain geochemical properties that bathers enjoy. The water most often flows through the pool and is not recycled through a filter, and there is no need to heat the water. Typically these pools are drained and cleaned every day. Disinfect-ants are often not added to hot springs and natural pools, which place bathers at risk of exposure to microorganisms shed by the bather next to them.
Whirlpool baths and birthing pools designed for a single userHydrotherapy pools, birthing pools and drain-and-fill whirlpool bath tubs are fundamentally different from the previously described features in that they are designed for a single user and are drained and cleaned between each use. These features are included in this chapter because most of them contain jets that are used to soothe sore muscles and promote relaxation. Typically, the jets are not readily accessible for cleaning, and if the water does not completely drain from the tubing or housing, then bac-terial biofilms may start to form. This poses a problem if the biofilm detaches while the jets are operating, exposing the bather to aerosolized bacteria [4, 8]. Maintenance of these systems re -quires adding a liquid disinfectant to the water once the bather has exited the bath and running the jets for a specified contact time.
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• Bulk water and surface (biofilm) samples to quantify numbers of viable organisms.• Engineering parameters that define the system such as number of turnovers per day; filtration type and rate, facility location, number of pools, etc.• Addition of other chemicals such as flocculants, algaecides, sequestering agents, degreasers, defoamers and stabilizing agents.• Hours of operation and number of users per hour.• Duration of the field test.• Description of the area around swimming pool, for instance is the pool surrounded by cement, grass, tile, carpet or sand?• Training received by facility operators.
A field test will not gauge a disinfectant’s “true” efficacy if biofilm samples are not collected alongside those from the bulk water [15, 17, 19–21]; this is particularly crucial for hot tubs [7] as pathogens in biofilms may be better protected from disinfect-ants [22–25]. Although information on the importance of bio-films in recreational waters dates back to the late 1980s, regulators, public health officials and facility managers have been slow to appreciate this.
Health effects
Swimming in public pools and sharing hot tubs is tantamount to communal bathing. While such activities may spread infections [26], there is a recent upsurge of interest in the potential of chemically-disinfected recreational waters to cause respiratory disorders, especially in young swimmers [27]. This section will address health issues from both infectious agents and chemicals in recreational waters.
Skin, ear and eye irritation and infectionDisinfectant chemicals frequently cause skin irritation in pool users, chlorine sensitivity being less common than the “bromine rash” which may be associated with dimethylhydantoin [28, 29]. Such skin sensitivity is related to the degree of exposure, and physiotherapists who may spend a lot of time in a hydrotherapy pool are particularly at risk. Initially, the rash may appear about 12 h after exposure but, once sensitized, it may do so almost immediately after contact with the water.
In contrast, the itchy rash from Pseudomonas aeruginosa infec-tion may take 12–24 h to manifest [28]. This condition, which is an infection of the hair follicles, resolves itself in about a week in otherwise healthy persons. It is more often associated with spa pools, where the raised temperature and agitation of the waters render the skin more susceptible. The introduction of P. aerugi-nosa in the follicles is also facilited by the pressure during water-massage.
Otitis externa may also be caused by chemical irritation or by infection with P. aeruginosa, especially when the uncovered head is submerged during swimming. The condition is more common in competitive swimmers and divers.
of stabilized chlorine are sodium dichloro-s-triazinetrione and trichloro-s-triazinetrione.
The strong oxidizing potential of chlorine also helps reduce the levels of organics in recreational waters, thus improving its overall quality. Incomplete oxidation results in the formation of com-bined chlorine compounds. The difference between the total chlorine concentration and FAC concentration is the combined chlorine concentration. If the combined chlorine concentration becomes too high (>0.2–0.3 mg/l), then the water should be sub-jected to breakpoint chlorination. The reaction of chlorine with organics in water may lead to the formation of potentially harmful disinfection by-products (DBPs), as discussed below. This also requires maintaining a fine balance between the necessary level of disinfectant residual while minimizing the generation of toxic DBPs. Improved water filtration is among the approaches used to reduce the risk of DBP generation in recreational waters [2, 12].
Numerous other options exist for disinfecting waters in re -creational facilities. Products based on other halogens such as bromine and iodine face many of the same challenges as described for chlorine. Ozone and UV light are also used to disinfect swim-ming pool water in many facilities. The use of ozone or UV does not impact the pH, odor or taste of water. However, neither ozone nor UV leaves a disinfectant residual and this may promote the formation of biofilms in the system. Therefore, ozone and UV should be used in conjunction with another disinfectant that is capable of maintaining a disinfectant residual. Additional options for recreational water disinfection include biguanides, silver and copper ions. These options require an additional chemical to oxidize the water. In addition to products formulated to sanitize and/or oxidize the water, many companies sell additives such as algaecides, scale removers, chelating agents, degreasers, defoam-ers, flocculants or enzymes to improve the overall quality of the water.
The rapid and continuing evolution of the disinfection of rec-reational waters market would quickly outdate any listing of current strategies. Nor is it likely that a “perfect” product or tech-nique will soon be found for this purpose. Thus, the selection from what is available must be based on the specific needs of the site, the age of the system under consideration and its user profile, while remembering that even the best system will likely fail without proper training of the operators and routine main-tenance and monitoring of the facility.
Efficacy testing disinfectantsMuch has been published on the testing of various swimming pool disinfectants [13–16] and the laboratory tests available for this purpose [17, 18]. Nevertheless, proper and routine testing under field conditions is vital for bather safety as well as longevity of the infrastructure. The list of parameters to monitor may include:• Dose (concentration and quantity) of disinfectant added.• Disinfectant residual maintained.• Daily record of the water chemistry parameters previously described.
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Much research has been carried out in many countries to deter-mine the exposure and doses of DBPs through domestic uses of drinking water [41, 44, 45]. Others European studies have tried to determine the exposure during swimming activities [38, 46–49]. THMs in pool water may reach much higher concentrations than those normally found and regulated in drinking water [48, 50]. Chloroform is the dominant and most abundant species in pools treated with chlorine and ozone, but brominated THMs levels are higher in pools treated with electrochemically generated mixed oxidants [51].
Outdoor pools are usually disinfected with chlorinated isocya-nurates (stabilized forms of chlorine more resistant to UV deg-radation). Thus potent irritants as chloramines, haloacetic acids or acetonitriles may be also found in such pools [52].
Given their volatility, THMs can be found in the airspace above the water and in the air in indoor swimming pools. Thus they may be taken up by swimmers through the skin, but also through ingestion and by inhalation. Studies on elite swimmers were among the first to suggest that the chlorinated atmosphere of indoor pools could be detrimental to the lungs by increasing the risk of asthma, bronchial hyperreactivity and airways inflam-mation [53–55]. Other studies performed on recreational swim-mers have provided further evidence that exposure to indoor chlorinated pools might contribute to the development of aller-gic diseases [56–58]. Life guards and others who work near a swimming pool are also at risk through the inhalation of DBPs, therefore this is also a problem of occupational health [43, 59, 60].
Studies on children attending indoor chlorinated swimming pools have shown that trichloramine, together with presumably aerosolized hypochlorous acid and chloramines, can damage the lung epithelium and promote the development of asthma, particularly among children with higher concentrations of total serum immunoglobulin IgE [27, 42, 61, 62]. A recent paper of Schöefer et al. [63], demonstrated during a 6-year follow-up of a prospective birth cohort study, some relationships between swim-ming pool attendance and health problems for swimming babies. Babies who did not participate in baby swimming programs had lower rates of infection in the first year of life (diarrhea: OR 0.68; otitis media: OR 0.81, airways infections: OR 0.85). No clear association could be found between late or non-swimmers and atopic dermatitis or hay fever until the age of 6 years, while higher rates of asthma were found (OR 2.15).
Another recent paper of Bernard et al. [52] illustrated a signifi-cant increase of ever and current asthma with the lifetime number of hours spent in outdoor pools by up to four and eight times, respectively, among adolescents with the highest attendance (>500 h) and a low exposure to indoor pools (<250 h). Use of residential outdoor pools was also associated with higher risks of elevated exhaled nitric oxide and sensitization to cat or house dust mite allergens. Thus even outdoor chlorinated swimming pool attendance is associated, according to this study, with higher risks of asthma, airways inflammation and some respiratory allergies.
Swimming bath granuloma, caused by Mycobacterium marinum, can be acquired in pools with cracked and roughened surfaces wherein the organism can proliferate. Infections with Mycobacterium avium and Mycobacterium abscessus have also been reported [30, 31]. Fungal infections of the feet and viral warts are often associated with pool use but are more likely to be spread from contact with contaminated surfaces surrounding the pool rather than the pool water itself. The sharing of towels and bath sponges was the likely cause of an outbreak of molluscum contagiosum, a viral infection of the skin [32].
Conjunctivitis is not an uncommon complaint among swim-mers but is usually the result of chemical irritation, such as with a low pH value or high combined chlorine levels. Infective con-junctivitis is more likely to be spread directly from person to person by shared towels than by the water, but outbreaks of eye infections due to adenoviruses can occur from swimming in pools with inadequate levels of disinfectant residuals.
Gastrointestinal infectionsOutbreaks of infections due to Giardia [33], Cryptosporidium [34], Escherichia coli O157:H7 [35], norovirus [36] and hepatitis A virus [37] have been reported in swimming pool users. Such outbreaks are now rare due to better maintenance and monitor-ing of disinfectant levels in public pools.
Respiratory irritation and infectionsSome bathers, asthmatics in particular, may experience wheezing from exposure to the chemicals in the pool atmosphere. This is now well established to be due to disinfection by-products [27].
Every swimmer contributes about 2.3–2.6 billion potentially pathogenic microorganisms in a swimming pool [38]. The micro-bicidal properties of several agents, especially chlorine, are used to avoid cross-transmission of such pathogens and eventual infec-tions [39]. But the reaction of chlorine with organic matter gener-ates some DBPs. Even though this topic is still controversial, in epidemiological studies the exposure to DPBs through drinking water consumption is linked with the development of bladder cancers [40] and less often colorectal cancers [41]. Recent works have discussed hazards for the workers and users of indoor swim-ming pools [42, 43] that come from acute respiratory exposure to trichloramine (or nitrogen trichloride).
The most common DBP is the family of trihalomethanes (THMs), which contains chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform. The trihalomethanes were chosen as the markers of DBP con-tamination because information about their toxicity and effects are known. Chloroform is classified as 2B (possible human car-cinogen) by the International Agency for Research on Cancer (IARC) and B2 (probable human carcinogen) by the US Envi-ronmental Protection Agency (EPA). The situation is identical for BDCM, which is classified as 3 by the IARC (not classifiable for human carcinogenicity) and C by the EPA (possible human carcinogen). Bromoform is classified as 3 by the IARC but 2B by the EPA.
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Taking into account the increased prevalence of asthma or atopic dermatitis among children and adolescents in Europe, even though this increase is certainly due to multiple factors, questions arises about the mandatory participation in swimming pool activities for school-age children. The debate continues, with some associations considering it to be a public health problem. Thus research is needed to confirm both the efficacy and toxicol-ogy of any new disinfectants.
In contrast with the frequency of these pulmonary irritation syndromes, other reported infections including legionnaires’ disease and Pontiac fever in users of spa pools, where water agi-tation can produce aerosols [64], are rare. A Pontiac fever-like illness was associated with a pool contaminated with Legionella micdadei [65]. Mycobacterium chelonae infection has been also reported in children with cystic fibrosis who used a poorly maintained hydrotherapy pool [66], and this leads to the more general question of immune-suppressed patients frequenting pools.
Other infectious diseasesUrinary tract infection with P. aeruginosa in a spa pool user is possible and primary amoebic meningoencephalitis in users of warm-water pools has been described in some countries [67]. Bloodborne infections, such as hepatitis B and human immunodeficiency virus infection, have not been associated with pool use.
Management and reporting
Ultimately, of the four factors that contribute to maintaining healthy water quality in a recreational water facility, facility man-agement is the most important [68]. Good management includes staff involved in the safe operation of the system according to the guidelines specified by the country in which the facility is located. All equipment will eventually fail, as will all disinfect-ants. Swimming pools will become contaminated with a variety of organisms and organic and inorganic compounds. When this happens, the staff must know how to immediately respond to minimize the risk to the bathers. A reporting system should be in place to alert public health officials of outbreaks so that they are immediately available to help document and contain the impact on human health. Facility operators should be in con-stant contact with the engineers who designed the system and the chemical suppliers.
Access to recreational water facilities is a great way for people to maintain a healthy lifestyle. The health benefits associated with recreational water will be negated if a bather’s health is put at risk due to an unsafe facility with poor water and/or air quality. A safe and healthy bathing experience will occur when the engineering design, water chemistry and disinfection are functioning opti-mally, and the entire system is being monitored by a highly trained facility manager.
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