UV Light Supplementary Swimming Pool Treatment

Transcription

1 UV Light Supplementary Swimming Pool Treatment Maintaining Good Pool Water Chemistry Swimming pool disinfection is necessary to create a healthy and safe environment for indoor pool recreation. The most common swimming pool treatments continue to revolve around chlorine. When most chlorine treatments are first added to pool water, they produce free chlorine as hypochlorous acid and hypochlorite ion residuals. These chemicals react very quickly to both oxidize and disinfect the contaminants introduced by both swimmers and the environment. This residual mechanism is advantageous due to the continuous addition of debris and germs by patrons requiring immediate treatment. Due to its relative low cost and high effectiveness in this role, chlorine continues to be used prominently around the world. Unfortunately, chlorine chemistry is often difficult to manage and can have undesirable effects on both swimmers and the environment. The addition of chlorine to pool water typically requires additional chemicals to maintain a comfortable ph around Therefore, not only are more chemicals entering the pool but additional costs for the chemicals, storage, and maintenance are added. Improper management of ph can result in bleached swimming suits, skin and eye irritation, and pitting of pool surfaces. Recent research has also discovered several microbes that are particularly resistant to chlorine disinfection. Two of these protozoan pathogens are Cryptosporidium and Giardia. Even with good maintenance of chlorine residual, cryptosporidium may remain active in pool water for more than a week. If an outbreak is expected, pools need to be closed for a day or two with excess levels of chlorine to kill off the germs. Prevention is often the best cure by scheduling periodic superchlorination of the pool. Obviously, this adds considerable cost for chemicals, maintenance, and pool down-time. Managing the quantity of free chlorine residual in the pool is also difficult as chlorine is quickly depleted by reactions with contaminants in the pool. When chlorine reacts with organic compounds, it may only partially oxidize the compounds resulting in intermediate products known as disinfection by-products (DBPs). A very strong chlorine smell is caused by DBPs and may be indicative of poor pool water chemistry. Chloramines, the most common DBPs, are directly attributable to swimmers complaints of skin irritation and eye burn. The long term effect of chloramines can also 2018 PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 1

2 have devastating effects to dehumidifying equipment and metallic supports as condensate laden with chloramines are extremely corrosive. Due to the above issues, there is a large demand for alternative disinfection methods to replace chlorine or atleast minimize its deleterious effects. This research paper attempts to define UV treatment as a possible solution to this issue. UV LIGHT: HOW IT IS GENERATED, DELIVERED, AND MEASURED UV light for disinfection involves generating UV light with the desired germicidal properties and delivering that light to the pathogens. In the electromagnetic spectrum, UV light is located between visible light and X-rays. UV light is divided further into four sub-categories with reference to the wavelengths as follows: vacuum UV ( nm), UV-C ( nm), UV-B ( nm), and UV-A ( nm). From research, the practical germicidal wavelengths have been determined as the range nm. UV light is generated by applying a voltage through a gas mixture. This process results in a release of photons at a wavelength that is predetermined from the components of the gas mixture and the temperature and pressure of the vessel. Most UV lamps use mercury as the primary component in this gas mixture although xenon is also known to release germicidal light. Low-pressure (LP) UV lamps contain mercury at low vapor pressure (2x10-5 to 2x10-3 psi) and at moderate temperature (40*C) to produce an output of monochromatic light at a wavelength of 254 nm. Medium-pressure (MP) UV lamps contain mercury at higher vapor pressure (2-200 psi) and much higher temperatures (600 to 900 *C) to produce polychromatic light over a range of wavelengths nm. In order to understand how UV works, how the light propagates from the lamp to the water needs to be discussed. There are several obstacles in the vessel that the UV light contacts including the quartz sleeves, the pool water, and the contaminants in the water. When UV light hits an obstacle, it reacts by reflecting, refracting, scattering, or absorption. In the first three, all involve a change in direction of the light whereas absorption ceases the transmittance of light. Once light is absorbed, that light can no longer be transmitted to other particles. Absorption involves the transformation of the light to other forms of energy. The amount of absorbance of a material depends on the materials composition. For example, a DNA molecule absorbs UV light most at wavelengths near 260nm. The turbidity of the water is another factor affecting the delivery of UV to the water. A UV system where the water is clear of debris is more efficient. This is due to a shadow effect where microbes may be shielded from UV treatment by excess suspended particles. Therefore, it is recommended that the UV system be installed after the filter/flocculator and before any chemical injectors for best results. Since water quality is an issue with determining the amount of light reaching the particle, quantifying the different variables in the water is important. The desired degree of disinfection depends on the amount of light absorbed by the pool water or UV dosage. Since there is no residual 100 nm 400 nm Gamma Rays X-Ray UV Visible Infared 254 nm Vacuum UV UV-C UV-B UV-A 280 nm 315 nm 100 nm 200 nm 300 nm 400 nm Fig. 1 UV light in the electromagnetic spectrum (EPA Guide 2006) 2018 PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 2

3 Fig. 2 Example of UV disinfectant equipment (EPA Guide 2006) UV in the water to measure, the dosage is determined from three factors: UV intensity, flow rate, and UV transmittance. One of these factors for UV light delivery is the measurement of the absorbance of a material. UV absorbance (A) measures the quantity of light absorbed over a certain distance. For water treatment applications, the absorbance of light at wavelength 254nm, A254(cm-1), is used to determine the amount light passing through the water and reaching target organisms. Similarly, UV transmittance (UVT) describes the percentage of UV light that passes through material over a certain distance. Flow rate is a function of the pool size and required turnover rate of the pool water and is thus a determining factor in the residence time of the reactor. This residence time is defined as the time that a particle spends in the reactor while exposed to UV light. Therefore, it can be reasoned that a faster flow results in a decreased dose. Another factor, UV intensity, is a fundamental property of the UV light being produced and has the units W/m2. Finally, UV dose is found by multiplying the UV intensity, the residence time in the reactor, and the UV transmittance of the water. This calculation provides units for UV dose that is usually given as mj/cm2. The generally accepted dose sufficient for disinfection of microbes and viruses is 60 mj/cm2. UV DISINFECTION EQUIPMENT UV reactors are designed for effective disinfection of the pool water. Equipment components of the typical UV system consist of the UV reactor, UV lamps, ballasts, lamp sleeves, cleaning systems, and UV sensors. This section provides detailed description on each component of a UV system. An illustration of an LP system with labeled components is given in Figure 2 for reference. UV Reactor The UV reactor for swimming pool disinfection is classified as closed channel. Typically composed of 316 stainless steel, the reactor is designed to provide efficient and costeffective dose delivery of the UV light. The flow through the chamber is turbulent to promote mixing while minimizing head loss. The lamp location, baffles, and inlet/outlet locations all affect mixing. Lamps are oriented to optimize dose delivery. All reactors are oriented perpendicular to the existing piping system. This setup allows removal of the UV lamps and easier maintenance on system components. The result of this configuration is that the lamps are also perpendicular to water flow. Orienting the inlet and outlet connections 90 degrees to the chamber also prevents eddying, short PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 3

4 circuiting, and dead zones. The inlet and outlet connections with respect to each other can either by in-line or off-set. The above figure shows a multi-lamp system with an offset inlet and outlet. In contrast, a medium pressure UV system typically has an in-line configuration. The shorter lamp length of an MP system lends itself to an in-line setup that results in reduced head loss and footprint size of the system while maintaining disinfection goals. Compared to other treatment equipment such as ozonators or chemical feed pumps, the UV reactor takes up a much smaller footprint. Often, the UV system can be installed with minimal modification to the existing piping system. This is an advantage over other systems as the installation time and cost is much less meaning less down-time of the pool. UV Lamps There are several types of UV lamps but the most common are low-pressure (LP), low-pressure high-output (LPHO), and medium-pressure (MP). LP and MP lamps have been briefly discussed above. LPHO lamps use a mercury amalgam mixture to produce a higher output of UV light. The amalgam is typically composed of gallium or indium metal. LPHO lamps operate at a slightly higher temperature ( degrees C) but require fewer lamps to deliver the same dose as LP lamps. Due to the higher monochromatic output at 254 nm, LP and LPHO lamps are actually more germicidally efficient than MP lamps. LP lamps are typically used in multiples and require less power than MP lamps. LP lamps have a longer lifecycle than do MP lamps. LP, LPHO, and MP lamps all consist of the following components: lamp envelope, electrodes, mercury fill, and inert gas fill. The lamp envelope is composed of a thin layer of quartz due to high UVT and temperature resistance. The envelope encapsulates and insulates the fill gases. Electrodes are used to maintain the appropriate temperature of the lamps by promoting heat transfer. In the case of LP and LPHO lamps, they are composed of a coil of tungsten with calcium, strontium, or barium oxides. For MP lamps, a tungsten rod is wrapped with a tungsten coil. While MP and LP both use liquid elemental mercury, LPHO uses an amalgam or solid mercury alloy with other metals. As the lamps heat up, the mercury vapor pressure increases. The amount of mercury vapor allowed to form differs between the lamp types. An inert gas fill, typically Argon, is used to increase the lifetime of the electrodes and mediate the mercury gas formation. In lieu of amalgam lamps, the output of LP lamps can also be increased by reinforcing the electrodes. This reinforcement enables the lamp to receive a higher current resulting in higher output PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 4

5 Upon start-up, the lamp s electrodes discharge electrons that ionize the inert gas. This ionized gas results in plasma allowing current to flow through the lamp and heating up the ionized gas. The hot gas vaporizes the mercury and the resulting collisions between mercury vapor and electrons in the plasma allow mercury s electrons to reach an excited state. As the electrons drop back down from the excited state to the ground state, energy is released as UV light. LP and LPHO emit UV light at 254nm and MP lamps emit UV light over a spectrum from nm. All UV lights also emit some visible light due to transitions associated with higher energy levels of mercury atoms. With use, UV lamps degrade over time resulting in a decreased output and thus lower UV dose. Fouling of the interior envelope is typical with electrode degradation. Exterior fouling from the water can also increase aging. Ballasts Ballasts are used to regulate the power input to the lamps electrodes. Ballasts for water treatment applications are either electrical or magnetic. Some manufacturers engineer magnetic ballasts to control the UV intensity of the lamps depending on the UVT of the water. As the UVT increases, the dosage required to treat the water is less. Since the lamps operate continuously, this ballast control provides a method for saving energy due to the variability in daily demand. However, operating in the low (~80% UV intensity) setting may cause a decrease in lamp lifetime due to electrode sputtering. Lamp Sleeves Lamp sleeves contain UV lamps to maintain the lamp s operating temperatures and prevent lamp breakage. Typically composed of a tube of quartz, lamp sleeves must be designed to withstand high temperatures, pressures, and ozone. Ozone protection is especially important in MP systems that produce ozone-forming wavelengths of UV light. An improperly designed lamp sleeve can result in offgassing of impurities that can foul the interior of the sleeve thus reducing UV dosage. Sleeve fracture is a concern when designing the system. Internal stress and external mechanical forces included wiper malfunctions and water hammer can damage the sleeve. When this happens, the colder pool water rushes in and contacts the hotter sleeve envelope. This interaction can crack the envelope resulting in a mercury release. Lamp sleeves can also be fouled externally by the components in the pool water, other photochemical processes, or thermal effects. External fouling can be removed by cleaning. Cleaning Systems There are three types of cleaning systems employed by manufacturers depending on the application. Manual chemical cleaning involves turning off the system, removing the lamps, and cleaning with a chemical solution of citric acid, phosphoric acid, or other manufacturer provided approved cleaning solution. Lamp sleeves can also be cleaned in place without removal by filling the chamber with the cleaning solution and allowing it to dissolve the 2018 PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 5

6 fouling. This process typically takes about 3 hours from shutdown to startup. Manual cleaning varies in frequency from monthly to yearly depending on water quality and fouling frequency. Alternatively, motor or magnetic powered wiper systems are used to clean the sleeves in place during operation. Mechanical wipers typically consist of stainless steel brush collars or teflon rings that move along the sleeve. Some wipers also contain cleaning solution to physically scrape and chemically dissolve the fouling during its sweep of the sleeve. MP lamps typically require wipers due to the increased temperatures causing more rapid fouling of the sleeves. Sensors UV sensors are used to monitor the intensity of the UV lamps at a certain point in the reactor. When used with flow rate sensors and possibly UVT sensors, it can determine the dose delivery of the system. This measurement correlates to changes due to aging, fouling, and power setting. The UV sensor receives UV light either through a monitoring window (external, dry sensors) or light pipe (internal, wet sensors). Other optical components, diffusers and apertures, are used to reduce the UV light reaching the photodetector to decrease sensor degradation. Filters are used to limit the wavelengths to the germicidal range nm. Fouling of the view window or wet sensor can occur and may require cleaning. Measuring UVT is also important in determining dose delivery and so UVT analyzers are often employed. If UVT analyzers are not used, other sensors for determining water quality may be used. As discussed previously, several manufacturers use the measurement of UVT to vary the lamp output so that an appropriate cost-effective dose is being delivered. There are two types of UVT analyzers available. One uses UV sensors at varying distances from the UV light source. The UVT is calculated by the differences in intensity between the sensors. The other type is a flow through spectrophotometer that uses light at wavelength 254 to measure the absorbance at 254 and thus calculate UVT. Temperature sensors are also used to monitor the reactor temperatures. If the temperature falls outside the recommended range, the reactor will shutoff to prevent damage to the system. Overheating can occur if air enters the reactor or the water flow stops. Temperature sensors are most prevalent in MP systems where the operating temperature is much higher. UV System Sizing Sizing of the UV system is most important for effective and efficient water treatment. A system that is too large will consume too much energy and burn free chlorine at a faster rate whereas a system that is too small will deliver insufficient UV dosage to treat the water. Most UV systems are designed to deliver a minimum 60mJ/cm2 as the UV design dosage required. In order to accomplish this dosage, two primary components used to size a UV system are the UV transmittance (UVT) of the water and the flow rate. This flow rate is typically characterized as the design peak or average flow rate depending on the demand to turnover the water. While design peak flow rate depends on the peak bather load of the pool, a quick calculation for average flow rate can be done. Average flow rate is calculated by dividing the volume of the pool (in gallons) by the desired turnover rate of the water (typically 4 hours to accomplish six turnovers per day). Additional conversions may be needed to convert flow rate in gallons per hour to other units. The UVT or water quality of a pool system is also an important indicator for sizing. UVT, turbidity, iron, hardness, and color are all indicators of water quality. This is a function of the bathing load of the pool as well as the effectiveness of existing pool treatment aspects such as filtration. Two pools with the same flow rate may require different sized UV systems if the water quality differs. Test kits are available to determine the water quality of 2018 PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 6

7 the pool. Other site-specific qualities factor in adequately sizing the UV system. Without going into great detail, these may include space restrictions, head loss limitations, and existing treatment components upstream of the UV reactor. Ultimately, the individuals disinfection goals for water treatment are the deciding factor in UV design. UV FOR WATER TREATMENT Disinfection UV light for water treatment has multiple purposes. The most typical application is for disinfection. The bactericidal mechanism for UV differs from that of chlorine residual. Chlorine disinfectants perform physical damage to cellular structures interfering with metabolism and hindering biosynthesis and growth. In contrast, UV light disinfection occurs by damaging the nucleic acid (RNA and/or DNA) of microbes. This action prevents them from replicating thereby eliminating their ability to infecting hosts. Since the optimum wavelength for nucleic acid damage is about 260nm, both MP and LP systems are effective at disinfection. addition to damaging the nucleic acid, other enzymes and proteins may be damaged by their absorbance to the additional range of wavelengths. The measure of a microorganism s sensitivity to UV light is termed microbial response. Unique to each pathogen, microbial response can vary significantly depending on the UV dose. The reduction of microbes due to UV light is typically given in terms of log inactivation or log reduction. Log inactivation is a convenient way to represent the number or percent of microorganisms inactivated through the disinfection process. For example, a 3-log inactivation means that 99.9% of a targeted microorganism has been inactivated. UV light disinfection is deemed especially effective in deactivating chlorine resistant microbes. Two especially chlorine resistant protozoan pathogens include Cryptosporidium and Giardia. To illustrate its effectiveness, UV dosage of just 20 mj/cm2 is enough to accomplish more than a 3-log inactivation of both pathogens. Viruses, such as rotovirus, often require a larger dose for inactivation. For this reason, the recommended UV dosage is 60 mj/cm2. Chloramine Reduction Another application of UV light is the reduction in chloramines. The phenomenon of photolysis is generally thought to be responsible. Photolysis is a chemical reaction in which a chemical compound is broken down by photons. In the case of chloramines, the optimum wavelengths for chloramine photolysis are 245nm for monochloramine, 297nm for dichloramine and 260nm and 340nm for trichloramine. Due to low-pressure UV lamps monochromatic output at 254nm, they are able to cause lysis in monochloramines. LP UV manufacturer s make the claim that since monochloramines are in the largest quantity in pool rooms and are a precursor to the other more hazardous chloramines, LP UV can effectively reduce chloramine levels. However, MP lamps are much more efficient in reducing chloramines. While low-pressure lamps can effectively eliminate monochloramine, medium pressure lamps simultaneously degrade all forms of chloramine. This is advantageous since the more troublesome chloramines are impacted immediately. However, some microbes can also repair their damaged DNA using enzymes by a process called photorepair, in the presence of light, or dark repair in the absence of light. The recommended UV dosage is increased to account for any repair. MP manufacturers also claim that the broader spectrum of UV light output of their MP systems (compared to LP systems) eliminates microbes ability for repair. In UV lamps also degrade free chlorine residual depending on the dose delivered. With increasing UV dose, increasing amounts of residual are removed from the water. This process is more significant for MP lamps than LP lamps due to the wider spectrum of wavelengths. However, in order to significantly reduce the chlorine residual, a dose ten to twenty times more than the disinfection dose (60 mj/cm2) is required. Even so, most UV manufacturers recommend chlorine feeders be placed after the UV system in the 2018 PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 7

8 treatment cycle. On the contrary, if an ozone system is used in conjunction with UV, these ozone systems are typically placed before UV systems as long as the ozone is properly quenched before reaching the UV chamber. These effects and others must be considered during the design phase to optimize treatment. Although UV does not impart any chemical residual in the water, by-products can result either directly from photochemical reactions or indirectly by reactions with the products of these reactions. From research, it has been found that UV light does not decrease the production of trihalomethanes (THMs, i.e. chloroform) or haloacetic acids (HAAs) when UV treated water is subsequently chlorinated. Furthermore, in some studies, it has been observed that the level of THMs actually increased. (D Cassan et al, 2006) While this increase remained below the action level for THMs (100 ug/l), the increase was significant to encourage monitoring of THMs for a potential hazard condition at the new level. This example simply illustrates that the implementation of UV disinfection does not cure all issues with chlorine disinfection. Regulations Standards require products to meet a set of minimum criteria for operation, durability, and safety. One such standard relevant to swimming pools is NSF Standard 50. The NSF (National Sanitary Foundation), a nonprofit, non-government organization is a leader in standards development, product certification, education, and riskmanagement for public health and safety. NSF standards focus primarily on the food, water, indoor air, and environment. NSF target audience includes industry, the regulatory community, and the general public. NSF standards are continuously evolving to improve existing standards and account for new technologies and filtration options available. Currently, 28 of 50 states have regulations requiring compliance or third-party certification of pool circulation components to NSF 50. Specifically, NSF 50 contains criteria for materials, components (such as pipe, fittings, valves, filters), and devices (such as chemical feeders and process equipment). As an example, supplementary disinfection systems are required to meet 3,000 hours life-cycle tests. Also, in order to be approved for use, the designed disinfection system must also meet a requirement of 3-log inactivation of problem organisms (i.e. cryptosporidium). NSF 50 also reflects the requirement for residual chlorine to be maintained with UV systems, Ozone systems, and ion generation systems. Disinfectants must be active in the pool since swimmers are continuously adding organics and pathogens. For UV systems, NSF 50 mandates that not less than 1ppm of free chlorine is maintained. In states where NSF 50 is not mandated, most regulations state a minimum 1ppm free chlorine residual as well. However, seven states prescribe a lower free chlorine 2018 PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 8

9 residual as sufficient for swimming pool disinfection. For example, in Pennsylvania the minimum is 0.4ppm free chlorine. Depending on the pool s local codes, cost savings will differ when switching to UV systems due to the variability in state regulations. UV System Cost Analysis Cost analyses will differ depending on the demands and size of the pool. For the purposes of this paper, a public indoor pool such as that found in a community center is used as an example. Due to its more efficient chloramine reduction, an MP type UV system will be used rather than LP or LPHO. The starting cost of an MP unit is on the order of $20,000-30,000. This pricing includes startup costs of roughly $5,000-$6,000. Installation and startup of an MP system is relatively simple when compared to installation of chemical feeders. The typical setup for an MP system is as an in-line unit often requiring minimal modification to existing piping. Installation generally takes 2-3 days with startup in an hour or less. Energy use and maintenance are periodic costs that add to the overall cost of the UV unit. The energy use in UV treatment is primarily from the power draw of the UV lamp employed. The power use of an LP lamp has been compared to the cost in operating a household light bulb or specifically Watts. MP lamps have significantly higher power draw in the range of 1,000-3,000 Watt due to the higher output required. As a reminder, while MP lamps power draw is much higher, LP systems typically require multiple lamps to deliver the same dose. Different components to the UV system may also require a different setup for power input. While the lamp itself is typically 3-phase V, the sensors may be single phase. Electrical maintenance considerations need to be determined during the design phase to minimize potential issues. Operation and maintenance steps are important to ensure that the unit is meeting the intended disinfection requirements. An operations schedule is typically adopted at startup with the manufacturer to include daily, weekly, monthly, and semi-annual tasks. Daily tasks include an overall visual inspection of the area, equipment and controls. This is to confirm all sensors and recording equipment are operating normally and within design limits. Weekly tasks may also require running the wipers in manual mode and checking to verify proper operation. The lamp lifecycle is inspected on a monthly basis. Lamps will need replaced if lamps operating hours exceed design values. Finally, semiannual tasks include checking the ballasts and any valves for irregular operation. Maintenance costs are fairly minimal relative to other disinfection systems. The primary concern is in replacing the UV lamp. Since the lamp ages with time, regular replacement of the lamp is recommended between 6-12 months depending on the manufacturer to ensure the lamp is capable of delivering sufficient UV dosage. As an example, the average cost for a new medium pressure lamp is in the $ range. Low-pressure lamps are typically cheaper and may also last longer than MP lamps. However, in order to deliver the same UV dosage as an MP lamp, more LP lamps are required thus increasing this replacement cost PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 9

10 Maintaining the cleaning system presents an additional cost. However, as mentioned previously, MP systems mostly use automated wiper systems that require little maintenance except in the case of breakage and replacement. The wipers operate automatically without requiring the unit to be shut-down. On the contrary, LP systems typically use manual chemical cleaning systems that do require shutdowns for removal of scale and fouling on the lamps. However, this cleaning is typically only required quarterly or semiannually depending on the water quality. UV sensors also require periodic calibration and replacement to ensure that the correct UV dosage is measured and employed. Calibration is general on an annual basis and can cost between $200 and $500. UV sensors generally last 5-10 years and can cost about $1200 to replace for MP units or $400 for LP units. Additional life cycle costs to consider on an individual basis are costs for sleeve renewal, ballast renewals, sensor calibration, sensor replacement, and disposal costs. While the total life cycle of a UV system is about 7-10 years, manufacturer warranty typically only covers the first year of use. Sleeves typically last 5-10 years and range in cost from $100 to $500. Much more expensive are ballasts that can last 5 or 10 years and can cost upwards $2000 to replace. Lamp disposal costs depend on the site-specific location. Since mercury is a hazardous chemical, municipalities and states often declare UV lamps as hazardous waste requiring a certain method for their disposal. However, as long as the quantity of lamps requiring disposal is low, the local EPA office may offer a free dropoff to recycle used lamps. Cost Recovery While the starting costs of UV systems are high, a return on investment can be realized in switching from chlorine to a UV system. The average pay back period is within three years of startup of the UV system. The return varies greatly depending on the demands of the pool and the existing chemical disinfection plan. This cost is recovered in the following ways: reduced chemical costs, less makeup water, less out-side air heating costs. While a chlorine residual is still required, UV systems make it easier and less costly to maintain the chlorine residual. Especially with an MP system, chloramines do not build-up thus eliminating the need for periodic superchlorination. The chance of a chlorine-resistant bug outbreak is also eliminated and further eliminates the need for superchlorination. By eliminating shock treatments, the costs associated with excessive chemical use, additional maintenance labor, and pool down-time are all eliminated. Similarly, it has been reported that significantly less makeup or dilution water needs to be added to the pool since the water is being continuously cleaned by the UV system. This reduction of water depends on the existing policy of the pool facility. Some facilities have noticed more than 50% reduction in the amount of makeup water required. The savings associated with this reduction are from water usage, water heating, and water treatment. Since UV systems clean the water and reduce the incidence of chloramines in the air, the demand for fresh outside air may be reduced. While ASHRAE has a minimum amount of fresh air that is required for the space, excess fresh air is often needed for pools with chloramine problems in an attempt to dilute the air. The costs associated with conditioning this outside air are large. By using a medium pressure UV system, these costs can be reduced. Conclusion While UV systems can solve many of the issues with chlorine treatment, UV cannot replace chlorine entirely. An active residual disinfectant is still needed to combat the continuous addition of germs from bathers. Furthermore, most state regulations place this minimum chlorine residual at 1ppm or 1mg/L. However, UV, especially medium pressure UV, greatly alleviates the pool owner from the complexity of chlorine chemistry management by reducing corrosive chloramines and treating chlorineresistant 2018 PoolPak LLC. All rights reserved. UV Light Supplementary Swimming Pool Treatment 10

11 pathogens. In fact, several studies have shown that a significant deduction in chlorine use and make-up water can be realized through the use of UV. Choosing the appropriate disinfection goals while designing the UV system is especially important in this regard. While the UV system is not maintenance free, the ease of installation and minimal maintenance are positive aspects compared to other more complicated systems and chlorine chemistry management in general. In addition to its efficiency in disinfection, these aspects make it a viable supplementary disinfection treatment for swimming pools. REFERENCES 1. Water Chemistry for Swimming Pools. North Carolina Division of Environmental Health, Department of Environment and Natural Resources March ehs/quality/wph.htm 2. Smith, David R. Swimming Pool Treatment with UV. Water Technology, Vol.27, Issue 6, February www. watertechonline.com/article.asp?indexid= Colleen Carpenter, Ronald Fayer, James Trout, and Michael J. Beach. Chlorine Disinfection of Recreational Water for Cryptosporidium parvum. Emerging Infectious Diseases. Vol.5, No.4, July-August February pdf/carpenter.pdf 4. Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced Surface Water Treatment Rule United States Environmental Protection Agency, Office of Water. 14 March uvguidance.pdf 5. Great Expectations: UV Treatment Transforms Pool Environments. Pool & Spa Mag. July March thewaterlandgroup.com/sites/p/poolandspaindustry/index. php?section=15&page= Linden, Karl G. Ph.D. UV Disinfection: An Age-old Emerging Technology for Safe Water. Presentation Online powerpoint. Naefrontiers.org. 14 March aspx?id= Hassle Free- Chemical Free- Chlorine Reduction in Water. UV Sciences Inc March, Dechlorination.html 8. Purkiss D. NSF Standard 50: Circulation System Components and Related Materials for Swimming Pools, Spas and Hot Tubs. 25 February presentationsp/purkiss_p.pdf. 9. Ormeci, Banu, Ishida, Gina and Karl G. Linden. Impact of Chlorine and Chloramine on Ultraviolet Light Disinfection. June Emperoraquatics-pool.com. 23 February emperoraquatics-pool.com/duke_unc_study.pdf 10. D. Cassan et al. Effects of medium-pressure UV lamps radiation on water quality in a chlorinated indoor swimming pool Chemosphere 62: February Ref%20docs/23%29%20UV%20trials%20in%20France% pdf Disinfection: CT and Microbial Log Inactivation Calculations. May Drinking Water Reference Guide. Colorado Department of Public Health and Environment, Water Quality Control Division- Engineering Section. cdphe.state.co.us/wq/. 14 March LogInactivationBrochure_2009.pdf With more than 45 years of experience in indoor pool dehumidification equipment manufacturing, PoolPak LLC is the most well-known brand in the industry. Our people and products work daily to improve the quality and comfort of indoor pool environments. PoolPak dehumidification solutions include a variety of heating, ventilation, and air conditioning systems, in addition to an industry-leading PoolPak support network. For more information, please visit Industrial Drive York, Pennsylvania USA Fax PoolPak LLC. All rights reserved. MKW00-ELUVL