rethinking pools to boost safety and minimise use of water

Safe pool solutions ensuring high water quality and minimised use of resources

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white paper

Rethinking pools to boost

safety and minimise use of water, energy and chemicals

Rethinking pools to boost safety and minimise use of water, energy and chemicals Safe pool solutions ensuring high water quality and minimised use of resources

Version 1.0

About this white paperThis white paper was developed by the Rethink Water network in Denmark. The work is coordinated by the Danish Water Forum.

The Rethink Water network consists of more than 60 technology and consulting companies, water utilities, water organisations and public authorities. It was established to support our partners internationally in developing the highest quality water solutions.

Quoting this white paperPlease quote this white paper and its articles: “Kristensen, G.H. (Tech. Ed.) & Klee, P. (Ed.in C.), 2014. Rethinking pools to boost safety

and minimise use of water, energy and chemicals. Safe pool solutions ensuring high water quality and minimised use of resources. The Rethink Water network and Danish Water Forum White Papers, Copenhagen. Available at www.rethinkwater.dk”

Editor in ChiefPia Klee, kickstarter for the Rethink Water platform [email protected]

Technical Editor DHI Gert Holm Kristensen [email protected] DHI Morten Møller Klausen [email protected]

Contributors COWI Torben Schack [email protected] Danish Rootzone Technology Jørgen Løgstrup [email protected] DHI Gert Holm Kristensen [email protected] DHI Morten Møller Klausen [email protected] inBlue Ole Grønborg [email protected] LiqTech Daniel Larsen [email protected] Rambøll Henning Hammerich [email protected]

Language Editor David Lalley, WordDesign

© The Rethink Water Network & Danish Water Forum 2014

mailto:[email protected]










Executive summary

Even if the practical and legal requirements with regard to the operation of public pools and water parks vary widely on a global scale, most of the technologies used have hardly changed in the last 100 years. For over a century, chlorine has been the preferred dis infectant for making sure the water is free of unhealthy bacteria and – due to the lack of alter natives – the continued use of chlorine is still the most realistic future scenario. Yet large quan tities are not always needed to keep the water safe, and lowering the chlorine content im proves the water and air, protecting people from the intense chlorine odour and itchy eyes and skin.

Improved water treatmentThe mechanisms controlling the formation of harm ful chlorinated disinfection by-products are very complex and still poorly understood, but there is a general consensus that the forma-tion rate increases with higher concentrations of chlorine. One option, therefore, is to lower the pH of the water – a measure that some coun tries have practised for years. Chlorine occurs in a much more active form at a lower pH, which means that the same disinfection effect can be achieved with a lower chlorine content. Another option is to redesign water treatment systems to remove solid impurities more often in order to avoid the chemical breakdown of contaminants with chlorine. An optimised water flow and drum filters will remove 90 to 95 per cent of solid organic substances up to 200 times

a day, which is much better than traditional systems that only remove pollution a few times a week, or even less. This filtration is typically combined with other technologies to remove the remaining particles.

Improved ventilationMuch of the remaining by-products are then removed with a gas stripper, UV technology and other equipment. The chlorinated com pounds are also removed at the surface of the pool by new kinds of ventilation. Nowadays most venti-lation systems in swimming pools are designed to keep the air over the water surface still, in order to cut down evaporation and thus reduce energy consumption. However, this is not good for the health of those using these pools.

Improved overall resource efficiencyAnother important perspective on the grow-ing pool market is the trends towards larger, advanced pools that in turn lead to an increased use of water, energy and chemicals. The risk is that operating costs rapidly escalate. There are, of course, physical limits for how efficient a very resource-intensive facility like a swimming pool can become, but the opportunity to bring down the consumption of water, chemicals and energy is certainly available. This white paper provides numerous examples of how owners of public pools have reduced their operating costs and at the same time achieved a more healthy environment.

First to embrace new concept, Sweden In Sweden, the Filborna Arena in Helsingborg was the first public swimming facility to embrace new technology concepts that avoid harmful chlorine by-products and thereby improve the indoor environment for swimmers. In 2010, new extended pool facilities, built as a green-field project, were added to the existing facility. A radically different water treatment concept, combined with an innovative air ventilation system, has reduced the level of chlorine by-products to detection limits, pro tecting people from an intense chlorine odour, itching of the eyes and skin, and respiratory ailments. In addition, the use of water, energy and chemi-cals were greatly reduced compared to the traditional facility, which is separated from the new by a glass door. In 2012 the Filborna Arena was the proud host of the Swedish swimming championships. (Courtesy: inBlue)

Walking through the glass door separating our old and our new facility you feel the huge difference between the new and the classic pool system. It really stresses the need for public pools to bring down the level of clearly harmful chlorine by-products

PER KERSMARKCEOFILBORNA ARENA, SWEDEN

WHITE PAPER - RECREATIONAL WATER | 4

Harbour pool in central Copenhagen, Denmark In natural water environments as rivers, lakes and the sea, the quantities and flow of water are normally huge, and bacteria that are part of a natural balance break down contaminants resulting from people bathing. As a rather unique story, the harbour of Copenhagen has been transformed from an industrial port to a vibrant cultural and social centre of the city in just a decade. People now swim and enjoy water playgrounds in the city centre in an impressive natural outdoor pool – the harbour itself. The industrial water traffic is gone, so modernising the sewer system and diverting local rainwater improved the water quality so the City of Copenhagen was able to open this public harbour bath in 2002. Protection against wastewater discharges during heavy rainfall is managed by integrated wastewater strategies and innovative technology. An integrated bathing water quality forecasting system measures sewer overflows, and hydrodynamic and bacterial models simulate the water quality in the harbour. This system provides real-time information about whether or not the water quality complies with the EU Bathing Water Directive. Download the white paper on wastewater treatment , which is part of the same series as this white paper on www.rethinkwater.dk/wastewater

Photo: Kontraframe/City of Copenhagen

Efficient solutions for treatment of wastewater

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In control of wastewater

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www.rethinkwater.dk/wastewater


1. A technology shift for better health and higher efficiency 1

2. Balancing safe water with a healthy pool environment 2

3. The full opportunities with an optimised design build from scratch 5

4. Upgrading of existing facilities to cut costs and improve water/air 9

5. Documenting performance of new water treatment technology 11

6. Design of water environments with no use of chemicals 15

If your goal is water efficiency, Denmark is ready as a partner 17

WHITE PAPER - RECREATIONAL WATER | 6 Photo: Iwan Baan

Outdoor pool World Expo 2010, China Many architects and designers are attracted and inspired by water and natural water environments. This was also the case when Denmark’s pavilion for the World Expo 2010 in Shanghai was designed by the award-winning Danish architectural firm BIG (Bjarke Ingels Group), and the Little Mermaid statue of Copenhagen was brought on a historic trip to China. The bronze-skinned statue has sat pensively on the edge of the harbour since 1913, created to commemorate the leading character in the 19th-century fairy tale The Little Mermaid by Danish author Hans Christian Andersen. It was brought to the World Expo 2010 as a token of China–Denmark friendship and as a symbol for the unique story of Copenhagen Harbour’s clean water, as explained on the previous page in this white paper. The pavilion was built around an artificial pond whose water represented the sea surrounding the statue at home in Copenhagen harbour. The water was kept clean and safe to take a swim in, using the same technology concept introduced in this white paper. (Courtesy: BIG and inBlue)


Recreational water facilities are popping up everywhere in the world, with fun and exotic water environments featuring pools, water slides, river rides, wave surfing, spa relaxation and so on. These facilities extend from public swimming pools for local citizens to major waterparks as tourism destinations. Even if the practical and legal requirements for operat-ing public swimming pools vary considerably throughout the world, most of the technologies used in these facilities have hardly changed in the last 100 years, no matter where the facility is located,. The technologies most commonly used for are sand filtration, activated carbon and chlorination, adapted from the purification of drinking water.

Increased resource efficiencyOne argument for a technology shift lies in the potential for reducing the consumption of water, energy and chemicals in a resource-intensive sector like swimming pool operations. Reduced consumption will play an increasingly important role in being able to follow the global trend towards larger and more advanced recreational water environments with more visitors, higher temperatures and other features that make a facility even more resource-intensive. If the costs of increasingly scarce resources such as

1. A technology shift for better health and higher efficiency

Technology shift in pool water treatment The mechanisms controlling the formation of harmful chlorinated disinfection by-products are very complex and still poorly understood, but there is a general consensus that the for ma tion rate increases with higher concen-trations of chlorine. By removing solid organic conta mi nants from the pool water before they dissolve and are broken down by chlorine, the the water quality and indoor air will be considerably improved and less chlorine is needed. The photo shows a sample of particles, mainly skin cells, collected by a drum filter up to 200 times per day. Imagine how these, if not passed to the sewer as waste, will react inside a sand filter. With hot chlorinated water stressing these particles for 7 days or more the skin cells will be dissolved and then return to the pool creating lots of unnecessary chlorine by-products that swimmers and bathing guests then will inhale. (Courtesy: inBlue)

Having worked most of my life in the facility, it is amazing to see this dramatic change in water and indoor air quality. Changing our Olympic-size pool to a family swimming centre with more pools was a complex project, since all the new equipment had to fit into the existing basement, but we were able to double the water treatment capacity and still keep water and energy consumption the same

JAN ASBJERGTechnical ManagerGREVE SWIM CENTRE, DENMARK

water and energy rise, the risk is that operating costs will go through the roof.

Attention of politicians importantAnother argument for a technology shift lies in the much healthier pool environments. Yet, the pool environment will probably not be a big selling point for most investors even if the many public swimming pools and water parks need to distinguish themselves from the many com pe titors that will be out there. The market is highly conservative and competitive, which means that the adoption of new technology concepts requires solid documentation for their economic validity. Attention from politicians and public authorities should then help push the pool market towards healthier and greener solutions based on relatively strict legislation, which then creates a demand for innovation in the supply chain. In Denmark, the political term “innovation promoting legislation” has already caught the attention of politicians as new Danish legislation (Number 623) for pools strictly limits chlorine by-products and guides pool owners towards reducing both pH and free chlorine. It also requires automated measure-ment of key parameters combined with daily manual measurements by staff and frequent monitoring checks by an accredited laboratory.


2. Balancing safe water with a healthy pool environment

Spending time in water is fun and gives numer-ous health benefits, but the moist, chlorine-scented air is often part of the experience. For over a century, chlorine has been the preferred disinfectant to ensure the water is free of unhealthy bacteria and – due to the lack of alternatives – the continued use of chlorine is still the most realistic future scenario. However, large quantities of chlorine are not always needed to keep the water safe and free of bacteria, and lowering the chlorine content protects people from the intense chlorine odour and itching of the eyes and skin.

Chlorine has negative health impactsWhen chlorine reacts with organic and inorganic matter like sweat, saliva, urine and skin resi-dues released from people, it forms disinfection by-products (DBP) that either remain in the water or evaporate into the air. The chlorine itself does not smell – the smell stems from the by-products formed when the chlorine breaks down the impurities. Unfortunately, a great deal of studies support that these chlorinated by-products – especially chloroform and chloramines – are more harmful than previously believed. The hypothesis laid down by some researchers is even that the chlorine compounds contaminating the air of indoor swimming pools are at least a partial cause of

Lowering a pool’s chlorine concentration is a three-step concept. First, the water flow is optimised to remove organic contaminants in a mechanical instead of a chemical process. Secondly, the pH is lowered to make the chlorine more active and thirdly the ventilation flow is designed to remove chlorine by-products from the water surface

GERT HOLM KRISTENSENHead of InnovationDHI

Saline pools, Denmark Saltwater treatment is known to relieve certain types of skin diseases and is also known to have a natural disinfecting effect. These features are used in a very unique wellness centre on the island of Læsø, which is a former church converted into this modern wellness centre, supported by architects and engineers. In this part of Denmark, the highly saline groundwater concentrations have been mined since the Middle Ages and are a landmark of the island. This water is now used for the highly saline pools with concentrations of 30 per cent salt. However, the use of dissolved salt as an alternative to chlorine is not allowed by the current Danish legislation, but the facility has been able to get dispensation to operate the pools at a lower chlorine concentration than required by this legislation. (Courtesy: COWI)

the steep rise in childhood asthma observed over the past decades. In Germany, parents are therefore now advised to refrain from baby swimming with children aged 0–2 years if allergies often occur in their family. Another important sign of problems with chlorine is the health of elite swimmers. Even though they live a more healthy life than ordinary people, research shows that they are diagnosed with asthma or asthma-like symptoms nearly twice as often. So even if all elite athletes have an increased risk of asthma, regardless of the type of exercise taken, research has shown that elite swimmers have a 50 per cent greater risk of asthma than tennis players, for instance.

Harmful by-products hanging in the airThe air in swimming pools may be the cause, as swimmers are often exposed to high levels of trichloramines, which are by-products formed when chlorine breaks down organic materials. Trichloramine has a damaging effect on the lungs, and Scandinavian researchers suggest that this may be one of the causes of the increased incidence of asthma for elite swimmers — The World Health Organization WHO set a trichloramine limit of 500 micro-grams per cubic metre, as any higher level gives the risk of acute injuries, but the researchers measured levels that are 8–10 times this figure.


Heated indoor pool in hospital, Australia Recreational use of water can deliver important benefits to health and wellbeing. Yet, there may also be adverse health effects associated with recreational use if the levels of chlorine by-products in the water and air is too high. This is why the Hyrondelle private hospital in Sydney in Australia decided to opt for a new technology concept in its heated indoor pool. The pool is part of the hospital’s hydrotherapy facilities, which are used for graduated exercising and treatment and allow physiotherapists to target specific muscle groups effectively, because warm water and buoyancy assist movement and encourage pain relief. (Courtesy: inBlue and Aquazure)

Changing air ventilation streamsMost ventilation systems in swimming pools are designed to keep the air over the water surface still, in order to cut down evaporation and thus reduce energy consumption. As a result, one way to improve the indoor environment is to redesign the air flow for faster removal of chlorine by-products. Scientific studies of the three-dimensional air flows in swimming pools have led to the development of a new design of the ventilation systems that draw away the air just above the water surface. This reduces not only the swimmers’ exposure to potentially harmful chlorine by-products, but also signifi-cantly improves the indoor air environment of the entire pool facility, which benefits the staff. However, changing existing ventilation systems into the new design is often difficult.

Changing water treatment systems Another way to improve pool environments is by redesigning water treatment systems. A new technology concept has proved it possible to improve the water quality and at the same time reduce the use of chlorine. The key is to remove solid impurities to avoid the chemical breakdown by chlorine. An optimised water flow removes the organic matter as fast as possible, with drum filters removing 90–95 per cent of solid organic substances up to 200 times a day (test by NSF, the Public Health and Safety Organization in USA). This is much better than traditional systems that only remove pollution a few times a week or even less. This rapid removal will maintain a lower chlorine concen-tration because the chlorine no longer has to degrade the organic materials.

Higher disinfection effect with lower pHAnother issue is to lower the pH of the pool water, which countries such as Germany and Austria have practised for years. Chlorine occurs in a much more active form at a lower pH, which means that the same disinfection effect can be achieved with a lower chlorine content. Lowering the pH to the recommended level of 6.5–7.0 makes it necessary to add a little more of the hydrochloric acid that is normally added. Further improvement of the water environ-ment might be possible, either through direct removal of chlorine by-products from the water or by removal of the so-called precursors for by-product formation – for instance by avoiding accumulation of particulate organic matters in the filters of the water system.


State-of-the-art aquapark, Sweden Around fifty swimming pools have so far embraced the new standardised concept and the new Hyllie Waterpark currently under construction in Malmö in Sweden is one of them. When opening in 2015, the facility will be among the largest water parks in Scandinavia, with seven water treatment systems based on the new concept operating in the basement. This state-of-the-art facility will feature an indoor environment that is free of chlorine by-products and probably the most energy and water-efficient water park in the world. If compared to conventional systems in Sweden, the consumption of water and energy is reduced to just half. The facility is just 25 kilometres from Copenhagen, making it an attractive excursion destination for Danes. too. (Courtesy: inBlue)


3. The full opportunities with an optimised design build from scratch

A collaboration involving scientists , owners of public swimming pools, a technology provider and a research institute has resulted in the entire water treatment and ventilation concept of public swimming pools being rethought and optimised into a standardised concept. This rethinking extends from the way in which the contaminated water circulates in the pool over the many water filtration steps to the design of the air ventilation set-up. More than 50 public pools in Denmark, Sweden, Australia and Germany have implemented the concept so far – many as greenfield projects, which gives the advantage of implementing the full concept.

Radical thinkingThe optimised water treatment and ventilation set-up is a radical new concept, and there is almost none of the traditional equipment in the technical spaces. The investment is the same as for a conventional high-quality system and the financial gains are certainly there as the use of water and energy are halved compared to the most ideal design using classic technology such as sand or DE-filter based systems. When start-ing out in the development phase, the scientists adopted a big-picture perspective by consider-ing the origins of the contaminants. Avoiding these contaminants is impossible, but would it be possible to avoid the harmful substances resulting from chlorine breaking down such contaminants? This led to the basic idea that chlorine is only used to ensure that people do not infect each other, not to break down waste

such as skin cells, urine, sweat, cosmetics and other impurities. If they are efficiently removed, the chlorine compounds in the air above the basins are almost eliminated, and, in addition, much less chlorine is needed for disinfection.

The new conceptThe new concept is divided into three steps. Firstly, 3D computer modelling is used to improve the circulation of water in the pool in order to remove the impurities as swiftly as pos-sible. Secondly, the filter system is completely altered. In the usual sand filters, chlorinated by-products are constantly generated when warm chlorinated water dissolves the impurities captured by the filter over a period of a week or two. With the new filter system, a drum filter equipped with a filter screen makes sure 90–95 per cent of the impurities released from the bathers are washed to the sewer within hours. To remove the last 5–10 per cent of particles, the drum filtration is normally combined with part-flow flocculant-enhanced sand filtration. Many of the chlorine by-products are removed with an air stripper, UV technology and other equipment. Thirdly, new innovatie ventilation principles are used to deal with any remaining volatile chlorinated compounds at the water surface of the pool.

Using gravity instead of pumpingThe ideal way to achieve the lowest pos-sible operating costs, and the safest and most healthy environment, is when the water

We started working with scientists 10 years ago to rethink water treatment and ventilation of public swimming pools. Three years later, our first full working pool was in place reducing the use of chlorine by up to 80 per cent. New facilities, like the new Hyllie water park in Sweden, are the final result of optimising design and construction in over 50 projects. This will be the ultimate experience, with the lowest possible utility costs

OLE GRØNBORGCEOINBLUE

Flow modelling The circulation of water must be optimised to remove the impurities as swiftly as possible. Flow modelling has three advantages over using standard construction design with standard fittings. 1. Particles are quickly transported to the cleaning system before dissolving 2. Treated water returns can be designed with a 90 per cent reduced head loss compared to standard returns, contributing to the overall reduced energy consumption. 3. Chlorine distribution is aligned perfectly with each unique pool design. The CFD model illus-trated is from the design of the pool with the Little Mermaid in section one. (Courtesy: inBlue)


Reducing energy consumption by 25 percent, Denmark The ideal way to ensure the best possible environment and lowest possible consumption of energy, water and chemicals is to design the system on a green-field basis, fully integrated with the overall design of the build-ing. This was the opportunity open to the Valby Water Culture Centre, owned by the City of Copenhagen, which was built from greenfield. The building challenges the visitor’s senses with its irregular angles and inclined walls. From a water playground, the visitor enters a water world with entertaining water staircases, water tunnels, counter-current canals, caves, a large wellness area with hot water basins, etc. Working together, the technical consultant and architects were able to create a pool facility that uses 25 per cent less energy compared to other Danish public swimming pools using classic technology. (Courtesy: Rambøll)


treatment system is an integrated part of the building’s design and as much water as possible flows by gravity rather than by pumping. In a building designed for best effect, it is possible to achieve a total headloss, of less than one metre (3 feet) through the entire system, from pool surface through equipment in the basement and back through the treated water return. A traditional sand or DE-filter system needs at least 10 metres (30 feet) of head, or 10 times more. Dramatic reductions in energy use will be needed to meet forthcoming demands for reduced environmental impacts and sustain-ability of swimming pools and water parks.

Energy-efficient buildingsBesides an energy-efficient design of technical installations for ventilation and water treat-ment, it is important to have energy-efficient swimming pool buildings. Designing everything from scratch is an interesting challenge and important opportunity for innovation. A lot

All our students swim at school, and many of our elite swimmers had respiratory problems. We therefore chose to be part of a three-year research project and are now very proud to be able to tell new students that we offer them the most healthy pool in Denmark

RENÉ THOMSENVice-PrincipalBERNSTORFFSMINDE CONTINUATION SCHOOL, DENMARK

Elite swimmers dropping asthma medicine The first development stage of the concept of improved water treatment and air ventilation was carried out at the Bernstorffsminde Private Continuation School in Denmark. The school serves young people as well as young elite swimmers. When the development project was kicked off, six of the 20 swimmers attending the school had asthma, but shortly after the new concept was implemented all of them stopped using asthma medication. This was also the case at other public pools with elite swimmers, which have also reported swimmers being able to dispense with their asthma medication. The photo shows Sabine Devantier Christensen explaining in Danish national news how her asthma problems disappeared when training for competitions in the Bernstorffsminde pool.

of energy is consumed by the pool sector, so increasing the energy efficiency should be a priority. In many countries, the incentives to reduce energy consumption are big, and in Denmark , which has some of the highest energy rates in the world, the need to reduce energy consumption has fuelled architects and engineers to come up with a variety of innovative many interesting projects. Besides minimising the evaporation from the pools, efficient heat recovery from ventilation systems is important as is optimising the buildings for the use of both active and passive solar heating. Energy consumption for lighting system can be greatly reduced by using the latest LED fixtures. A design with a more natural ventilation during the summer months saves heat and electricity for ventilation systems. Also heat recovery through heat exchangers for transfer of heat from used shower water to heating the new shower water is a common feature in public pools and water parks.

Upgrading of existing facilities, Denmark When Greve Swim Centre was renovated, the new water treatment concept was imple mented to provide a more healthy indoor environment . The renovation project has turned this classic facility with an Olympic-size pool into a family centre with several pools instead. The project was a complex project because all new equipment had to fit into the existing basement , but it has paid off as the post-renovation water and energy consumption is on the same level as the old system, while the capacity of the water treatment system for the new – higher loaded – pools has been doubled, in accordance with the Danish national regulations. (Courtesy: inBlue)


Solving challenges expanding outdoor facilities, Denmark The tropical holiday and activity centre Lalandia located in the southern part of Denmark faced a set of challenges when expanding its outdoor facilities, as the load is extremely heavy in warm and sunny holiday seasons. The extension included a new children’s pool, a large spa pool and a new water slide able to handle 2,600 people per hour, corresponding to 20 times the capacity of the traditional water slide. Water treat-ment must always be dimensioned to a pool’s maximum bathing load and installing a drum filter before conventional sand filters proved to be a solution able to handle this intense load. In addition , 3,000 tons of water (800,000 US gallons) were saved as the backwash water of both membrane filters and sand filters is regenerated and reused for the basins as well as for backwash of the sand filters. (Courtesy: Rambøll)


4. Upgrading of existing facilities to cut costs and improve water/air

The market for swimming pools and water parks is trending towards larger, more advanced pools with higher temperatures and more resource-intensive features, leading to an increased use of water, energy and chemicals. This involves a risk that operating costs go through the roof when energy and water prices are not stable.However, investing in increased capacity goes hand in hand with a more resource-efficient system design. The potential to improve pool environments and at the same time reduce the use of resources certainly also exists for existing pools. The best time to look into this is when an overall renovation is coming up. The limited space available for technical installations in current facilities is rarely a limitation, because modular and highly engineered designs make it easy to fit new technology elements into space-constrained facilities.

Reduced use of chlorine and waterBesides ensuring much fewer harmful chlorine by-products, a shift to new techno logy provides up to 30 per cent savings in chlorine. This may not make a great difference in the overall cost picture, but for most operators it is still a benefit to reduce chlorine consumption. The savings

in water consumption might play a bigger role then as they are much more significant. Rede-signing water treatment systems typically give 50-60 per cent savings in water consumption compared to traditional systems. These are for instance achieved by reusing the regenerated backwash water from the sand filters. A differ-ent and more radical step in the renovation pro-cess would be to swap most of the sand filters for water- and energy-saving drum filters. Such a solution might save more than 50 per cent in water consumption.

Significant savings in energy consumptionUpgrading water treatment systems also leads to energy savings. Typically 20-30 percent savings in electricity consumption and 15-20 percent savings in heat consumption can be achieved. Savings might also be found by replacing old recirculation pumps with mordern energy-efficient pumps. This can be combined with redesign and replacement of the piping, aiming towards reduced headloss for the large recirculation flows and with new intelligent control of the recirculation flow adapting to the actual number of pool users, and operating with a reduced flow during the night.

There are physical limits for how efficient you can be when renovating a very resource-intensive facility like a swimming pool, but the opportunity to bring down the consumption of water, chemicals and energy is certainly there

HENNING HAMMERICHSenior ConsultantRAMBØLL

Upgrading public swimming pool, DenmarkWhen the public swim centre in Køge was renovated and upgraded to a new capacity of 300,000 visitors per year, it involved renova-tion of the roof, steel structures, ventilation, plumbing, electrical systems and a new water treatment system. The water flow within the existing technical areas was increased by almost 60 per cent, thereby improving the water quality in the pools, baby pool and hot tub. This technical solution includes drum filters, which remove larger particles, and polymer membrane filters for removing the fine particles that make up 10–15 per cent of the organic mass. Regenerated water is reused for priming and backwashing the membrane system. The total savings achieved are a reduc-tion of energy consumption by 20 per cent and water consumption by 55 per cent. (Courtesy: Rambøll)

stable.However

stable.However


Online monitoring reveals potential for system optimisation Detailed online monitoring of water quality has helped the public swimming centre in Gladsaxe, Denmark reduce its electricity consumption for pumping by 40 per cent, because the water flow is now automatically adjusted according to the numbers of pool users. In addition, the online monitoring has been used to test and comprehensively document four different UV-based technologies for reducing the level of combined chlorine. The efficiency of the technologies as well as the financial picture involved in installation and operation were then evaluated on the basis of these results. The test proved that using these technologies to their full potential is possible when combined with on-line monitoring of combined chlorine, as they can be operated in energy-saving mode. (Courtesy: DHI)

Photo courtesy:: Danish Arthritis Society


5. Documenting performance of new water treatment technology

Positive health effects and an increased need for resource efficiency in recreational facilities can push the pool and water park markets towards new water quality standards. However, any radically change of basic water treatment concepts is indeed a challenge because in most places the pool market is both highly conservative and very competitive. Solid documentation for the performance of new water treatment technology is therefore crucial for a market breakthrough, since investors are normally positive with regard to using technology suppliers as a source of information.

Supporting market breakthroughsPool facilities are often operated in accordance with relevant national legislation, and this is the market situation that technology suppliers have to address. The day-to-day checking of water quality is a low-frequent grab sampling and analysis, and online data from the plant control system is not used to check and optimise the pool system. This means pool owners and technical staff do not normally have any extensive knowledge and understanding about the workings of their systems. They often only rely on documentation from technology suppliers . As a result, a supplier’s in-depth know ledge of the underlying fundamental physico- chemical mode of action of a particular

technology, combined with comprehensive performance testing and documentation, not only help to fine-tune the technology. It also provides an important support in setting new standards for water quality and water treatment systems in swimming pools.

Testing response of the entire systemTemporal variations in water quality parameters make the testing and documentation of tech-nology performance difficult. This is due to the complex interaction between bather load, chlorine reaction chemistry, circulation and treatment of water, which together govern the water quality in recirculated pool systems. This complexity makes it insufficient to test new technologies just by characterising the efficiency of the addition or removal of specific components. The testing must include a monitoring of the response of the entire pool system, which is further complicated because the water quality parameters are low in concentration and difficult to measure. This then means the testing and documenting of new water treatment technology requires that comprehensive in-depth monitoring of water quality is conducted using both frequent off-line measurements as well as online monitoring of the most relevant parameters.

To push technology change, the performance testing and documentation of new water treatment technology should include solid data for the response of the entire pool system. We have documented huge temporal variations in water quality using advanced online monitoring techniques

MORTEN MØLLER KLAUSENSenior Process Research EngineerDHI

New filter technology saving water For the new public swim centre in Randers in Denmark, investment in new filter technology was good business. The centre’s hot water pools and a 50-metre Olympic pool will be kept clean with a new filter technology called ceramic membrane filtration in the six water treatment systems. This technology replaces the classic sand filters. For this facility, flushing these sand filters would have required up to 100 cubic metres of water per week. Instead, the ceramic filters fitted with a membrane made of silicium carbide are automatically cleaned with air and just a small amount of fresh water. This reduces the water consumption by as much as 90 per cent, which for a large Danish facility like this amounts to annual savings of 30,000 euros. (Courtesy: Provital Solutions and Liqtech)


THM reduced when chlorine is reduced Trihalomethanes (THM) are unwanted volatile components formed in pool water as a result of the reactions between the chlorine and the pollution caused by the bathers. The figure shows the impact on THM formation at two different chlorine concentrations in a warm pool. At the low chlorine level of 0.4 mg/litre, the THM in the pool water is around 20 µl/litre while at the higher chlorine level of 1.5 mg/litre the THM level is 40–50 µl/litre. This leads to the conclusions that pools should be operated at the very lowest level of chlorine possible, just ensuring the hygienic quality of the pool water. (Courtesy: DHI)

Huge variations in water quality over timeResearch in pool water chemistry over the last decade using advanced online monitoring techniques has shown that the concentrations of disinfection by-products and related water quality parameters are highly variable both within a single hour and from day to day. Observed by-products are trihalomethanes (THM) and combined chlorine, which are both regulated normally, and water quality parameters dissolved organic carbon (DOC). Observations have clearly shown that plant operation – as well as the interpretation of experimental results – may be misleading and unable to show correlations between the performance of processes/technologies and

water quality. In addition, a better insight into the parameters of importance to the pool water quality has shown that the traditional direct coupling between the circulation of pool water for chlorine distribution and the treatment for maintaining the pool water quality is inappropriate. Improved knowledge about the actual processes taking place in the pool water will therefore open up new possibilities for optimised technology/system design with reduced energy consumption combined with improved water quality.

Potential improvements in pool operations Many facilities therefore have unexploited potential with regard to significantly improving

Huge variations in pool water quality Many pool facilities have unexploited potential for significantly improving both the water quality and pool treatment operations through a better understanding of how the dynamics of the water quality interact with variations in treatment plant concept, system operation and bathing load. The figure illustrates the daily and day-to-day monitoring in trihalomethane concentrations in a warm water pool measured during technology assessments using advanced online monitoring technology. (Courtesy: DHI)

the pool water quality and operations. A better understanding of the link between the dynamics of the water quality with the variations in treatment plant and system operation as well as bather load is needed, and can be accomplished with comprehensive monitoring. This monitoring should include using online monitoring and frequent off-line measurements and registrations of bather load, thus establishing the data required for system analysis and documentation. Based on such data, improvement options can be identified and prioritised based on their cost and ease of implementation. The effect is normally documented by a follow-up monitoring programme .


Water playground used in all seasons, Denmark Water is often used to enhance the urban environment and this is also the overall idea for a new water-activity playground in one of the parks in central Copenhagen, the capital of Denmark. In this playground the universal story of water is paired with the story of the city for children and youngsters to get a playful and natural understanding of water and how it plays a key role in day-to-day life, both in history and in the present day. They get a unique opportunity to combine play and exercise, and also cool off in the hot summer months. It is built as a city and shows the water flowing from clouds via the city’s rivers and sewers and into the ocean. While some activities run automatically, other activities require physical activity to work. The playground works both with and without water, and will therefore also be used as an ordinary playground outside the summer season. The water used is – for health reasons – clean drinking water delivered by the city’s water supply and the plant is emptied every day after use. (Courtesy: Force4 Architects)


6. Design of water environments with no use of chemicals

In many cities, recreational water is an increasingly important element of the city’s development, in urban planning and in land-scaping. The inhabitants in urban areas often value water highly and in many different ways because it influences – for instance – local climate, humidity, air pollution and health. In addition, the sound and view of water are always a pleasure for people – both adults and children alike. Along with this, the increasing risk of extreme weather events and heavy rainfall causing damage in urban areas can be tackled with integrated solutions that both deal with the water and provide citizens with recreational value at the same time.

Ensuring safe water always importantBuilders, architects, landscapers, engineers and artists are thus integrating water as a key feature in urban environments. Recreational water extends from fountains, water sculptures , aquariums and park lakes over swimming pools and wellness centres to outdoor city baths and beaches. Many try to avoid the use of chemicals because of their many negative aspects, but in all recreational situations where people are exposed to water

For recreational water facilities designed without chlorine disinfection, it is essential to always carry out a proper quantitative microbial risk analysis. This ensures that the water is kept safe and pathogens do not spread to an unaccep-table extent, which would make many people sick

HANS-JØRGEN ALBRECHTSENProfessor, Department of Environmental EngineeringTECHNICAL UNIVERSITY OF DENMARK

it is still important to ensure the water is of a sufficient quality and safe, not placing people’s health at risk.

Designing safe solutionsEnsuring and checking the water quality should therefore always be a core element in recreational water designs. The required water quality always depends on what it is to be used for. For instance, an acceptable level of microbial organisms in an aquarium is higher (poorer water quality) than the acceptable level of microbial organisms in an outdoor city swimming facility, where bathers may ingest the water. In the design of water environments , an assessment of health risks should therefore always be conducted to define an acceptable level of safety and a correspondingly acceptable level of water quality. An acceptable risk could be equal to the risk accepted in the European Bathing Water Directive. Such a risk assessment comprises a hazard identification (what are the relevant pathogens), evaluation of exposure (pathogen dose) and calculation of the risk of infection. Any requirements for treatment efficiency to the applied treatment systems are thus determined by comparing the acceptable quality with the quality of the available water.

Rootzone treatment, Netherlands The open-air swimming pool in Amersfoort in the Netherlands uses local groundwater and each day 3–15 cubic metres (800-4,000 US gallons) of fresh water is pumped into the pool, depend-ing on the levels of evaporation and other kinds of water loss. Dimensioned for the needs of 2,500 visitors a day, the water is circulated and treated in a constant flow around a 300-square metres rootzone island. The volume of the pool is 5,000 cubic metres (1.3 million US gallons) and each day 150–600 cubic metres of water (40,000-160,000 US gallons) is filtered and treated by the rootzone filter constructed with a high content of hard lime sand. The rootzone is covered with reeds – Phragmetis Australis – and is part of the natural wetland. (Courtesy: Transform Danish Rootzone Technology)


Independent advisor ensuring best technical solution, Denmark In some cases it is of great value to not just rely on technology providers, but to hire an independent advisor to help decide on the best technical solution. The Blue Planet in Copenhagen, which is currently northern Europe’s largest and most modern aquarium, used an independent consulting company when designing what is today the most advanced – but also most cost-effective – water treatment system for aquariums. The many advanced recirculation solutions and different types of water to be treated fill the basement of the aquarium with 4,500 square metres (nearly 50,000 square feet) of advanced technology. The tender documents and the associated technical requirements were prepared by a Danish consulting company with the main goal of minimising the energy and water consumption. Each of the 12 recycled water treatment plants was thus systematically described and the potential resource savings were defined. For instance, to save energy, emphasis was placed on placing each water treatment plant at the same height as the actual aquariums, and on using pipework with a low pressure drop. The contractor was also asked to establish drives for pumps and use energy-saving pumps. To save water, for instance, the salt water aquariums take in water from the sea at a depth of 10 metres and 1,600 metres in the sea when the salinity is high enough, the water for plants in the Amazon and freshwater aquariums are collected rainwater. The backwash water from all the filtration steps is passed to a shared tank where it is cleaned and then reused. (Courtesy: COWI)


Denmark is surrounded by water, yet fresh water is still a scarce resource for us. For 30 years, we have been rethinking water and building expertise within water effi ciency. Today, our tap water is as pure as the fi nest spring water and the water in the harbour of Copenhagen, our capital, is so clean that people swim in it.

Denmark knows waterThe knowledge we have about water resources , water security and water effi ciency is no coin cidence. Successive governments have addressed our country’s limited natural resourc-es, concentrating on using them effi ciently, and as a nation we strive to provide a safe, pleasant and healthy environment for people to live in.

Knowledge transferDenmark is not physically powerful, but know-ledge is power. Long ago we as Vikings spread fear across the seas. Today, we want to spread something entirely diff erent: know ledge and collaboration on how to globally protect water resources and improve water effi ciency. Water is an increasingly scarce resource in most parts of the world. We need to rethink how we use it.

For mutual benefi tAs a country, we see great opportunity for mutual benefi t in the transfer of knowledge and the growth in both partners’ business. Our expertise is in assisting customers and stakeholders reach safe and eff ective water solutions , while developing their ability to profi t from that knowledge. In our work we maintain a healthy respect for diff erent perspectives and agendas, as well as for the environment.

Rethinking water togetherRethink Water is a global network specialising in water effi ciency. So far, we are over 60 consult-ing companies, technology providers, utilities, research institutes and governmental bodies. The network brings together an unusually diverse and valuable mix of clients, consultants , researchers, technology experts and govern-mental bodies. We have joined forces to share knowledge and create even better water solutions , in Denmark and around the world. We invite you in to collaborate on solving your water challenges and to explore our expertise at www.rethinkwater.dk/whitepapers

Customers and their

stakeholders worldwide

Consulting companies

Water utilities

Government and Public authorities Organisations

Technology companies

Export credit agency

Danish water companies have shown their courage and drive by working with their competitors in order to create the Rethink Water platform. They are showing the world that Denmark is ready to take responsibility and contribute to fi nding solutions to the major water challenges the world faces

Research organisations

KIRSTEN BROSBØLMinister for the EnvironmentDENMARK

If your goal is water effi ciency, Denmark is ready as a partner

Solutions for water effi ciency

WHITE PAPER - RECREATIONAL WATER | 18 WHITE PAPER - URBAN WATER | 1

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Consulting companies Alectia alectia.com Bonnerup Consult bonnerup.net COWI cowi.com EnviDan envidan.com Gromtmij grontmij.dk Moe & Brødsgaard moe.dk Orbicon orbicon.com NIRAS niras.com Rambøll ramboll.com TREDJE NATUR tredjenatur.dk Øllgaard ollgaard.dk

Technology companies Adept Water Technology adeptwatertech.com AKVA group Denmark akvagroup.com Aquaporin aquaporin.dk AVK avkvalves.com Billund Aquaculture billund-aqua.dk Biokube biokube.com Blue Control bluecontrol.dk Danfoss danfoss.com Danish Rootzone Technology rootzone.dk EcoBeta ecobeta.com Envotherm envotherm.com Freewater freewater.dk Grundfos grundfos.com HOH BWT hoh.com I -GIS i-gis.dk Kamstrup kamstrup.com LiqTech International liqtech.com MJK Automation mjk.com Mycometer mycometer.com NOV Flexibles nov.com/fps Novozymes novozymes.com OxyGuard International oxyguard.com PROAGRIA Environment proagria.dk RK Plast rkbioelements.dk Scandinavian No-Dig Centre no-dig.dk Siemens siemens.com/energy/aeration Silhorko-Eurowater eurowater.com SkyTEM Surveys skytem.com Sorbisense sorbisense.com Stjernholm stjernholm.dk UltraAqua ultraaqua.com Wavin wavin.com Aarhus Geophysics aarhusgeo.com Per Aarsleff aarsleff .com

Research institutes & demonstration projects Danish Technological Institute teknologisk.dk DHI dhigroup.com Geological Surveys of Denmark and Greenland geus.dk Kalundborg Industrial Water Demonstration Site symbiosis.dk

Water utilities Greater Copenhagen Utility hofor.dk VCS Denmark vcsdenmark.com North Water nordvand.dk Aarhus Water aarhusvand.dk

Organisations related to water Association of Waterworks in Denmark fvd.dk AquaCircle aquacircle .org Copenhagen Cleantech Cluster cphcleantech.com Confederation of Danish Industry di.dk Danish Water Technology Group dk-water.com Danish Water and Wastewater Association danva.dk Danish Water Forum danishwaterforum.dk Danish Water Services danishwater.dk State of Green Consortium stateofgreen.com Water In Urban Areas Network waterinurbanareas.dk

Governmental bodies & other sponsors City of Copenhagen kk.dk Capital Region of Denmark regionh.dk Danish Trade Council um.dk Danish Ministry of the Environment mim.dk Danish Nature Agency naturstyrelsen.dk The Branding Denmark Fund mfonden.dk

Find more white papers, learn more about the Rethink Water network and get in touch with us at:

www.rethinkwater.dk

rethinking pools to boost safety and minimise use of water

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