Frequency and Magnitude of Crypto Contamination Events - 10th International Conference on Swimming Pool and Spa - Italy 15-17 February 2023.
Professor Rachel Chalmers of the Cryptosporidium Refence Unit, Swansea is presenting conclusions of our collaborative modelling work on the frequency and magnitude of Crypto contamination events to the 10th International Conference on Swimming Pool and Spa being held in Italy 15-17 February 2023. This was based on analysis of the survey data collected in the PWTAG funded survey carried out in 2017. The results suggest that ‘unseen’ contamination of pool water from asymptomatic bathers is likely on most days in very busy pools. But how risky is this? The paper we published in 2021 can be found here
To view the presentation please click here.
Pool Sentry at SPATEX February 2023
Pool Sentry once again delivered a paper at SPATEX this year on how remote monitoring can help you run your pool with less hassle and less cost. The presentation included:
Identifying and auditing savings of energy, water and chemicals.
Historical water quality data for compliance auditing
Fault diagnosis, with faults often being diagnosed before the pool operator is aware of them, and reducing engineer call outs
Assessing the impacts of any changes in pool operation (e.g. pump speeds, AHU fan speeds, set points) on the effectiveness and efficiency of the pool
Read more about the benefits in the presentation, which can be found here.
Pool Sentry Science Underpins The Future for Pools – PWTAG Conference March 2022
Pool Sentry was delighted that our science-based approach to managing commercial swimming pools to support the delivery of excellent water quality whilst optimising the use of resources and minimising running costs and carbon footprint was at the core of two excellent presentations at the PWTAG Virtual Conference on Monday 28 March 2022.
The conference theme of “The Future for Pools” included a paper on “Pool water treatment - targeting net zero carbon” presented by Tom Devin of Devin Consulting and described by Janice Calvert, PWTAG Chair, as ground-breaking. Lester Simmonds, Senior Technical Consultant for Pool Sentry was a key member of the technical team behind the guidance note on “Net Zero Carbon Pools - Water Treatment Issues”, much of which was underpinned by research carried out by Pool Sentry. The guidance note is available online at
This was followed by “A Review of the Operation of 3 micron Ceramic Swimming Filters in the United Kingdom” by Steve Carder of Total Pools who made a case for the benefits of this alternative to sand and glass filtration systems, and included reference to the research carried out by Pool Sentry on a system installed at a commercial leisure centre in 2017. This involved the use of our unique mobile lab facility which we have used to measure the effectiveness of a range of filtration systems in removing particles of different sizes.
Energy Cost of Water Circulation - Pool Sentry at SPATEX February 2022
Pool Sentry was virtually present at Spatex 2022 to share initial findings from our joint research with Loughborough University on Reducing the Energy Requirement for Water Treatment in Swimming Pools.
Starting with an analogy - most car drivers will have a good idea of what to expect in terms of fuel consumption (miles per gallon or litres per 100 km) and whether their fuel consumption is excessive. By contrast, most pool operators won’t have the same awareness of the ‘fuel consumption’ of their pool water circulation system. This important EPI (energy performance indicator) can be expressed as the power (in Watts or kW) used to circulate each cubic metre of pool water per hour. The Passive House Institute has suggested targets of 25-40 W per m3/hour, but a recent analysis of our UK customer pools (surveyed previously as part of our standard service) showed that only 20% of pools were achieving this.
We’ve now been able to apply some science to understand the factors limiting energy efficiency in commercial swimming pools. The early findings suggest that the energy savings that might be expected from the drive towards ‘low headloss’ circulation systems can be comprised by pumps operating very inefficiently in ‘high flow-low head’ conditions encountered in swimming pool circulation systems.
Click here to view the presentation.
Pool Sentry revisit the Gage-Bidwell Law of Dilution and come up with a science-based approach for managing Cryptosporidium and dirt in pools September 2021
We were delighted to team up with Professor James Amburgey of University of North Carolina at Charlotte, USA and Dr Tim Marjoribanks of Loughborough University, UK to revisit the 1926 Gage and Bidwell Law of Dilution. We discovered just how groundbreaking these ideas from almost a century ago (and contained in just 625 words) were, and how useful they are today in providing insights into how we can improve the management of swimming pools. Following peer review, our paper has been accepted for publication in the special edition of the journal Water https://doi.org/10.3390/w13172350. This is a special edition of the journal devoted to the urgent need for scientific underpinning of the management of recreational waters.
The transfer of water from a swimming pool to the treatment location is key in determining the effectiveness of water treatment by filtration in removing turbidity and managing the risk from particulate material, including microbial pathogens, such as Cryptosporidium spp. A key recommendation for pool operators when dealing with an accidental faecal release (the likely main source of high Cryptosporidium oocyst concentrations in pools) is that the pool water should be filtered for at least six turnover cycles prior to use. Our paper briefly outlines the theoretical basis of what has become known as the Gage–Bidwell Law of Dilution, which provides a basis for this recommendation, and extends the idea to account for the impact of filter efficiency.
The Gage–Bidwell Law reveals that for each pool turnover 63% of the water resident in the pool at the start of the turnover period will have been recirculated. Building on this, we demonstrated that both filter efficiency and water-turnover time are important in determining filtration effectiveness and can be combined through a single parameter we term ‘particle-turnover’. We then used this to link circulation rate with bathing load and filter efficiency.
We showed that, provided the filtration is relatively good (at least 90% efficient in removing particles), operating a pool at 1.7 m3 circulation/bather (0.58 bather/m3 circulation) should maintain equilibrium turbidity of the pool water within an acceptable range (no more than 0.3 NTU even with dirty bathers).
We’re now using these insights to develop recommendations for the reducing the carbon footprint of leisure pools in the UK.
Pool Sentry contributes to first ever survey of Cryptosporidium in UK leisure pools May 2021
We were delighted to team up with Professor Rachel Chalmers of Public Health Wales and colleagues at Public Health England, Latis Scientific and IDEXX Technologies to use our modelling work on oocyst contamination events to help interpret the results of the first ever survey of Cryptosporidium oocysts in leisure pools in the UK. We took a chance on Monte Carlo analysis and it paid off! Following peer review, the paper has been accepted for publication in the special edition of the journal Water https://doi.org/10.3390/w13111503. This is a special edition of the journal devoted to the urgent need for scientific underpinning of the management of recreational waters.
Cryptosporidium is a major cause of diarrhoea outbreaks linked to swimming pools, but little is known about the frequency of contamination. The primary aim of this research was to investigate the frequency of occurrence and magnitude of concentrations, through sampling and modelling, of Cryptosporidium oocysts in leisure pools. Secondary aims were to compare detections with operational parameters, provide the evidence base for guidance, and improve sampling capacity and interpretation for public health investigations. Up to 1000L of pool water was sampled during swim sessions once weekly for 10 weeks from 8th August 2017 at six volunteer pools. Oocysts were detected by microscopy in 12/59 (20 per cent) of pool water samples, at least once in each pool; 8/12 (66 per cent) detections were in August when bather loads were highest, though we suspect that there were more frequent occurrences with concentrations below the detection limit. The probabilities of a bather contaminating the pool with detectable amounts of oocysts ranged from 1 in 1000 to over 1 in 10,000. Monte Carlo analysis showed that when high bather numbers there is likely to be measurable contamination on most days. For example, a busy pool with 3000 bathers a day will have measurable contamination events on about 70% of days, with multiple shedding events per day being more likely than single events.
We’re now taking this forward as part of our work on Quantitative Microbial Risk Assessment (QMRA) to assess what the risk of infection is for the UK population.
Role of filtration in managing the risk from Cryptosporidium in commercial swimming pools - PWTAG Conference Nov 2019
We received a great billing for our recent presentation at the 2019 PWTAG Annual Conference at Loughborough University:
“This review, one of the most significant and far reaching studies in the effectiveness of pool filtration, explains the mechanisms by which filters remove particles of different sizes, factors that affect the efficiency of particle removal (such as filtration velocity), current recommended management practices, and identifies further work to support the development of a risk-based management approach for the management of waterborne disease outbreaks from swimming pools. The findings go to the heart of swimming pool operation.”
Pool Sentry presents latest research at the Potable Water Network Meeting 64 on Depth Filtration, Cranfield University 2nd October 2019
We were pleased to be invited to give a presentation on “Understanding and optimisation of filtration systems in commercial swimming pools using particle counting” to the UK Potable Water Network at Cranfield University. The Network is a forum for innovation managers from the major UK Water Companies, including Thames Water and Severn Trent Water, to discuss the latest developments in technology and research. We had some great feedback on our Mobile Lab (particle counting and turbidity) studies on swimming pool filtration systems. It was clear from the discussion that followed our presentation that the drinking water and swimming pool industries face some common challenges, and there could be opportunities going forwards for exchange of knowledge and ideas.
Pool Sentry at PWTAG Conference 2018 and SPATEX 2019
We presented the latest findings from our world-leading Mobile Lab facility at the PWTAG Conference Dec 2018 and Spatex Feb 2019. The results of our particle counting studies to measure the actual performance of commercial pool filtration systems might surprise you! A summary of the presentation is available for download here. Don’t worry - we were able to identify the causes of the problems and help the sites improve their filtration. As a result of our involvement the sites were able to significantly improve their risk management procedures.
Pool Sentry team up with Cranfield University and Public Health Wales to publish a review of the science of swimming pool filtration May 2019
We are delighted to announce publication in the peer-reviewed Journal of Water and Health of our paper on the science of swimming pool filtration written in collaboration with colleagues from Cranfield University and Professor Rachel Chalmers of the Cryptosporidium Reference Unit, Public Health Wales. In our paper we explain the mechanisms by which swimming pool filters remove particles of different sizes (including Cryptosporidium oocyst-size particles, typically 4-6 µm), factors that affect the efficiency of particle removal (such as filtration velocity), current recommended management practices, and we identify further work to support the development of a risk-based management approach for the management of waterborne disease outbreaks from swimming pools. The publisher selected this paper to be available free of charge because of its importance and potential widespread readership. The paper will be available in the June edition and can be downloaded here