The Test Data
Why, where and when was this research performed?
eco3spa is a new product and both the manufacturer and potential users need to have confidence that it is safe to use in a hot tub sanitising environment. There is traditionally a great deal of resistance to using any product other than chlorine or bromine to sanitise hot tub water, mainly because it has been felt that sufficient test data has not been available to prove the efficacy of other options. The prevalent use of Active Oxygen sanitation worldwide during the Covid 19 pandemic has raised its profile as an extremely effective method of sanitation but, prior to this research, hard data was not available to prove the use of the product in a hot tub environment. This research was performed at Swansea University jointly within the faculty of Life Sciences and the faculty of Chemical & Environmental Engineering between October 2019 and January 2021. A further programme of research started in October 2021 to look in more detail at the at the biocidal performance of the product over time and also to study the function of the eco3spa Step 2 Water Conditioner in conjunction with the Step 3 Sanitising Tablets.
What were the objectives of the research?
The key objectives of this first phase of research were: To test the efficacy of the eco3spa Step 3 Sanitising Tablets (Multi-function Active Oxygen Tablets) as a biocide against the prevalent hot tub infectious agents Pseudomonas Aeruginosa and E-coli at a range of concentrations and water pH values and at water temperatures typically found in hot tubs. To test the efficacy of the eco3spa Sanitising Tablets at preventing Pseudomonas Aeruginosa and E-coli biofilm formation at a range of water pH values and temperatures. To compare the efficacy of the eco3spa Sanitising Tablets to that of chlorine at a range of temperatures and pH values.
How was the research performed?
A Microtiter plate is a flat plate with multiple "wells" used as small test tubes. These plates enable many variations of an experiment to be performed in parralel. Microtiter plate experiments were performed at two different temperatures (25°C and 37°C). Selected strains of E. coli and P. aeruginosa bacteria were diluted and exposed to a solution of the product being tested. Each product was disolved in water at a range of concentrations and a range of pH values. A stain was then added which passed through any live bacteria cell membranes to stain the cell neuclei. The growth of bacteria could then be measured by measuring the optical density of each well in the plate.
Efficacy of eco3spa Sanitising Tablets for prevention of bacterial growth
The graphs below show the bacterial growth of E-coli and Pseudomonas Aeruginosa measured as a function of the concentration of eco3spa Active Oxygen in water at both 25C and 37C and a range of pH values. The dilution is equivalent to the number of tablets stated used in a 1200 litre hot tub. The vertical axes represent the Optical Density of the sample. A higher Optical Density represents a higher bacterial growth. Calibration data is available in the full report. The calibration varies slightly between E-coli and Pseudomonas Aeruginosa and is a function of temperature but, broadly, an Optical Density of 0.2AU represents a log reduction of between 3.5 and 4 or a 99.97% - 99.99% reduction in potentially harmful bacteria. The conclusion from the above results is that no measurable planktonic growth was seen for both E-coli and Pseudomonas Aeruginosa at any Active Oxygen concentration above 1 tablet dissolved in 1200 litres water at any pH between pH 7 and pH 8 at both temperatures. A slight degradation in performance is seen in the cooler water at pH 8, but even in this case the planktonic growth is minimal.
Efficacy of eco3spa Sanitising Tablets in preventing biofilm formation
The graphs below show the formation of E-coli and Pseudomonas Aeruginosa biofilm measured as a function of the concentration of eco3spa Active Oxygen in water at both 25C and 37C and a range of pH values. As above, the dilution is equivalent to the number of tablets stated used in a 1200 litre hot tub and the vertical axes represent Optical Density. Both E-coli and Pseudomonas Aeruginosa exhibit similar levels of susceptibility to Active Oxygen, with no or very little absolute biofilm formation observed at concentrations above 1 tablet dissolved in a 1200 litre hot tub.
Comparison with chlorine at a range of pH and temperature values
In the graphs below AO represents 1 eco3spa Sanitising Tablet disolved in 1200 litres of hot tub water and the effectiveness of this solution at inhibiting planktonic bacterial growth of both E-coli and Pseudomonas Aeruginosa is compared to chlorine in concentrations of 3ppm and 5ppm. The conclusion from these graphs is that in all cases eco3spa performs at least as well as chlorine at 5ppm. (Note that although there could be some doubt in the case of Pseudomonas Aeruginosa at pH 8 and 25C the AO result has a very large error bar meaning that the absolute result in very uncertain).