A. Birmpa, D. Papadopoulou, A. Kokkinos, A. Vantarakis, Poster: “Evaluation of disinfectant efficacy by ultraviolet in a laboratory swimming pool model”.

Swimming pool water disinfection is essential in order to minimize the risk of microbiological hazards and to protect swimmers from infection. Traditionally, chlorine is used to disinfect swimming pools. However, it produces residual toxic compounds such as trihalomethanes, halogenic acetic acids, haloacetonnitrils which are toxic for the bather’s health. An alternative, promising and environmentally friendly disinfection method is the use of UV light. Using UV for disinfection lowers the chemical cost and usage, provides instantaneous disinfection (chemicals require a residence time), lowers disinfection by-products and provide for less intensive maintenance. It generally creates a healthier swim environment for the bathers. The aim of this study was to assess the effect of disinfection of different microorganisms with the use of UV-C light using a swimming pool lab model which simulated the conditions of an actual swimming pool and. The pool model simulated an actual swimming pool of Olympics’ dimensions and was constructed from Plexiglas material in scale 1:250. The tank dimensions were (33x25x2) cm and the maximum capacity was 58 l. The circulating water system with an enclosed U.V treatment apparatus (10W lamp) was used. The lamp had a maximum capacity of water purification of 500 ltr/h. A peristaltic pump circulated water at a flow rate of 18l/h. A thermostat was put in the centre of the pool model and adjusted the temperature at 25 °C. The bacterial strains that were used were Escherichia coli NCTC 9001, Enterobacter aerogenes NCTC 10006, Staphylococus aureus NCTC 6571 and Pseudomonas aeruginosa NCTC 10662. Ps.aeruginosa is an opportunistic bacterium which can accumulate in biofilms and it is very common causing infection problems in swimming pools. S.aureus has been used as it is a pathogen causing several health problems. E.coli and E.aerogenes have been used as they are indicators of water quality. The water recirculation was completed in 2.5 hours. After a zero time, sample was obtained, the UV light was turned on and samples were obtained at different time intervals (up to 9 hours) for 2 consecutive days. The reduction of all the microorganisms was effective and reached up to 1-3 logs after 6 hours of continuing UV disinfection apart from Ps.aeruginosa which didn’t show significant reduction. The data obtained during this study suggested that u.v. disinfection can effectively reduce or eliminate bacteria existing in circulating water systems, thus reducing problems concerning public health and creating a healthier environment for the bathers.