The swimming pool of Benfica’s local municipality sports facilities, in Lisboa, is open to the public for more than ten years. With 25 meters and five tracks, this roofed swimming pool receives 3200 swimmers per week.
To control the Legionella bacteria on the hot water distribution system of the swimming pool, the local municipality used the thermal shock treatment method at 75°C, with water running in the showers between 2 and 3 minutes.
The swimming pool water disinfection parameters were manually controlled. This situation leads to variations of the chlorine and pH values. To solve this problems the company responsible for maintaining the swimming pool, Actipail, decided to propose the installation of an automatic control system, composed of a Conex DIP measuring and amplifier controller and two dosing pumps Smart Digital DDA.
With this new system it’s now possible to control the main parameters automatically and, at the same time, ensure the same chlorine, pH and Redox levels no matter how many users are at the swimming pool.
Regarding Legionella control, the local municipality decided to install an Oxiperm Pro chlorine dioxide system. The monthly water consumption is approximately 500 m3 and the water temperature for baths is nearly 38°C. With this new solution, it was possible to reduce the temperature of the two tanks (2000 liters each) from 65°C to 50°C. After one month of operation, the local municipality registered a reduction in gas consumption of 2000 m3.
The chlorine dioxide acts permanently on the biofilm, where Legionella lives, which guarantees a continuous treatment against these bacteria. Besides that, it eliminates phenols and it doesn’t smell badly.
The chlorine dioxide is revealing to be more effective than chlorine when it comes to the elimination of spurs, bacteria, virus and other pathogenic organisms in the same residual basis (including cryptosporidium and giardia) and in removing compounds of iron and magnesium, especially in complex limits. Also, it has not been yet verified any kind of corrosion associated with high concentrations of chlorine dioxide. On the contrary, chlorine
dioxide contributes for the reduction of maintenance costs on a long term basis. The control analyses also did not reveal the presence of any type of Legionella.
According with José Guimarães, from Actipail, the local municipality manages to save nearly 2000 m3 per month in gas spending only approximately 10 € per month in reagents – which, in general, amounts for savings of nearly 1500 € per month. Having these costs in mind, it is expected that the return of investment occurs in less than 12 months.
1 Oxiperm Pro chlorine dioxide system
1 Conex DIP measuring and amplifier controller
2 dosing pumps Smart Digital DDA
Installer: Actipail Lda
Maintenance company: Actipail Lda