Good practice:

Closed-cycled water overflow in “Sports Bay”

Each pool has overflow gutters by which the water splashed out of the pool volume is returned to a tank in the pool basement. The pool basement tanks are covered to prevent evaporation of the contents.

The water in this closed cycle is disinfected and filtered with positive-pressure auger filters that comprise a total of approximately 200 cartridges.

The water is fed into the filters under positive pressure and treated while passing layers of diatomic earth deposited on the fabric which surrounds the filter auger part.

Downstream of the filters, the water is chlorinated with a chlorine compound produced on site with an electrolyser, which forms a salt bridge and chlorine gas from NaCl; this form of delivery is much more efficient than liquid chlorine compounds.

Next, the chlorinated water is passed under an UV lamp. The UV lamp provides photo-oxidation-driven disinfection, which efficiently neutralises and inhibits the growth of bacteria, viruses and other microbes.

Finally, the water is recycled back to the pool via a system of piping and pool bottom inlet nozzles (with a total number of approximately 100 units). A pool with a total service capacity of 3,300 m3 has 3 to 4 full water changes a day.

The water lost by evaporation, carried out on the bodies and splashing amounts to approx. 100 m3 a day is replenished from the district mains; this make-up water is already treated.

The swimming pool water quality is monitored online.

The investment cost was about PLN 130 million (EUR 29.5 million)

Unlike most swimming pools in Poland and the world, water disinfectant is produced on site by membrane electrolysis from a salt solution. The resulting disinfectant (gaseous chlorine) has 80 times higher effectiveness than the commonly used sodium hypochlorite.

100 m3 a day is replenished from the district mains; this make-up water is already treated.

The technologies used allow to achieve reused water quality exceeding the standards for drinking water.

This kind of investment is possible to be carried out everywhere, taking into account the costs and high competence of those responsible for implementing the technology.

For the investment to be successful it may be necessary for many entities to work together. The "Sports Bay" has been financed by resources from the Łódź University of Technology, Łódzkie Voivodeship, the Łódź City Hall, Ministry of Sport and Tourism and the Ministry of Science and Higher Education.