Filtration for removal of microparticles in swimming pool water

Filtration is an effective method for removing particles larger than 10–15 µm in swimming pool water. However, the removal of smaller particles poses a significant challenge. Tests were conducted to improve the filter's performance. These tests included choice of filter cloth, long-term filtration operation, pre-coating with filter aids (Arbocel and Harbolite). As expected, the choice of filter cloth affects particle rejection, but other strategies can be employed to improve the process. During long-term operation, particle rejection continuously improved for all filter cloths, and after 30 min, 50 % of particles as small as 2 µm were removed. Since, the concentration of particles in swimming pool water is low, only part of the filter cloth is covered by particles even after 30 min. Higher particle rejection could also be achieved by recycling particles from the filter cloth or using filter aids. Additional particles have been removed from the filter cloth by rinsing the filter cloth with water followed by the recirculation of part of the rinse water or the coagulated rinse water. Higher particle removal can also be obtained by using filter aids, whereby it is possible to cover the entire surface of the filter. When using Harbolite as the pre-coat material, more than 80 % of the particles with a size of 2 µm or larger can be removed when 100 g Harbolit was used per m² filter cloth.