By replacing the filter sand with Filtralite, Bedrichov Water Treatment Plant reduced energy cost by 75 %, doubled the production capacity of each filter and today delivers the best drinking water ever
Time is running out
The use of sand for water filtering is most likely the oldest method in history for treating water for consumption. Sand is still today widely used in water purification plants throughout the world, mainly because of its availability. Few alternatives to sand have nevertheless been presented.
Now time seems to be running out for sand as a filtering medium in modern processes. The main disadvantage of sand is the large amount of energy required for daily backwashing, taking an increasing toll on operating costs. Sand also has problems keeping up with modern efficiency and does not efficiently filter out microscopic particles, like small cyanobacteria, which today represent a threat to public water quality and has been related to public health issues.
Limitatons in sand
“When you filter by sand it is the network of sand grains hat trap and hold back the particles. The water pass through the space air to reverse the water flow, there formed between the grains. Since the sand grains are uniform in size, these “openings” are identical throughout the filter. However, the particles you want to filter out differ greatly in size, leading to frequent clogging of sand filters, and a need for very frequent backwashing,” explains Petr Dolejs, professor at Brno University of Technology, who has been responsible for the pilot tests leading to the new filtering material at Bedrichov. The flushing requires a lot of energy in using water and compressed
Filtralite: An open medium
Filtralite is a modern product, made from expanded clay, develpped especially for water filtering purposes. Filtralite works by a slightly different principle than sand, and the two kinds of Filtralite used at Bedrichov has the sizes of 0,8-1,6 mm(HC) and 1,5-2,5 mm(NC) respectively. Filtralite can be characterized as small hard pieces of open sponge, full of internal pores of different sizes. As the water passes through the filtering bed, the particles we want to take out are trapped in the pouches on the Filtralite. The water is also free to pass right through the particle body itself, making clogging almost impossible. Thanks to its porous structure Filtralite is therefore a more openfiltering medium, with extra large room for storing particles.