The major part of the water treatment plant is taken up by the filtration halls. These are sand filters, which remove organic pollution. As a finishing touch, these are followed by filtration through granular activated carbon.
Sand filtration
Water containing clumps of “floc” from the previous stage of treatment is pumped into sand filters. These are tanks with a layer of water-treatment sand, which catches the clumps of contamination while the water itself flows on to the next stage of treatment. When a filter gets fully clogged up, it is shut down for cleaning and the trapped “flocs” of pollution are washed out of the filter sand. This washing process is repeated every 24 to 72 hours, depending on the level of impurities in the raw water.
After the water has been purified by the sand filters, the next step of treatment is ozonation, i.e. powerful oxidation. Injecting ozone into the water is a sure way to break down viruses, bacteria and other organic substances, whose residues are then removed in the following filtration stage.
An important stage of water treatment is its filtration through granular activated carbon, known as GAC filtration. Activated carbon is a highly porous material that has a huge internal surface area, allowing it to adsorb a wide range of substances, including the residues of broken down organic matter. The result is clear drinking water without unwanted flavours and odours. As well as undesirable substances, the GAC could also absorb any disinfectant added, which is why chlorination only comes at the end of the water treatment process.
All the sludge that is generated during the washing of the sand and GAC filters is pumped into a sludge tank neighbouring the water treatment plant.
In its early days, thanks to the quality of the water, it was enough for the water treatment plant to use flocculation and coagulation, followed by sand filtration and chlorination. With the passage of time, though, the development of more advanced technologies made it possible to improve water treatment by adding ozonation in 1991 and significantly upgrading the process in 2010.
The final step towards state-of-the-art water treatment was the incorporation of GAC filtration in 2021. Several alternatives were considered, including the option of modifying the existing sand filtration tanks. But in the end it was decided that an entirely new building would be constructed to house this water filtration process. Following this latest modernisation of the plant in 2021, it is now Prague’s biggest and most up‑to-date water treatment plant.
... over the 50 years of its existence, the water treatment plant has produced 4,882,881,839 m3 of drinking water, i.e. enough to fill the Švihov Reservoir 16 times?
If you’d like to learn more, continue to the other parts of the treatment plant...
