Where does the water come from?

If you are building a family house or a holiday cottage, you are certainly thinking about supplying the building with drinking water. In our territory, we are lucky that water is available via public water supply practically anywhere in the built-up area. You can also use drinking water from your own well, but we will look at those in more detail in other articles. Today we will discuss the preparation and process of treating the water that flows into our water supply line.

Water from a public source

This water is used by most households, the public sector, industry and other sectors of the national economy. Water supplied by water supply organizations is potable, meets all hygienic and other requirements. Drinking water suppliers must meet the requirements of a number of legal regulations.

The adjustment of raw water to the parameters of drinking water in water plants is carried out as follows:

  • Airing (aeration). During aeration, the water gets rid of free carbon dioxide (CO 2 ) and is saturated with oxygen (O 2 );
  • Flocculation (lime dosing). It consists in pouring milk of lime into raw water. This removes excess insoluble ferric hydroxide (FeOH 3 ) from the water;
  • Sedimentation (deposition of substances from water). The water flows through the settling tank very slowly for approximately 2 hours. During this time, almost all precipitated ferric hydroxide (FeOH 3 ), calcium carbonate (CaCO 3 ), hydrates, organic and other substances settle out of the water ;
  • Filtration (capture of dispersed substances). Through the layer of siliceous sand, fine substances are captured. Depending on the size of the filter, the sand layer is up to 150 cm high;
  • Disinfection (hygienic quality assurance). Chlorine protects the water against the microbiological revival of organisms in the water.

Where does the water come from?

Water plants obtain raw water from water reservoirs (surface water) or from wells. Acid rain, dust in the air and other impurities in the air have a great influence on the quality of raw water. They are the cause of much more demanding treatment of raw water to drinking water parameters. Treatment of water from water reservoirs is almost always more demanding than from wells. According to the standard ČSN 75 7221 Water quality – Surface water quality classification [5], surface water is divided according to 46 criteria into 5 quality classes: very clean water, clean water, polluted water, heavily polluted water and very heavily polluted water.

Most groundwater almost always passes through several meters of soil before being collected. It is partially purified by this. The treatment costs are therefore lower than when treating surface water from reservoirs. However, the majority of water treated in waterworks comes from waterworks reservoirs.

Dosing milk of lime into raw water

Advantages of taking drinking water from a public source:

  • continuous supply of water with guaranteed quality;
  • in the event of a water supply failure, the water supply organization will transport a tank with drinking water;
  • there are no worries about building a well and its maintenance.

Disadvantages of taking drinking water from a public source:

  • in the event of a pipe failure, the repair may take several hours or even days;
  • consumers also pay for water that they do not use and that is lost to the ground in damaged (leaking) pipes during transport to the collection point.

It is often stated that the price of water supplied from waterworks is high and is one of the disadvantages. Nevertheless, the majority of water consumed in the Czech Republic comes from a public source. The amount of drinking water consumed from wells is much less than water supplied from waterworks.

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