Water used in production processes, mainly in heat and power generating plants for cooling. This is usually hot water, which causes so-called thermal pollution of water.

Cooling water, including water coming from cooling cycles, not requiring treatment, has to meet the following conditions:

1. it is drained off to surface waters via a separate drainage system and are not mixed with other waste water which requires treatment,

2. the quantity of pollutants in cooling water (after the production process) is not greater than the amount of pollutants in water collected for cooling purposes,

3. the temperature specified in legal water permit for cooling water drained off to: - lakes and their tributaries does not exceed +26 degrees centigrade or the natural temperature of water in case it is higher than +26 degrees centigrade; - other waters, except territorial sea, does not exceed +35 degrees centigrade.

In case of draining off cooling water without a valid legal water permit, all such water should be regarded as untreated waste.

• Act of 20 July 2017, New Water Law
  Place of publication: (Dz. U. z 2024 r. poz. 1087, z późn. zm.)