Blowdown

Periodic removal of water from an evaporative cooling system (also known as a wet closed-cycle cooling system) to control the buildup of impurities and maintain the concentration of dissolved minerals in the circulating water. Blowdown typically involves the release of less than 10% of the total water volume in the cooling system and typically occurs after completion of as many as five cycles. Blowdown is either discharged to a surface water body under a permit that limits both chemical content and temperature, or directed to an evaporation pond where mineral residues are later collected and removed for disposal.