A cooling tower is a heat rejection device which rejects waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Common applications include cooling the circulating water used in oil refineries, petrochemical and other chemical plants, thermal power stations and HVAC systems for cooling buildings. Poor water treatment lets water interact with the surfaces of pipes and vessels which contain it. Cooling towers can scale up and corrode, but left untreated, the warm, dirty water they contain will encourage bacteria to grow. If water treatment is left neglected, it can cause defective products and domestic water can become unsafe to drink.
It's best to just get the water for your boiler and cooling towers treated.