Even when not required by environmental regulations, the following best practices are recommended. In some instances, best practices presented here are actually required by regulations. Reducing the potential impact of a power plant’s cooling water on the environment may be accomplished by one (or a combination of) of the maintenance and operational practices described below.
Maintenance Practices
- Maintain the cooling tower properly (i.e., according to the manufacturer’s specifications). This will ensure the equipment operates efficiently and properly, which will potentially reduce the amount of contaminants found in cooling water. Scheduling routine monitoring and maintenance activities are additional ways to maintain the cooling tower(s) effectively.
- Include guidelines addressing chemical substitution options into service contracts to ensure potentially hazardous additives are not used or their use is minimized.
- During repair or reconstruction of existing open recirculating tower systems, limit the use of copper-based materials, which will potentially reduce the metal content of cooling water discharges.
Alternative Operational Practices
- Identify the optimal chemicals for the prevention of biological growth and corrosion. For example, chlorinated biocides are less toxic than brominated biocide; and polyphosphate and organophosphate inhibitors are less toxic than chromate corrosion inhibitors.
- Consider using electrically powered water conditioning units. For example, automatic bleed/feed controllers enables the facility to continuously monitor the concentration of dissolved material in the cooling water. When the concentration exceeds a preset level, the controller opens the bleed valve and activates the chemical feed pump, thereby keeping the tower at the optimal concentration at all times and unintentional discharge of active chemicals is eliminated.
- Consider magnetic water conditioning, which reduces the need for chemical additives.
- Consider using ozone treatment in lieu of common biocide use. However, several documented disadvantages associated with this practice need to be weighed: 1) the potential for corrosion in cooling towers unless careful dosing of ozone practiced; 2) potential rapid fouling on high temperature surfaces in recirculating systems; and 3) health and safety issues related to potential worker exposure to ozone.
- Consider pretreating makeup water to reduce the chemical treatment requirements for scale and corrosion control and increase the ability to recycle the water.
- Consider using materials of construction for cooling tower equipment and piping such as polyethylene, titanium, and stainless steel, which require less scale/corrosion inhibitors.