NPDES > Overview

Water treatment additives including polyphosphates, polyester, phosphates, chlorine, bromine, and polyacrylates may be used by your power plant to control such characteristics as pH and metals concentration associated with wastewater discharges, especially cooling water systems. As a reminder, there are two broad types of cooling water systems:

• One-pass cooling
• Recirculating systems

One-pass cooling water systems typically take water into the plant from surface waters and pass it through the condenser(s) where it absorbs heat and is then discharged to a receiving water. Chlorine is added intermittently to control biofouling and is a pollutant of concern in cooling water discharge.

Recirculating cooling water systems transfer heat from the water to the atmosphere via cooling towers, cooling ponds, or spray facilities. These systems are subject to metal corrosion, scale formation, and biological fouling, which have a direct effect on system operating efficiency; reliability, longevity and the composition of the bleed off sent to drain. Commonly used water treatment additives address these problems; however, some additives may contain metals in and of themselves, such as copper, zinc, hexavalent chromium, tributyltin and other organo-metallic compounds, which are pollutants of concern in cooling water discharge.

As you may know from having visited other locations on your EVC tour, the United States Environmental Protection Agency (EPA) regulates the discharge of water from facilities through provisions of the Clean Water Act, including provisions of the National Pollutant Discharge Elimination System (NPDES) program. EPA has authorized many states to implement and monitor the NPDES program. NPDES permits establish the level of performance the discharger must maintain and specify monitoring, inspection, and reporting requirements and other actions necessary to achieve compliance. NPDES permits set specific requirements regulating the characteristics of the discharged water based on national technology-based effluent limitations and applicable water quality standards.

Applicability of NPDES requirements to a typical college or university power plant vary greatly depending on the activities or discharges associated with the facility and the interpretation by the state regulatory agency charged with enforcing the Federal NPDES program (in states where that is the case; not all states have been delegated with this authority). Typically the discharge of process water from a power plant to surface water would require a NPDES permit.

If you have an NPDES permit for surface water discharges or for storm water discharge or believe one is required for your power plant, continue on to the expanded content to learn more about NPDES permit requirements.