Treatment of a Duke Energy Power Plant wastewater by Thermal Evaporation: a review

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Abstract Wilson, Leanne. Master of Environmental Assessment. Treatment of a Duke Energy Power Plant wastewater by Thermal Evaporation: a review Water resources are an integral part of providing industries, especially electric generating facilities the ability to operate. A downside is the amount of wastewater that is produced. With the adoption of North Carolina's Clean Smokestack Act and National Air Quality standards on SO2 emission into the atmosphere, many fossil fueled plants have converted their facilities with FGD or Flue Gas Desulfurization systems in order to "scrub" the SO2 from their emission sources. Having to clean up one medium, the air, introduced new opportunities to create wastewater. Under the Clean Water Act, facilities that generate wastewater are responsible for adhering to the facility's National Pollutant Discharge Elimination System or NPDES permit. With the conversion to FGD, a Duke Energy facility installed the use of a Bioreactor system that uses heterotrophic bacteria to reduce pollutants in the wastewater. Problems arose with increased concentrations of metals, i.e., Selenium, Mercury, Boron, Thallium and Manganese that were not meeting the facility's NPDES limits. After a special order of consent was issued by NCDEQ and a 3rd party wastewater study conducted, the decision was made to seek new FGD treatment technologies by Duke Energy to comply with the NPDES limits of the receiving waterbody. The treatment that was selected was the Zero Liquid Discharge (ZLD) or Thermal Evaporating system. In the years following the commissioning of the ZLD, there has been significant improvements to the water quality and chemistry of the discharge coming from the plant into the receiving reservoir. All metals of concern decreased with Selenium at 94.81%, Mercury at 93.21%, Boron at 64.88%, Thallium at 50.43 % and Manganese at 68.79%.