Wastewater Treatment in Support of Ash Pond Closures

Abstract

The Environmental Protection Agency (EPA) is evaluating rules that will not permit the storage of coal combustion residuals (CCRs) in surface impoundments, and require CCRs to be stored in Subtitle C or Subtitle D landfills. In addition, the EPA is evaluating more stringent effluent guidelines for water discharges which may impact NPDES permits in the future. To support these changes, the Tennessee Valley Authority (TVA) is evaluating the elimination of wet CCR handling and surface impoundments at their coal fired facilities. If CCR conveyance is converted to dry methods and the surface impoundments are closed, the other wastewater streams that utilize these impoundments as a point of discharge will also be affected. Therefore, TVA is investigating options to handle the miscellaneous wastewater streams that currently discharge to the impoundments, and meet more stringent effluent limits that may be implemented in the future. This investigation includes characterization of the existing wastewater streams, determining the effects on wastewater streams associated with future plant modifications and anticipated regulatory changes, developing methods to reduce and reuse wastewater streams to avoid discharge, and developing methods to treat the remaining wastewater streams that may be discharged in accordance with potential future effluent limits. TVA is in the forefront of addressing the pending EPA rules that may affect CCR handling and storage, and water discharges. This paper discusses and presents the process being used by TVA to address these changes, the results obtained to date, and how this may be applicable to others potentially impacted by these changes.