A review on fly ash from coal-fired power plants: chemical composition, regulations, and health evidence

Throughout the world, coal is responsible for generating approximately 38% of power. Coal ash, a waste product, generated from the combustion of coal, consists of fly ash, bottom ash, boiler slag, and flue gas desulfurization material. Fly ash, which is the main component of coal ash, is composed of spherical particulate matter with diameters that range from 0.1 μm to >100 μm. Fly ash is predominately composed of silica, aluminum, iron, calcium, and oxygen, but the particles may also contain heavy metals such as arsenic and lead at trace levels. Most nations throughout the world do not consider fly ash a hazardous waste and therefore regulations on its disposal and storage are lacking. Fly ash that is not beneficially reused in products such as concrete is stored in landfills and surface impoundments. Fugitive dust emissions and leaching of metals into groundwater from landfills and surface impoundments may put people at risk for exposure. There are limited epidemiological studies regarding the health effects of fly ash exposure. In this article, the authors provide an overview of fly ash, its chemical composition, the regulations from nations generating the greatest amount of fly ash, and epidemiological evidence regarding the health impacts associated with exposure to fly ash.

Wastewater Treatment in Support of Ash Pond Closures

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.