Removing heavy metals from power plant wastewater to meet EPA regulations
Two Environmental Protection Agency (EPA) regulations, intertwined and consistently in flux, are having an impact on waste streams in power plants.
Important power plant wastewater regulations include Effluent Limitation Guidelines (ELGs) for flue gas desulfurization (FGD) and limitations for coal combustion residuals (CCRs) for coal ash ponds. Coal-fired utilities are looking for solutions to remove the heavy metals found in both scenarios.
The EPA 2015 ELG rule regulates discharge of ash transport water and sets limits on the levels of toxic heavy metals that can be discharged from FGD systems at steam electric power generating stations. The proposed regulations were recently updated. (See chart below.)
The need for heavy metals removal in power plant wastewater will be required in almost all FGD systems. In WesTech`s interpretation of these ELG regulations, systems that have a high flow rate, low utilization boilers, or systems that will be retired by 2028 may be exempt from meeting proposed EPA regulations for heavy metals removal. All other FGD wastewater systems will need a solution to remove heavy metals to the limits set by the EPA, which are based on a physical-chemical biological treatment system.
Also, the limitations for CCRs will require coal-fired utilities to consider ways to eliminate coal ash ponds and minimize the use of process water in handling CCRs and wet FGD systems.
Utilities that research options for meeting this continually changing regulatory landscape and proactively seek solutions that work for their sites will be one step ahead.
An effective treatment to consider is a physical-chemical biological solution for eliminating heavy metals in both types of coal-fired utility waste streams, for coal ash ponds and FGD systems. For coal ash ponds, these systems may include reaction tanks, clarifiers, and pressure filters. Solutions for FGD systems might include mixing tanks, clarifiers, ultrafiltration, and continuous backwash filters.
Ideal solutions will accommodate varied and unique site conditions. Though the solution may start with a standardized approach, utilities should work with solutions providers who can customize and modify existing treatment methods to meet the unique needs of their site.
The following case studies represent conditions at two coal-fired power plants – one concerned with meeting the ELG rule and one with CCR requirements. In both cases, a physical-chemical solution was customized to eliminate the heavy metals contamination and protect local groundwater.