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New wastewater discharge standards for coal-fired power plants

July 30, 2024
New wastewater discharge standards for coal-fired power plants

Earlier this month, a new rule went into effect that establishes more stringent wastewater discharge standards for coal-fired power plants. The Environmental Protection Agency’s (EPA’s) new rule sets effluent limitations guidelines (ELGs) to enforce the Clean Water Act (CWA) through industry-specific, technology-based regulations. The final revisions were published on May 9 for the steam electric power generating point source category, with prior revisions promulgated in 2015, 2020, and 2023.

The 2015 revisions established discharge limits for toxic metals and introduced subcategories for electric generating units (EGUs) less than or equal to 50 MW (small EGUs) and oil-fired EGUs. The 2020 final rule revised flue gas desulfurization (FGD) wastewater and bottom ash (BA) transport water requirements. The 2020 rule retained both 2015 rule subcategories and introduced three new subcategories: low utilization electric generating units (LUEGUs), high FGD flow facilities, and EGUs permanently ceasing coal combustion by December 31, 2028. The subcategory applicability is dependent on the waste stream generated and, when applicable, allows for less stringent requirements than those for facilities that do not fit into a subcategory.

What’s new in the 2024 rule?

Effective July 8, the new rule establishes more stringent limitations based on Best Available Technology Economically Achievable (BAT) for FGD wastewater, BA transport water, and combustion residual leachate (CRL). The new rule also provides clarity for some legacy wastewaters and establishes a subcategory for EGUs that permanently cease coal combustion by 2034.

Let’s take a closer look at the new rule, which is limited to existing sources, since the EPA has assumed that most, if not all, plants subject to the new rules will be classified as existing sources. However, the new rule also set limitations for CRL for new direct and indirect sources.

Flue gas desulfurization wastewater

The new rule establishes zero discharge limitations for FGD wastewater based on chemical precipitation plus membrane filtration technology and 100% recycle of the permeate. Direct dischargers will be required to meet the new limitation by no later than December 31, 2029, and indirect dischargers will be required to achieve compliance by May 9, 2027, unless one of the following conditions are met:

  • The discharger is enrolled in the Voluntary Incentives Plan (VIP)—available to direct dischargers only.

  • The water is sourced from a small EGU or an oil-fired EGU.

  • The water is sourced from an EGU that will permanently cease coal combustion by 2034.

  • The water is stored in an impoundment that commences closure after July 8, 2024.

Bottom ash transport water

The new rule establishes zero discharge limitations for BA transport water based on dry handling or closed-loop technology. Direct dischargers will be required to meet the new limitation by no later than December 31, 2029, and indirect dischargers will be required to achieve compliance by May 9, 2027, unless one of the following conditions are met:

  • The water is sourced from a small EGU or an oil-fired EGU.

  • Direct discharges only: bottom ash transport water is used in the FGD scrubber (in this case, the permittee shall follow guidelines for FGD wastewater).

  • The water is sourced from an EGU that will permanently cease coal combustion by 2034.

  • The water is stored in an impoundment that commences closure after July 8, 2024.

Combustion residual leachate

The new rule establishes zero discharge limitations for combustion residual leachate for active facilities based on multiple zero-discharge system technologies (membrane filtration systems, spray dry evaporators, and thermal evaporation systems) and any necessary pretreatment (e.g., chemical precipitation) or post-treatment (crystallization). Direct dischargers will be required to meet the new limitations by no later than December 31, 2029, and indirect dischargers will be required to achieve compliance by May 9, 2027.

The EPA acknowledges that retired facilities will continue to generate and discharge CRL; therefore, the EPA has established nonzero limitations for arsenic and mercury following a plant’s retirement. Such limitations also apply to impoundments that commence closure after July 8, 2024. The nonzero limitations for CRL are based on membrane filtration for CRL permeate and thermal evaporation for CRL distillate.

Unmanaged combustion residual leachate

The rule adds a new subcategory of “unmanaged combustion residual leachate,” which the rule defines as:

Combustion residual leachate which either:

  1. Is determined by the permitting authority to be the functional equivalent of a direct discharge to a Waters of the United States (WOTUS) through groundwater, or

  2. Has leached from a waste management unit into the subsurface and mixed with groundwater prior to being captured and pumped to the surface for discharge directly to a WOTUS.

The new rule establishes nonzero arsenic and mercury limitations for unmanaged CRL using the same technology basis for nonzero CRL limitations. The EPA notes that the determination of a functional equivalent direct discharge (FEDD) is out of the scope of the new rule and is at the discretion of the permitting authority.

Legacy wastewater

The new rule allows permitting authorities to establish BAT Technology-Based Effluent Limitations (TBELs) for some legacy wastewaters on a case-by-case basis using best professional judgement. The EPA has rejected surface impoundments as BAT for legacy wastewater, noting there are more effective technologies for discharges, as discussed for other wastewaters. The EPA does not specifically refer to “legacy wastewater” in updated 40 CFR 423.19 but defines legacy wastewater as the following in Appendix A to the rule’s preamble:

FGD wastewater, BA transport water, FA transport water, CRL, gasification wastewater, and/or FGMC wastewater generated before the “as soon as possible” date that more stringent effluent limitations from the 2015 or 2020 rules would apply

The new rule acknowledges that the EPA is adding a definition for “legacy CCR surface impoundments” in a separate, yet concurrent, rulemaking. On May 8, 2024, the EPA finalized a new rule entitled “Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals From Electric Utilities; Legacy CCR Surface Impoundments” (Legacy Rule). The Legacy Rule extends many of the requirements of the current CCR rule to previously unregulated CCRs in inactive surface impoundments at inactive power plants (referred to as “legacy CCR surface impoundments” or “legacy ponds”) and CCR Management Units (CCRMU), a new category of CCR unit established by the final rule.

It’s important to note that:

  • Existing groundwater remediation systems that pump CRL and groundwater into a process water loop that is not discharged to a WOTUS would not trigger new restrictions under the rule.

  • Active facilities will have zero discharge requirements for CRL until retirement. The ELG allows facilities to discharge CRL upon retirement.

  • Other parameters not listed in the ELG rule may have National Pollutant Discharge Elimination System (NPDES) permit limits based on water quality criteria.

Assessing your facility

The new rule will likely impact facilities with existing and planned discharges. We recommend facilities assess their closure plans to prepare for any new rule changes that may affect planned discharges. Barr has been assisting facilities with navigating the evolving steam ELGs and the related power sector rules since before the CCR and ELG revisions began in 2015. The most common type of evaluation is conducting “what if” scenario development with cost modeling to assess what, if any, changes may be needed to existing permits and/or processes. 

We have also developed a science-based framework for evaluating whether a functional equivalent discharge to a WOTUS is present or likely. We strongly suggest you consider the hydrogeology of your site before engaging local regulatory authorities so there is a shared understanding of the actual groundwater flow conditions rather than speculation.   

Contact our team to learn how Barr can support you in navigating the new water discharge rules for your facility.

About the authors

Kate Sinner, environmental engineer, works primarily with clients in the manufacturing and power generation sectors. Her experience includes helping clients navigate permitting and compliance challenges, particularly those related to NPDES permits, in multiple states and EPA regions. Kate has conducted discharge feasibility studies for clients, including for coal-fired power plants seeking discharge options.

Valerie Venier, chemical engineer, supports clients in the manufacturing, fuels, and power sectors across the Midwest and upper Midwest regions. She evaluates NPDES discharge limitations based on federal and state rules and assists facilities with ongoing compliance.

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Tags:

Power CCR NPDES Clean Water Act (CWA) Effluent Limitation Guidelines (ELG) Steam Waters of the United States (WOTUS)

 

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Kate Sinner
Environmental Engineer
 

 

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Valerie Venier
Chemical Engineer
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