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July 3, 2024
Wastewater Discharge Standards for Steam Electric
Power Plants
Overview
existing, and the category of pollutant discharged. ELGs are
The Clean Water Act (CWA) prohibits the discharge of
based on the performance of specific control technologies,
pollutants from any point source into “waters of the United
but the regulations do not require a facility to use a specific
States” without a permit. Thus, industrial and other
technology.
facilities that discharge to waters of the United States must
obtain permits from the U.S. Environmental Protection
CWA Section 304(m) directs EPA to annually review
Agency (EPA) or delegated states that set limits on
existing ELGs to determine whether revisions are
pollutants in facilities’ effluents. To inform the limits set in
appropriate. During its 2005 review, EPA identified the
permits for industrial dischargers, EPA publishes Effluent
steam electric power industry ELGs for possible revision
Limitation Guidelines (ELGs)—nationally applicable
based in part on data showing that the industry ranked high
regulations that establish technology-based standards for
in discharges of toxic and nonconventional pollutants. EPA
categories of industrial dischargers. Since 1972, EPA has
initiated a study, completed in 2009, which found that the
promulgated ELGs for 59 industrial categories, including
1982 regulations did not adequately address the pollutants
the steam electric power industry—which covers power
being discharged and had not kept pace with changes in the
plants that use nuclear or fossil fuels (e.g., coal, oil, and
industry. The study focused primarily on coal ash handling
natural gas) to generate steam used to produce electricity.
operations and flue gas desulfurization (FGD) systems (i.e.,
scrubbers) used at coal-fired power plants to control air
In 2015, EPA published revised ELGs for the steam electric
pollution. While scrubbers reduce pollutant emissions into
power industry (2015 Rule) to replace rules issued in 1982.
the air, some create a significant liquid wastestream. The
EPA determined that new ELGs were necessary to reflect
study further noted that pollutants in wastewater at some
changes in the industry. For example, improvements in air
coal combustion plants have the potential to degrade water
pollution control technologies since 1982, particularly at
quality when discharged to surface waters or leached into
coal-fired power plants, reduced air pollutant emissions but
groundwater.
transferred some of these pollutants to liquid wastestreams,
increasing pollutant discharges to surface waters. EPA
In 2009, environmental groups sued EPA to compel the
promulgated the 2015 Rule to address those water quality
agency to commit to a schedule for issuing revised ELGs
impacts by establishing new or additional requirements for
for this industry. Pursuant to a consent decree, EPA
several wastestreams from steam electric power plants.
promulgated a final rule in 2015. The 2015 rule included
the first federal limits on toxic metals and other pollutants
Since that time, EPA has published additional regulations to
in wastewater discharges from steam electric power plants.
update the 2015 Rule to reflect developing treatment
The rule included new or additional requirements for both
technologies and new performance data, and to address
existing sources and new sources in several wastestreams.
legal challenges. EPA published its most recent ELG
These wastestreams (some of which are shown in Figure 1)
update for the steam electric power category in May 2024
included the following:
(2024 Rule). The Biden Administration announced the rule
as one of a suite of final rules to reduce pollution from
• Flue gas desulfurization (FGD) wastewater: wastewater
fossil-fuel-fired power plants. The announcement garnered
generated from the wet FGD scrubber system (used to
congressional and other stakeholder interest, both in support
prevent air emissions of sulfur dioxide) that contacts the
of and in opposition to the rule.
flue gas or the FGD solids
Background and the 2015 Rule
• Fly ash transport water: wastewater that is used to
convey fly ash from an ash collection or storage
ELGs set technology-based standards, including numeric
equipment, or boiler, and has direct contact with the ash
limits, for specific wastewater pollutants. For point sources
that introduce pollutants directly into U.S. waters—direct
• Bottom ash transport water (BATW): wastewater that is
dischargers—EPA or delegated states incorporate the limits
used to convey bottom ash from an ash collection or
set in ELGs into National Pollutant Discharge Elimination
storage equipment, or boiler, and has direct contact with
System (NPDES) permits. For sources that discharge to
the ash
publicly owned treatment works (POTWs)—indirect
•
dischargers—EPA promulgates pretreatment standards that
Flue gas mercury control (FGMC) wastewater:
are enforced by POTWs and federal and state authorities.
wastewater generated from an air pollution control
system installed or operated for the purpose of removing
The CWA requires industrial dischargers to achieve
mercury from flue gas
specified levels of pollution control based on whether a
discharger is direct or indirect, whether a source is new or
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Wastewater Discharge Standards for Steam Electric Power Plants
• Gasification wastewater: wastewater generated at an
and included new data for EPA to consider. In response,
integrated combined cycle plant from the gasifier or the
EPA agreed to reconsider the ELGs for two waste
synthetic gas cleaning, combustion, and cooling
streams—FGD wastewater and BATW—for existing
processes
sources. EPA finalized a 2017 rule postponing compliance
•
deadlines for those wastestreams to allow the agency time
Combustion residual leachate (CRL): leachate from a
to revise the limits.
landfill or surface impoundment that contains
combustion residuals
In 2020, EPA published a final rule revising the limits for
Figure 1. Selected Wastestreams from Steam Electric
existing facilities for those two wastestreams (the 2020
Power Plants
Rule). EPA concluded that more affordable technologies
capable of removing similar pollutant amounts had become
available since 2015, and changed the technology basis for
treatment of the two wastestreams. The 2020 Rule
established new subcategories and varying requirements for
high flow facilities, low utilization units, and units retiring
by 2028. Some of these changes reflected less stringent
standards for the new subcategories.
2024 Rule
In May 2024, EPA published a final rule to “strengthen” the
wastewater discharge standards that apply to coal-fired and
other steam-electric power plants. EPA explained that better
performing treatment technologies have continued to
develop since the issuance of the 2020 Rule, and that there
is more information about their performance. The 2024
Rule establishes more stringent standards for three
wastestreams generated at existing facilities: FGD
wastewater, BATW, and CRL. These standards include a
Source: EPA, “Steam Electric Power Generating Effluent
zero- limitation for pollutants in FGD wastewater, BATW,
Guidelines,” https://www.epa.gov/eg/steam-electric-power-
and CRL. The 2024 Rule also establishes numeric
generating-effluent-guidelines.
discharge limitations for mercury and arsenic for
Notes: ACI is activated carbon injection, ESP is electrostatic
unmanaged CRL (i.e., certain discharges through
precipitator, FGD is flue gas desulfurization, POTW is publicly owned
groundwater) and for discharges of legacy wastewater from
treatment works, and Hg is mercury.
certain surface impoundments.
Specifically, the 2015 Rule established effluent limits for
arsenic, mercury, selenium, and nitrogen for FGD
The 2024 Rule also eliminates less stringent requirements
wastewater at existing sources, as well as more stringent
for two subcategories of facilities (high flow facilities and
limits for these pollutants and a limit on total dissolved
low utilization energy generating units) that were contained
solids for new sources. The 2015 Rule also set limits on
in the 2020 Rule. The 2024 Rule also includes certain
arsenic, mercury, selenium, and total dissolved solids in
implementation flexibilities. For example, facilities that
gasification wastewater at existing and new facilities, with
permanently cease coal combustion by 2034 (whether
more stringent limits at newer facilities. The rule also
through closing or switching to fuels that generate fewer
required zero discharge of pollutants in fly ash transport
pollutants) may continue to fall under the requirements in
water, BATW, and FGMC wastewater for existing and new
the 2015 and 2020 rules, rather than the more stringent
sources. For CRL, the rule established limits for total
2024 Rule requirements.
suspended solids (TSS) for existing facilities and for arsenic
Stakeholder and Congressional Interest
and mercury at new facilities.
Some stakeholder groups and Members of Congress have
The 2015 Rule maintained requirements from the 1982
supported the 2024 Rule, and some have opposed it. Those
regulations (which were focused on settling out particulates
in support of the new rule point to EPA’s analysis that it
rather than treating dissolved pollutants) for TSS and oil
will reduce hundreds of millions of pounds of pollutants
and grease. Additionally, EPA established limitations for
from entering waterways each year. Those who oppose the
legacy wastewater equal to the 1982 limitations on TSS for
rule argue that the new regulations are unachievable for
several wastestreams. EPA defined legacy wastewater to
many facilities, and will force their premature retirement. In
mean FGD wastewater, fly ash transport water, bottom ash
May 2024, some Members introduced H.J.Res. 151, a joint
transport water, FGMC wastewater, or gasification
resolution of disapproval for the 2024 Rule under the
wastewater generated prior to a date specified by the
Congressional Review Act. If the joint resolution is
permitting authority (to be set between November 2018 and
enacted, the 2024 Rule would have no force or effect, and
December 2023).
EPA would be prohibited from issuing a substantially
Revisions to the 2015 Rule
similar rule.
The 2015 Rule faced legal challenges and EPA received
Laura Gatz, Specialist in Environmental Policy
two petitions for administrative reconsideration, which
IF12705
raised “wide-ranging and sweeping objections to the rule”
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Wastewater Discharge Standards for Steam Electric Power Plants
Disclaimer
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https://crsreports.congress.gov | IF12705 · VERSION 1 · NEW