On August 31, 2020, the United States Environmental Protection Agency (EPA) issued the pre-publication notice of a final rule that revises two aspects of the technology-based effluent limitations guidelines and standards (ELGs) for the steam electric power generating industry set by the Obama Administration in 2015. The final rule takes effect 60 days after EPA publishes it in the Federal Register. Its revisions apply to two waste streams, flue gas desulfurization (FGD) wastewater and bottom ash (BA) transport water, and may afford certain power plants increased flexibility to achieve compliance.

Background. As we previously blogged, EPA updated the ELGs for the steam electric power generating industry in 2015 for six types of waste streams: FGD wastewater, BA transport water, fly ash transport water, flue gas mercury control wastewater, gasification wastewater, and combustion residual leachate. Various groups challenged the 2015 rule, and in April 2017, EPA responded by publishing a postponement of compliance deadlines of the 2015 rule that had not yet passed. This stay, which we also blogged about, likewise drew several legal challenges. In August 2017, EPA announced its decision to conduct a rulemaking to reconsider and potentially revise the technology-based ELGs for FGD wastewater and BA transport water. The Fifth Circuit Court of Appeals subsequently granted EPA’s request to put the legal challenges related to the ELGs for these two waste streams on hold pending EPA’s rulemaking. EPA then published a proposed rule for public comment in 2019, and this final rule followed last week.

The 2020 Final Rule. Primary changes reflected by the 2020 final rule include:

  • BA transport water. The 2020 ELG determines that the Best Available Technology Economically Achievable (BAT) for BA transport water is a high recycle rate system rather than dry or closed-loop systems as found by the 2015 rule. Based on the 2020 BAT determination, the ELG no longer requires zero discharge. Instead, the final rule requires high recycle rate systems and allows for a site-specific discharge, which cannot exceed 10 percent of the BA transport water system volume and is to be determined by the permitting authority. The 2020 ELG also sets concentration values based on the Best Practicable Control Technology Currently Available (BPT), which permitting authorities are to use to calculate technology-based effluent limitations for total suspended solids (TSS) and oil and grease by multiplying the values times BA transport water flow:
Values to Determine BPT Effluent Limitations
Daily Maximum Limit Monthly Average Limit
TSS (mg/L) 100.0 30.0
Oil and grease (mg/L) 20.0 15.0

 

  • FGD wastewater. Somewhat similarly to the 2015 rule, the revised ELG determines that BAT to control FGD wastewater is chemical precipitation followed by a low hydraulic residence time biological reduction treatment and sets concentration values permitting authorities are to use to calculate technology-based effluent limitations for arsenic, mercury, selenium, and nitrate/nitrite as nitrogen by multiplying the values times FGD wastewater flow. But the revisions establish the following different concentration values (the values from the 2015 rule are in parenthesis below):

 

Pollutant or pollutant property Values to Determine BAT Effluent Limitations
Daily Maximum Limit Monthly Average Limit
Arsenic, total (ug/L) 18 (11) 8 (8)
Mercury, total (ng/L) 103 (788) 34 (356)
Selenium, total (ug/L) 70 (23) 29 (12)
Nitrate/nitrite as N (mg/L) 4 (17) 3 (4.4)

 

By contrast, the revised ELG retains the concentration values of the 2015 rule for TSS and oil and grease in FGD wastewater, based on the BPT:

 

Values to Determine BPT Effluent Limitations
Daily Maximum Limit Monthly Average Limit
TSS (mg/L) 100.0 30.0
Oil and grease (mg/L) 20.0 15.0

 

  • New subcategories. The final rule allows for different limits for certain subcategories of power plants. Specifically, the ELG provides different FGD wastewater and BA transport water limits for the following subcategories of electric generating units (EGUs), the latter three of which were not subcategories under the 2015 rule.
    1. Small EGUs (i.e., 50 MW or less);
    2. Oil-fired EGUs;
    3. Low-utilization EGUs (i.e., those with a certified two-year average annual capacity utilization rating under 10 percent);
    4. EGUs permanently ceasing the combustion of coal by December 31, 2028; and
    5. EGUs with FGD flows above 4 million gallons per day. For this subcategory, the new ELG retains the following concentration values of the 2015 rule for FGD wastewater to use with flow to calculate effluent limitations:

 

Values to Determine BAT Effluent limitations (FGD Wastewater flows > 4MGD)
Pollutant or pollutant property Daily Maximum Limit Monthly Average Limit
Arsenic, total (ug/L) 11 8
Mercury, total (ng/L) 788 356

 

  • Compliance deadlines. Like the 2015 rule, compliance deadlines and effluent limits are to be established through the NPDES permitting process by permitting authorities. The 2020 rule allows each permitting authority to set a deadline to comply with the revised limits as early as one year from the date of publication in the Federal Register or as late as December 31, 2025 (except for power plants falling within one of the above subcategories).
  • Voluntary Incentives Program. If a power plant adopts additional process changes and controls that achieve more stringent limits on mercury, selenium, arsenic, nitrate/nitrite, bromide, and total dissolved solids in FGD wastewater, it will qualify for EPA’s Voluntary Incentives Program (VIP), which will afford the plant more time — until December 31, 2028 — to achieve compliance with the rule.
    • The VIP sets limits based on membrane filtration (replacing the 2015 rule VIP limits based on evaporation technology), which are calculated based on the quantity determined by multiplying the flow of FGD wastewater by these concentrations:

 

Values to Determine BAT Effluent limitations
Pollutant or pollutant property Daily Maximum Limit Monthly Average Limit
Arsenic, total (ug/L) 5 N/A
Mercury, total (ng/L) 23 10
Selenium, total (ug/L) 10

 

 

N/A
Nitrate/Nitrite (mg/L) 2.0 1.2
Bromide (mg/L) 0.2 N/A
TDS (mg/L) (mg/L) 306 149

 

The final rule does not revise the limits for any other waste stream covered by the 2015 rule (fly ash transport water, flue gas mercury control wastewater, gasification wastewater, combustion residual leachate, legacy wastewater, and non-chemical metal cleaning water). However, the Fifth Circuit Court of Appeals vacated the ELGs applicable to legacy wastewater and combustion residual leachate, and EPA states in the final rule that it intends to address this vacatur in a subsequent action. We also expect that the final rule will be challenged once it is published in the Federal Register.