On December 27, 2016, EPA proposed amendments to its National Emission Standards for Hazardous Air Pollutants (NESHAP) for Publicly Owned Treatment Works (POTW) to comply with the residual risk and technology review provisions of the Clean Air Act. EPA initially promulgated a NESHAP for the POTW source category on October 26, 1999 and amended it on October 21, 2002. While EPA does not find any unacceptable residual risk from hazardous air pollutant (HAP) emissions associated with POTWs in its newly proposed rule, EPA is proposing certain amendments to the applicability provisions of the NESHAP, as well as the underlying standards. The public comment period on the proposed rule was extended until March 29, 2017.

The POTW NESHAP applies to owners and operators of a POTW (primarily municipalities) that is either a major source of HAP emissions or accepts waste streams from an industrial facility subject to another NESHAP. Additionally, to be subject to the NESHAP, such POTWs must also develop and implement a pretreatment program as defined by 40 CFR 403.8. EPA estimates that currently only six POTWs are subject to the 2002 NESHAP out of approximately 16,000 POTWs in the United States. The primary reason is domestic wastewater generally does not contain significant concentrations of HAPs. But EPA notes in the preamble that it is concerned some POTWs may not be accounting for HAP emissions from collection systems that are required to be considered under the existing rule, in addition to HAP emissions from treatment plants, in determining whether HAPs exceed the major source threshold. That would include HAPs from pump stations, manholes and vents on collection systems emitted to the atmosphere.

As a result, EPA is proposing clarifications to the applicability criteria for the POTW NESHAP. Specifically, EPA is proposing to clarify that regulated POTWs include those having a design capacity to treat at least five million gallons of wastewater per day and receive wastewater from an industrial or commercial facility, and are either: (1) are a major source of HAPs emissions from the POTW and collection system as a whole (i.e., a Group 2 POTW); or (2) receive a wastewater stream regulated by another NESHAP from an industrial/commercial facility (i.e., Group 1 POTW). Even with these clarifications and revisions, it is not expected that the proposal would significantly increase the universe of POTWs subject to the NESHAP.

As noted above, no amendments are proposed to further reduce HAPs based upon residual risk. However, EPA is proposing the addition of several other control standards to the NESHAP. First, EPA is adding a requirement that all POTWs subject to the standard implement pretreatment programs for industrial/commercial dischargers as defined by 40 CFR 403.8. EPA is also requesting comment on requiring POTWs to develop pretreatment requirements specifically designed to reduce HAP emissions from the POTW by establishing local limits for volatile organic HAP. For Group 1 POTWs, EPA is proposing to amend the NESHAP to require existing POTWs to meet the requirements of the existing Group 2 POTW NESHAP and any other applicable NESHAP for the industrial waste streams that make it a Group 1 POTW. For Group 2 POTWs, which are independently major sources of HAP, EPA is proposing existing POTWs must operate with an annual rolling average HAP fraction emitted from primary treatment units of 0.08 or less. (Fraction emitted means the fraction of the mass of HAP entering the POTW wastewater treatment plant which is emitted prior to secondary treatment.) EPA is also taking comment on alternatives to the 0.08 HAP fraction standard for existing POTWs, such as installing covers on primary clarifiers and treatment units. Finally, EPA proposed other changes to the NESHAP regarding startup-shutdown-malfunction plans, performance testing and annual reporting.