MACT Basics for Wastewater Treatment
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EPA has streamlined the hazardous air pollution (HAP) provisions of the 1990 Clean Air Act (CAA) with presumptions concerning its maximum achievable control technology (MACT) for wastewater treatment facilities. The EPA has identified head works (including bar screens and grit chambers), clarifiers (settling processes), aeration basins (activated-sludge processes where volatile organic chemicals are digested by bacteria) and solids-handling operations (including digestion and dewatering prior to disposal) as HAP emission points at POTWs. MACT's Title III includes a generic list of 189 HAPs. The Synthetic Organic Chemical Manufacturing Industry negotiated this number down to 108 for its industry. AMSA (the Association of Municipal Sewage Authorities), arguing nationwide survey results for POTW HAP emissions and extensive fate modeling with model wastewater treatment plants, got the EPA to accept just 76 compounds for POTW emissions. Additional AMSA efforts persuaded the EPA to consider just 29 compounds as representative of HAP emissions at POTWs. Although not officially endorsing this short list, the EPA has allowed it as possible and has included the list in Appendix B of the "Presumptive MACT Document." The outcome may be that the POTWs plan on using the list of 76 compounds, with a state or local agency shortening the list on a case-by-case basis. The EPA has deemed that a POTW apply controls if any two of the following three criteria are met: As another criterion the HAP control efficiency of all affected sources will be surveyed, and existing sources will be required to meet this minimum. New sources will be required to demonstrate the control efficiency of the best performing source. EPA has identified two compliance options for POTWs: (1) pretreatment flow control and (2) limited volatilization. In the pretreatment option, POTWs would limit the amount of HAPs that could be discharged to influent (something now accomplished through the National Pollutant Discharge Elimination System permit). The controlling of emissions at the site could involve physically covering all treatment processes prior to biological treatment or lowering weir heights or using fine-bubble aeration. EPA originally required that facilities measure influent VOHAP concentrations solely using EPA Method 305. However very few laboratories can perform such analyses. EPA has indicated that other methods may be used if corrected to the fractional recovery predicted for Method 305 (using fractional measured correction factors listed in "Presumptive MACT," Appendix A). Title V of the CAA amendments (40 CFR, Part 70) regulates emissions of HAPs and criteria pollutants (including nitrogen oxides, sulfur oxides, particulate matter, carbon monoxide, volatile organic compounds, lead). Major sources for criteria pollutants and HAPs are required to obtain Title V operating permits. The Title V permit must contain all of a facility's permitted and non-permitted equipment, permit conditions, compliance certifications and compliance plans, emissions summaries (for both criteria pollutants and HAPS) as well as monitoring, reporting, and record-keeping requirements. Most states and local air-pollution-control agencies are in the process of reviewing applications and issuing Title V permits for criteria air pollutants. As MACT standards are promulgated, their requirements will be added to the Title V permit and will be subject to enforcement. EPA's intention to involve states, industry, and environmental groups in promulgating MACT standards is encouraging. Using this process, MACT standards can be developed that will effectively reduce air toxics. |