Quantifying methane, nitrous oxide, and ammonia emissions from wastewater treatment plants using mobile sensing and inverse Gaussian methods
Abstract
Methane (CH4) and nitrous oxide (N2O) are potent greenhouse gases with a radiative impact 34 and 298 times that of carbon dioxide over a 100-year time horizon, respectively. Ammonia (NH3) is the main atmospheric base and is a precursor to particulate matter (PM2.5), which can be detrimental to air quality. Wastewater treatment plants (WWTPs) are significant sources of these important trace gases, particularly in urban areas, and emission rates vary over orders of magnitude based on treatment capacity, methods, age, and influent type. Existing emission measurements focus on specific processes at limited sites, which may not represent the national distribution of emission rates. We employ a mobile sampling technique, in conjunction with integrated Bayesian source rate estimation to determine emissions from 13 WWTPs in the Mid-Atlantic ranging from 1 to ~150 million gallons of influent per day. To explore the temporal evolution and reproducibility of this approach, numerous plants were resampled on different days. CH4 emission factors range three orders of magnitude from 2.9 x 10-3 to 1.2 x 10-1 g CH4 (gallon treated)-1 with a mean of 3.4 x 10-2 g CH4 (gallon)-1. Preliminary results suggest that smaller plants emit more CH4 per gallon than larger plants, implying that centralization of WWTPs may mitigate emissions. Large concentrations have also been observed for N2O and NH3 downwind of WWTPs. These facility-integrated emissions are broadly consistent with those based on Environmental Protection Agency (EPA) and Intergovernmental Panel on Climate Change (IPCC) guidelines, which depend on treatment type and may not consider fugitive emissions. We discuss the existence and causes of discrepancies between the mobile sampling and EPA/IPCC estimates. Results from this study improve our understanding of the complex relationships between plant processes and trace gas emissions, informing future best practices toward decreasing the industry's environmental impacts and increasing its overall sustainability.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA115.0006M
- Keywords:
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- 0368 Troposphere: constituent transport and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 0490 Trace gases;
- BIOGEOSCIENCES