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Comparison of N2O Emissions and Gene Abundances between Wastewater Nitrogen Removal Systems
- Brannon, Elizabeth Quinn, Moseman-Valtierra, Serena M., Lancellotti, Brittany V., Wigginton, Sara K., Amador, Jose A., McCaughey, James C., Loomis, George W.
- Journal of environmental quality 2017 v.46 no.5 pp. 931-938
- denitrification, environmental impact, genes, greenhouse gas emissions, greenhouse gases, microorganisms, nitrogen, nitrous oxide, quantitative polymerase chain reaction, spectroscopy, tanks, wastewater, wastewater treatment, Rhode Island
- Biological nitrogen removal (BNR) systems are increasingly used in the United States in both centralized wastewater treatment plants (WWTPs) and decentralized advanced onsite wastewater treatment systems (OWTS) to reduce N discharged in wastewater effluent. However, the potential for BNR systems to be sources of nitrous oxide (N₂O), a potent greenhouse gas, needs to be evaluated to assess their environmental impact. We quantified and compared N₂O emissions from BNR systems at a WWTP (Field’s Point, Providence, RI) and three types of advanced OWTS (Orenco Advantex AX 20, SeptiTech Series D, and Bio-Microbics MicroFAST) in nine Rhode Island residences (n = 3 per type) using cavity ring-down spectroscopy. We also used quantitative polymerase chain reaction to determine the abundance of genes from nitrifying (amoA) and denitrifying (nosZ) microorganisms that may be producing N₂O in these systems. Nitrous oxide fluxes ranged from −4 × 10⁻³ to 3 × 10⁻¹ µmol N₂O m⁻² s⁻¹ and in general followed the order: centralized WWTP > Advantex > SeptiTech > FAST. In contrast, when N₂O emissions were normalized by population served and area of treatment tanks, all systems had overlapping ranges. In general, the emissions of N₂O accounted for a small fraction (<1%) of N removed. There was no significant relationship between the abundance of nosZ or amoA genes and N₂O emissions. This preliminary analysis highlights the need to evaluate N₂O emissions from wastewater systems as a wider range of technologies are adopted. A better understanding of the mechanisms of N₂O emissions will also allow us to better manage systems to minimize emissions.