Project title: Preliminary assessment of greenhouse gas emissions from advanced nitrogen removing onsite wastewater treatment systems
Mentor: Jose Amador
Abstract: Coastal ecosystems have been severely impacted by nitrogen (N) pollution. One source of N in Rhode Island is onsite wastewater treatment systems (OWTS), which serve 1/3 of all households in the state. To reduce N-loading to Narragansett Bay, state regulations require the installation of advanced biological N-removal technologies in N-sensitive areas within the watershed. However, N-removing OWTS have the potential to produce potent greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). We collected preliminary measurements of GHG emissions in June and October from three of the most commonly installed advanced N-removal OWTS technologies within the watershed: Orenco Advantex AX20, Bio-Microbics MicroFAST, and SeptiTech D Series. To evaluate differences within and between N-removal technologies, two measurements (one each in denitrification and aerobic compartments) were made at 9 sites (3 per technology). A cavity ring-down spectroscopy analyzer connected to a closed chamber was used to measure CO2, CH4, and N2O emissions in real time from the technologies. Our results indicate that there are significant differences in CO2 and CH4 emissions between compartments. None of the GHG emissions differed between dates. The results from this study can be used to improve system designs to reduce GHG emissions while maximizing N-removal.