Title: Nitrous oxide emissions from polluted lotic water bodies and full-scale aerobic treatment systems in Southeastern Brazil

Biography:

Renato Pereira Ribeiro, Ph.D. in Environmental Geochemistry, professor and researcher at the Experimental Center for Environmental Monitoring and Mitigation, located at the Federal Institute of Rio de Janeiro. Has experience in Sanitary Engineering, focusing on greenhouse gases emissions (N₂O and CH₄) from different wastewater treatment systems (with and without biological nitrogen removal - BNR) and water bodies that receive domestic wastewater discharges (treated and untreated).

Abstract

Increasing atmospheric nitrous oxide (N₂O) concentrations is of great environmental concern due to the role of this gas in climate change and stratospheric ozone destruction. Nitrogen-enriched lotic water bodies are significant sources of N₂O. However, N₂O emissions from rivers and streams, particularly those that receive untreated or insufficiently treated wastewater discharge are poorly understood, especially in Brazil. In addition, monitoring strategies to reduce N₂O emissions from wastewater treatment plants (WWTPs) play an important role in regulating the atmosphere's climate. Different operating conditions can favor the occurrence of partial nitrification and denitrification processes in WWTPs, thus creating conditions for N₂O accumulation in the liquid phase, due to increases in production rates. In this context, the present study aimed to evaluate the effects of reactive nitrogen inputs due to the discharge of untreated or insufficiently treated wastewater on the spatial and temporal variability of N₂O emissions from different streams located in Ilha Grande hydrographic unit, in Southeastern Brazil. In addition, another aim of this study was to evaluate the variability of N₂O emissions from two aerobic treatment systems (AS: activated sludge and TF: trickling filter) operated as post-treatments in anaerobic reactor effluents with different aeration systems (artificial and natural) located in different regions of Brazil. High spatial and temporal variability in N₂O emissions were noted, with the highest emissions in urban areas. Therefore, the differences observed between N₂O fluxes from the studied streams seem to be associated with different lotic water body conditions, such as availability of reactive nitrogen and dissolved oxygen. Both studied full-scale aerobic treatment systems displayed high temporal variability in N₂O emissions associated with different operational and environmental conditions, such as: (1) aeration intermittency and high amplitudes of influent nitrogen loads for the AS system, (2) recirculation of treated wastewater and different wastewater temperatures for the TF system.