Greenhouse Gas (CH4, CO2 and N2O) Emission Levels by Wastewater Treatment Plant (WWTP) Ponds in Brazil

Abstract:

This study measured greenhouse gas emissions (GHG) by Facultative Ponds on Wastewater Treatment Plants. The most studied GHGs include CO₂, CH₄and N₂O. The level of GHG (CO₂, CH₄ and N₂O) emissions by WWTPs in Australian-type stabilization ponds was measured in the city of Lins (22º21’S, 49º50’W), state of São Paulo (SP), Brazil. GHG collection was carried outusing a collection chamber installed at the center of the facultative pond’s final third. The effluent’s pH and temperature (ET) were registered by probes, and meteorological information regarding air temperature (AT) and solar radiation (SR) were obtained from INMET, Brazil. GHG collection was carried out for 72 consecutive hours in June 2014, on an hourly basis, once every 5 minutes, for the first 30 minutes, and once every 10 minutes from 30 to 50 minutesand subsequently analyzed by gas chromatograph (GC).After three days of data collection, the average AT, SR, ET and pH values were, respectively, 18^oC, 2583kJm^-2, 23^oC and 8.2. Average values for GHG emission levels (CH₄, CO₂ and N₂O) were 79.01; 100.65 and 0.0 mg m^-2 h^-1, respectively. GHG emission levels were divided into light periods (morning, afternoon and evening)in order to verify the periods with the highest GHG emissions.The highest CH₄ emission levels were measured between morning and early afternoon. The maximum CO₂ emissions were observed from evening to early morning. N₂O emissions were constant and values were close to the ones found in the atmosphere, which shows the emission of N₂O by facultative ponds does not contribute to greenhouse gases emissions.The results enabled us to characterize and quantify GHG emission levels per Facultative Pond on Wastewater Treatment Plant. Acknowledgment to FAPESP and SABESP, Brazil.