CONTROLLING FACTORS OF NITROUS OXIDE EMISSIONS FROM A CONVENTIONAL ACTIVATED SLUDGE WASTEWATER TREATMENT PLANT

Resumo

Nitrous oxide emissions were determined in three campaigns in the aeration tank of a full scale conventional activated sludge wastewater treatment plant. During these experiments, the carbonaceous organic matter (BOD and COD) removal was high and rather constant (97-98% and 93-96%). The results indicate that the concentration of total nitrogen in the influent wastewater, especially NH₄⁺, and the aeration flow rate are key controlling factor of N₂O emissions from the aeration tank. Nitrification was the major source of N₂O, suggested by the behavior of DO concentrations, NO₃^-/NH₄⁺ ratio and pH values along the six interlinked zones of the aeration tank. Excessive air flow intensified N₂O transfer from the liquor to the atmosphere by air stripping.