Impact of N 2 O Emissions on Nitritation in Two Sequencing Batch Reactors: Activated Sludge Reactor and Biofilm System

Abstract

Abstract

The objective of this study was to evaluate nitrous oxide (N₂O) emissions on nitritation in activated sludge sequencing batch reactor (ASSBR) and sequencing batch biofilm reactor (SBBR) treating ammonium-rich wastewater at two different influent ammonium concentrations. During stable operation, there was no significant difference of \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $${ \rm NH}_4^ + { {\hbox {-}} { \rm N}}$$ \end{document} removal efficiencies between the two reactors. At the end of nitrification, both nitrite accumulation rates were above 85%. However, SBBR had a better total nitrogen (TN) removal efficiency (81.7% ± 1.5%) than that of ASSBR (66.5% ± 5.7%). According to typical cycles, when influent \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $${ \rm NH}_4^ + { {\hbox {-}} { \rm N}}$$ \end{document} concentrations were 120 mg/L and 240 mg/L, N₂O emissions during nitritation in SBBR accounted for 2.3% ± 0.4% and 6.5% ± 0.9% of the TN removed, respectively, which were 1/3-1/2 of that in ASSBR (6.6% ± 0.6%, 14.1% ± 1.6%). In addition, N₂O production increased with increase of feed ammonia concentration in both reactors. These results contribute to further understanding of N₂O emission in partial nitrifying system.