Effects of aeration and internal recycle flow on nitrous oxide emissions from a modified Ludzak–Ettinger process fed with glycerol

Kang, Song; Suenaga, Toshikazu; Harper, Willie F., Jr; Hori, Tomoyuki; Riya, Shohei; Hosomi, Masaaki; Terada, Akihiko

Effects of aeration and internal recycle flow on nitrous oxide emissions from a modified Ludzak–Ettinger process fed with glycerol

2015

Nitrous oxide (N₂O) is emitted from a modified Ludzak–Ettinger (MLE) process, as a primary activated sludge system, which requires mitigation. The effects of aeration rates and internal recycle flow (IRF) ratios on N₂O emission were investigated in an MLE process fed with glycerol. Reducing the aeration rate from 1.5 to 0.5 L/min increased gaseous the N₂O concentration from the aerobic tank and the dissolved N₂O concentration in the anoxic tank by 54.4 and 53.4 %, respectively. During the period of higher aeration, the N₂O–N conversion ratio was 0.9 % and the potential N₂O reducers were predominantly Rhodobacter, which accounted for 21.8 % of the total population. Increasing the IRF ratio from 3.6 to 7.2 decreased the N₂O emission rate from the aerobic tank and the dissolved N₂O concentration in the anoxic tank by 56 and 48 %, respectively. This study suggests effective N₂O mitigation strategies for MLE systems.

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