Nitrous oxide emissions from denitrifying activated sludge of urban wastewater treatment plants, under anoxia and low oxygenation

Nitrous oxide emissions from an intermittent aeration activated sludge system of an urban wastewater treatment plant

“…[12][13][14][15][16] Laboratory and full-scale studies have suggested that the main operating conditions leading to elevated N 2 O production are: dissolved oxygen concentration ≤1 mg O 2 L -1 ; elevated nitrite concentrations, and low chemical oxygen demand (COD) to nitrogen ratio. 8,14,15,[17][18][19] In our previous study, 11 we focused on estimating N 2 O emissions from an activated sludge WWTP with prolonged aeration process and found that approximately 90% of N 2 O emissions derived from the aeration tank, which was consistent with the findings of Czepiel et al 5 The aim of the present study was to investigate N 2 O emission and production during both aerated and non-aerated sequential stages in the intermittent aeration process of an activated sludge WWTP. Hitherto, as far as we know, there is only one study available on N 2 O emissions from full-scale domestic wastewater treatment with the intermittent aeration process.…”

Effect of Stubble Heights and Treatment Duration Time on the Performance of Water Dropwort Floating Treatment Wetlands (FTWS)

“…The lower pH compared with the zero control reflected the better buffer capacity on water alkalinity and acid perspiration of Water Dropwort FTW in our experiment. It is reported [34] that: (1) when DO concentration in water is over 2 mg/dm 3 , only nitrification process occurs; (2) when DO concentration in water is lower than 0.5 mg/dm 3 , only denitrification occurs; and (3) when DO concentration in water is between 0.5 and 2 mg/dm 3 , both nitrification and denitrification occur at the same time. Likewise, Hao [35] described the optimal conditions of pH: (1) best pH for nitrate bacteria is 5-8; (2) best pH for nitrite bacteria is 7-9; (3) the best pH for denitrification process is 7.…”

The influence of solid retention time on IFAS-MBR systems: Assessment of nitrous oxide emission

“…Several operational conditions and influent features that might favour N 2 O production/emission have been identified: low dissolved oxygen (DO) concentrations, nitrite accumulation, dynamic conditions as well as low carbon-tonitrogen (C/N) ratio values during denitrification (Kampschreur et al, 2009;Chiu and Chung, 2000;Park et al, 2000;Zeng et al, 2003;Tallec et al, 2008;Mannina et al, 2017a). Amongst the main operational variables, the sludge retention time (SRT) has been recognized able to influence N 2 O production.…”