Strategies of intermittent aeration to regulate microbial activities in membrane-aerated biofilm reactors: energy-efficient nitrogen removal and low nitrous oxide emission

Abstract The effect of intermittent aeration and an influent distributary on NH4+-N removal, total nitrogen (TN) removal, nitrous oxide (N2O) emission and the abundances of nitrogen removal and N2O emission functional genes in four types of ecological soil wastewater infiltration systems (ESWISs) (which were conventional ESWIS 1 (operated without aeration and influent distributary), ESWIS 2 (operated with intermittent aeration), ESWIS 3 (operated with influent distributary) and ESWIS 4 (operated with intermittent aeration and influent distributary)) were studied. Intermittent aeration in ESWIS 2 and 4 created aerobic conditions above 50 cm depth of the matrix and anoxic or anaerobic conditions in the lower matrix (below 80 cm depth). ESWIS 4 improved NH4+-N (to 90.1%) and TN (to 87.8%) removal efficiencies and increased the abundances of eight nitrogen removal and N2O emission functional genes (amoA, nxrA, narG, napA, nirS, nirK, qnorB and nosZ) in contrast with other ESWISs. The combination of intermittent aeration and influent distributary achieved the lowest N2O emission rate of 34.7 mg/(m2 d) in ESWIS 4. Intermittent aeration combined with influent distributary was recommended for ESWISs to enhance nitrogen removal and reduce N2O emission.

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Unravelling nitrogen removal and nitrous oxide emission from mainstream integrated nitrification-partial denitrification-anammox for low carbon/nitrogen domestic wastewater

Journal of Environmental Management ◽

10.1016/j.jenvman.2020.110872 ◽

2020 ◽

Vol 270 ◽

pp. 110872 ◽

Cited By ~ 1

Author(s):

Xin Zhou ◽

Jingjing Song ◽

Gonglei Wang ◽

Zeyang Yin ◽

Xiwei Cao ◽

...

Keyword(s):

Nitrous Oxide ◽

Nitrogen Removal ◽

Domestic Wastewater ◽

Nitrous Oxide Emission ◽

Low Carbon

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Autotrophic nitrogen removal in sequencing batch biofilm reactors at different oxygen supply modes

Water Science & Technology ◽

10.2166/wst.2008.527 ◽

2008 ◽

Vol 58 (10) ◽

pp. 1889-1894 ◽

Cited By ~ 8

Author(s):

C. Wantawin ◽

J. Juateea ◽

P. L. Noophan ◽

J. Munakata-Marr

Keyword(s):

Nitrogen Removal ◽

Nitrogen Loss ◽

Ammonia Concentration ◽

Anammox Bacteria ◽

Ammonia Oxidizing Bacteria ◽

Intermittent Aeration ◽

Biofilm Reactors ◽

Air Supply ◽

Nitrite Oxidizing Bacteria ◽

Sequencing Batch Biofilm Reactors

Conventional nitrification-denitrification treatment is a common way to treat nitrogen in wastewater, but this process is costly for low COD/N wastewaters due to the addition of air and external carbon-source. However, ammonia may alternatively be converted to dinitrogen gas by autotrophic bacteria utilizing aerobically autotrophically produced nitrite as an electron acceptor under anoxic conditions. Lab-scale sequencing batch biofilm reactors (SBBRs) inoculated with normal nitrifying sludge were employed to study the potential of an oxygen-limited autotrophic nitrification-denitrification process initiated with typical nitrifying sludge for treating a synthetic ammonia wastewater devoid of organic carbon in one step. The ring-laced fibrous carrier (length 0.32 m, surface area 3.4 m2/m) was fixed vertically in a 3 L reactor. Two different air supply modes were applied:continuous aeration to control dissolved oxygen at 1.5 mg/L and intermittent aeration. High nitrogen removals of more than 50% were obtained in both SBBRs. At an ammonia loading of 0.882 gm N/m2-day [hydraulic retention time (HRT) of 24 hr], the SBBR continuously aerated to 1.5 mg DO/L had slightly higher nitrogen removal (64%) than the intermittently alternated SBBR (55%). The main form of residual nitrogen in the effluent was ammonia, at concentrations of 25 mg/L and 37 mg N/L in continuous and intermittent aeration SBBRs, respectively. Ammonia was completely consumed when ammonia loading was reduced to 0.441 gm N/m2-day [HRT extended to 48 hr]. The competitive use of nitrite by aerobic nitrite oxidizing bacteria (ANOB) with anaerobic ammonia-oxidizing bacteria (anammox bacteria) during the expanded aeration period under low remaining ammonia concentration resulted in higher nitrate production and lower nitrogen loss in the continuous aeration SBBR than in the intermittent aeration SBBR. The nitrogen removal efficiencies in SBBRs with continuous and alternating aerated were 80% and 86% respectively. Specific microorganisms in the biofilm were characterized using fluorescence in situ hybridization. Aerobic ammonia-oxidizing bacteria (AAOB) occurred side by side with putative anammox bacteria (cells hybridizing with probe AMX820) throughout the biofilm, though ANOB were rarely detected.

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