Performance and N2O Formation of the Deammonification Process by Suspended Sludge and Biofilm Systems—A Pilot-Scale Study

Abstract

Abstract:A two-stage deammonification pilot plant with two different second-stage reactors, namely a sequencing batch reactor (SBR) with suspended sludge and a moving bed biofilm reactor (MBBR) with biofilm carriers, was investigated over a 1.5-year period to compare reactor performances. Additionally, dissolved nitrous oxide (N 2 O) was measured to determine the reactors' N 2 O formation potential. Although the nitritation performance was moderate (NO 2 -N/NH 4 -N effluent ratio of 0.32 ± 0.15 in combination with SBR and 0.25 ± 0.14 with MBBR), nitrogen turnover and degradation rates exceeding 500 g N/(m 3 ·day) and 80%, respectively, were achieved in both second stages, yet requiring additional aeration. The SBR's average nitrogen removal was 19% higher than the MBBR's; however, the SBR's nitrite influent concentration was comparably elevated. Concerning N 2 O formation, the nitritation reactor exhibited the lowest N 2 O concentrations, while the buffer tank, interconnecting the first and second stages, exhibited the highest N 2 O concentrations of all reactors. Given these high concentrations, a transfer of N 2 O into the second stage was observed, where anoxic phases enabled N 2 O reduction. Frequent biomass removal and a decreased hydraulic retention time in the buffer tank would likely minimize N 2 O formation. For the second stage, enabling anoxic periods in the intermittent aeration cycles right after feeding to support N 2 O reduction and thus minimize the stripping effects or the implementation of a complete anoxic ammonium oxidation will mitigate N 2 O emissions.

Unexpected Diversity and High Abundance of Putative Nitric Oxide Dismutase (Nod) Genes in Contaminated Aquifers and Wastewater Treatment Systems

“…3). Both are biological nutrient removal systems removing nitrogen by partial nitritation, followed by anammox (22)(23)(24). The biomass samples were from thick biofilm carriers for Kempten and large biomass granules from the swing-redox reactor.…”

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“…Process optimization can also be carried out to constrain the N 2 O stripping stimulation. Leix et al 45 managed to reduce the stripping effects by rearranging the aerobic and anoxic periods after feeding to allow for a reduction of N 2 O without aeration.…”

Techno-economic analysis of sidestream ammonia removal technologies: Biological options versus thermal stripping

“…In a comparison between deammonification technologies and conventional nitrification/denitrification, it was found that the first emitted less nitrous oxide [50,51]. However, past studies also highlighted that the nitrous oxide emissions of deammonification can exceed the nitrification/denitrification when leaving the partial nitritation step uncontrolled with nitrite concentrations >20 mg N L À1 [52,53]. Additionally, a range of indirect greenhouse gas emissions are associated with the power consumption from the grid.…”