Full-scale comparison of N2O emissions from SBR N/DN operation versus one-stage deammonification MBBR treating reject water – and optimization with pH set-point

Abstract

To be able to fulfill the Paris agreement regarding anthropogenic greenhouse gases, all potential emissions must be mitigated. Wastewater treatment plants should aim to eliminate emissions of the most potent greenhouse gas, nitrous oxide (N2O). In this study, these emissions were measured at a full-scale reject water treatment tank during two different operation modes: nitrification/denitrification (N/DN) operating as a sequencing batch reactor (SBR), and deammonification (nitritation/anammox) as a moving bed biofilm reactor (MBBR). The treatment process emitted significantly less nitrous oxide in deammonification mode 0.14–0.7%, compared to 10% of total nitrogen in N/DN mode. The decrease can be linked to the changed feeding strategy, the lower concentrations of nitrite, a lower load of ammonia oxidized, a shorter aeration time, the absence of non-optimized ethanol dosage or periodic lack of oxygen as well as the introduction of biofilm. Further, evaluation was done how the operational pH set point influenced the emissions in deammonification mode. Lower concentrations of nitrous oxide were measured in water phase at higher pH (7.5–7.6) than at lower pH (6.6–7.1). This is believed to be mainly because of the lower aeration ratio and increased complete denitrification at the higher pH set point.

Lessons Learned from 10 Years of ANITA Mox for Sidestream Treatment

“…The N 2 O emission was divided by half (2-4% of N-load) when the granular SBR was operated under a new continuous aeration strategy. Similar observation was made by [16] comparing N 2 O emission of a full-scale sidestream SBR operated in nitrification/denitrification (N/DN) mode at Slottshagen WWTP in Sweden to that of a deammonification MBBR unit replacing the existing SBR for reject water treatment. While the N 2 O emission of the N/DN SBR was averaging 10% of incoming N-load, it was reduced to an average of 0.1-0.7% of incoming N-load for the deammonification MBBR operated under continuous feed and continuous aeration.…”

“…Nitrous oxide (N 2 O) emissions from sidestream deammonification processes have been often linked to specific operation control strategies employed by the different technologies such as feeding regime (continuous vs. batch), aeration control (continuous vs. intermittent), and substrate concentration gradient in the reactor [15,16]. Ref.…”

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

“…Chemical addition in the SBR could further lead to elevated carbon dioxide emissions from the bacterial reactions [8]. 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].…”

Optimization of the Aeration Strategies in a Deammonification Sequencing Batch Reactor for Efficient Nitrogen Removal and Mitigation of N2O Production

“…However, Blum et al 12 suggested that pH may regulate the rates between N 2 O production and consumption. Indeed, Kanders et al 50 showed that more N 2 O could be reduced via complete denitrification at higher pH (7.5−7.6 vs 6.6−7.1). However, in the present study, such influence was avoided by controlling a narrow pH range (7.5−7.9).…”