Stable Partial Nitrification in an Up-Flow Fixed-Bed Bioreactor Under an Oxygen-Limiting Environment

Abstract

Stable partial nitrification followed by a denitrification or anammox process is a cost-effective alternative to conventional biological nitrogen removal processes, especially for wastewaters having a low carbon-to nitrogen (C=N) ratio. This article addresses partial nitrification in an up-flow fixed-film bioreactor operated for more than 265 days using low C=N synthetic wastewater. The study was carried out in the absence of external aeration, for further cutting down the cost of treatment. By controlling influent dissolved oxygen (DO) at 1 mg=L, stable partial nitrification with more than 85% efficiency was achieved (influent NH 3 N: 102.6 AE 4.6 mg N=L). Maximum ammonium removal rate of 210.5 AE 6.7 mg N=L=day was obtained at a hydraulic retention time (HRT) of 18 h. Oxygen uptake at influent DO concentration of 1 mg=L was practically negligible compared to the amount of ammonia oxidized to nitrite. Partial nitrification was taking place devoid of oxygen consumption. A possible mechanism of partial nitrification with negligible DO uptake is proposed in this article. The nitrogen oxide (NOx) cycle may be playing a major role for such low oxygen requirement. This strategy of developing a stable partial nitrifying biosystem under a low oxygen environment without external aeration, can lead to considerable savings in aeration cost in the treatment of ammonia laden wastewaters.

Alkalinity and dissolved oxygen as controlling parameters for ammonia removal through partial nitritation and ANAMMOX in a single-stage bioreactor

“…The experiments were conducted with simulated wastewater as per our previous study [6] and no organic carbon was added. Ammonia was added as (NH 4 ) 2 SO 4 in the required concentration for feed preparation (Fig.…”

“…The seed biomass was obtained from mixing biomass from two lab-scale reactors, one from an oxygen-limited, ammonia-oxidizing fixed film reactor [6] and another from a laboratory-scale ANAMMOX reactor treating ammonia under anaerobic conditions for more than 300 days (Bagchi et al, personal communication). The AOB and NOB populations in the fixed film bioreactor were confirmed through fluorescence in situ hybridization (FISH) assay using 5 0 fluorescein tagged Nsm 156 and Nit 3 probes.…”

“…These three groups of microorganisms are closely interlinked with common electron donor and acceptors. Many workers have reported that by controlling the concentration of DO and nitrite, partial control of NOB activity could be achieved [4,[6][7][8][9]. NOB competes with AOB and ANAMMOX bacteria for DO and nitrite, respectively.…”

Start-up and stabilization of an Anammox process from a non-acclimatized sludge in CSTR

“…DO in the bioreactor and in the effluent was always below detectable limits, indicating the consumption of residual DO. Although DO loading of 0.05 mg O/(mg N day) in the bioreactor was negligible as compared to the NLR, our previous experiments showed that aerobic nitrifying bacteria have the ability to survive under such a limiting DO environment [28]. To decrease the NOB activity, a strategy bioreactor.…”

“…nitrite and oxygen. Although AOB also requires oxygen as substrate, studies have revealed that many AOB species are able to adapt their metabolism even in acute absence of oxygen [28,29].…”