Domingo Felez, Carlos

Ma, Yunjie

Plósz, Benedek G.

Smets, Barth F.

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 18, 2017Suppression of nitrite-oxidizing bacteria in intermittently aerated biofilms: a model-based explanationMa, Yunjie; Domingo-Felez, Carlos; Plósz, Benedek G.; Smets, Barth F.Publication date:2016Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Ma, Y., Domingo Felez, C., Plósz, B. G., & Smets, B. F. (2016). Suppression of nitrite-oxidizing bacteria inintermittently aerated biofilms: a model-based explanation. Poster session presented at MEWE and biofilms IWAspecialist conference, Copenhagen, Denmark.yuma@env.dtu.dk                             @Metlab_DTU                            Research supported by:   • Short-cut ammonium (NH4+) removal via nitrite (NO2-) is energy- and cost- efficient. The challenge is to suppress nitrite-oxidizing bacteria (NOB).  • Despite successful NOB suppression versus ammonium-oxidizing bacteria (AOB) in activated sludge based on differential growth kinetics, maintaining long-term nitritation in biofilms can be challenging1. • Pellicer-Nàcher2 observed that fully nitratation membrane-aerated biofilm reactors accumulated NO2- immediately after switching from continuous to intermittent aeration. • The purpose of this study was to develop and calibrate an improved biofilm model incorporating pH calculation, systematically  evaluate potential causes for NOB suppression associated with intermittent aeration. Introduction & Aims Suppression of nitrite-oxidizing bacteria in intermittently aerated biofilms: a model-based explanation Counter diffusion biofilm system NOB suppression exploration • Intermittent aeration supports efficient nitritation in membrane aerated biofilm reactors.  • A pH-explicit 1-D multispecies nitrifying biofilm model reveals that NOB suppression- associated with intermittent aeration- is primarily governed by periodic FA inhibition, which is the consequence of transient pH upshifts. These pH upshifts caused by alkalinity increases during non-aeration are mainly due to carbon dioxide stripping to the membrane lumen. • In counter diffusion biofilms pH effects appear more important than DO effects on NOB suppression. Conclusions References: 1 PMID: 15303723 2 DOI: 10.1021/es1013467 3 DOI: 10.1002/bit.21213 4 DOI: 10.1016/j.procbio.2007.09.010 Y. Ma*, C. Domingo-Fèlez, B. G. Plósz, B.F. Smets Department of Environmental Engineering, Technical University of Denmark, Kongens Lyngby, Denmark. Model development & Model calibration • NOB suppression challenges • Long solids retention times • Strong spatial chemial gradients • Multiple simultaneous chemical gradients • Spatial protection of bacteria at the biofilm base • Intermittent aeration The multi-species nitrifying biofilm model is a one-dimensional model based on Terada3, incorporating explicit pH calculation.  • A physical gas diffusion link between compartments 𝐴 ∙ 𝑘𝑀,𝑖(1𝐻𝑖𝐶𝑖,𝑎𝑖𝑟 − 𝐶𝑖,𝑏𝑎𝑠𝑒)  • Biological process, e.g. AOB 𝜇𝐴𝑂𝐵,𝑓 𝑝𝐻 4 · 𝑋 ·𝑆𝑂2𝐾𝑂2 + 𝑆𝑂2·𝑆𝐹𝐴𝐾𝐹𝐴𝐴𝑂𝐵 + 𝑆𝐹𝐴 + 𝑆𝐹𝐴 · 𝑆𝐹𝐴 𝐾𝐼,𝐹𝐴𝐴𝑂𝐵 ·𝐾𝐼,𝐹𝑁𝐴𝐴𝑂𝐵𝐾𝐼,𝐹𝑁𝐴𝐴𝑂𝐵 + 𝑆𝐹𝑁𝐴 • Chemical process: pH calculation 𝐻+ + 𝐻𝐶𝑂3− ↔ 𝐻2𝐶𝑂3 (𝐶𝑂2) Sensitivity ranking of kinetic parameters with default ASMN values  • Microsensor setup An intermittent aeration:  6-hour aeration period (100% air) + 6-hour non-aeration period (100% N2) Microprofiles measured within the biofilm in the aeration periods at steady state Experimental (symbols) and predicted (lines) concentrations (A) the first aeration hour (B) the last aeration hour (C) bulk profiles in a 12-hour cycle • μmax- the most determinant kinetic parameter in N conversion simulation. • In-situ microprofiling data is more informative than bulk measurements.  (A) Specific growth rate of AOB and NOB within the biofilm in a 6-hour aeration period at day 15 (B) individual effect on AOB and NOB within the 100 μm-aerated biofilm base (0- strong limitation/inhibition effect, 1- no limitation/inhibition effect) • AOB preferentially utilize oxygen and outcompete NOB.  • FA inhibition caused by pH substrate-speciation is the crucial factor in suppressing NOB in intermittently aerated biofilms.  • Strong FA inhibition at the onset of aeration causes lag phase of NOB activity over AOB. strong effect      no effect A       B 

Suppression of nitrite-oxidizing bacteria in intermittently aerated biofilms: a model-based explanation

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Suppression of nitrite-oxidizing bacteria in intermittently aerated biofilms: a model-based explanation

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