N2O production in a single stage nitritation/anammox MBBR process

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age equal to the hydraulic retention time, and by controlling the pH to get the desired ammonium/nitrite ratio: NH HCO 0.75O 0.5NH 0.5NO CO 1.5H O (2.5.1) The effluent from the Sharon reactor is then feeding the anammox process that converts nitrite and ammonium to elemental nitrogen according to eq. (2.1.7). Some nitrate is formed in the anammox process as biomass is formed from inorganic carbon with nitrite as electron donor (van Dongen et al., 2001). 2.5.2 Canon The Canon process (completely autotrophic nitrogen removal over nitrite) is a single stage process for nitrogen removal with ammonium oxidisers and anammox bacteria, (Third et al., 2001), see Figure 6 for system description. Figure 6. Canon process scheme The Canon reactor has to be oxygen limited to allow the co-existence of both ammonium oxidisers and anammox bacteria in the same environment. Ammonium oxidation into nitrite is performed under oxygen limitation by aerobic ammonium oxidisers eq. (2.5.3). Anammox bacteria are oxidising ammonium with nitrite into dinitrogen gas eq. (2.5.4). The resulting over all chemical reaction for the Canon process is described by eq. (2.5.5), (Third et al., 2005). Partial nitrification:NH 1.5O NO 2H H O (2.5.3) Anammox: NH 1.3NO N 0.26NO 2H O (2.5.4) Canon process: NH 0.85O 0.4N 0.13NO 1.3H O 1.4H (2.5.5) 16
The Canon process is often implemented with granular sludge and it is important that large biomass flocs with decreasing oxygen gradient within the floc are allowed to form. This in order to achieve an environment suitable for both aerobic ammonium oxidisers and anammox bacteria in the same reactor set up (Third et al., 2005). 2.5. 3 Deammonification The deammonification process is also a one stage process for nitrogen removal through partial nitrification and anammox. The process scheme resembles that of the Canon process illustrated in Figure 6. The greatest difference between deammonification and the Canon process is that deammonification is a biofilm process utilising a carrier material to support biofilm growth. Conversion of ammonium into dinitrogen gas takes place at different biofilm depths. Nitrification of ammonium into nitrite is carried out by nitrifiers in the outer aerobic layers of the biofilm. This process together with diffusion provides the anammox bacteria in the deeper anaerobic layers with their substrates (Egli et al., 2003), see Figure 7. The diffusion depth of oxygen is dependent on the DO concentration in the water bulk phase and it influences to which extent the conventional nitritation process takes part in the biofilm (Helmer et al., 2001). Figure 7. Conversion of ammonium to dinitrogen gas takes place through two separate reactions at different biofilm depths. (Adapted from Rosenwinkel and Cornelius, 2005) To ensure anoxic conditions for the anammox bacteria the system must be operated at low oxygen concentrations or with alternating aeration. Low oxygen concentrations in a biofilm system also inhibits aerobic nitrite oxidisers which is needed to make sure that only the first step of nitrification is performed. The growth rate of aerobic ammonium oxidisers (AOB) is higher than for nitrite oxidisers at low oxygenation, AOB are also faster at recovering in activity after the anoxic phase.Temperatures over 20°C are also favouring the growth rate of AOB over nitrite oxidisers (Rosenwinkel and Cornelius, 2005). Biofilm systems are suitable for the anammox process since the bacteria are slow growers that require high biomass retention (Abma et al., 2006). 17
Page 1: Water and Environmental Engineering
Page 5 and 6: Summary Wastewaters contain abundan
Page 7: Acknowledgements I would like to ex
Page 11 and 12: Table of content Chapter 1 ........
Page 13 and 14: Chapter 1 1. Introduction Nitrogen
Page 15 and 16: 1.3 Objectives The aim with this ma
Page 17 and 18: Chapter 2 2. Background 2.1 Biologi
Page 19 and 20: are intermediates in the chemical r
Page 21 and 22: minimum concentration of 2 mg/l sho
Page 23 and 24: 2.3 Biofilm reactors Biofilm reacto
Page 25 and 26: 2.3.4 Moving bed reactor Another wa
Page 27: To enable efficient nutrient remova
Page 31 and 32: 2.5.1 Nitrification as a source of
Page 33 and 34: Table 3. N 2O emission from differe
Page 35 and 36: The microsensor is connected to a p
Page 37 and 38: Chapter 3 3. Material and Methods 3
Page 39 and 40: 3.3 Analytical methods Concentratio
Page 41 and 42: Figure 11. Calibration setup for mi
Page 43 and 44: Chapter 4 4. Results 4.1 Process pe
Page 45 and 46: 10 8 DO concentration, pH & tempera
Page 47 and 48: concentration), while the maximum p
Page 49 and 50: of N2O during aeration was slightly
Page 51 and 52: Table 13. Average N 2O concentratio
Page 53 and 54: 12 NO₂-N (mg/l) 10 8 6 4 2 NO₂-
Page 55 and 56: Aeration 1.6 (l/min) with carriers
Page 57 and 58: % produced N₂O 12 10 8 6 4 2 Prod
Page 59 and 60: laboratory system might be underest
Page 63: 6. Conclusions The following conclu
Page 67 and 68: 8. References Abma W.R., Schultz C.
Page 69 and 70: Hippen A., Rosenwinkel K-H., Baumga
Page 71 and 72: Metcalf & Eddy I. (2003). Wastewate
Page 73: van Niftrik L.A., Fuerst J.A., Sinn
Page 79 and 80:
Appendix B Calculations of N2O emis
Page 81 and 82:
The rN value is calculated with the
Page 83 and 84:
Appendix C Microsensor measurements
Page 85 and 86:
12 090927 Prolonged unaerated perio
Page 87:
12 091016 Continuously operation, D
Page 90 and 91:
350 090921 NH₄-N 350 090922 NH₄
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300 090926 Prolonged unaerated peri
Page 94 and 95:
091010 NOx-N 091013 NOx-N NOx-N (mg
Page 96 and 97:
35 091015 NO₃-N 70 091016 NOx-N 3
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350 091018 NH₄-N 35 091018NO₃-N
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The bacteria performing the microbi
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Typical profiles of how N2O and DO
Page 104 and 105:
12 10 091014 Continously operation,
Page 106:
Mulder A.V.A, Robertson L.A., Kuene
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N2O production in a single stage nitritation/anammox MBBR process

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