N2O production in a single stage nitritation/anammox MBBR process

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NH 1.5O NO 2H 2H O (2.1.1) The intermediate of the nitrification process (NO2 − ) is then further oxidised into nitrate by nitrite oxidisers: NO 0.5O NO (2.1.2) The nitratation step is performed by species like Nitrobacter and Nitrococcus (Prescott et al., 2005). The overall nitrification reaction can be described by: NH 2O NO 2H 2H O (2.1.3) Energy gained by the bacteria during nitrification is used in the electron transport chain to make adenosine triphosphate, (ATP is the energy currency of the cell making chemical transport possible), (Prescott et al., 2005). Nitrifying bacteria are slow growers since nitrification processes gives a low energy yield, (see Table 1) and the nitrifiers have to oxidise large amount of inorganic material for their growth and reproduction, (Prescott et al., 2005). 2.1.2 Denitrification Denitrification is nitrate respiration under anoxic conditions carried out by a large number of different heterotrophic bacteria. Nitrate is used to oxidate organic carbon into elemental nitrogen and carbon dioxide: NO organic carbon N CO (2.1.4) Denitrifying bacteria need an easily biodegradable carbon source and their demand for removal of one gram of nitrogen corresponds to 3-6 grams of chemical oxygen demand, (COD). If the COD/N ratio of the wastewater becomes too low an additional carbon source like methanol must be added in order to achieve nitrogen removal of nitrate through denitrification (Gillberg et al., 2003) Pseudomonas, Paraccocus, and Bacillus are examples of bacteria denitrifiying under anoxic conditions. Most denitrifiers are facultative anaerobes which means that they generally respire with oxygen as final electron acceptor, this since the oxygen route yields more energy than nitrate respiration (Prescott et al., 2005). 2.1.3 Anaerobic ammonium oxidation Anammox bacteria are obligate anaerobe autotrophs using inorganic nitrogen and carbon for energy supply and growth, the process offers a short cut in the nitrogen cycle as illustrated in Figure 1(Jetten et al., 1999). Ammonium is converted into dinitrogen gas with nitrite as electron acceptor (2.1.6), hydrazine (N2H4) and hydroxylamine (NH2OH) 6
are intermediates in the chemical reaction. This reaction is the catabolic and energy supplying part in anammox metabolism, it has to be carried out 15 times to fix one molecule of carbon dioxide with nitrite as electron donor in the cellular synthesis or anabolism (2.1.7) which produces nitrate (van Niftrik et al., 2004). NH NO N 2H O (2.1.6) CO 2NO H O CH O 2NO (2.1.7) Broda, (1977), predicted this microbial process through thermodynamic calculations for over thirty years ago. The anammox process was discovered in the early nineties in a rotating-disk plant treating landfill leachate at Mechernich, Germany (Rosenwinkel & Cornelius, 2005). Mulder et al. also identified the anammox process in a denitrifying fluidised bed reactor in Deltft, the Netherlands, at about the same time (Mulder et al., 1995). Total stoichiometry of the anammox process has been estimated by Strous et al., (1998): 1NH 1.32NO 0.066HCO 0.13H 1.02 N 0.26NO 0.066CH2O . N . 2.03 H O. (2.1.7) The bacterium performing the anammox reaction has been identified as a new member of the order Planctomycete (Strous et al., 1999). Until now totally five anammox genera have been identified, four from enriched wastewater sludge: Kuenenia, Brocadia, Anammoxoglobus and Jettenia, the fifth genera of anammox bacteria Scalindua is often found in marine environments (Jetten et al., 2009). Planctomycetes are gram-negative bacteria with phenotypic properties such as absence of peptidoglycan in the cell wall, budding reproduction and internal cell compartmentalisation due to two membranes on the inside of the cell wall (Prescott et al., 2005). Anammox bacteria are characterized by their deep red colour and ability to form bio-films (Abma et al., 2006). Anammox cell structure is divided into three compartments. The outer region closest to the cell wall called the paryphoplasm encloses the second compartment which is the riboplasm. The riboplasm contains the nucleoid and the anammoxosome, the third compartment where anammox catabolism takes place, see Figure 2. All compartments are separated by bilayer membranes constituted of impermeable and high density ladderane lipids (van Niftrik et al., 2004). The higher membrane density is of importance to the anammox bacteria of two reasons, one that it creates an electro potential force driving the ATP synthesis, and two it keeps the toxic intermediates from the anammox process hydroxylamine and hydrazine inside the anammoxosome (van Niftrik et al., 2004). 7
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: Chapter 2 2. Background 2.1 Biologi
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 and 28: To enable efficient nutrient remova
Page 29 and 30: The Canon process is often implemen
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
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12 090927 Prolonged unaerated perio
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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
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091010 NOx-N 091013 NOx-N NOx-N (mg
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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
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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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