N2O production in a single stage nitritation/anammox MBBR process

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The main objective with this master thesis work was to study the production of nitrous oxide from a laboratory single stage nitritation/ anammox MBBR. The N2O measurements were performed online in the water phase with a Clark–type microsensor developed by Unisense, Århus, Denmark. The reactor was operated at both intermittent and continuous aeration. The results from the experiments are summarised below: At intermittent aeration % reduction and removal rate in gN/m 2 d were in the range of 47-59% and 0.9-1.1 gN/m 2 d respectively. As the reactor mode was shifted into continuous aeration at a lower DO concentration both % reduction and removal rate in gN/m 2 d was more stable and higher than during intermittent aeration. % nitrogen reduction was between64-65% and the removal rate in the interval of 1.3-1.6 gN/m 2 d. The MBBR system produced N2O regardless of operation mode. The nN2O production was determined through measurements of initial accumulation of nitrous oxide in the water phase when aeration was turned off Intermittent aeration at high dissolved oxygen concentrations 3 mg/l was resulting in significant nitrous oxide production ranging from 6-11% of removed inorganic nitrogen. Operation at continuous aeration yielded nitrous oxide emissions corresponding to about 2-3% of removed inorganic nitrogen. Higher process performance may be an explanation to smaller amounts of emitted N2O. Conclusions that can be made from the experiments are summarised below: • The single stage nitritation/anammox system produced significant amounts of N2O with a minimum production of 2% of removed inorganic nitrogen. • Operating the MBBR at intermittent aeration with a DO of ~3 mg/l gave the highest N2O production with initial and maximum productions of 6-11% and 10- 30% respectively. • Smaller amounts of N2O were produced by the partial/nitritation anammox system during continuous operation at DO in the interval 1-1.5 mg/l. The initial N2O production was found to be 2-3% and the maximum N2O production corresponded to 2-6%. • When the MBBR was exposed to a longer period of anoxic conditions both ammonium oxidation and N2O production ceased. • From results of mixing with N2 gas during the anoxic period it cannot be said with certainty that the N2O production is the same during aeration and anoxic phase. The absolute number on overall N2O production for an operation mode (based on the measurements of N2O accumulating during the anoxic phase) could be both overestimated or underestimated and should therefore be used as a comparative tool. ii
Acknowledgements I would like to express my gratitude to everyone who have inspired and supported me during the work with my master thesis. My genuine appreciation goes to: My supervisor Magnus Christenson at AnoxKaldnes for all guidance, support, sharing off valuable knowledge and experiences, also for giving me the opportunity to get to know the fascinating anammox process. My supervisor Professor Jes la Cour Jansen at Water and Environmental Enigneering Department of Chemical Engineering, Lund University for scientific guidance and encouragement, for all your valuable aspects on my work and always reminding me of looking into things from a wider perspective. To Lars H. Larsen at Unisense for all help and support with the microsensors. To everyone at AnoxKaldnes for all kindness, support and for creating an inspiring environment to work in. Special thanks to Maria Ekenberg for always answering my questions about the laboratory MBBR process and for all help in the laboratory. To Carolina Shew Cammernäs for all patients and time while helping me with the FIA analyses. To Stig Stork for all technical support. To David Gustavsson at VA SYD for exchanging your ideas and knowledge about N2O emissions in wastewater treatment processes. Last but not least I would like to thank my mother and my sister, Gustav and Helena for always encouraging and supporting me. Thank you! iii
Page 1: Water and Environmental Engineering
Page 5: Summary Wastewaters contain abundan
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 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
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laboratory system might be underest
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6. Conclusions The following conclu
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8. References Abma W.R., Schultz C.
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Hippen A., Rosenwinkel K-H., Baumga
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Metcalf & Eddy I. (2003). Wastewate
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van Niftrik L.A., Fuerst J.A., Sinn
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Appendix B Calculations of N2O emis
Page 81 and 82:
The rN value is calculated with the
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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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