N2O production in a single stage nitritation/anammox MBBR process

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3.3.2 Prolonged study, intermittent aeration........................................................................... 28 3.3.3 Continuous aeration ................................................................................................................ 28 3.4 Calibration of microsensors ......................................................................................................... 28 3.5 Diffusivity tests of N2O ................................................................................................................... 30 Chapter 4 .................................................................................................................................. 31 4. Results .................................................................................................................................. 31 4.1 Process performance ...................................................................................................................... 31 4.3 N2O emissions from partial nitritation/anammox MBBR ................................................ 33 4.3.2 Intermittent aeration. ............................................................................................................. 34 4.3.2 Prolonged unaerated period. ............................................................................................... 35 4.3.3 Continuous operation at DO ~1.5 mg/l ........................................................................... 36 4.3.4 Continuous operation at DO ~1.0 mg/l ........................................................................... 37 4.3.5 Effect of mixing with N2 gas during unaerated phase, continuous operation at DO ~1.0 mg/l and ~1.5 mg/l .......................................................................................................... 38 4.4 NO2-N biosensor ............................................................................................................................... 40 4.5 Diffusivity and stripping test of N2O ......................................................................................... 41 Chapter 5 .................................................................................................................................. 44 5. Discussion ............................................................................................................................. 44 5.1 Process performance ...................................................................................................................... 44 5.2 N2O production .................................................................................................................................. 44 5.3 Measurements with NO2-N biosensor ...................................................................................... 47 5.4 Diffusivity and stripping test of N2O ......................................................................................... 48 6. Conclusions ........................................................................................................................... 51 7. Future research .................................................................................................................... 53 8. References ............................................................................................................................ 55 Appendix A ............................................................................................................................... 63 Calculation of concentrations in calibration solutions for N2O and NO2-N microsensors ......................................................................................................................................................................... 63 Appendix B ............................................................................................................................... 67 Calculations of N2O emissions ............................................................................................................ 67 Appendix C................................................................................................................................ 71 Microsensor measurements ................................................................................................................ 71 Appendix D ............................................................................................................................... 77 Nitrogen grab samples ........................................................................................................................... 77 Appendix E Scientific Article ..................................................................................................... 87 viii
Chapter 1 1. Introduction Nitrogen is one of the main building blocks in proteins and is therefore a vital element for all living organisms. The elemental form of nitrogen is made available to the biosphere through microbial fixation of dinitrogen gas which constitutes 79% of the atmosphere. Combustion of fossil fuels, the use of nitrogen in industry and fertilizers, waste and wastewater streams results in large amounts of anthropogenic nitrogen lost to nature. The human contribution to nitrogen cycling impacts the environment negatively through eutrophication of aquatic environments and emissions of nitrogenous compounds to the atmosphere. Release of binary nitrogenous gases contributes to the greenhouse effect and depletion of ozone layer with consequences on a global scale lasting for centuries. Since the start of the industrialisation human activity has increased the emissions of greenhouse gases (carbon dioxide, chlorofluorocarbons, methane, ozone and nitrous oxide), to the atmosphere with about 30%, with global warming as a result (Liljenström & Kvarnbäck, 2007). In 2004 the global amount of anthropogenic emitted greenhouse gases corresponded to 49 billion tons carbon dioxide equivalents, (a measurement standard where the weight of a greenhouse gas released in to the atmosphere is converted into the weight of carbon dioxide that would cause the same temperature rise in Earths ecosystem). Carbon dioxide stands for the greatest proportion of the emissions with 79% followed by methane and nitrous oxide contributing with 14% and 8% respectively, (Naturvårdsverket, 2009). Wastewater treatment plants produces greenhouse gases through; (i) burning of fossil fuels for coverage of the energy demand, (ii) transportation of chemicals for on-site usage and final disposal of solids, (iii) biologic treatment processes where nutrients, (organic matter, nitrogen and phosphorus) are removed through microbial processes. Biologic wastewater treatment processes are known to produce three of the major greenhouse gases carbon dioxide(CO2), methane (CH4) and nitrous oxide (N2O) (Bani Shahabadi et al., 2009). Nitrous oxide which is the strongest of these greenhouse gases is known to be produced during nitrification and denitrification, processes used to remove nitrogen from the wastewater. The global warming potential of N2O is 320 times stronger than that of CO2. Release in to the atmosphere not only amplifies the warming of Earth’s surface temperature it also contributes to depletion of the ozone layer (Jacob, 1999). During a thirty year period from 1990 to 2020 the N2O emissions associated with microbial nitrogen degradation of both treated and untreated wastewaters are estimated to increase with 25% from 80 to 100 megaton carbon dioxide equivalents. Emissions from the post-consumer waste sector are approximately 1300 megaton carbon dioxide equivalents which corresponds to
Page 1: Water and Environmental Engineering
Page 5 and 6: Summary Wastewaters contain abundan
Page 7: Acknowledgements I would like to ex
Page 11: Table of content Chapter 1 ........
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
Page 59 and 60: 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
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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
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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,
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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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