N2O production in a single stage nitritation/anammox MBBR process

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3.2 Reactor medium The reactor was fed with a synthetic wastewater with an inorganic nitrogen concentration corresponding to 314 mg/l. The synthetic wastewater contained all vital nutrients the microorganisms needed, including trace elements, see Table 4 and Table 5 for composition of reactor medium and trace element stock solution. Table 4. Composition of synthetic medium fed to the MBBR. Component NaHCO3 2.6 NH4Cl 1.2 Concentration g/l KH2PO4 5.67∙10 -3 Peptone 3.0∙10 -3 trace element solution 1 0.40 ml/l trace element solution 2 0.40 ml/l Table 5. Composition of trace element stock solution. Component Stock solution 1 MgSO4∙7H2O 4.80 MnCl2∙2H2O 1.60 CoCl2∙6H2O 0.48 NiCl2∙6H2O 0.24 ZnCl2 0.26 CuSO4∙5H2O 0.10 FeCl2∙4H2O 1.44 BH3O3 0.104 Na2MoO4∙2H2O 0.440 Na2SeO3∙5H2O 0.288 Na3WO3∙2H2O 0.280 Stock solution 2 CaCl2∙2H2O 5.80 Concentration g/l Initially the medium was mixed in a 600 litres container situated in the workshop and pumped to the second floor where the laboratory is situated. Microbial growth in the tank and pump tubing were causing large differences in composition of the influent medium to the reactor. Due to these problems the medium was mixed in a 100 litres tank kept in the laboratory in close connection to the reactor set up. 26
3.3 Analytical methods Concentrations of NH4-N, NO2-N and NO3-N were determined with Dr Lange’s spectrophotometry kit after filtration through Munktel 1.6 µm glass fibre filters. During cycle studies NO2-N and N-tot were analyzed directly with Dr Lange’s method. Samples were frozen and flow-injection analysis was used to determine NH4-N and NOx, the sum of NO2-N and NO3-N. The NO3-N content was calculated by subtraction of NO2-N from the sum of the two NOx species. Dissolved oxygen and pH was sampled with a portable meter, HQ40d with mounted oxygen and pH probe. Parameters analysed and method used are summarised in Table 6. Table 6. Analysed parameters and methods. Analysed parameter Method NH4-N LCK 303/FIA NO2-N LCK 342/341/Bio sensor NO3-N LCK 339 NOx FIA N-tot LCK 238 DO HQ40d pH HQ40d 3.3 Cycle studies To examine which operation conditions which seemed to produce the largest amounts of N2O gas, the reactor was operated at different DO concentrations during intermittent and constant aeration. A study where the anoxic phase was prolonged to two hours was performed to observe how the N2O production was influenced. Mixing with N2 gas at the same aeration flow as in the aerated period was tested to see how stripping influenced the amount of N2O in the water phase. Parameters monitored online in the reactor, every minute were; DO, pH, N2O and NO2-N. To examine the concentration changes of NH4-N, NO2-N and NO3-N grab samples were taken in both influent and effluent water. 3.3.1 Intermittent aeration The reactor was operated at a DO concentration of ~3 mg/l during the aeration phase. One reactor cycle lasted for one hour with 40 minutes of aeration and 20 minutes of mechanical mixing. The study started at the same moment as aeration went on after the anoxic period and lasted for 66 minutes in order to overlap the initial conditions. Grab samples in the effluent were taken with 6 minute intervals to get two measure points in the anoxic phase. Only three measurements of the influent medium was taken 27
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 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: Chapter 3 3. Material and Methods 3
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
Page 92 and 93:
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
Page 98 and 99:
350 091018 NH₄-N 35 091018NO₃-N
Page 100 and 101:
The bacteria performing the microbi
Page 102 and 103:
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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