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Example of Project Competition of Ammonia-Oxidizing and Nitrite-Oxidizing Bacteria

Example of Project Competition of Ammonia-Oxidizing and Nitrite-Oxidizing Bacteria. CE 60330 Environmental Biotechnology University of Notre Dame. Problem: Eutrophication. www.dep.state.pa.us. Major Cases of Eutrophication. Gulf of Mexico. Chesapeake Bay.

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Example of Project Competition of Ammonia-Oxidizing and Nitrite-Oxidizing Bacteria

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  1. Example of ProjectCompetition of Ammonia-Oxidizing and Nitrite-Oxidizing Bacteria CE 60330 Environmental Biotechnology University of Notre Dame

  2. Problem: Eutrophication www.dep.state.pa.us

  3. Major Cases of Eutrophication Gulf of Mexico Chesapeake Bay http://www.ncat.org/nutrients/hypoxia/hypoxia.html http://www.cbf.org/site/PageServer?pagename=resources_facts_deadzone Long Island Sound http://www.longislandsoundstudy.net/pubs/reports/sh03_p1.pdf

  4. Biological Nitrogen Removal 1) Nitrification Ammonia oxidizing bacteria (AOB) (Nitrosomonas) NH4+ + O2 NO2- Nitrite oxidizing bacteria (NOB) (Nitrobacter, Nitrospira) NO2- + O2 NO3-

  5. Biological Nitrogen Removal 2) Denitrification Heterotrophic denitrifying bacteria (DB) NO3- + BOD  NO2- NO2- + BOD  N2

  6. Nitrogen Removal DB DB NO2- N2 3e- 2e- • SHORTCUT: • 25% reduction in oxygen • 40% reduction in BOD Conventional N removal Shortcut N removal NOB AOB NO2- NH4+ NO3- 2e- 6e-

  7. Nitrification • Under ambient conditions and DO over 2 mg/L, growth kinetics are similar for AOB and NOB • High temperatures: AOB significantly faster than NOB • Low DO: AOB outcompete NOB for oxygen

  8. Hollow-Fiber Membrane-Supported Biofilms O2 BOD O2 281 m • Hydrophobic polymers • High specific surface area • Variable driving force • J=K(CL-C) • Low energy consumption Water 1 m

  9. Hollow-Fiber Membranes for Gas Transfer 2 m 1 mm 1 mm

  10. Membrane Aerated Biofilm Reactor (MABR) NB BOD Liquid (anoxic) O2 DO LDL Biofilm Membrane attachment Alternative approach HB liquid (aerobic) NB HB DO BOD Biofilm LDL Solid attachment surface

  11. Research Needs • Under conditions observed in the HMBP process: • How does bulk liquid DO impact stratification and activity of AOB and NOB? • How does membrane gas pressure impact stratification and activity of AOB and NOB?

  12. Reactor Conditions • Anticipated effluent ammonia will vary between 2 and 3 mgN/L • Expose pressurized single membrane in a column to 3 mgN/L ammonia at a very high loading rate • Small decrease in ammonia will be observed due to high loading

  13. Reactor Conditions • What does bulk liquid concentration matter? • Monod kinetics • Concentration observed by the biofilm controls growth of bacteria • Therefore, the effluent concentration expected in the HMBP will control the ecology of the biofilm

  14. Modeling • Aquasim 2.0 software • Biofilm compartment and membrane compartment • Simulates impact of bulk liquid DO and membrane pressure on biofilm • Same modeling concepts as used for HMBP (Downing and Nerenberg, 2007b)

  15. Modeling • Conditions modeled • 50 day simulation • Steady-state conditions

  16. Modeling Results - Activity 10 psi, 2 mg/L DO 10 psi, 0 mg/L DO Ammonia (♦), nitrite (■), and nitrate (□). 5 psi, 0 mg/L DO

  17. Modeling Results - Ecology 10 psi, 2 mg/L DO 10 psi, 0 mg/L DO AOB (♦) and NOB (◊) 5 psi, 0 mg/L DO

  18. Modeling Results - Ecology • NOB yield: 0.083 mgVSS/mgNO2- • AOB yield: 0.34 mgVSS/mgNH4+ NOB biomass with 10 psi and 2 mg/L DO (▲), 10 psi and 0 mg/L DO (■), and 5 psi and 0 mg/L DO (♦)

  19. Discussion • Oxygen gradients select for AOB over NOB • Higher DO provides an advantage to NOB • Oxidation to nitrite rather than nitrate saves energy and addition of exogenous donor

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