ENV3+4 Flashcards
How do the processes of nitrification and denitrification differ?*
Nitrification and denitrification are both important processes in the nitrogen cycle, but they occur under different conditions and serve different purposes.
Nitrification:
Oxidation of ammonium/ammonia to nitrite and then to nitrate by specialized bacteria.
Two steps:
1. Ammonia oxidation: Ammonia is oxidized to nitrite by ammonia-oxidizing bacteria through the reaction:
2NH4^+ + 3O2 –> 2NO2^- + 4H^+ + 2H2O
- Nitrite oxidation: Further oxidation by other bacterias:
2NO2^- +O2–> 2NO3^-
Nitrification typically occurs under aerobic (oxygen-rich) conditions in soils and aquatic environments.
SUMMED to:
2NH4^+ + 4O2 –> 2NO3^- + 4H^+ +2H2O
Electron donor: NH4^+ , NO2^-
Electron acceptor: O2
Autotrophs: Indicates that they are capable of synthesizing organic compounds from carbon dioxide as their carbon source.
Denitrification:
Denitrification is the process by which nitrate (NO3-) is reduced to gaseous nitrogen compounds (such as nitrogen gas, N2) or nitrous oxide (N2O) by facultative anaerobic bacteria.
From nitrate to N2
2No3^-+10e^-+12H^+ –> N2+ 6H2O.
Anoxic, high C/N required (much organic carbon)
NO3^- + 40 gCOD+ H^+ –> 0.5N2+15 g biomass
Combined reaction:
NH4^+ + 2O2+ 40 g COD–>0.5N2+H2O+H^+ + 15 g biomass.
40 g COD is needed. Therefore more C is needed to be doped. Often CH4 because it is cheep.
Advanced treatment over nitrite results in much less COD is needed. And less biomass is created. It is a good thing because less biomass is needed to be removed.
chemo‐organoheterotrophs. Organic matter is used to
synthesize new biomass,
unable to fix C to form
their own organic
compounds
How do nitrification and anammox differ?*
Nitrification and anammox are both processes involved in the nitrogen cycle, but they differ in their mechanisms and the types of nitrogen compounds they transform.
Nitrification is the biological oxidation of ammonia (NH3) or ammonium (NH4+) to nitrite (NO2-) and then to nitrate (NO3-) by specialized bacteria.
The process occurs in two steps:
Ammonia oxidation: Ammonia is oxidized to nitrite by ammonia-oxidizing bacteria (AOB).
Nitrite oxidation: Nitrite is further oxidized to nitrate by nitrite-oxidizing bacteria (NOB).
Nitrification typically occurs under aerobic (oxygen-rich) conditions in soils and aquatic environments.
Anammox is a biological process in which ammonia (NH3) and nitrite (NO2-) are converted directly into nitrogen gas (N2) under anaerobic conditions.
The process is carried out by specialized bacteria known as anammox bacteria, such as members of the genus “Brocadia” and “Candidatus Kuenenia”.
The overall reaction is:
NH4+ + NO2- -> N2 + 2H2O
Anammox bacteria use nitrite as an electron acceptor to oxidize ammonia, producing nitrogen gas and water as end products.
Anammox occurs primarily in environments where low oxygen levels or anoxic conditions prevail, such as oxygen-depleted zones in oceans, wastewater treatment plants, and sediments.
Conditions:
Nitrification: Occurs under aerobic (oxygen-rich) conditions.
Anammox: Occurs under anaerobic (low or no oxygen) conditions.
Pathway:
Nitrification: Involves the oxidation of ammonia or ammonium to nitrite, and then to nitrate by specialized bacteria.
Anammox: Involves the direct conversion of ammonia and nitrite into nitrogen gas by specific anaerobic bacteria.
Nitrogen Compound Conversion:
Nitrification: Converts ammonia or ammonium into nitrite and then nitrate.
Anammox: Converts ammonia and nitrite directly into nitrogen gas.
Microorganisms:
Nitrification: Involves ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB).
Anammox: Carried out by specialized anammox bacteria, such as “Brocadia” and “Candidatus Kuenenia”.
End Products:
Nitrification: Produces nitrate as the end product.
Anammox: Produces nitrogen gas and water as the end products.
Environmental Occurrence:
Nitrification: Commonly occurs in soils, aquatic environments, and wastewater treatment systems.
Anammox: Found in environments with low oxygen levels or anoxic conditions, such as oxygen-depleted zones in oceans, wastewater treatment plants, and sediments.
Why is the incomplete oxidation of ammonia essential for effective treatment of sludge brine
using the anammox process?*
Reduce the need for aeration (iltning) da anammox er anaerob–> reduce energy needs
Reduce the need for additional org. cabon
Less sludge. Used to treat streams with low C/N as found in effluent from anaerobic digester.
Anammox process:
NH4^+ /NO2^- –>N2/ NO3^-
Reduced Energy Requirements: Anammox bacteria perform the oxidation of ammonia under anaerobic conditions, which requires less energy compared to conventional aerobic processes. This can lead to significant energy savings in wastewater treatment operations.
Nitrogen Removal Efficiency: The anammox process directly converts ammonia and nitrite into nitrogen gas, bypassing the need for fully oxidizing ammonia to nitrate. By skipping the nitrate formation step, the anammox process achieves higher nitrogen removal efficiency per unit of nitrogen compared to nitrification-denitrification processes.
Cost Reduction: By eliminating the need for additional aeration and organic carbon sources required for denitrification (as in traditional nitrification-denitrification processes), the anammox process can lead to cost savings in terms of energy consumption, chemical usage, and sludge handling.
Reduced Sludge Production: Since the anammox process operates under anaerobic conditions and does not require external organic carbon sources, it generally produces less excess sludge compared to aerobic processes. This can lead to reduced sludge handling and disposal costs.
Suitability for High-Ammonia Wastewater: Sludge brine often contains high concentrations of ammonia, making it challenging to treat using conventional aerobic processes due to high oxygen demand and potential inhibition of nitrifying bacteria. The anammox process, which is effective under anaerobic conditions and utilizes ammonia directly, is well-suited for treating such high-ammonia wastewaters.
What advantages does the anammox process have over classical wastewater treatments for
nitrogen removal?*
So the classical wastewater treatment combines nitrification and dentrification to convert nitrogen compounds into harmless nitrogen gas. But these processes requires a low of carbon as electron donor or energy source for the involved bacteria. Nitrification: While nitrification itself doesn’t directly use carbon, the presence of organic carbon in wastewater can indirectly affect the process. Organic carbon can act as a substrate for heterotrophic bacteria that compete with nitrifying bacteria for oxygen. If heterotrophic bacteria consume too much of the available oxygen, it can inhibit the activity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), thereby hindering nitrification.
Denitrification: In denitrification, carbon serves as the electron donor for the reduction of nitrate (NO₃⁻) or nitrite (NO₂⁻) to nitrogen gas (N₂) or nitrous oxide (N₂O). Denitrifying bacteria use organic carbon as a source of energy to drive the reduction reactions. Without sufficient carbon, denitrification rates may be limited, leading to incomplete removal of nitrogen compounds from the wastewater.
Reduce the need for aeration reduce energy needs
Reduce the need for additional org. carbon
Less sludge. Used to treat streams with low C/N as found in effluent from anaerobic digester
The anammox (anaerobic ammonium oxidation) process offers several advantages over classical wastewater treatments for nitrogen removal:
Energy Efficiency: Anammox processes typically require less energy compared to traditional methods like nitrification-denitrification. This is because anammox bacteria can directly convert ammonium and nitrite into nitrogen gas under anaerobic conditions, bypassing the need for aeration in the nitrification step.
Reduced Carbon Footprint: Since anammox bacteria use less oxygen and organic carbon compared to conventional processes, the carbon footprint associated with nitrogen removal is significantly reduced.
Space Savings: Anammox processes can be more compact than conventional methods due to their higher biomass density and the elimination of the nitrification step, which can reduce the footprint of treatment facilities.
Lower Operating Costs: The reduced energy and chemical requirements, as well as the smaller footprint, contribute to lower operating costs over the long term.
Minimal Sludge Production: Anammox bacteria have a slow growth rate and produce less excess sludge compared to aerobic bacteria used in conventional treatments. This results in less sludge disposal and lower associated costs.
Resistance to Oxygen Fluctuations: Anammox bacteria are tolerant to oxygen fluctuations, which can be advantageous in wastewater treatment plants where oxygen levels may vary.
High Nitrogen Removal Efficiency: Anammox processes have high nitrogen removal efficiency, often exceeding 90%, making them effective for treating high-strength nitrogen wastewaters.
Reduced Chemical Usage: Compared to conventional treatments, anammox processes often require fewer chemicals for nitrogen removal, further reducing operational costs and environmental impact.
Write the correct and balanced stoichiometric reaction for denitrification using acetate as an
electron donor*
CH₃COO⁻ + NO₃⁻ → CO₂ + N₂ + H₂O, The balanced equation is CH₃COO⁻ + 8NO₃⁻ → 3CO₂ + 4N₂ + 9H₂O
The stoichiometric reaction for denitrification using acetate (C2H3O2-) as an electron donor can be represented as follows:
5CH3COO- + 8NO3- + 7H+ -> 5CO2 + 4N2 + 13H2O
This reaction represents the complete reduction of nitrate (NO3-) to nitrogen gas (N2) using acetate as the electron donor under anaerobic conditions. It involves the following steps:
Oxidation of acetate to carbon dioxide:
CH3COO- + 2H2O -> 2CO2 + 8H+ + 8e-
Reduction of nitrate to nitrogen gas:
8NO3- + 8H+ + 8e- -> 4N2 + 12H2O
The overall balanced equation combines these two steps, ensuring that mass and charge are conserved.
Name and describe the 4 phases of the microbial growth curve*
Lag Phase: Microorganisms adapt to the new environment, with little to no growth.
Exponential (Log) Phase: Rapid, exponential growth occurs as cells divide at their maximum rate under optimal conditions.
Stationary Phase: Growth rate slows down as nutrient depletion and waste accumulation stabilize population size.
Death Phase: Cell death exceeds cell division, leading to a decline in population size due to unfavorable conditions.
Write the correct and balanced stoichiometric reactions for nitrification*
Ammonium oxidation:
2NH4^+ +3O2–>2NO2^- + 2H2O +4H^+
Nitrite oxidation:
2NO2^- + O2–> 2NO3^-
Total:
2NH4^+ + 4O2–> 2NO3^- +4H^+ + 2H2O
Which of the following are aerobic treatment processes and which are anaerobic: nitrification,
anammox, denitrification?*
Nitrification and denitrification are aerobic and anaerobic processes, respectively, while anammox is an anaerobic process.
Nitrification: Aerobic process. It involves the oxidation of ammonia (NH3) to nitrite (NO2-) and then to nitrate (NO3-) by specialized bacteria under aerobic (oxygen-rich) conditions.
Anammox (Anaerobic Ammonium Oxidation): Anaerobic process. Anammox bacteria directly convert ammonia (NH3) and nitrite (NO2-) into nitrogen gas (N2) under anaerobic (low or no oxygen) conditions.
Denitrification: Anaerobic process. Denitrification is the biological reduction of nitrate (NO3-) to gaseous nitrogen compounds (such as nitrogen gas, N2) or nitrous oxide (N2O) by facultative anaerobic bacteria under anaerobic conditions.
In summary, nitrification occurs aerobically, anammox occurs anaerobically, and denitrification occurs anaerobically as well.
Identify the most appropriate set of names that describe the following microorganism 1 that
have different physiological properties*Microorganism 1: uses ammonium as nitrogen and energy source and fixes CO 2 as carbon source
CHEMO (energy source) : obtains energy through chemosynthesis, a process where enegy is derived from the oxidation of inorganic compounds. In this case the microorganism uses ammonium as the source of energy.
AUTOTROPIC (carbon source): Since it can fix CO2 to synthesize organic compounds.
LITHO (electron source): Obtains energy from inorganic sources. In this case, the microorganism utilizes ammonium as an inorganic energy source.
Define the true growth yield for microbial growth, Y*
The amount of new cellular biomass that is synthesized per unit of substrate (electron donor) consumed.
Microbial growth yield( Y )= Mass ob biomass formed / Mass of substrate consumed
Y Provides a direct link between new biomass synthesized and substrate depleted
Y=-dX/dS
The yield coefficient is a parameter used to calculate true growth yield
the amount of biomass produced per unit of substrate consumed.
Look at the calculation examples in ”Bacterial growth” by Maier and Pepper (Section 3.1)*
Calculation of the Number of Cells in a pure Culture.
Problem:
If a cell culture starts with 10.000 cells that has a generation time of 2 h,
HOW MANY CELLS WILL BE IN THE CULTURE AFTER 4, 24 AND 48 h?
The formula:
X(n)=2^n*X0
x0: initial number of cells
n: number of generations
X: number of cells after n generations.
After 4 hours:
number of generations n=4 hours/2 hours=2 generations
X(2)=2^210^4=410^4 cells
What is Aerobic ammonia oxidation
NH4^+ + O2–>NO2^- + H2O
Ammonium oxidized to nitrite
Oxygen is reduced to H 2 O
* No use of organic matter for
synthesis of biomass!!
these organisms fix CO2
They are chemo‐lithoautotrophs
Slow growth
4 phases of the nitrogen cycle
Nitrification
Denitrification
N2 Fixation
Anammox
(Ammonifaication, but basically the breaking down of organic material )
What is nitrogen fixation
Reduction of N2 to NH3
- Ammonia is used for cellular nitrogen (assimilation)
Only in Bacteria and Archaea
Biological nitrogen fixation makes N accessible to animals and plants
Chemical nitrogen fixation: Haber-Bosch process.
N2+8H^+ + 8e- —>2NH3+H2
N2 fixation is an energetically expensive process
performed by few selected organisms
What is nitrification
Ammonia to nitrate. The ammonium comes from decomposition of organic matter.
NH4^+–> NO2^-
Two step process:
- Conversion of ammonia to nitrite (Ammonia-oxidizing bacteria convert NH3 into NO2^- , Oxygen is the electron acceptor)
- Conversion of nitrite to nitrate (Nitrite-oxidizing bacteria, oxygen is the electron acceptor,
