Download Cell Energy - Kuliah FTSL

AEROBIC, ANAEROBIC, AND
ANOXIC PROCESSES
Cited from:
kidswebs.katyisd.org
BioE 202 Iowa State University
http://iqtma.uva.es/instrat/Presentaciones_pdf/Chapter%203Principles%20of%20Biological%20Wastewater%20Treatment%20_%
20Process%20SelectionR.pdf
week 5- aerobic, anaerobic, anoxic
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Biochemical Environment
 Aerobic Conditions: Oxygen is used as
electron acceptor
 Anoxic Conditions: Nitrate is the electron
acceptor
 Anaerobic Conditions: absence of oxygen
and nitrate and organic compounds are
converted to biomass, CO2, CH4 and H2S.
Organic matter + H2O
CH4 + CO2 + NH3 +
H2S+ new cell
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Cell Energy (Photosynthesis and Respiration) Notes
Energy:
• Energy for living things comes from food. Originally,
the energy in food comes from the sun.
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• Organisms that use light energy from the sun to
produce food—autotrophs (auto = self)
Ex: plants and some microorganisms (some bacteria
and protists)
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• Organisms that CANNOT use the sun’s energy to make
food—heterotrophs
Ex: animals and most microorganisms
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Cell Energy:
• Cells usable source of energy is called ATP
• ATP stands for adenosine triphosphate
Adenine
Ribose
3 Phosphate groups
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• ADP stands for adenosine diphosphate
Adenine
Ribose
2 Phosphate groups
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• All energy is stored in the bonds of compounds—
breaking the bond releases the energy
• When the cell has energy available it can store this
energy by adding a phosphate group to ADP, producing
ATP
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• ATP is converted into ADP by breaking the bond between
the second and third phosphate groups and releasing
energy for cellular processes.
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Photosynthesis:
• Photosynthesis is the process by which the energy of
sunlight is converted into the energy of glucose
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• Photosynthesis occurs in the chloroplasts of plants
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• Light absorbing compound is a pigment—pigments
absorb some wavelengths of light and reflect others—
the color our eyes see is the color that the pigment
reflects
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• Chlorophyll is the pigment inside the chloroplast the
absorbs light for photosynthesis
As the chlorophyll in leaves decays
in the autumn, the green color fades
and is replaced by the oranges and
reds of carotenoids.
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•General formula for photosynthesis
carbon dioxide + water + light
6CO2 + 6H2O + light
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:
glucose + oxygen
C6H12O6 + 6O2
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Reactants
•Diagram
Light
H2O
CO2
NADP+
ADP + P
Light
Dependent
Reaction
Calvin
Cycle
ATP
NADPH
Chloroplast
O2
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Products
C6H12O6
Glucose
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Summary:
• Light Dependent
Reaction—H2O is
broken down and light
energy is stored
temporarily in inorganic
energy carriers, ATP
and NADPH
• Calvin Cycle—energy is
transferred from ATP
and NADPH to the
organic compound
glucose
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Cellular Respiration: (2 kinds—Aerobic and Anaerobic)
• Cellular respiration is the process by which the energy
of glucose is released in the cell to be used for life
processes (movement, breathing, blood circulation,
etc…)
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• Cells require a constant source of energy for life processes but
keep only a small amount of ATP on hand. Cells can regenerate
ATP as needed by using the energy stored in foods like glucose.
• The energy stored in glucose by photosynthesis is released by
cellular respiration and repackaged into the energy of ATP.
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• Respiration occurs in ALL cells and can take place
either with or without oxygen present.
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Aerobic Respiration: requires oxygen
• Occurs in the mitochondria of the cell
• Total of 36 ATP molecules produced
• General formula for aerobic respiration:
C6H12O6 + 6O2
6 CO2 + 6H2O + 36 ATP
glucose + oxygen
carbon dioxide + water + energy
Human cells contain a
specialized structure – the
mitochondrion – that
generates energy.
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• Diagram
Electrons carried in NADH
Mitochondria
In Cytoplasm
Glucose
Krebs
Cycle
Glycolysis
2
2
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Electrons
carried in
NADH and
FADH2
Electron
Transport Chain
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Summary:
3 steps: 1st glycolysis
2nd Krebs cycle
3rd Electron Transport Chain (ETC)
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Anaerobic Respiration:
occurs when no oxygen is
available to the cell (2 kinds: Alcoholic and Lactic Acid)
• Also called fermentation
• Much less ATP produced than in aerobic respiration
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•Alcoholic fermentation—occurs in bacteria and
yeast
Process used in the baking and brewing
industry—yeast produces CO2 gas during
fermentation to make dough rise and give bread
its holes
glucose
ethyl alcohol + carbon dioxide + 2 ATP
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• Lactic acid fermentation—occurs in muscle cells
Lactic acid is produced in the muscles during rapid
exercise when the body cannot supply enough oxygen
to the tissues—causes burning sensation in muscles
glucose
lactic acid + carbon dioxide + 2 ATP
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• First step in anaerobic respiration is also glycolysis
Diagram
Anaerobic Respiration
Cytoplasm
C6H12O6
glucose
Alcoholic fermentation
Bacteria, Yeast 2 ATP
glycolysis
Lactic acid fermentation
Muscle cells
2 ATP
Aerobic Respiration
36 ATP
Krebs
Cycle
ETC
Mitochondria
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Advantage of anaerobic processes
• Less energy requirement as no aeration is needed
0.5-0.75 kWh energy is needed for every 1 kg of COD removal by aerobic
processes
• Energy generation in the form of methane gas
1.16 kWh energy is produced for every 1 kg of COD fermented in anaerobic
process
• Less biomass (sludge) generation
Anaerobic process produces only 20% of sludge compared with aerobic
CO2 + H2O
process
Soluble BOD
1 kg
Biodegradabl
e COD
1 kg
Aerobic process
Anaerobic
process
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0.5 kg
New
biomass
0.5 kg
CH4 gas
> 0.9 kg
New
biomass
< 0.1 kg
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Advantage of anaerobic processes
• Less nutrients (N & P) required
Lower biomass synthesis rate also implies less nutrients requirement : 20%
of aerobic
• Application of higher organic loading rate
Organic loading rates of 5-10 times higher than that of aerobic processes
are possible
• Space saving
Higher loading rates require smaller reactor volumes thereby saving on
disposal cost
• Ability to transform several hazardous solvents
including chloroform, trichloroethylene and trichloroethane to an easily
degradable form
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Comparison between anaerobic and
aerobic processes
Anaerobic
Aerobic
Organic loading rate
High loading rates:10-40 kg COD/m3-day
Low loading rates:0.5-1.5 kg COD/m3-day
(for activated sludge process)
(for high rate reactors, e.g. AF,UASB, E/FBR)
Biomass yield
Low biomass yield:0.05-0.15 kg VSS/
kg COD
(biomass yield is not constant but depends
on types of substrates metabolized)
High biomass yield:0.35-0.45 kg VSS/kg COD
(biomass yield is fairly constant irrespective
of types of substrates metabolized)
Specific substrate utilization rate
High rate: 0.75-1.5 kg COD/kg VSS-day
Low rate: 0.15-0.75 kg COD/kg VSS-day
Start-up time
Long start-up: 1-2 months for mesophilic
: 2-3 months for thermophilic
Short start-up: 1-2 weeks
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Comparison between anaerobic and
aerobic processes
Anaerobic
Aerobic
SRT
Longer SRT is essential to retain the slow
growing methanogens within the reactor
SRT of 4-10 days is enough for the
activated sludge process
Microbiology
Anaerobic processes involve multi-step
chemical conversions and a diverse
group of microorganisms degrade the
organic matter in a sequential order
Aerobic process is mainly a onespecies phenomenon, except for
nutrient-removal processes
Environmental factors
The process is highly susceptible to
changes in environmental conditions
The process is more robust to
changing environmental conditions
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Anaerobic degradation of organic substances to biogas
Proteins, Carbohydrates, Fats
Aminoacids, Sugar, Glycerole, Fatty acids
Hydrolyses
(facultative
anaerobic bacteria)
Formation of acids
(facultative
anaerobic bacteria)
HPO42NH4+/NH 3
H 2S
H2/CO2
Acetic acid
Propionic acid
Butyric acid
Alkoholes
H2/CO2
Acetic acid
Formation of acetic acid
(acetogenic bacteria)
Formation of methane
(methanogenic bacteria)
~70% CH4, ~30% CO2
(M. Kolb, Fachhochschule Aalen)
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Anoxic carbon removal
• There are several definitions of what anoxic conditions are. In
WWTPs, this often means that O2 is absent and replaced by
nitrate or sulfate as electron acceptor.
• Nitrate as electron acceptor
C10 H19O3N + NO3- + nutrients → C5H7NO2 + CO2 + N2 + …
This process is also known as denitrification (N-removal)
• Sulfate as electron acceptor
C10H19O3N + SO42- + nutrients → C5H7NO2 + CO2 + H2S+ …
H2S formation results in bad smells & corrossion
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Denitrification Chemistry
•
•
•
•
Ammonia First Passes Through Anoxic Zone
Ammonia is Converted to Nitrate in Aeration Zone
Nitrate are Recycled to Anoxic Zone
Nitrate are Converted to Nitrogen gas in Anoxic Zone
NO3 Converted to N2
NH3 Converted to NO3
N2 Gas
RECYCLE
Effluent
Influent
Anoxic Zone
(Denitrification)
Aeration Zone
(Nitrification)
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