CE3503 Environmental Engineering
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Transcript of CE3503 Environmental Engineering
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Energy Flow in Ecosystems (Section 5.3)
Representation by Effect (Section 2.5.4)
Biochemical Oxygen Demand (Section 5.4)
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Energy Flow in EcosystemsEnergy Flow in Ecosystems
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Energy Flow in EcosystemsEnergy Flow in Ecosystems
Energy fixationOrganic matterAutotrophsHeterotrophs
Aerobic respiration
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Energy Flow in EcosystemsEnergy Flow in Ecosystems
Nitrate removal
Drinking water
Mercury cycling
Sludge digestion
Anaerobic respiration
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Energy Flow in EcosystemsEnergy Flow in Ecosystems BiomassProduction
AutotrophsPrimary producersAlgaePhytoplankton
HeterotrophsSecondary producersPrimary ConsumersHerbivoresZooplankton
HeterotrophsSecondary consumersPlanktivores
HeterotrophsTertiary consumersPiscivoresCarnivores (also omnivores)
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Energy Flow in EcosystemsEnergy Flow in Ecosystems
Food chainFood web
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Energy Flow in EcosystemsEnergy Flow in Ecosystems
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Energy Flow in EcosystemsEnergy Flow in Ecosystems
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Energy Flow in EcosystemsEnergy Flow in Ecosystems Microbial loop(sustainable?)
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Other types of units: representation by effect. Other types of units: representation by effect.
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Other types of units: representation by effect. Other types of units: representation by effect.
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Other types of units: representation by effect. Other types of units: representation by effect.
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Organic Matter.Organic Matter.
2 2CO H
… what’s in here?
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Organic Matter.Organic Matter.
2 2CO H
Carbohydrates(sugar and the polymers starch and cellulose)
Proteins(polymers of amino acids)
Fats ( Fats(formed from glycerol and fatty acids)
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Organic Matter.Organic Matter.
2 22 2 ( )C H OC H O OO
Photosynthesis
2 2 22( )C O HO COH O
Respiration
also …mineralizationoxidationstabilization
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Representation by Effect - Organic Matter.Representation by Effect - Organic Matter.
2 2CO H
2 2 22( )C O HO COH O
Respiration
When organic matter is used as a substrate for respiration,
… when it is oxidized… when it is mineralized… when it is stabilized
it exerts a “biochemical oxygen demand” or BOD.
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BOD - Representation by Effect. BOD - Representation by Effect.
… impacts on lakes and rivers?
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Biochemical Oxygen DemandBiochemical Oxygen Demand
BOD: the amount of dissolved oxygen (mg/L) required to oxidize the organic matter in water.
CBOD: BOD exerted through oxidation of carbonaceous material.
NBOD: BOD exerted through oxidation of ammonia.
2 2 2 2( )C H O O CO H O
4 3 2 3 2 22 2 2 3NH HCO O NO CO H O
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Biochemical Oxygen DemandBiochemical Oxygen Demand
NBOD is simple stoichiometry,
Stoichiometry does not work for CBOD because not all of the organic matter present is biodegradable.
Thus the CBOD is never greater and almost always less than the theoretical BOD (ThBOD).
but for wastewater, not so much!
2 2 2 2( )C H O O CO H O
4 3 2 3 2 22 2 2 3NH HCO O NO CO H O
6 12 6 2 2 26 6 6C H O O CO H O
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Biochemical Oxygen DemandBiochemical Oxygen Demand
Distance or TimeTime (yr)
Co
nc
en
tra
tio
n
L
dLk L
dt
0 exp Lk ttL L
L0
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BOD Exerted (y)
BOD Remaining (L)
0 exp Lk ttL L
Biochemical Oxygen DemandBiochemical Oxygen Demand
0t ty L L
0 (1 exp )Lk tty L
0 0 exp Lk tty L L
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BOD Exerted
BOD Remaining
Biochemical Oxygen DemandBiochemical Oxygen Demand
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5-day BOD is a laboratory measurement.
Ultimate BOD is for field aplications.
Biochemical Oxygen DemandBiochemical Oxygen Demand
5-day BOD and Ultimate BOD
0 1 exp L
tk t
yL