Energy Flow in Ecosystems (Section 5.3)

Representation by Effect (Section 2.5.4)

Biochemical Oxygen Demand (Section 5.4)

Energy Flow in EcosystemsEnergy Flow in Ecosystems

Energy Flow in EcosystemsEnergy Flow in Ecosystems

Energy fixationOrganic matterAutotrophsHeterotrophs

Aerobic respiration

Energy Flow in EcosystemsEnergy Flow in Ecosystems

Nitrate removal

Drinking water

Mercury cycling

Sludge digestion

Anaerobic respiration

Energy Flow in EcosystemsEnergy Flow in Ecosystems BiomassProduction

AutotrophsPrimary producersAlgaePhytoplankton

HeterotrophsSecondary producersPrimary ConsumersHerbivoresZooplankton

HeterotrophsSecondary consumersPlanktivores

HeterotrophsTertiary consumersPiscivoresCarnivores (also omnivores)

Energy Flow in EcosystemsEnergy Flow in Ecosystems

Food chainFood web

Energy Flow in EcosystemsEnergy Flow in Ecosystems

Energy Flow in EcosystemsEnergy Flow in Ecosystems

Energy Flow in EcosystemsEnergy Flow in Ecosystems Microbial loop(sustainable?)

Other types of units: representation by effect. Other types of units: representation by effect.

Other types of units: representation by effect. Other types of units: representation by effect.

Other types of units: representation by effect. Other types of units: representation by effect.

Organic Matter.Organic Matter.

2 2CO H

… what’s in here?

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)

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

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.

BOD - Representation by Effect. BOD - Representation by Effect.

… impacts on lakes and rivers?

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

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

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

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

BOD Exerted

BOD Remaining

Biochemical Oxygen DemandBiochemical Oxygen Demand

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