Nutrient Input and Eutrophication 1

• Agricultural activities and sewage add nutrients, as well as disease organisms, to marine environments

Nutrient Input and Eutrophication 2

• Agricultural activities and sewage add nutrients, as well as disease organisms, to marine environments

• Eutrophication is the addition of dissolved nutrients to a water body, resulting in large increases of phytoplankton production

Nutrient Input and Eutrophication 3

Eutrophication sources from land:1. Point sources such as sewage treatment outfall pipes2. Point sources such as sewer overflows, which may be

connected to sewage systems (Combined Sewer Outflows or CSOs)

3. Commercial fertilizer used in agriculture - can be in runoff - non-point source

Nutrient Input and Eutrophication 4

Eutrophication sources from land:1. Point sources such as sewage treatment outfall pipes2. Point sources such as sewer overflows, which may be

connected to sewage systems (Combined Sewer Outflows or CSOs)

3. Commercial fertilizer used in agriculture4. Animal waste in “lagoons,” connected to waterways

Typical Urban Solution - When it rains, pollution spills over into estuary

Rain water

Nutrient Input and Eutrophication 5

Nutrient Input and Eutrophication 6

Atmospheric sources:1. Aerosols from agricultural fertilizer2. Nitrogen oxide deposited as nitrates on

coastal ocean from fossil fuel emissions

Nutrient Input and Eutrophication 7

Atmosphericnitrate 25%

Fertilizers34%Point Sources

23%

Atmosphericammonium

14%

Animal waste4%

Contributions of nitrogen to Chesapeake Bay watershed

Nutrient Input and Eutrophication 8

Effects of Eutrophication:Development of Hypoxia1. Nutrients stimulate phytoplankton growth2. Not all phytoplankton is grazed3. Bacteria consume dead phytoplankton4. Oxygen declines5. If water is stratified or circulation is sluggish:

benthic animals die (or emigrate) owing to oxygen loss

Development of hypoxia

Nutrient Input and Eutrophication 9Treatment of Sewage:1. Primary treatment - solids intercepted by screens2. Secondary treatment - more toxic nitrogenous

compounds and colloids are stirred in aerobic tanks so that only phosphates, nitrates, ammonium released in coastal water

3. Tertiary treatment - dissolved phosphates, nitrates, and ammonium removed (use of chemical techniques, microbial approaches to remove N compounds)

Nutrient Input and Eutrophication 10

Treatment of Sewage:

Objective of primary treatment: to reduce organic material input, to reduce Biological oxygen demand (BOD)

Primary treatment has been successful in the increase of dissolved oxygen in polluted water bodies such as New York Harbor

Nutrient Input and Eutrophication 11

BOD Loadings from NYC (metric tons/day)

% O

xyge

n S

atur

atio

n

Relation of input of organic solids to oxygen in water - NY Harbor