1
Q
What are the different zones in a polluted river?
A
- Clean zone
- Decomposition zone
- Septic Zone
- Recovery zone
- (returns to Clean zone)
2
Q
Clean zone
A
- Zone of river with no pollution
- Normal diversity/abundance of organisms: trout, perch, bass, mayfly, stonefly
- DO at 8ppm
3
Q
Decomposition zone
A
- Zone of river where pollution enters the stream
- Populated by “trash fish”: gars, leaches
- BOD spikes due to increased organic matter that requires oxygen for decomposition
- DO drops due to oxygen demand by bacteria
4
Q
Septic zone
A
- Anaerobic zone
- Fish absent; fungi, sludge worms, bacteria present
- Very low DO due to bacterial decomposition
- BOD decreases as anaerobic activity increases
5
Q
Recovery zone
A
- Less contamination present than in decomposition and septic zones
- trash fish present
- BOD declines b/c most organic material has settled as sludge
- DO increases
6
Q
Urban runoff
A
- major pollution source with lots of BOD, suspended solids, nutrients, and microorganisms
- important in cities because urban runoff increases with hard top surfaces, no percolation into soil
- rates of runoff depend on rainfall
7
Q
Remediation strategies for urban runoff
A
- Settling basins
- Recharge basins
- Interception of runoff
8
Q
Settling basins
A
- Can be used to remediate urban runoff
- Removes SS and BOD, some nutrients/toxins are absorbed
- System may be overwhelmed by storms, requires long residence time and slow flow
9
Q
Recharge basins
A
- Allows percolation of water into the ground
- Soil acts as filter to remove SS
- Dissolved contaminants will percolate into groundwater
10
Q
Eutrophication
A
- enrichment of an ecosystem w/ chemical nutrients, typically N or P, resulting in a depletion of dissolved oxygen
- Can occur due to natural N/P cycling
- Occurs more quickly due to wastewater discharge, urban runoff, etc.
ENST 510 Exam 2
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