Management of Non-Point Source Pollution CE 296B

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Management of Non-Point Source PollutionCE 296B

• Department of Civil Engineering
• California State University, Sacramento

Lecture 8, February 26, 1998 Sources of
Pollutants - Part IV
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Recall that we were looking at the six categories
of pollutants
1. Toxic inorganics - e.g. metals 2. Synthetic
organics - e.g. solvents 3. Biostimulants - BOD,
nutrients? Left off here 4. Sediment - clay,
silt, sand, gravel 5. Pathogenic organisms -
viruses, bacteria, protozoa 6. Trash - use your
imagination
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And the framework for acquiring knowledge about
each category
1. What are the sub-categories in each category
and what are representative members? 2. What are
the origins of pollutants? 3. How pollutants are
introduced to the flow stream? 4. How pollutants
behave in water?? and here
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IV. The third category of pollutant to examine is
biostimulants. (cont.)

• E. Examine the concept of a rate limiting
  nutrient
• 1. On a dry weight basis, the primary members of
  the food chain have a relatively similar make-up
  in terms of proportions of elements.

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Typical Elemental Proportions in Microorganisms
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IV. The third category of pollutant to examine is
biostimulants. (cont.) E. Examine the concept of
a rate limiting nutrient (cont.)

• 2. Primary members of the food chain require
  elements roughly in the proportions listed.
  Excluding the oxygen and hydrogen associated with
  cell water, we are left with
• Carbon - 50 of total
• Nitrogen - 14 of total
• Phosphorous - 8 of total

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Representation of Limiting Nutrient Concept
Balanced amount of each nutrient
Amount of each nutrient available, nitrogen
controls here
Amount of each nutrient actually used
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IV. The third category of pollutant to examine is
biostimulants. (cont.) E. Examine the concept of
a rate limiting nutrient (cont.)

• 3. Thus, for each water body, there will be a
  limiting nutrient. Because of the ability of
  algae to fix CO2 via oxygenic photosynthesis, the
  rate limiting nutrient is usually nitrogen or
  phosphorous. If nitrogen is not the rate
  limiting nutrient, it will eventually be
  denitrified to molecular nitrogen. If
  phosphorous is not the rate limiting nutrient, it
  may accumulate in the system.

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IV. The third category of pollutant to examine is
biostimulants. (cont.) E. Examine the concept of
a rate limiting nutrient (cont.)

• 4. As it is difficult to assess if a water body
  is nitrogen or phosphorous limiting, it has been
  considered good practice to limit the
  introduction of both in excess.
• 5. It is also difficult to assess just how much
  nitrogen or phosphorous is required for the water
  body to be healthy.

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Discussion Break

• Imagine that, through an extremely aggressive
  program, both nitrogen and phosphorous inputs to
  Santa Monica Bay were lowered to an extremely low
  level, below the natural input.
• What might happen to the Kelp Harvesting
  Industry there?
• Something like this has happened to the south
  bay from the San Jose Wastewater Treatment Plant.

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Discussion Break

• What kind of environmental trade-offs might
  exist in a substantial campaign to plant trees in
  a city?

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IV. The third category of pollutant to examine is
biostimulants. (cont.)

• F. How do biostimulants behave in water?
• 1. Carbon
• a. Aerobic oxidation of organic compounds
  consumes dissolved oxygen.
• Desirable fish species (trout, bass, etc.) are
  more sensitive to reduction in D.O. concentration
  than rough fish (e.g., carp).
• D.O. concentrations are most often a central
  Water Quality Objective.

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Discussion Break

• If one where to establish priorities for Water
  Quality Objectives, where would dissolved oxygen
  rank?
• Why?
• Which reasons are scientific and which are
  emotional?

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IV. The third category of pollutant to examine is
biostimulants. (cont.) F. How do biostimulants
behave in water? 1. Carbon (cont.)

• b. It is usually considered a minor
  consideration, but as organic material is
  oxidized and CO2 is produced, the alkalinity of
  the water increases.
• c. Organic compounds that are less degradable
  remain in system for an extended period of time.
  They may
• Decay anaerobically in bottom sediments
• releasing NH3, PO4-3, and producing H2S
• Complex with other constituents, e.g. metals

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IV. The third category of pollutant to examine is
biostimulants. (cont.) F. How do biostimulants
behave in water? 1. Carbon (cont.)

• d. Become part of beneficial natural processes.
• 2. Nitrogen
• a. Undergo transformations associated with
  nitrogen cycle. Note that as with carbon, there
  is an escape route for nitrogen. It may be
  transformed by denitrification to N2.
• b. Nitrification process consumes D.O. and
  produces strong acid.

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IV. The third category of pollutant to examine is
biostimulants. (cont.) F. How do biostimulants
behave in water? (cont.) 2. Nitrogen (cont.)

• c. Free ammonia (NH3) can be toxic to fish.
• The Tulare Basin Plan has a water quality
  objective of 0.025 mg/L as N. The concentration
  of free ammonia is a function of three things
• Total ammonia concentration (NH3 plus NH4)
• pH
• Temperature
• Equilibrium Relationship

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Discussion Break

• Ammonia is toxic to fish everywhere. Some Basin
  Plans specifically list ammonia concentrations in
  the Water Quality Objectives. The Los Angeles
  Region and Tulare Basin are two examples. Other
  Basin Plans simply give an acceptable pH range.
  The Colorado Basin and Central Valley Basin are
  two examples.
• Which approach to you prefer? Why?

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IV. The third category of pollutant to examine is
biostimulants. (cont.) F. How do biostimulants
behave in water? (cont.) 2. Nitrogen (cont.)

• d. In the capacity of a rate limiting nutrient,
  excess nitrogen would stimulate excess growth of
  primary members of the food chain, particularly
  algae. This would in turn lead to a depletion of
  D.O. and the subsequent negative effects
  associated with depressed D.O. levels.

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IV. The third category of pollutant to examine is
biostimulants. (cont.) F. How do biostimulants
behave in water? (cont.)

• 2. Phosphorous
• a. Major difference between phosphorous and the
  other two major biostimulants, carbon and
  nitrogen, is that the phosphorous cycle does not
  have a gas phase component. Thus, in the absence
  of a flushing mechanism, phosphorous inputs to a
  water body will continue to accumulate.

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IV. The third category of pollutant to examine is
biostimulants. (cont.) F. How do biostimulants
behave in water? (cont.) 2. Phosphorous (cont.)

• b. As with nitrogen, if phosphorous is the rate
  limiting nutrient, excess phosphorous would
  stimulate excess growth of primary members of the
  food chain, particularly algae. This would in
  turn lead to a depletion of D.O. and the
  subsequent negative effects associated with
  depressed D.O. levels.

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Discussion Break

• Every water body requires some input of
  biostimulants to remain healthy.
• How might we draw the line between required
  biostimulants and excess biostimulants?
• What would the implications of incorporating
  this idea into the Clean Water Act?

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Recall that we were looking at the six categories
of pollutants
1. Toxic inorganics - e.g. metals 2. Synthetic
organics - e.g. solvents 3. Biostimulants - BOD,
nutrients 4. Sediment - clay, silt, sand, gravel
? On to here 5. Pathogenic organisms - viruses,
bacteria, protozoa 6. Trash - use your imagination
23
And the framework for acquiring knowledge about
each category
1. What are the sub-categories in each category
and what are representative members? 2. What are
the origins of pollutants? 3. How pollutants are
introduced to the flow stream? 4. How pollutants
behave in water?
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V. The fourth category of pollutant to examine is
sediment.

• A. Define what a sediments are
• Sediments are the dirt under our feet.
• 1. Components are

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V. The fourth category of pollutant to examine is
sediment. A. Define what a sediments are (cont.)

• 2. Important considerations associated with
  gravel
• Requires a substantial current to transport, only
  during flood events
• Could conceivably contribute to clogging of
  shipping channels or damage of habitat, but
  generally, this is not something associated with
  gravel.
• Is a crucial ingredient for spawning beds

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Discussion Break

• What about gravel mining (aggregate operations)
  along stream beds?
• Pollution effects?
• Non-point or point source pollution?

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V. The fourth category of pollutant to examine is
sediment. A. Define what a sediments are (cont.)

• 3. Important considerations associated with sand
• Current required to transport is still
  substantial.
• Contributes to clogging type problems, both for
  navigation and habitat degradation.
• Active ingredient for beaches
• Helpful in spawning grounds
• Low surface to volume ratio, little adsorption
  takes place.

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V. The fourth category of pollutant to examine is
sediment. A. Define what a sediments are (cont.)

• 4. Important considerations associated with silt
• Easy to transport, slow current will do.
• May have substantial contributions to clogging
  type problems, both for navigation and habitat
  degradation.
• Moderate surface to volume ratio, some adsorption
  takes place.
• Will have a substantial effect on turbidity

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V. The fourth category of pollutant to examine is
sediment. A. Define what a sediments are (cont.)

• 5. Important considerations associated with clay
• Very easy to transport, slow current will do.
  Small enough to behave as a colloidal particle,
  settles very slowly in a water column.
• May have substantial contributions to clogging
  type problems, both for navigation and habitat
  degradation.
• Moderate surface to volume ratio, some adsorption
  takes place.

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V. The fourth category of pollutant to examine is
sediment. A. Define what a sediments are
(cont.) 5. Important considerations associated
with clay (cont.)

• High surface to volume ratio, substantial
  adsorption takes place. Associated with clay
  particles may be high concentrations of
• Organic acids (humic and fulvic)
• Metals
• Synthetic organics
• Will have a substantial effect on turbidity

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V. The fourth category of pollutant to examine is
sediment. (cont.)

• B. Sources of sediments
• Seems obvious and it is. Two groups
• 1. Soil as nature delivered it. Soil horizon
• 2. Dirt that has been relocated by humans. All
  mixed up.

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Discussion Break

• With respect to soil components, what difference
  would it make if erosion took place in a soil
  environment vs. a fill environment?

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V. The fourth category of pollutant to examine is
sediment. (cont.)

• C. How are sediments introduced to the flow
  stream?
• 1. Atmospheric scrubbing during rainstorms.
  Wetfall. There can be notable concentrations of
  suspended solids in a rainstorm.
• 2. Erosion I. Sheet flow over exposed soil, no
  plant cover or pavement, mobilizes soil particles.

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V. The fourth category of pollutant to examine is
sediment. (cont.) C. How are sediments
introduced to the flow stream? (cont.)

• 3. Erosion II. Stream flow over exposed soil, no
  plant cover or pavement, mobilizes soil
  particles.
• 4. Raindrop Energy. Raindrops striking the
  earths surface liberate soil particles for
  transport in sheet flow.

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V. The fourth category of pollutant to examine is
sediment. (cont.) C. How are sediments
introduced to the flow stream? (cont.)

• 5. Sediments residing on human created surfaces,
  pavement, roofs, etc., are incorporated into
  run-off by either sheet flow or raindrop energy.
  These particles tend to be fine and are purported
  to be associated with substantial concentrations
  of metals and/or synthetic organics.

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Discussion Break

• Erosion is a natural process.
• The Clean Water Act does not specifically
  recognize it as such.
• What kind of language, in a law, would correctly
  differentiate between natural and unnatural
  erosion?