Water Pollution

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Water Pollution

• Text Chp. 17
• Sources, common types and criteria
• Eutrophication
• Removal
• I.Sources, common types and criteria
• Pollution the presence of a substance in the
  environment
• that because of its chemical composition or
  quantity
• prevents the functioning of natural processes and
  produces
• undesirable environmental and health effects.

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General strategies for dealing with pollution

• Identify material causing pollution.
• Identify source of material.
• Develop and implement prevention strategy
• Develop substitute.
• Note how all of the above can be applied to
  atmospheric
• pollution problems.
• Two source categories
• Point source gt easy to identify, monitor and
  regulate through reduction or treatment at end of
  pipe.
• Non-point source gtpoorly defined, treat through
  source reduction (problem of multiple sources so
  hard to monitor)

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Point and non-point sources of pollution
Atmospheric deposition (np)
Storm water runoff (np)
(Also power plants, mines)
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Pollution categories

• Sources from water and land
• Nutrient oversupply
• Solid wastes
• Toxic chemicals
• Pesticides/herbicides
• Nuclear waste

• Types of Water Pollutants
• Pathogens
• Organic Wastes
• Chemical
• Sediments
• Nutrients

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Pathogens

• Def Disease-causing agents (see Table 17.1)
• Safety measures (more important than treating
  disease)
• purification of public water supply
• sanitary collection/treatment of sewage
• sanitary practices when processing food
• public education re personal hygiene

Implicit in all above is monitoring for sewage
contamination. Indicator trackedgte-coli counts.
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Organics

• As organics are broken down, decomposers use up
  oxygen, which is about 10 ppm in water (compare
  to 200,000 ppm in air)
• Dissolved oxygen (DO) in the water is depleted
  during decomposition of organic wastes.
• Water quality test.
• Biochemical oxygen demand (BOD) ie how much
  required to break down organics. Higher BOD,
  lower DO.
• Fish-kills occur when DO falls below 2-3 ppm

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Chemical pollutants

• Inorganic chemicals
• Heavy metals, acids, road salts
• Organic chemicals
• Petroleum, pesticides, detergents
• Some are toxic at low concentrations other
  concentrated
• up food chain through biomagnification

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Sediments

• As landforms weathergtsediment washed by overland
  flow into water bodies.
• Human actvities such as deforestation, ranching,
  mining sites, construction sites, roads can all
  lead to increased sediment loads.
• Particle size affects velocity of sediment
  transport.
• Transportation takes place through the following
• Solution or dissolved load
• Suspended load of fine-grained particles
• Traction (dragging) of bed load of coarse
  material
• Saltation (bouncing) of bed load of coarse
  material

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Effect of Sediments on Stream Ecology

• Poor light penetration
• Loss of hiding-resting places for small fish.
• Attached aquatic organisms scoured from the rocks
  and sand.
• Through flocculation, some toxics attach to
  sediment.
• Nutrients (see Eutrophication section)
• From sewage outfalls and storm drains (point
  source).
• Agricultural runoff, golf courses, lawns
  (non-point source).

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Policy Response

• National Recommended Water Quality Criteria for
  158 criteria pollutants gt Criteria max.
  concentration (single dose)
• gtCriterion continuous concentration
  (over long period lower than CMC above)
• National Pollution Discharge Elimination Program
  issues permits for point sources.
• Total Maximum Daily Load evaluates all sources
  entering water body.

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II. Eutrophication

• Def process of becoming nutrient-rich.
• Aquatic plant life made up of
• Benthic plants
• Emergent vegetation
• Submerged aquatic vegetation (SAVs)
• Phytoplankton (single cell organism)
• SAVs thrive in oligotrophic or nutrient-poor
  water since
• uptake comes from bottom sediments.
• Oligotrophic bodies are prized for recreational
  and aesthetic
• activities.

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• With nutrient enrichment gtphytoplankton
  increases
• gt turbidity increases (less UV) gt SAV die-off
  gt reduced habitat less oxygen from reduced
  phtosynthesis gt smaller fish pop.
• As phytoplankton increases to max. pop. density
  gtdie-off occurs gtdecomposition lowers DO gtfish
  kills due to hypoxia.
• Natural vs. cultural eutrophication
• Natural eutrophication
• aquatic succession
• occurs over several hundreds of years (can be
  shorter50 yrs)
• Cultural eutrophication
• driven by human activities
• occurs rapidly

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Eutrophication

• As nutrients are added from pollution, an
  oligotrophic condition rapidly becomes eutrophic.

Oligotrophic
Eutrophic
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Combating Eutrophication

• Attack the symptoms
• Chemical treatment
• Aeration
• Harvesting aquatic weeds
• Drawing water down

Problem gt unless attack root causes,
symptoms will reappear.
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III. Removal

• Getting at root cause of eutrophication
• EPA set stds. Phosphorus 8 ug/L
• Nitrogen 0.24 mg/L
• Controlling point sources
• Ban phosphate detergents
• Sewage-treatment improvements
• Controlling non-point sources
• Best Management Practices (BMP)
• (See Table 17-2)

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Strategy through TMDL program (compare with slide
2)

• Identify pollutant causing problem
• Estimate amount from source
• Estimate assimilation capacity of receiving
  water body.
• From 3) come up with max. pollution loading for
  receiving water body
• Use models to link 4) to 5) and allocate
  allowable concentration levels at source.

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Sewage

• Two kinds of wastewater collection gtstorm drains
  sanitary sewers.
• Raw sewage or wastewater is what comes out of
  collection systemgt 99.9 water 0.1 waste.
• Output per person per day about 150-200 gal. or
  500-600 l.
• Pollutants in sewage are
• Debris and grit
• Particulate organic material
• Colloidal and dissolved organic material
• Dissolved inorganic material

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Wastewater treatment
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Alternative Treatment Systems

• Individual septic systems
• Wastewater effluent irrigation
• Reconstructed wetland systems
• Beaumont, TX
• The waterless toilet

• Septic Tank Treatment
• Aerobic digestion of solids in septic tank.
• Flow of liquids into drain field for evaporation,
  infiltration, or irrigation.