Chapter 21 Water Pollution and Treatment

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Chapter 21 Water Pollution and Treatment

• Categories of water pollutants
• Diseases of drinking water
• Point vs. non point source pollution
• BOD
• Eutrophication
• Sediment
• Acid Mine Drainage
• Aquifer Pollution
• Waste Water treatment
• Environmental Laws to protect drinking water

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Categories of Water Pollutants

• Sediment
• Heavy metals
• Radioactive isotopes
• Heat
• E coli, pathogens, viruses
• Nutrients
• Dead organic matter

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Introduction

• US EPA sets standards for over 700 water
  pollutants
• Disease free water available in U.S., not
  necessarily problem except in developing world
• Sources of surface and groundwater pollution
  (industry, agriculture, urban)
• Runoff
• Spills
• Leaks
• Sediment
• Air fallout
• Seepage

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BOD

• What is it?
• Water quality parameter
• Measured before after at treatment facility and
  in stream
• Measure of oxygen for biochemical decomposition
  processes
• Amount of oxygen consumed by microorganisms in
  organic matter breakdown

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BOD Trends

• Natural and unnatural sources BOD
• 1/3 BOD comes from ag runoff
• Threshold- lt5mg/l water
• Vocabulary- pollution zone, active decomposition
  zone, recovery zone

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Relationship BOD vs. Dissolved Oxygen
Stable amounts
Break down organic matter Low O2 species
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Water Borne Diseases

• Outbreaks (sudden occurrences) examples
• Cryptosporidium - resistant to Cl, caused 100
  deaths in Milwaukee
• sources cattle, sewage, snow melt
• Installed new filtration system
• E coli Ontario, delayed reporting and
  treatment, boil water, 500 sick, source?- cow
  manure
• continuously monitored, lt200 cells/100ml water,
  EPA standard, exceed this amount beach closing
  and precautions

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Nutrients-N and P
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Sediment
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Acid Mine Drainage
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Surface WatersPoint vs. Non point
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Groundwater Treatment
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Septic Tanks Sewage Disposal Systems
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Hypoxia
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Waste Water Treatment Plants

• Divided into three categories
• Primary (30-40 BOD removal)
• Raw sewage passed through series of screens to
  remove large materials
• Grit chamber-removes sand, stones
• Sedimentation tank- settle out solids (sludge)
• Sludge- removed to digester

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Waste Water Treatment Plants

• Secondary treatment
• Waste water from primary treatment enters
  aeration tank
• Bacteria in sludge uses oxygen and consumes
  organics, further reducing BOD
• Anaerobic bacteria added to further degrade
  sludge
• Methane gas (anaerobic digestion) either used for
  energy or burned off
• Wastewater treated with chlorine is discharged or
  used for irrigation
• 90 BOD removal
• Sludge- applied to land or special disposal
  (heavy metals)

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Waste Water Treatment Plants

• Advanced water treatment
• N, P, organics, and heavy metals require carbon
  and sand filters, chemical treatment

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p.461 Environmental Laws

• 1899- Refuse Act
• 1972- Clean Water Act
• 1974- Safe Water Drinking Act
• 1984- Amendment to Resource Conservation and
  Recovery Act
• 1987- Water Quality Act

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LAND APPLICATION OF WASTEWATER
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