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Water Purity and Pollution

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Water Purity

• Difficult to define
• Means different things to different people
• Water is a solvent
  • Takes into solution some of almost everything it touches
• Water is most pure when it evaporates, but
  • Picks up matter from the atmosphere when falling to the ground
  • On the ground, dissolves and carries some of almost everything it touches
  • Naturally occurring impurities may give it bad taste, color, or odor, or cloudy appearance (turbidity)
• Surface water
  • Contains more suspended solids, but less mineral and iron than groundwater
    • makes surface water softer than groundwater
  • Easily contaminated, but relatively easy to purify
• Groundwater
  • Can be contaminated from surface water
  • Cleaning can be difficult and time consuming
  • Pollutants introduced by people include pathogens (bacteria and viruses), heavy metals, pesticides (mostly organic), and other organic chemicals from manufacturing, industry, and agriculture
  • In Alabama,
    • Bacteria and nitrates are the greatest pollution threat to rural groundwater
    • Eroded sediments and animal wastes are the major sources of agricultural pollution, particularly from poultry farms
    • Most common source of pollution in urban areas are chemicals leaking from pipelines and tanks, concentrated chemical spills, and leaching waters from landfills and buried wastes.

Scope of Water Pollution

• Pollution
  • Occurs when the natural quality of water is degraded through the activity of people
  • Most occurs when the natural capacity of water to purify itself to a certain standard in reference to a particular pollutant and particular use is exceeded
• Sources of pollution
  • Point source
    • Enters water from a specific point through a pipe, ditch, or culvert
    • Common sources are factories and municipal sewage treatment plants
  • Nonpoint Source
    • A major problem (at least half of all pollution)
    • Difficult to quantify and control
    • Generally regarded as runoff and sedimentation
    • Common sources
      • Urban stormwater runoff
      • Manufacturing and industrial sites
      • Streets and parking areas
      • Construction runoff
      • Mines
      • Logging and timber cutting
      • Leaching water from septic tanks, landfills, or waste disposal areas
      • Leaking chemical storage tanks and pipelines
    • Major types
      • Sediment
      • Plant nutrients
      • Toxic chemicals
      • Animal wastes or organic materials
    • Factors influencing NPS
      • Rainfall
      • Vegetation
      • Soil erodibility
      • Topography
      • Human alteration of physical features

Source: Water Quality and Pollution Handbook, Circular ANR-970, Alabama Cooperative Extension Service, Auburn University, Alabama