2.4 The Dead Zone and Solutions to Water Pollution

watersheds and estuaries

  • watershed: the area of land that drains into a river or river system
      * the Mississippi River watershed (the largest in the world) drains 52 states
  • estuary: the mouth of a river, where the freshwater of the river meets the saltwater of the ocean

the Gulf of Mexico

  • home to many birds and fish
  • economically important to north/south American trade

combatting water pollution

  • fertilizing gardens with compost rather than commercial fertilizers
  • minimizing the use of pesticides
  • not pouring paints/solvents/antifreeze/etc. down the drain or onto the ground
  • not flushing unwanted medications down the toilet

large-scale solutions to water pollution

technical solutions

  • sewage treatment plants
      * sewage: wastewater
      * when sewage reaches a treatment plant, it can undergo three levels of purification
        * level one — primary treatment: removes solids from water
          * water passes through a metal grate that removes debris (eg. sticks, stones)
          * half of suspended organic solids settle to the bottom of the primary sedimentation tank as sludge
        * level two — secondary treatment: aerobic bacteria are used to remove up to 90% of biodegradable, oxygen demanding organic waste (biological treatment process)
        * level three — tertiary treatment: removes plant nutrients and pathogens
          * plant nutrients eg. nitrates and phosphates, pathogens eg. chlorine
      * sewage treatment in minnesota
      * COVID detection in sewage
  • ecological wastewater treatment: an environmentally friendly approach to wastewater treatment
      * created by Dr John Todd
      * uses no chemicals
      * includes tertiary treatment
      * low operational cost

laws and policy

  • the Clean Water Act (1972) made it unlawful to discharge any pollutant from a point source into navigable waters unless a permit was obtained
  • the Environmental Protection Agency’s mission is to protect human health and the environment
      * develops and enforces environmental regulations
      * allocates grant funding
      * studies environmental issues
      * teaches public about the environment
  • the Safe Drinking Water Act (1974) is meant to protect drinking water quality
      * allows EPA to set minimum standards to protect tap water
      * requires all owners or operators of public water systems to comply with these standards

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