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