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