Do Now:

• Where does our water go when we flush the toilet? Wash our hands in the sink? Water our lawns, wash our cars?

Aim: How Can We Best Deal with Water Pollution?

Concept 20-5 Reducing water pollution requires we prevent it, work with nature to treat sewage, cut resource use and waste,

reduce poverty, and slow population growth.

Reducing Surface Water Pollution from Nonpoint Sources

• Agriculture– Reduce erosion– Reduce the amount of fertilizers– Plant buffer zones of vegetation– Use organic farming techniques– Use pesticides prudently – Control runoff– Tougher pollution regulations for livestock

operations– Deal better with animal waste

Pause…Think…Write…

• Should we greatly increase efforts to reduce water pollution from non point sources even though this could be quite costly?

Laws Can Help Reduce Water Pollution from Point Sources

• 1972: Clean Water Act : sets limits for 100 water pollutants and requires polluters to get permits that limit how much they can discharge.

•1987: Water Quality Act: strengthened the federal water quality regulations by providing changes in permitting and adds substantial penalties for permit violations.

Laws Can Help Reduce Water Pollution from Point Sources

• EPA: experimenting with a discharge trading policy that uses market forces– Cap and trade system– Could this allow pollutants to build up? Lower the

cap!

Do you understand how laws can be both good and bad?

Case Study: The U.S. Experience with Reducing Point-Source Pollution

• Numerous improvements in water quality

• Some lakes and streams are not safe for swimming or fishing -40%

• Treated wastewater still produces algal blooms

• High levels of Hg, pesticides, and other toxic materials in fish

Case Study: The U.S. Experience with Reducing Point-Source Pollution

• Leakage of gasoline storage tanks into groundwater

• Many violations of federal laws and regulations (unclear which water ways are covered under CWA)

• Need to strengthen the Clean Water Act: fines are cheap!

Solutions: Septic Tank System

Waste water treatment from flush to finish movie

What happens during the primary, secondary, and tertiary treatment of waste water?

Solutions: Primary and Secondary Sewage Treatment

We Can Improve Conventional Sewage Treatment

• Peter Montague: environmental scientist– Remove toxic wastes before water goes to the

municipal sewage treatment plants– Reduce or eliminate use and waste of toxic

chemicals– Use composting toilet systems

• Wetland-based sewage treatment systems

Science Focus: Treating Sewage by Working with Nature

• John Todd: biologist

• Natural water purification system– Sewer water flows into a passive greenhouse– Solar energy and natural processes remove and

recycle nutrients– Diversity of organisms used

Solutions: Ecological Wastewater Purification by a Living Machine, RI, U.S.

There Are Sustainable Ways to Reduce and Prevent Water Pollution

• Developed countries– Bottom-up political pressure to pass laws

• Developing countries– Little has been done to reduce water pollution– China : ambitious plan

Summary:

• What role does population growth play in the problems of groundwater and coastal water pollution?