Ch12 - Water Pollution

Learning Objectives


After reading and studying this chapter, students should
* Be able to define water pollution and discuss some of the common water pollutants
* Understand the methods for treating groundwater pollution
* Understand the important processes related to wastewater treatment and renovation
* Understand drinking water standards and legislation related to water quality

Chapter 12 Summary
This chapter focuses on several aspects of water pollution. The chapter begins with a discussion of the importance of water pollution to water supplies worldwide, and a description of several common water pollutants. Subsequent sections focus on surface water pollution, including point sources and non-point sources, and on aspects of groundwater pollution, including its importance, sources, assessment, and treatment. The chapter closes with a discussion of water-quality standards, of wastewater treatment, including septic systems, municipal treatment systems, wetland treatment of wastewater, and wastewater renovation and recycling, and of federal legislation related to pollution prevention and treatment.

Chapter 12 Outline
I. An overview of water pollution
A. Water pollution
1. degradation of water quality as measured by biological, chemical, or physical criteria
2. judged according to the intended use of the water
3. a pollutant is a substance that, in excess, is known to be harmful to desirable living organisms
B. Primary water pollution problem worldwide
1. lack of clean drinking water free of disease-causing organisms or substances
2. particularly acute in developing world
II. Selected water pollutants
A. Oxygen-demanding waste
1. organic matter in streams is decayed by aerobic bacteria
2. decay process consumes oxygen
3. biochemical oxygen demand: measure of oxygen used for bacterial decomposition
4. 33% of BOD results from agriculture
5. urban areas may add considerable BOD during storms
B. Pathogenic organisms
1. disease-causing microorganisms
2. fecal coliform bacteria level is used as indicator of biological pollution
3. Escherichia coli
4. epidemics of waterborne disease largely eliminated in U.S. by separating sewage and drinking water, but incidents remain
5. outbreaks exacerbated by natural disasters
C. Nutrients
1. phosphorous and nitrogen are the most important human-released nutrients
2. cultural eutrophication results from high human-caused concentrations of nitrogen and phosphorous
3. seaweed blooms
4. Gulf of Mexico: summer “dead zone” off Louisiana
D. Oil
1. can cause major pollution problems
2. largest discharges from oil-tanker accidents
3. Exxon Valdez spill
E. Toxic substances
1. hazardous chemicals: synthetic organic and inorganic compounds
2. heavy metals: lead, mercury, zinc, cadmium, and others
3. radioactive waste
F. Sediment
1. greatest water pollutant by volume
2. depletes soil at source
3. reduces water quality
4. may deposit undesirable materials on productive croplands
G. Thermal pollution
1. artificial heating of waters
2. primarily caused by industrial operations and power plants
3. heated water contains less oxygen, can favor undesirable species
4. can enhance survival of desirable species during winter
III. Surface-water pollution and treatment
A. Point sources of surface-water pollution
1. discrete and confined sources
2. sources are typically pipes from industrial or municipal facilities
3. typically treated on-site and regulated by permit
B. Non-point sources of surface-water pollution
1. diffuse and intermittent sources
2. common urban sources include runoff from streets
3. rural sources generally from agriculture, mining, forestry
4. difficult to control and contains variety of pollutants
C. Reduction of surface-water pollution
1. in U.S., concerted effort is underway to reduce water pollution
2. effort assumes safe water is a basic human right
3. Cuyahoga River success story: most polluted river in 1960s is now much cleaner
IV. Groundwater pollution and treatment
A. One-half of U.S. population relies on groundwater for drinking water supplies
1. problem of groundwater pollution becomes more apparent as testing becomes more common
2. effects of chronic exposure to low pollutant levels are not known
B. National water-quality assessment program
1. significant investment in pollution prevention and significant improvement in water quality over past 25 years
2. U.S. Geological Survey in 1991 started program to assess water quality nationwide
3. Delaware River basin project
C. Saltwater intrusion
1. results from overpumping of groundwater in coastal areas
2. has caused problems in New York, Florida, California, and other states
3. as cone of depression forms in freshwater, a cone of ascension develops in adjacent saltwater
D. Groundwater treatment
1. reducing pollution of groundwater is a difficult task
2. preventing pollution is best approach, but not always possible
3. variety of methods exist for treating groundwater (Table 12.2)
V. Water-quality standards
A. Health effects of chronic exposure to very low levels of chemical contaminants is unknown
B. Safe Drinking Water Act of 1974
1. expanded in 1986 to include 83 contaminants
C. EPA has set standards for many contaminants
1. only coliform bacteria and nitrate are thought to pose immediate health hazard
2. National Primary Drinking Water Standards (Table 12.3)
VI. Wastewater treatment
A. Contaminated waters must be treated before release into U.S. waters
1. wastewater reclamation and use can reduce stress on water supplies
B. Septic-tank sewage disposal
1. an important method of disposal where collective sewage systems are inadequate or absent
2. underground tank collects waste and permits bacterial degradation of solid portions
3. liquid portions drain into ground, where further purification occurs
4. geologic factors affect suitability of septic systems
5. septic system failure
C. Wastewater-treatment plants
1. primary treatment
2. secondary treatment
3. advanced treatment and wastewater reclamation
4. handling and disposal of sludge
D. Wetlands as wastewater-treatment sites
1. wetlands can treat wastewater or other poor-quality water
2. alternative to expensive treatment facilities
3. municipal wastewater treatment
4. agricultural wastewater treatment
E. Wastewater renovation
1. wastewater renovation and conservation cycle
2. geology, topography, climate, and vegetation play significant roles
3. Clayton County, Georgia: wastewater applied to pine forest
VII. Federal legislation
A. Rewriting of major environmental laws
1. mid 1990s: debate and controversy regarding water pollution
2. purpose of amendments was to provide greater flexibility to industry
3. strong public support for clean air and water caused backlash
B. Imposition of new rules
1. President Clinton imposed new pollution controls in 2000
a. focused on non-point source pollution
b. will take at least 15 years to implement fully