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21
Water Pollution: Sustainably
Managing a Renewable
Resource
Chapter Outline
The Pollution of Surface Waters
Sources of Water Pollution
Point and Nonpoint Sources
Organic and Inorganic Nutrients
Infectious Agents
Toxic Organic Water Pollutants
Toxic Inorganic Water Pollutants
Sediment
Thermal Pollution
Groundwater Pollution
Effects of Groundwater Pollution
Cleaning Up Groundwater
Ocean Pollution
Oil in the Seas
Plastic Pollution
Medical Wastes and Sewage Sludge
Red Tide
The Case of the Dying Seals
Water Pollution Control
Legislative Controls
Controlling Nonpoint Pollution
Preventing Groundwater Pollution
Water Pollution Control Technologies: End-of-Pipe Approaches
Sustainable Solutions
Key Terms
water pollution point source nonpoint source
cross-media contamination organic nutrients inorganic nutrients
biochemical oxygen demand cultural eutrophication natural eutrophication
natural succession infectious agents chlorinated organics
sedimentation streambed aggradation thermal shock
groundwater pollution ocean pollution red tide
end-of-pipe controls primary treatment secondary treatment
tertiary treatment pretreatment
Objectives
1. List the major types, sources, and environmental effects of water pollution.
2. Define the following terms and give an example of each: “point source,” “nonpoint source,” “organic nutrient,” and “inorganic nutrient.”
3. Discuss natural and cultural eutrophication of lakes.
4. List the important infectious agents that are found in polluted water.
5. Discuss the major toxic chemical pollutants in surface and groundwater.
6. Summarize the major sources of ocean pollution and their environmental effects.
7. Summarize the major provisions of the Clean Water Act.
8. Discuss the current water pollution control technologies (end-of-pipe approaches).
9. List some sustainable solutions to pollution of surface and groundwater.
Lecture Outline
The Pollution of Surface Waters - Water pollution is any physical or chemical change in water that adversely affects organisms.
Sources of Water Pollution
Water pollutants arise from natural and anthropogenic causes. Pollutants can travel freely from one location to another through rivers, streams, and groundwater.
Point and Nonpoint Sources
Point sources are discrete, easily identified and controlled locations of concentrated pollution discharge.
Nonpoint sources are large, less discrete areas over which dispersed pollutants are generated and discharged.
The major nonpoint pollution source in the United States today is agriculture.
Organic and Inorganic Nutrients - Nutrients in excessive amounts become pollutants.
Organic Nutrients
These include feedlot and slaughterhouse wastes, sewage treatment effluent, and some industrial wastes.
Organic nutrients are oxygen-demanding substances since their metabolism by bacteria is aerobic.
The greater the organic nutrient load of water, the greater the biochemical oxygen demand.
Inorganic Nutrients - Nitrates and Phosphates
These nutrients, primarily nitrogen and phosphorus, stimulate the growth of aquatic plants; this can result in excess aquatic plant growth and oxygen depletion.
Nitrogen fertilizer and phosphate-containing laundry detergents are major sources of inorganic nutrient pollution in freshwater systems.
Eutrophication and Natural Succession
Eutrophication is nutrient enrichment of a body of water. It can be either natural or cultural.
Eutrophication and erosion result in the natural succession of lakes and ponds into swamps and, finally, dry land; humans have greatly accelerated this process.
Infectious Agents
Pathogenic organisms may enter water through sewage effluent, animal wastes and processing byproducts, and certain wildlife species.
Toxic Organic Water Pollutants
Thousands of these may contaminate water and pose aesthetic, environmental, or human health problems.
Toxic Inorganic Water Pollutants
Mercury
A common toxic heavy metal, mercury is widespread and harms aquatic organisms and humans.
Nitrates and Nitrites
These come from fertilizer and animal and human wastes; in high concentrations, they can poison infants who drink contaminated water.
Salts
Salts, often used on roads during winter, can kill nearby organisms and pollute ground and surface water.
Chlorine
A widely used disinfectant, chlorine can react with organic compounds to produce various carcinogens and mutagens in water.
Sediment
The most voluminous water pollutant in the United States, sediment is generated by forestry, agriculture, mining, and construction.
Sedimentation aggravates pollution problems, fills in lakes and streams, and damages human property.
Thermal Pollution
Unnatural changes in water temperature that adversely affect organisms are instances of thermal pollution.
Thermal pollution increases metabolism and decreases dissolved oxygen in aquatic systems and may interfere with reproduction and migration of some species.
Power plants are the major sources of thermal pollution.
A sudden, dramatic change in water temperature is thermal shock; this can be fatal for many organisms.
Groundwater Pollution
Effects of Groundwater Pollution
Groundwater is subject to contamination from a variety of surface sites and activities.
Common pollutants include chlorides, nitrates, heavy metals, hydrocarbons, pesticides, and organic solvents; many are known carcinogens.
Cleaning Up Groundwater
Since groundwater renewal and recovery is quite slow, prevention is the best method of protection.
Ocean Pollution
Oil in the Seas - Sources include natural seepage, well blowouts, tanker and pipeline discharges, tanker spills, and urban runoff
Biological Impacts of Oil
The effects of oil pollution vary with the amount and rate of release, location, and water temperature.
Reducing the Number of Spills
New tanker designs and operational procedures are aimed at minimizing the risk of major oil spills.
Plastic Pollution
Discarded plastics ensnare, entangle, starve, or suffocate hundreds of thousands of fish, marine mammals, and birds yearly.
Medical Wastes and Sewage Sludge
Illegal dumping of medical wastes and legal and illegal dumping of sewage and sewage sludge have caused environmental damage and pose a serious human health threat. Legislation aimed at stemming these practices has been enacted.
Red Tide
Outbreaks of microscopic and often highly toxic algae appear to be on the rise worldwide. These outbreaks may be caused by an increase in inorganic nutrient pollution from agriculture, industry, and the human population.
The Case of the Dying Seals
Massive seal die-off in the late 1980s caused by a virus may have resulted from immune system suppression caused by a common pollutant, PCBs.
Water Pollution Control
Legislative controls
The Clean Water Act primarily regulates point source pollution
Though enhanced sewage treatment can effectively reduce point source pollution, these gains are often offset by increasing nonpoint source pollution.
Controlling Nonpoint Pollution
Zoning ordinances, soil conservation programs and other legal requirements can help reduce nonpoint source pollution.
Preventing Groundwater Pollution
Many states, under EPA advisement, have developed programs to protect groundwater supplies through zoning and discharge regulation.
Water Pollution Control Technologies: End-of-Pipe Approaches
Primary Treatment
Primary sewage treatment consists of mechanical screening and settling and removes large objects and solids.
Secondary Treatment
Secondary sewage treatment utilizes microorganisms to digest biodegradable organic matter.
Tertiary Treatment
Specialized filters and processes can remove chemicals left by secondary treatment; however, such tertiary sewage treatment is costly.
Use of holding ponds, land disposal, and other innovative techniques can further reduce pollution from sewage treatment systems.
Sustainable Solutions
Pollution prevention through conservation and recycling combined with new approaches for waste utilization and restoration to address existing pollution problems comprise the basics of a sustainable water pollution management system.
Each of us can take steps to minimize our personal contribution to water pollution problems and to minimize our overall environmental impact.
Suggestions for Presenting the Chapter
Ÿ A visit to your local water treatment facility and sewage treatment facility are excellent ways to study how our public systems work.
Ÿ Instructors should emphasize the effectiveness and necessity of personal action in reducing our environmental impacts. The end of the chapter contains some excellent suggestions in Table 22-6 that can be discussed in class.
Ÿ The importance of nonpoint sources of pollution should be discussed. The potential impacts of agriculture on water quality are particularly important. The relationship between farming practices/soil conservation and water quality should be stressed.
Ÿ An examination of local groundwater contamination is always interesting. Your state agencies can provide useful information about the water in local aquifers.
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