ECOLOGY AND THE CONSERVATION OF NATURAL RESOURCES
|Energy Resources and Demands
|Science in Society
||Societal Needs 4.4c
To develop an understanding of the interdependence of all organisms and the need for conserving natural resources
An adequate and continuous supply of soil, water, air, and energy are essential to the survival of living things.
Ecology O2.00 To understand methods of preserving water quality
INSTRUCTIONAL OBJECTIVES: The learner will:
2.01 List ways point source pollution can be abated.
OUTLINE OF CONTENT:
2.02 List ways non-point source pollution can be abated.
2.03 List ways fresh water supplies can be enhanced.
I. Abatement of point source pollution
A. Waste water treatment
II. Abatement of non-point source pollution
B. Treatment of industrial waste
4. Removal of chemicals
1. Handling hazardous waste
C. Water supply treatment
2. Disposal of toxins
a. Isolation from environment
3. Source reduction
b. Destruction or conversion
a. Using waste audits to pinpoint sources
4. Reduction at household level
b. Preventative steps
1. Suspended particles settle
2. Send filtered
3. Alum and lime added
5. Charcoal filtration
III. Enhancement of water supplies
B. Ground water protection
2. Urban land development
3. Toxic waste accidents
1. Install water saving devices
2. Check plumbing
3. Good water use habits
a. Shorter, lighter showers
b. Flushing toilet less often
c. Washing only full loads of clothes and dishes
d. Watering garden and lawn only as necessary
C. Cloud seeding
D. Dams, water sheds, collection basins
E. Water from icebergs
COMPONENT OF SCIENCE: Science in Society
To enable students to demonstrate positive attitudes toward science in solving problems and making personal decisions about issues affecting the individual, society and the environment.
4.4 SOCIETAL NEEDS - Science establishes the basis for applying technology to needs within a society.
STANDARD: The learner will understand that:
4.4c - Science and technology may produce changes that affect society and groups within societies.
BENCHMARK: Technology throughout history has been a product of human culture. Access to any given technology may greatly impact socio-economic lifestyle.
Two instructional periods
Speaker from the Soil and Water Conservation District, local maps of county
When you flush your toilet or let out your bath water where does it go? (pause) It depends on whether you are connected to a sewer system. Today we are going to talk about what happens to a city or town wastewater. When you turn on a faucet where does your water come from? (pause) Again it depends on if you are connected to a community water supply system. We are going to learn what is done to water before we get it.
Water that has been used by homes, hospitals, and schools contains food residues, human excrement, paper, soap, detergents, dirt, cloth, other miscellaneous debris, and microorganisms. This mixture is called domestic sewage. This water may also be joined by run-off water from rain. These waters flow through a network of sewage pipes and follow either of two paths: 1) It can be returned to surface waters without purification (raw sewage) 2) It can be piped into a sewage treatment plant where it is processed.
The first stage, or primary stage, allows the water to pass through large screens where large objects are removed. It is then held in settling tanks where heavy suspended solids can settle out.
Secondary treatment involves getting rid of the organic matter and other impurities remaining that do not settle and cannot be easily filtered. This process is done with accelerated biological action. One method is the trickling filter. Long pipes rotate slowly over a bed of stones, distributing the water in continuous sprays. As the water trickles over and around the stones, it offers its nutrients in the presence of air to an abundance of different forms of life. A fast-moving food chain is set in operation. Bacteria consume molecules of protein, fat, and carbohydrates. Protists consume bacteria. Farther up the food chain are worms, snails, flies, and spiders. An alternative technique is the activated sludge process. After primary treatment, the sewage is pumped into an aeration tank, where it is mixed with air and bacteria-laden sludge. The biological action is similar to that of the trickling filter. The treated water then flows to a sedimentation tank where bacteria laden solids settle out.
The water is still laden with bacteria and chemicals and is not fit for discharge, let alone drinking. The final step in the disinfecting process is chlorination. Chlorine gas injected will kill 99 percent of the harmful bacteria.
Tertiary or advanced treatments deal with the pollutants and excess chlorine still in the water that must be eliminated. One method is called flocculation. Lime, alum, and some salts of iron are added to cause the inorganic particles to stick together, creating large enough particles that eventually settle out. Another method is absorption. This is the process by which molecules of a gas or liquid adhere to the surface of a solid. The solid used is carbon, which is particularly effective in removing chemicals that produce offensive tastes and odors.
The Clean Water Act of 1972 requires that all communities that are served by sewage treatment plants treat their wastewater through the secondary treatment stage. Some communities are satisfied with meeting EPA standards, but others choose to bear the cost of further treatment in the interest of producing cleaner water.
The final step in sewage treatment is disposal. Most communities discharge their treated wastewater into nearby waterways, while mm dispose of their wastewater on land to utilize the natural filtering action of the soil.
Industries that must dispose of polluted wastewater have three possibilities. They may be treated separately from the municipal waste and discharged into the waterways. They might require separating the toxins from the water and disposing of them separately or destroying or converting the toxins. Raw wastewater may be discharged to the municipal plant for complete treatment. This would involve making sure the municipal facility could handle the operation. The industry would be responsible to make sure no problems would occur because of changes or accidents in the water the municipal would be receiving. The third choice is for industries to pro-treat their waste. Facilities for pretreatment of industrial wastes are frequently an integral part of plant design.
There are approximately 240,000 public water supply systems in the United States. Where do you get your water? The Safe Drinking Water Act of 1974 requires that public suppliers of drinking water meet standards for physical, chemical, biological, and radio-active components. Since most ground water is sufficiently pure, it requires only chlorination before it is distributed. Surface water is generally stored for several days in a reservoir to allow the suspended materials to filter out. If additional treatment is necessary the steps are similar to waste water treatment. Sand filters remove algae and bacteria. Suspended materials are removed through coagulation and settling procedures. The calcium and magnesium that cause hardness in water can also be removed by the addition of alum and lime.
Chlorination then occurs to eliminate pathogens. This is monitored carefully. In some cases chloroorganic compounds such as chloroform may be formed. Since haloforms such as these are known as carcinogens, water supplies are monitored to assure that they do not exceed the EPA limit of 100 ppb (parts per billion). Water supplies that exceed this level must be charcoal filtered.
(Have students list the steps in waste water treatment and water supply treatment).
Independent practice: Have the students draw a schematic of how sewage water leaves their house, arrives at a treatment plant and the processes it undergoes and finally is disposed of in local waterway. (They may need to obtain information from the library or local treatment plant).
This classroom connector addresses Instructional Objective 2.02.
Has anyone ever seen dead fish along the bank of a pond or lake and yet the lake supposedly looked clean? The lake was probably polluted yet there are no visible reasons why. You didn't see raw sewage or chemicals pumped into the water. When sources of pollution come from other hard-to-define areas these are called non-point source pollution. Today we are going to list some ways these non-point sources can be abated.
Pollutants from non-point sources are more subtle and difficult to control than those from point sources because the concentrations are low and the volumes are enormous. Nutrients, sediments, trace quantities of toxic metals and pathogenic organisms are the most common offenders. Requiring control strategies is controversial, because the person who must control the level of pollutants often do not benefit directly from their efforts.
Many lakes across the United States have eutrophication problems that are entirely due to non-point source pollution. Excessive nutrients and sediments comprise the most common type. The loss of vegetative cover commonly increases the rate of flow of sediments into nearby waterways.
Construction sites constitute major sources of pollution in urban areas. Exposed ground should be covered as soon as possible by mulching newly seeded areas and by sodding waterways. Retention basins should be built to trap sediments that are present in the runoff from the construction site. Some cities have passed ordinances that require builders to prepare plans for control of erosion and runoff before new developments can be started. In some areas, developers must submit their plans to county Soil and Water Conservation Districts for approval.
Problems that result from non-point pollution in agricultural areas can be reduced by using conventional soil conservation practices. These practices include strip cropping, contour plowing, keeping livestock out of streambeds, adding riprep (a disordered layer of good-sized rocks to stream beds, and preventing barnyard and feedlot run-off from entering streams by impounding it in small lagoons. Unfortunately, farmers view soil conservation practices as bothersome and expensive. One recently developed farming technique that does offer an economic incentive is the soil-saving "no-till" planting method. (Discussed in detail in 1.04) Another related technique, called minimum tillage, is also gaining acceptance.
Some non-point water pollution problems can be solved by regulating the use of specific chemicals, especially herbicides and pesticides used by farmers. For example, since the EPA banned the widespread use of DDT, the concentrations of that pesticide in aquatic ecosystems have declined greatly.
Ground water is also continually being subjected to non-point sources of pollution. As water slowly migrates downward, it can carry a variety of substances with it. The first step in the management of ground water is to identify ground water flow patterns and recharge areas. Human activities in recharge areas determine the composition of future ground water supplies. Water managers are beginning to recognize that certain practices must be stopped in certain areas in order to protect ground water that is going somewhere else. Pesticides and fertilizers used by farmers in an area where they quickly migrate downward must be monitored or even banned. Farmers are reluctant to change farming practices because they are time-consuming, cut crop yields, and are more expensive.
The contamination of ground water by toxic chemicals is another major problem. Accidental spills from transportation accidents, accidental discharges from plant equipment, and leakage from storage banks are everyday occurrences. The use and indiscriminate disposal of toxic chemicals is also a major problem. The public must put pressure on the chemical transportation industry to insure that they are prepared in the event of an accident and proper disposal methods are being used.
Mining activities contaminate ground water by releasing toxic heavy metals, increasing acidity of water, and changing ground water levels and flow patterns.
To provide adequate future water supplies, each region must determine its own optimal conditions for the use of surface water and ground water.
1. Invite a speaker from the Soil and Water Conservation District to speak to class.
2. Investigate the effects DDT had on the environment.
3. Find out from local Ferner's Co-op or extension service what chemicals are used by farmers in your area.
4. Plot on a local map, areas that in your community might be non-point sources of pollution.
Many water experts believe that conservation is the beat way of ensuring that there is an adequate water supply. Individual conservation can make a tremendous impact. A government study shows that 45% of the water used by the average American family gets flushed down the toilet. That is 90 gallons per day for the family of four. The conventional flush toilet uses 5 to 8 gallons of clean fresh water with each flush when 2 1/2 to 3 gallons is sufficient. Installing a water saving kit or the simple act of putting a space consuming object such as a brick in the toilet, could cut a family's water use by 20%.
Taking a shower in a regular shower contains about 7-9 gallons of water a minute. Installing a water sever shower head could help sow families use 70% less water in the shower. Think how much water could be saved if each person would just cut his shower time by one minute. Leaks should be repaired quickly. Example A faucet that is dripping.
Good water use habits should be a part of everyone's routine. Some simple habits could be to take shorter showers, flush the commode less often, wash only full loads of clothes and dishes, and water garden lawn only when necessary. Can you think of others? (List on board.)
There are people working on ways to increase our water supplies. One method is desalination. Since 97% of all water on earth is ocean, it is tempting to think that removal of salts from seawater might solve some freshwater supply problems. Many methods of desalination exist, but all require great amounts of energy and, therefore, are expensive.
There has also been research going on in cloud seeding. This is the process of injecting nucleesting agents into clouds to trigger precipitation. There are many problems with this procedure. First, not all clouds can be successfully seeded and second, scientists do not clearly understand the exact conditions that trigger precipitation formation. Conflicts also arise concerning the effects of precipitation in areas. For example, people along the Colorado River could benefit from added precipitation. It would increase their water supply, increase hydroelectric power supply, and increase economy based on the ski industry. But if the snow were thicker and longer lasting, this would reduce the amount of land available for cattle and sheep grazing, shorten the growing season, increase danger of avalanche, and make road travel more difficult. Moreover, rainmaking by cloud seeding may merely redistribute fixed supplies of rain; thus increasing precipitation in one area and decreasing in another.
Has anyone ever been in a large dam? Dams are built to collect water during wet periods and store until needed, to provide water for irrigation, to generate hydroelectric power, and to control floods. Dams are always controversial. There are many pros and cons when a dam is being built. Think of some of these as we list them on the board.
Water sheds where water drains to a man-made collection basin must be carefully planned. The disturbing of a natural water could cause serious problems during heavy rains. Collection basins must be carefully located so as not to cause problems elsewhere.
The water from icebergs is pure. Why could we not drag an enormous iceberg to southern coastal areas where it could melt and provide fresh water? There have been studies done, but as of now the towing and handling the Antarctic "monsters" is still impractical.
Independent practice: (Have students monitor the water they use in their homes in a single day. Working individually or in teams, students can decide which uses are measurable and develop ideas for monitoring. Some suggestions are: measure water we use to brush teeth, wash hands, or take a shower by closing the drain and determining the amount used by a measuring cup or gallon milk container. Water all plants in house and keep track of how much used. Fill gallon jugs and label them "cooking only", then determine how much was used at the end of the day. Student should look for other water uses. Give them this list to add to their estimates: dishwasher - 25 gallon per load; washing machine - 20 gallon per load; shower - 7-9 gallon per minute; toilet - 5-8 gallon per flush.)
List some ways we can increase our water supply.
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