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ลำดับตอนที่ #14 : [[R.S.]]Summary of Science Chapter 12~Freshwater Resources::20.2.08

The Summary of…

Chapter 12::Freshwater Resources

 

Section 1~Water to Drink [[Page.394]]

-          The Earth’s liquid fresh water is found on the surface in rivers, lakes, reservoirs, and aquifer.

-          Our drinking water comes from either a public or private water supply.

·         Most large communities maintain public water supplies, but in smaller communities & rural areas, people rely on private wells for individual families.

-          Water from both public and private supplies often needs some treatment to ensure that the water is safe and appealing to drink.

-          Cloudiness, odor, and color are three factors that affect water quality.

-          Water quality is a measurement of the substances in water besides water molecules.

·         The pH of the water is a measurement of how acidic or basic it is, on scale of 0 to 14.

ð Pure water is neutral, meaning it’s neither an acid or a base, and has pH of 7.

ð The lower the pH, the more acidic the water and the higher the pH, the more basic the water.

·         The level of two minerals – calcium and magnesium – in water is referred to as hardness.

ð Hard water contains high levels of those minerals. It doesn’t suds well when mixed with soap and it also form deposits that can clog pipes / machinery.

ð Soft water contains lower levels of those minerals and it leaves fewer deposits and forms better soapsuds than hard water.

·         Another factor affecting water quality is the presence of disease-causing organism.

ð The coliform count measures the number of Escherichia coli bacteria

ð  The higher the coliform count, the more chance for water to have other disease-causing organisms.

·         The Environmental Protection Agency [[EPA]] has developed water-quality standards for drinking water, which set concentration limits for certain chemicals, minerals and bacteria in drinking water.

ð A concentration is the amount of one substance in a certain volume of another substance.

-          Drinking-Water Treatment

·         The first step in treating water from a lake or river is usually filtration.

ð Filtration is the process of passing water though a series of screens that allows the water through but not larger solid particles. It removes fish, leaves, branches, and trash from the water.

·         In the second step, a chemical such as alum is added to cause sticky globs, called flocs, to form.

·         Other particles in the water stick to the flocs, a process called coagulation.

·         The heavy clumps sink to the bottom in the settling basins and water is then filtered again.

·         The next step is to add chlorine to the drinking water in order to kill disease-causing microorganisms.

·         Sometimes other chemicals are added to the water to kill specific organisms before distributed to homes.

-          From a treatment plant, water goes to a central pumping station and then pumped into an underground network of steel/concrete pipes called water mains.

·         The water mains branch off the smaller pipes and feed into smaller copper/plastic pipes that carry water into houses and other buildings.

-          Water pressure causes the water to move through this system of pipes.

-          The wastewater and the different kinds of wastes in it are called sewage.

-          In many communities, a network of pipes called sanitary sewers carries sewers away from homes.

·         Sanitary sewers are separated from storm sewers, which drain rainwater and runoff from sidewalks, lawns, and parking lots.

-          Most communities treat their wastewater to make it safe to return to the environment.

-          One typical wastewater treatment process is called a trickling filter system.

·         During primary treatment, deposits of fine solids called sludge settle out from the wastewater.

ð Sludge is a useful material that can be treated and use as fertilizer.

ð Sometimes bacteria are added to the sludge to create “activates sludge”. This sludge is mixed into waste water and the bacteria in sludge then break down the remaining sewage in the water.

·         In secondary treatment, wastewater is filtered through a gravel which colonies with bacteria. [[bacteria that I just explained above ar =___=^^^]]

·         Chlorine may be added before releasing the treated water.

-          Some people use the method of septic system to dispose sewage instead of using a tricking filter system.

·         A septic system includes a septic tank, an underground tank containing bacteria that treat wastewater as it passes through.

·         Sludge settles to the bottom of the tank and the remaining water filters out through holes in the septic tank into ground around it.

·         The area around the septic tank that the water filters through is called a leach field.There, the remaining water breaks down naturally in the soil.

 

Section 2~Balancing Water Needs [[Page.404]]

-          A water shortage occurs when there is too little or too great a demand in an area – or both

-          Places that normally get enough precipitation may experience a few years of scare rainfall, a condition known as a drought.

·         Without precipitation to recharge the aquifer, the amount of groundwater in the aquifer decreases and the well runs dry.

-          When the water is used up faster than the aquifer can be recharged, the aquifer is depleted or emptied.

-          Also when too much water is pumped out of an aquifer, the ground above the aquifer can sink or collapse.

·          To prevent collapse we can pump water from wastewater treatment plants or industrial cooling water into shallow ponds that feed the aquifer.

·         Another way is to inject water down wells directly into the saturated zone.

-          Using a resource wisely so that it will not be used up is called conservation.

·         In the home

ð There are many simple ways to conserve water around the home.

ð For example, stop taking shower!!! Hehehe =]

ð For example [[this is the real one la na ^_^]], take shorter showers, turn off the faucet while brushing your teeth, scrub vegetables in a basin of water, keep a pitcher of drinking water in the refrigerator, run washing machine only when you have a full load, etc.

·         In agriculture

ð When water is carried into fields in open canals or ditches, much of it is lost through evaporation, so the farmers found the methods of using pipes to carry the water to reduce the time that water is exposed to the air.

ð Those two methods are sprinkler irrigation and drip irrigation.

·         In industry

ð Reducing water use, recycling water, and reusing water are three major forms of water conservation by industries.

-          People have tried many different methods to make salty ocean water drinkable.

·         The process of obtaining fresh water from salt water is called desalination.

ð One method of desalination, called distillation, is to boil water so that it evaporates, leaving the salt behind. The water vapor is then condensed to produce liquid fresh water.

ð Another method involves freezing the water, which also leaves the salt behind.

ð Still another method is to pump water at high pressure through a very find filter which separates out pure water and returns saltier water to the ocean.

·         An iceberg can also provide millions of liters of pure water that could be piped to shore as the iceberg melted.

 

 

Section 3~Freshwater Pollution [[Page.411]]

-          The addition of any substance that has a negative effect on water or the living things that depend on the water is called water pollution.

·         Water pollution can result from both natural causes and human activities.

-          The substances that cause water pollution are called pollutants.

·         Examples of pollutants are disease-causing organisms like Cryptosporidium, toxic, or poisonous, chemicals and metals, also radioactive substances.

-          A very small amount of the pesticide DDT in water can build up to harmful levels in living things.

-          Over a long time, tiny amounts of certain pollutants that we eat from the fish, which may comes from a pond with toxic chemicals, can build up to levels that can cause illnesses.

-          The major sources of water pollution are human wastes, industrial wastes, agriculture chemicals, and runoff from roads.

·         Each of these sources of pollution can be a point source or a nonpoint source, depending on how the pollution enters a body of water.

ð A point source is a specific source of pollution that can be identified.

Ex. from the pipe

ð A nonpoint source is a widely spread source of pollution that can’t be tied to a specific point of origin.

Ex. the chemicals, sewage, or radioactive materials that flow into a lake/river or seep into ground water

-          Human Wastes

·         In 1854, an English doctor named John Snow discovered the cause of cholera [[a disease caused by bacteria]] outbreak in London. His work showed the danger of releasing untreated sewage into bodies of water that might be used for drinking water.

·         While water treatment usually kills the bacteria some viruses and parasites are able to resist chorine and other water treatment process.

ð So people are often told to boil the water for drinking and cooking after the flood [[during the floods, sewage from the sanitary sewers can pollute the water]]

·         In rural areas, people must be careful where they locate septic tank.

ð If a tank is too near a stream or on a hill, wastewater cam leak into the stream or flow into the area of a well downhill.

ð Wastes from cattle, pigs, and chickens [[win!!!]] can also be a problem because they contribute disease-causing bacteria.

-          Industrial Wastes

·         Chemicals, smoke, and heated water are three types of industrial pollutants.

ð Chemicals

~Some factories release toxic chemicals and strong acids directly into nearby rivers and lakes.

 ~Another problem is leftover. Many industries buried the containers of toxic wastes underground and over years many of them broke & chemicals leaked out, polluting both the soil and groundwater.

ð Smoke and Exhaust

~When coal, oil, and gasolineare burned from the power plants, factories, cars, trucks, buses, the molecules of the gases sulfur dioxide and nitrogen react with water, forming sulfuric and nitric acid.

~The result is rain or other forms of precipitation that are more acidic than normal, called acid rain.

~When acid rain falls, it makes the water to become so acidic that fish and other wildlife cannot survive.

ð Heat Pollution

~Factories use water to cool machinery or metal objects and that warm water can act as a pollutant.

~Warm water released by a factory into a nearby river or pond raises the temperature of the water and harm the living things there.

-          Agriculture Chemicals

·         When farmers spray fertilizer on their fields and rain falls on those fields, it washes some of the chemicals away as runoff.

ð The fertilizers in the runoff are a nonpoint source of pollution

·         The rich supply of nutrients from fertilizers encourages the growth of plants and algae in and around nearby bodies of water.

·         With the addition of fertilizers, the process of eutrophication speeds up [[can u still remember eutrophication? T^T]]

·         Pesticides are chemicals intended to kill insects and other organisms that damage crops. They can be sprayed on crops and then run off.

-          Runoff from Roads

·         When it rains, the oily sheen caused by gasoline and motor oil are washed off along with the runoff.

ð This runoff is a nonpoint source of pollution.

·         Gasoline, oil, and salt [[from the road]] pollutes rivers, lakes and can seep down into groundwater and pollute wells or entire aquifer.

-          Living things in lakes, streams, and wetlands filter out and break down waste materials.

-          Passing through the sand or rock of an aquifer naturally filters and purifies groundwater but it cannot remove or destroy many pollutants.

·         We can clean the polluted groundwater by pumping the water to the surface, sending it though a treatment plant, and returning it to a lake.

-          It is often easier to avoid causing the pollution in the first place than cleaning up the water that already pollute.

-          In the late 1960s, people urged the government to create laws to control pollution.

-          Many recycling techniques that help conserve water also help to lessen pollution.

-          Many kinds of water pollution are so difficult to clean up, the most important place to stop pollution is at its source.

 

 

Section 4~Water as an Energy Resource [[Page.419]]

-          For centuries, people have used the energy of moving water to turn water wheels and run machinery.

-          When the water is moving it has kinetic energy.

·         Kinetic energy is the form of energy that an object has when it is moving.

-          Energy can change from one form to another. If the water’s movement is stopped, all of its energy becomes potential energy.

·         Potential energy is energy that is stored and waiting to be used.

-          Hydroelectric power is electricity produced by the kinetic energy of water moving over a waterfall or a dam.

·         To generate hydroelectric power, engineers build a dam across a river. Water stored behind a dam has potential energy, which is changed to kinetic energy when it’s released.

-          Hydroelectric power plants capture the kinetic energy of moving water and change it into electrical energy

-          Hydroelectric power is clean, safe, and efficient. Although building a dam is expensive, the water is free and is naturally renewed by the water cycle.

-          But hydroelectric plants do have limitations, only certain locations are suitable for building a dam.

-          A fast-moving river is necessary, as is an area that can be flooded to create a reservoir [[hydroelectric plant]]

-          Dams affect all living things in the area around them.

·         Flooding the land behind a dam can destroy wildlife habitats as well as farms and towns.

·         Some organisms cannot survive the change when a fast-moving river becomes still.

·         It prevent fish from traveling to the parts of a river where they usually lay their eggs and young fish are hatched.

·         As a river slows down, it deposits some of the sediments it carries and they can build up behind a dam instead of being carried downstream to enrich the food plain near the river’s mouth.

·         People whose homes of farms are located where a dam’s reservoir have had to face large dam flood that can cover towns and valleys with water, so they need to relocate.

-          For countries that want to build up their industries, hydroelectric power often seems the best way to provide the electricity they need.

-          Besides electricity, dams can supply water for irrigation and help in flood control.

-          In some places, people have suggested building small dams to supply power to a local area. Smaller dams uproot fewer people and do less harm to the environment, while still providing energy for a region to grow.

-          Large dams, on the other hand, produce great amount of power, but they also have a major effect on the land around them.

 

 

Concept Map of Chapter 12

 

Ps₁. The concept map เรียบเว่อร์มากเลย...แถมเรายังไม่รู้ว่ามันจะถูกรึเปล่าด้วย

ถ้าผิดก็อย่าว่ากันนะ TT^TT

Ps₂. If I type anything wrong, kor sorry na ka

 

I know it’s boring to read all the pages

But please think about me before you feel bore

I must read, summarize, type, and proofread blah blah blah for many hours

A lot more boring =____=^^^



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