原版英语RAZ 教案(U) What Happens When You Flush__DS.pdf
When You Flush?Visit www.readinga- for thousands of books and materials.Writing and ArtDraw a diagram of the route sewage takes after a toilet is flushed.Label your diagram and write a step-by-step explanation of the process.Social StudiesWrite a paragraph describing how modern sewerage systems have solved sewage problems of the past.Discuss your ideas with a partner.ConnectionsWhat Happens When You Flush?A Reading AZ Level U Leveled BookWord Count:1,310www.readinga-ORUWritten by Lisa MeltzerWhat HappensWhen You Flush?LEVELED BOOK Uwww.readinga-Where does sewage go,and how is it treated?Focus QuestionWritten by Lisa MeltzerWhat Happens When You Flush?16Glossaryaeration(n.)the process of pumping oxygen into sewage to help break it down(p.8)clarifier(n.)a tank in which solid sewage settles to the bottom(p.9)digester(n.)a large tank in a sewage treatment plant where microorganisms break down solid waste(p.9)drainage an open area of land where the liquid field(n.)waste from a septic tank drains(p.10)effluent(n.)liquid waste(p.11)methane(n.)an invisible,odorless,flammable gas;also called“natural gas”(p.7)organisms(n.)living things(p.7)percolates(v.)trickles slowly through something with small holes or openings(p.11)septic system a system for treating and disposing (n.)of sewage that uses a septic tank and drainage field(p.10)sewage(n.)human waste that is carried away from buildings through a system of pipes(p.5)sewage a place where sewage is cleaned and treatment processed to make it safe for the plant(n.)environment(p.7)sewerage networks of drains,pipes,and pumps systems(n.)that collect water and sewage and carry it away(p.6)16Page 3:This pond at a sewage treatment plant helps bacteria grow.The bacteria in turn break down the sewage.Photo Credits:Front cover:Rasulovs/iStock/Thinkstock;title page:Brett Rabideau/Hemera/Thinkstock;page 3:Phil Degginger/Science Source;page 6:Wissam Al-Okaili/AFP/Getty Images;page 12:Sklifas Steven/Alamy Stock Photo;page 14:Past Pix/SSPL/The Image Works;page 15:Collection of the New-York Historical Society,USA/Bridgeman ImagesData Source:Page 5(chart):DeOreo,W.B.,P.Mayer,B.Dziegelewski,and J.Kiefer.2016.Residential End Uses of Water,Version 2.Project#4309A.Denver,Colo:Water Research Foundation.2016 Water Research Foundation.Reprinted with permission.Illustration Credit:Pages 4,6,8,10:Signe Nordin/Learning AZWords to Knowaerationclarifierdigesterdrainage fieldeffluentmethaneorganismspercolatesseptic systemsewagesewage treatment plantsewerage systemsCorrelationLEVEL UQ4040Fountas&PinnellReading RecoveryDRAWhat Happens When You Flush?Level U Leveled Book Learning AZWritten by Lisa MeltzerAll rights reserved.www.readinga-15In the mid-1800s,experts began to realize that streets flowing with waste were also flowing with deadly diseases.New York began building sewer systems so the waste would have somewhere to go.By 1914,New York City had nearly 850 miles(1,368 km)of sewers.These laid the foundation for our modern sewage treatment systems.Today in the United States,most people take the sewerage system for granted.Waste disappears down toilets and sinks as if by magic,but now you know how it really works.So,the next time you flush,take a moment to appreciate the wonders of the modern sewerage system!Men work in the New York City sewer around 1911.What Happens When You Flush?Level U153Table of ContentsIntroduction .4Where Does Waste Come From?Where Does It Go?.5Inside the Treatment Plant .7The Septic SystemAnother Way to Deal with Waste .10Sewage Through the Ages .12Glossary .16What Happens When You Flush?Level U14As if dumping poop into local rivers wasnt bad enough,some of the night-soil men got lazy.They dumped their carts into the streets.Some people would allow their privies to overflow and wash into the streets.There were no storm sewers back then for the waste to wash down,so it would pile up where people walked and children played.The stench was unbearable.A night-soil crew moves waste in Rochdale,England,around 1870.4IntroductionSWOOSH!You hear this sound every time you flush a toilet.Did you ever stop to wonder where everything that you flush down winds up?Getting rid of waste involves more than just pushing the lever on a toilet.In fact,it often involves a highly complex process.That process can stretch over(or under)many miles in your community.1 Water in the tank and bowl are at their maximum levels.3 Once the tank is empty,the valve closes and the tank and bowl begin to refill.4 Water in the tank and bowl are back to their maximum levels.bowltraptankvalveFirst,the Flush2 When the toilet is flushed,the valve opens,and clean tank water passes into the bowl.Dirty water passes down the trap.13This was a great improvement on flinging buckets of waste out of windows and onto the streets(and sometimes people).However,it polluted the nearby water sources with harmful bacteria that carried deadly diseases.The water made people sick.Over the centuries,sewage management improved little by little.Large cities,such as New York,still had a hard time managing waste,though,even in the 1800s.Because New York City was growing so fast,there were no sewage treatment plants.Sewage piled up all over the city.There were too many people and too much waste!Peoples homes had a privy or outhouse,which was sometimes just a hole in the ground.Since there was no way to flush,human waste would pile up in the hole.When the privy was full,a night-soil man came to remove the backed-up waste.He came at night so people would not have to see him hauling buckets to the street and dumping them in his horse-drawn cart to be taken away.When the night-soil mans cart was full,he would usually dump it in the nearest river.Sometimes the shorelines became so thick with poop that they had to be dug out before ships could dock!What Happens When You Flush?Level U5Where Does Waste Come From?Where Does It Go?Human waste comes in many forms and from many different places.It is all referred to as sewage.In typical households,it is created by using the toilet,taking showers,doing the dishes,washing clothes,and by other activities that make water dirty.The average American turns about 100 gallons(380 L)of water into sewage each day.Many factories use chemicals,some of them toxic,to make their products,and chemical waste becomes sewage,too.Restaurants create waste when they use chemicals to wash dishes or pour grease down the drain.This waste could eventually reach our rivers,reservoirs,and groundwaterthe fresh water we rely on every daymaking them unsafe to drink.What Makes Up My Sewage?This information comes from a 2016 survey that sampled 23,749 homes spread throughout the United States.Toilet24%Shower20%Faucet19%Clothes washer17%Leaks12%Other 4%Bath 3%Dishwasher 1%What Happens When You Flush?Level U12Sewage Through the AgesThink the modern sewerage systems are gross?Think again.The first sewerage systems were built thousands of years ago in places such as ancient Greece and Rome.These early systems were a simple series of pipes and canals.They sent human waste and storm water away from cities and directly into nearby waterways.An ancient sewer canal still remains in modern Greece.6More than two billion people around the globe have no flush toilets or sewerage systems.Most of their waste either piles up on the land or runs into lakes and rivers.This creates dangerous environments full of terrible diseases.In fact,millions of people die each year from diseases that come from untreated sewage.Experts are working hard to solve this problem,but it is a huge task.Fortunately,the sewer pipes in our homes,schools,and stores dont just empty into our sources of drinking water.Instead,in many cities and towns,all of this dirty water swirls down drains and ends up in the local sewerage system.Small sewer pipes join up to form bigger and bigger pipes.Some are so big that humans can walk through them!A boy drinks from a water pipe crossing an uncovered sewage canal.11Both the septic tank and drainage field are located in the homeowners yard.The concrete septic tank is buried underground.Any waste from the home runs straight into the tank.Inside the tank,the solids settle to the bottom and separate from the liquids.The liquids,called effluent,run out through a series of underground pipes into the drainage field and spread into the soil.The soil filters the effluent as it percolates through the ground,naturally removing harmful pollutants before they reach groundwater.The septic tank collects all of the solid sludge,which builds up over time.When there is too much sludge in the tank,the homeowners must have a septic business pump out the tank.What Happens When You Flush?Level U7Inside the Treatment PlantThis large network of pipes carries all the wastewater to a sewage treatment plant.Here,the wastewater is cleaned for reuse.Once broken down,most of what makes up the sewage is safe for the environmentfertilizers,methane,and water.First,though,organisms that can cause disease and other pollutants in the wastewater need to be removed.Not all sewage treatment systems are alike.The type of treatment depends on the location and number of people in the area.One common type of treatment plant,which is often found in areas with lots of people,cleans sewage in the following way:Two Underground Systemscatch basinsewer pipehousehold sewage(toilets,sinks,and so on)storm sewer pipeSewer pipes carry waste to the sewage treatment plant.Some storm sewer pipes carry rainwater to the plant as well.Others carry rain directly to creeks,ponds,and other waterways.What Happens When You Flush?Level U10The Septic SystemAnother Way to Deal with WasteMany homes in rural areas are far apart from each other.Building a sewerage system large enough to service homes so far away from one another would be expensive and impractical.Instead,these homes need another way to manage human waste.Each home sends waste to a septic system,which is a mini sewage-treatment system that serves only one home.It consists of a septic tank and a drainage field.Septic systems send liquid to the soil,which filters it.Solids stay in the tank.septic tankyard or field where liquid is filteredgroundwaterThe Septic System8STEP 1 A big screen(think of a giant kitchen strainer)removes large objects such as rocks,sticks,and garbage so that they dont jam the treatment plants machines.STEP 2 What is left over after the screening process is called sludge,which is thick,dirty water.The treatment plant pumps air into the sludge,which promotes the growth of helpful bacteria a process called aeration.These bacteria eat the sludge and break it down.The tanks many city plants require are huge.San Francisco,California,has a water treatment plant that handles 60 million gallons(227 million L)a day and 250 million gallons(946 million L)on rainy days.1324The Water Treatment ProcessThe four basic steps in this diagram match the four steps on pages 89.9STEP 3 Once aeration is complete,the broken-down sludge is sent to a clarifier.In this machine,all of the solid waste settles to the bottom.The water at the top is sent to another filter that cleans it further.Once its safe,this water can be sent to a local waterwaya stream,lake,or the seaor used to water crops.STEP 4 Meanwhile,the solids are sent to a giant,enclosed tank called a digester.Here,a second kind of helpful bacteria eatsand digestsmuch of the sludge.This process is called anaerobic digestion because the digestion takes place without oxygen.The digester breaks down the solid sludge even further and pulls more water from it.It converts the sludge into carbon dioxide and methane gas.About half of the sludge is converted into these gases.The other half is dried and becomes a material similar to soil.The treatment plant uses methane gas as a source of energy that helps power its machines.The leftover sludge is often used on farm fields because it adds organic matter and fertilizer to poor soils.Other times,the sludge is sent to a landfill.What Happens When You Flush?Level U
