Sewage Treatment Year 4 7 Lesson Plan

Transcription

1 Lesson plan Sewage Treatment Year 4 7 Lesson Plan If this lesson is the second in a series of lessons presented by Council, replace the shaded area with the Summary Quiz. Time Activity Lesson Equipment 1 Introduction: My name is.. Moreton Bay Water (part of Moreton Bay Regional Council) MBW Responsibilities (see below) What we are talking about today (see below) 1. Summary Quiz MBRC Responsibilities Council look after roads, rubbish collections, animal control and a large part of our work is water and sewerage. MBW Responsibilities Moreton Bay Water looks after water and sewage. We make sure that when you turn on the tap nice clean water comes out and that when you flush the toilet that all of the waste is taken away and cleaned (treated) before it goes back into the natural water cycle. We make sure nobody is using too much, or more than their fair share of water to make sure we don t run out of water in the future. We work with businesses that use a lot of water to make sure they are saving and recycling as much water as they can. We enforce the water restrictions that are written by the Queensland Government and these apply to both households and businesses. We teach people how to save water because it is very precious. We give presentations to community groups, teachers and students just like what I m doing today. To show how important our water and sewerage netwok is. What we are talking about today Today we will be talking about sewage. We will discuss where water comes from, where sewage comes from, how sewage gets to the sewage treatment plant, what is in sewage, and how Council treats sewage to make it clean enough to reuse or put back into the water cycle. Sewage is water that we have finished using in the laundry, bathroom, kitchen or toilet that enters the sewer through the drain in your sink or by flushing the toilet. Sewage comes from homes and from industry, businesses, shopping centres, schools etc. 1 Importance of Water OK, so how have you used water today?. RESPONSES What have you put into the sewer today? Sewage treatment Year 4-7 Lesson Plan Page 1 of 10

2 RESPONSES Conclude: Water is very important. It is vital for us to survive and to live the way we want to. We use a lot of water each day, and the amount of water we use is directly related to the amount of sewage we produce. Also, water is also used in places you wouldn t even expect. Water is used to make everything we own and use, like the tables and chairs in this classroom, making the carpet, making a burger or making clothes. So factories and businesses also produce sewage, the water they have used to clean and from their toilets/kitchen, etc. 1 Natural Water Cycle Overview Show students a picture of a dinosaur drinking water. Explain that this could be exactly the same water we drank this morning! 3. Dinosaur drinking water picture. Can anyone tell me why? Show students a picture of the Earth from space. The Earth has the same amount of water on it as it did at the time of the dinosaurs, it just gets cycled around and around in the water cycle. We cannot get any more water. Explain that we can t just get more water from outer space, so we have to look after our water sources. This is one of the reasons we clean sewage before we let it flow back into our waterways. 2. Picture of Earth from Space The Earth has the same amount of water on it as it did at the time of the dinosaurs, it just gets cycled around and around in the water cycle. Show students the DERM Natural Water Cycle poster to explain the processes involved in the natural water cycle e.g. (The sun heats up the water on Earth and some evaporates. Once the water vapour gets high up in the sky it cools and forms a cloud with lots of other water vapour particles. Once the cloud becomes full and the water droplets become very heavy, the water droplets fall to the ground as rain to begin the cycle again, water transpires from trees, water from underground becomes part of the cycle again etc.) Tell students you are leaving a copy of this poster for them to investigate further later. The problem now is that despite there still being the same amount of water on the planet as there was when the dinosaurs roamed, there are more people living here now than there were dinosaurs in the past. Plus, because we use water to make almost everything we use throughout the day, it is obvious that humans use a lot more water than the dinosaurs did! 37. DERM natural water cycle poster.. We also need to realise that the population in the World is increasing, putting additional strain on water resources. Closer to home, the situation is even worse! The population in SE Queensland is increasing very rapidly, faster than most other places in the World, and our water needs will double by Therefore we need to make sure that there is enough water available for everyone to share. It is especially important for Australians to save water whenever we can because Australia is the driest inhabited continent on Earth (explain). We have long periods of time when no rain falls (called droughts). And because the ground is usually so dry, when the rains come it seeps into the soil for a long time before it eventually runs off into the dams. Another problem we face is that we don t live where the most rain falls. North Queensland is a lot wetter than SE Queensland, but many more people live down here. Similarly, there are variations in SE Queensland, for instance Toowoomba and Brisbane are drier than the Gold Coast or Sewage treatment Year 4-7 Lesson Plan Page 2 of 10

3 the Sunshine Coast. That s why we now have a water grid in SE Qld so that we can link all the dams together to supply water to where it s needed. This is part of the urban water cycle. So, with all these problems combined, we always need to be saving water and storing it in our dams, even if it is raining or the dams are already quite full. We never know when the next drought will come or how long it will last for, but we do know that we all need to use clean water every day for survival, to keep ourselves and our belongings clean, and to have all the things we want and need. 3 Urban Water Cycle overview Discuss how humans need to interrupt the natural water cycle to ensure that we have the quantity and the quality of water we need each day and so that we can clean up our sewage before we discharge it back into the river. 89. Total water cycle management poster Using the DERM Poster (Total water cycle management) explain that water has to be treated before it comes into homes. A lot of energy and money goes into getting clean water to homes including the building and maintenance of dams, maintaining water quality in dams, maintaining/laying pipes, water treatment, the cost of chemicals etc. This is another reason why we have to be very careful with water. Water that comes out of the tap is not free and as we use more water it becomes more expensive. Then, once we have used the water, it has to be pumped to a sewage treatment plant to ensure it is cleaned to a standard that is acceptable for people to reuse (generally for watering sports ovals, golf courses, public gardens or for road construction) or to be discharged into the local river. 4 Water, sewage and stormwater infrastructure Photos of: Dirty water can make us very ill because it can spread disease. This was the primary reason why people, up until the 19 th century, had much shorter life spans. Similarly, nowadays in countries less developed than Australia, which don t have the same level of water and sewerage services, people tend to die younger often because of water borne disease or simple lack of sanitation (explain that by this we mean they lack the water/sewerage network required to provide them with clean water to drink and to use for cleaning, and the facilities to flush away human waste). Therefore, we are very lucky that we have a whole network of systems underground (that you can t see) that are helping to keep us healthy. We will quickly discuss this water and sewerage network before we move onto discussing sewage treatment because it is important you understand that sewage treatment is only one part of a network that Council operates. Show students the photo of a water treatment plant. Demonstrate using the picture of a house that drinking water comes in through an underground pipe and that sewage leaves via an underground pipe to be taken to the sewage treatment plant. Water: Explain that underground pipes bring clean drinking quality water to their houses, and on the pipe that comes into their house there is a water meter. The water meter is in the front yard or on the footpath on one side 16.WTP photo. 17. WWTP photo. 24. Picture of house. 11. Water meter box 12. Water meter Sewage treatment Year 4-7 Lesson Plan Page 3 of 10

4 of the yard. The water meter ticks around like a petrol pump when water is used in the home, so Council reads the meter to determine how much water has been used and how much to charge the homeowner. Show students the photos of the water meter box and water meter showing the reading. Stormwater: Show students the photo of the car washed off the road. Ask: What type of water is this? Where did all this water come from? Explain that this is called stormwater. Stormwater is the rainwater that we see flowing down the streets and off our gardens when there has been a storm. Because this water is so unpredictable and because it often falls very fast we can t catch it all and most of the water flows into stormwater drains and is taken directly to the local rivers without any treatment. This means it is vital that we don t drop litter and that we clean up after our dogs because anything that is on our lawns, the footpaths or the roads will get washed straight into the rivers and then the sea. Litter and harsh chemicals used on gardens or lawns harms the fish, birds and plant life that live on riverbanks and the coastline. Show students the photo of a stormwater drain. Mention the lizard and show that he lives there. Also mention that there is other infrastructure designed to control and direct stormwater during times of flooding. Show photo of culverts. Explain that stormwater and sewage are different, because sewage is treated before being discharged to nature, while stormwater is not. 13. Car washed off road 15.Stormwater drain 14. Stormwater culverts/drainage channels. Sewerage: Explain that the sewage flows into underground pipes and is pumped to the sewage treatment plant where it is cleaned so that we can use it again (building roads or watering golf courses), or put it back into a river as part of the water cycle. Explain that manholes are the lid to a hole that leads down into the sewerage system. Manholes should be available for Council to access at all times. Manholes should be available for Council to access at all times. Cars should never be parked on top of manholes and manholes should not be hidden in gardens. If something goes wrong Council needs access quickly to prevent sewage backing up into houses. Sewage can back up through the shower or outside drain if there is a blockage. 10. Sewer manhole Only authorised and trained personnel should ever enter a manhole. Explain that pump stations are needed to pump sewage up hill, and if students see the light on a pump station flashing they should get an adult to call Council as soon as possible. The flashing light indicates there is a problem like a broken pump that needs to be fixed quickly before the sewage spills out. 9. Pump station Tree roots can break or block sewer pipes causing big problems for Council. But, lots of problems are also caused by people putting silly things down the toilet or drain and it will become clear, as the lesson progresses, why certain items can be a serious problem for the sewerage network. If you learn one thing from this lesson, let it be: Nothing but toilet paper and what comes out of you should ever go down the toilet. Sewage treatment Year 4-7 Lesson Plan Page 4 of 10

5 1 What is sewage? Let s think how much water we put down the sewer. A four minute shower 4 buckets, and the water is not very dirty, just soap and the dirt from our bodies. Full flush of a single flush toilet more than one bucket, again a lot more water than waste. Leaving the tap running for a minute - a whole bucket, could be perfectly clean. Leaving the tap running when you brush your teeth - more than two buckets, again very clean, just a bit of toothpaste. So, when you think of this quantity of water going into the sewerage system, how much do you think is actually dirt/waste? RESPONSES 99% water, 1% true waste. But, it s all mixed together. In 200L (almost a wheelie bin) there is only the equivalent of 1 tablespoon of dirt/waste. 3 What is in sewage? What kind of things could be in the sewers? Have any of you tried poking things down the drain, or flushing things away that you shouldn t have? RESPONSES Sewage from homes contains waste from us going to the toilet but also shampoo, laundry detergent, chemicals from household cleaning products. Sometimes things get dropped down the toilet by accident, things like mobile phones, keys or glasses and these should be taken out and not flushed away! Some people put paint, oil, nappies, baby wipes, cotton buds and even prawn shells down the toilet - This is bad! The toilet is not a bin. Sand, grit and stones can get into the sewage system during maintenance works. Only waste from us and toilet paper should ever go down the toilet 74. Picture of sewer and stormwater infrastructure underground. How did I say sewage got to the sewage treatment plant? RESPONSES Pumped through pipes. So anything big or hard, or that takes a while to decompose/breakdown can block up the pipes. Causing sewage to back up through showers and outside drains in nearby houses. Secondly the pumps. Anything solid that should not be put down the drain or toilet can get caught in the moving parts of the pump. This can damage or destroy the pump, and can cause a blockage meaning that sewage can again back up. The pumps are expensive to repair Some large objects do make it through the pipe system and into the sewage treatment plant. They can then damage the screens at the sewage treatment plant. Nothing but toilet paper and what comes out of us should go into the sewer! There are other things in sewage that are too small for us to see. They include: Sewage treatment Year 4-7 Lesson Plan Page 5 of 10

6 Phosphates (come from cleaning products) Nitrates (come from cleaning products and our urine) Chemicals such as bleach. Bacteria Virus Salts. It is important for sewage treatment to remove the phosphates and nitrates from the sewage before it is discharged because if these nutrients are not removed during sewage treatment, and enter the waterways, they can cause an algal bloom. (Algal blooms can cover the surface of the water and stop the sunlight entering the water. This means the water plants can t produce oxygen for the fish meaning that the fish, plants and other living organisms in the waterway die.) Explain that sewage is cleaned using a natural process at the sewage treatment plant. It is very convenient that the tiny bugs (bacteria) that live in our stomachs, and that are flushed to the sewage treatment plant, thrive on these nutrients and can do a lot of the treatment for us. But, if strong chemicals are flushed into the sewer these can kill the bugs meaning the sewage is not treated as well as it could be. Show students the photos and props of what not to put down the sewer. Explain that these are things that are often found in sewage but shouldn t be. 7. Photos of what not to put down the sewers. Go into some detail about what should be done with common items that end up in the sewer to increase meaning for the students. E.g.Tell students to pull the hair out of the drain and put it in the bin rather than poking it through the drain or throwing it into the toilet. The same applies when cleaning a hair brush. Explain that hair from lots of people can get all caught up in the machinery and is difficult to remove. Explain that once the person who s cooked using oil is finished, they should let it cool, pour it into a container and put it in the bin rather than putting it down the sink. Reiterate briefly why each should not be put down the sewer. Industrial sewage. I also said that sewage comes from industry. Do you think all industry would have similar things to homes in their sewage? RESPONSES There would be some similarities but there could be a lot of extra things like chemicals from manufacturing processes etc. The sewage from industry is often called trade waste and it is sometimes required to be treated before we allow it into the sewerage system. Sometimes, if the sewage contains sugar or other nutrients that the good bugs/bacteria like to eat at the sewage treatment plant, we let it enter the system. 5 What would happen if we didn t treat sewage? Choose the most appropriate set up for class: Quiet thinking (30 secs) Think-pair-share (alone, with partner, with 2 others) (1min/1min/1min) Group work (3 mins) 75. A3 laminated sign What would happen if we didn t treat sewage? Ask students to think of the environment, social issues, health, recreational etc. As many things as possible that would result if we didn t treat sewage. Sewage treatment Year 4-7 Lesson Plan Page 6 of 10

7 Teaching Hint: Place a sign on the board or write on the whiteboard What would happen if we didn t treat sewage? so that you can silently redirect students who drift off task. Listen to the class to determine if they ve understood the question. Re-iterate if necessary. RESPONSES illness, disease, wouldn t be a nice place to live, lots of pollution, waterways would be very unhealthy, animals, birds and people would end up dying. Not nice socially, dirty, smelly, no nice water to play on such as rivers, sea would be dirty. Conclude: Treating sewage is very important. Historically treating drinking water and sewage has saved more lives than medicine. 1 Why does Council look after sewage treatment? This has shown us how important treating sewage is. Therefore, there are some good reasons that Council looks after sewage treatment: Council can check that everything is working properly and meeting set standards. We have full-time staff devoted to looking after the treatment plant meaning the treatment process is reliable and hence safer. Council takes on the associated responsibilities. Individual treatment is impractical in suburban areas with limited space, plus homeowner s treatment systems may not be maintained properly meaning they could become smelly and hazardous to health. Some students may have septic tanks, BIO plants or other systems. Ask them to discuss pros and cons. Note that these systems are only permitted on large blocks with the space to treat sewage. And the treated water can only be reused in certain ways away from the house. 13 Group Activity How do you think we should treat sewage? Tell student you ve given them lots of hints how we treat sewage. Explain that students will work in groups to discuss how they would get each of the different types of dirt out of the water, ask them to write their answers on the worksheet. 69. A class set of bottles with all ingredients. 71 Sewage treatment worksheet. Give each group a bottle of dirty water (water + mud, some settled, others not) and a sewage treatment worksheet. In place of the label on the bottle, there should be a sticker saying what is in the bottle. Cotton buds, stones, mud, nitrates and phosphates, bacteria & virus, oil, salt. Give students 3 minutes to discuss and write responses. While students are discussing write cotton buds, stones, mud, nitrogen and phosphorous, bacteria & virus, oil, salt labels in a list on the board. Get the responses from each group. Write up the responses. Explain how the students own ideas are incorporated into the real life process. 2 Sewage Treatment. Poster of relevant Sewage treatment Year 4-7 Lesson Plan Page 7 of 10

8 Show students on the schematic poster the series of processes the sewage goes through taking from homes and industry, the pump stations, through to the treatment process. Sewerage System. 73. Schematic diagram of processes. Explain that the sewage is treated physically, biologically and chemically. We take the big or solid objects out first. First by filtering with large sieves and then by letting them settle out. The oils float and we scrape them from the top. Then we let the micro-organisms from our stomachs remove the nutrients. Then we settle out more of the waste and finally treat with chlorine and other disinfection processes e.g. UV or Ozone. In some sewage treatment plants we treat the water even more by filtering out really small particles (so small we can t see them). This is called advanced sewage treatment. 2 Physical Treatment The things in sewage vary in size and therefore vary in how easy they are to remove. The treatment depends on the size of the thing being removed. Big things like plastic, nappies, materials etc can be caught using screens, therefore screens are the first step in WWT. Grit removal is the next step (centrifugal force in a round tank).grit passes but can be caught because it is heavy. Get a student to swing the tennis ball on the string. Ask them if they feel the ball pulling at their hand. The ball is doing the same as the grit would if it was swirled around. So the grit goes to the outside of the round tank and is fed out the bottom of the tank because it is heavy. Soil and mud, called Suspended Solids are easily taken out because they settle. Put mud in water bottle and shake. Add coffee to water as a comparison with soil. We also can add chemicals that help join the really small particles together so they become heavier and sink. Then the sludge is scraped away. Show students at the end of the demonstration how the mud has settled because it is heavy but the coffee hasn t because it has dissolved into really small particles. Fine sand and hair get caught in particle filters. This is the limit that we can actually see and the limit of normal sewage treatment plants. However, advanced sewage treatment plants remove really tiny particles and organisms that are so small they are impossible to visualise. Show students 1 millimetre on a ruler. Ask them to imagine the mm divided into 100, then 1000, then a million, then 10 million, too small for anyone to imagine and far too small to see. Only powerful microscopes could see things this small, but in some sewage treatment plants they manage to take out particles of contaminants this small. 81. Sign saying Physical Biological Chemical 82. Bottle, water + mud. 83. Bottle, water + salt. 77. Bottle, water + coffee. 78. Bottle, water + oil 84. Poster with examples of things in sewage stuck on, their names and the level of filtration required. 72. Ruler. 76. Tennis ball n string (dog toy). 84. Poster of things in sewage. Refer to poster and show how much of the treatment is invisible. Don t need to mention all the names, just give students the idea of just how small these things are as they often ask. Bacteria caught in micro filters. 1mm/100 Sewage treatment Year 4-7 Lesson Plan Page 8 of 10

9 Clay, in microfiltration. 1mm/10000 Virus in ultrafiltration. 1mm/100,000 Sugar in nanofiltration. 1mm/1,000,000 Salt in reverse osmosis. 1mm/10,000,000 Explain that salt is the most difficult thing to remove from sewage or water because it is so small when it dissolves. Show students the bottle of water + salt. Explain that it has dissolved and that it would be really difficult to remove. What we must realise is that even though water looks clear it can still be very bad for us, so never drink untreated water just because it looks clear. Some things that can harm us are too small to see. Ask students what type of water contains a lot of salt? Desired response seawater. That s why using sea water to make drinking water is really expensive and uses a lot of energy. Also the waste product (the salt they remove) is very concentrated and difficult to dispose of. Plants that do this are called desalination plants. There is one on the Gold Coast. But if we are treating sewage only for reuse that we will not be drinking, we don t need to treat it to this level. 2 Biological Treatment. We need to remove nitrates and phosphorous from the sewage as these are particularly harmful to the environment. These are molecules that look like this. We do a lot of filtering, scraping, settling but the stars of the show are the bugs that live in your stomachs!! We value these little bugs/bacteria so much we give them their own little houses at some sewage treatment plants (Cab only) to encourage them to multiply. We also give them food, and just the right amount of oxygen to keep them alive whilst still making them need the nutrients that we require them to use up. 85. Plasticine nitrate model with oxygen and nitrogen atoms. 86. Denitrification beads. The bugs/bacteria in sewage get rid of nitrates by using the oxygen from the nitrates meaning the nitrogen gas is released into the atmosphere (demonstrate pulling the oxygen off the plasticine nitrate model). The air around us is mostly nitrogen so this is not a problem. The sewage is kept anerobic (meaning there is no oxygen in the sewage) which means that for the micro-organisms to survive they need to use the oxygen from the nitrates, which converts the nitrate into nitrogen gas. Compare chemical name with H 2 0, nitrate is nitrogen atom plus three oxygen atoms. There are lots of processes that are too small for us to see. 1 Chemical Treatment Chlorine is added as a final disinfection before being released to the environment or used by recycled water users. Chlorine does not stay in the water for a long period of time so some plants use Ozone and UV treatment to reduce chemical use in water that is being discharged into the waterways. 1 End of treatment Sewage treatment Year 4-7 Lesson Plan Page 9 of 10

10 Once the sewage is treated it can be used by water carters for dust suppression and some irrigation, it is also piped to some golf courses and sporting grounds for irrigation. At some of our treatment plants, further treatment occurs to make the water even safer where it is then used for industrial purposes and it is piped to some new homes for irrigation and car washing. The remaining unused water is released into the local waterway where it returns to the natural water cycle. The sludge that has been removed from the bottom of various tanks during the treatment process is put on conveyer belts and squashed to squeeze out all the water (called dewatering). This dried sludge is taken away in trucks and used for composting in locations where this is allowable. The sewage would have to be treated a lot more, with much finer filters and very complex technology if it were to be treated to a drinking quality water. This is not the type of sewage treatment being discussed today. 1 Summary So you can now see that treating sewage is quite complicated and costs lots of money. The treatment plant operates 24 hours a day 7 days a week, to ensure that our sewage is treated before being re-used or released back to the natural water cycle. We need to remember that the more water we use inside (at home and school), the more sewage is produced. So by saving water, we also save unnecessary sewage treatment. Therefore, if we save water, we are not only protecting this valuable resource, but we are limiting the water that flows to the sewage treatment plant, saving money and the environment. Ask students to sum up the other reasons why we need to save water. Make sure the following are highlighted: To save money homeowners, Government (water treatment), Councils (infrastructure maintenance). To protect the environment leave water for nature, to prevent new dams, to save energy for unnecessary treatment. To make sure there is water available for droughts and future generations. Ask students to share one new thing they ve learnt about water or saving water during the lesson. 1 Conclusion Any questions? Explain that you have left worksheets for the students to complete later to help them remember what has been talked about today. Tell the that there are brochures for everyone to take home and discuss with their family including a mini buckets poster and information on how to work out how much water your family uses by reading the water meter. Thank students and teacher. Sewage treatment Year 4-7 Lesson Plan Page 10 of 10