CHILDREN’S WATER FESTIVAL IAWEA PRESENTATION - CLEANWATER HEROES INTRODUCTION (5 minutes) Our presentation title is Clean Water Heroes. Our organization is the Iowa Water Environment Association. We represent people who design, build, supply equipment, operate, monitor, regulate and manage wastewater treatment plants in Iowa. [Have everyone from IAWEA introduce themselves, tell where they work and why they chose their career.] Overview of presentation: (2 minutes) Today we are going to take you on an imaginary tour of a wastewater treatment plant. Each of you will be assigned different roles. Some of you will be different types of wastewater and some of you will be microorganisms. In your assigned roles you will learn about the different treatment processes in a wastewater treatment plant. You will learn what wastewater is and where it comes from. You will also learn how wastewater is treated and why that is important to you! First we need to cover some important basic information, including what wastewater is and why we treat it. Background Information Before We Begin (5 minutes) What is wastewater? [Ask kids for a definition of wastewater] Wastewater is the flow of used water from a community. [Ask the kids what percentage of wastewater is water? Answer: 99.94% is water and only 0.06% is waste that is dissolved or suspended in the water.] [Ask the kids where wastewater comes from in their home. Sink drains, toilet drains, shower/bathtub drains, dishwasher drains, and washing machine drains. [Ask the kids how many gallons they think they each contribute per day to their community’s wastewater flow? Answer 70-150 gal/day or 265-568 liters/day. Give out gummy worms]. [Ask the kids what other sources of wastewater there are: commercial, industrial]
Why do we treat wastewater? [Ask the kids why they think we treat wastewater. Hand out gummy worms.] The goal of most wastewater treatment operations is to produce a stream of treated water that is safe for return to the environment. Through several environmental protection laws, communities are required by law to treat their wastewater before it can be discharged to streams, rivers or lakes. We use treatment plants to do two basic things: 1) speed up the natural purification processes that occur in our streams, rivers, and lakes and 2) reduce toxic contaminants that might otherwise interfere with the natural processes. [Ask the kids what could happen if we didn’t treat wastewater before it entered a stream?] [Ask how many kids like to swim, boat and fish in lakes, rivers or streams] [Ask kids if it would be healthy for them or fish if wastewater was not treated before it entered a stream or lake] How do we treat wastewater? [Ask the kids who knows where their local wastewater treatment plant is located] [Ask the kids who has visited a wastewater treatment plant before] Hand out gummy worms. What happens in a wastewater treatment plant is similar to what happens naturally in a stream or lake. Wastewater treatment facilities are used as supplements to the natural process. In a wastewater treatment plant, bacteria and other organisms consume or eat the wastes, just as in the natural process, but under more controlled conditions. Once most of the wastes have been converted to simpler, more stable forms with the release of energy (known as oxidation) by the bacteria, the treated water can be discharged without harm to the receiving stream. Wastewater from the sewer system either flows by gravity or is pumped into the treatment plant. Treatment usually consists of two major steps, primary and secondary, along with a process to dispose of solids removed during the two steps.
Class Activity-Imaginary Tour of a Wastewater Treatment Plant (15 minutes) 1. Hand out signs to all kids. 2. Gather those that are the waste stream at the head of the plant. Put those that are microorganisms and oxygen into the aeration tank. 3. Starting at the head of the plant, start the discussion that follows. Have operators walk the kids through and decide where everyone should go. Primary Treatment: Physics First. Primary treatment – the objective is to physically remove suspended solids from the wastewater either by screening, settling, or floating. Parts of the process include: Screens, Grit Chamber, and Sedimentation Tank [Have the children walk slowly, single file, into primary treatment. Explain each process and have operators pull children out according to where they fall out within the treatment process. Those that are pulled out should stand on the outside of the green tarp in the area of primary treatment.] Screens remove large floating objects from the incoming wastewater stream. (Pull out rags, wood, plastics, diapers, etc.) Explain that these items could clog pipes and disable treatment plant pumps if not removed. Grit chamber removes sand, grit and gravel by slowing the wastewater flow enough to let these items drop to the bottom of the large tank. Sedimentation tank-removes solids that are too light to fall out in the grit chamber. The suspended solids drift to the bottom of the tank over several hours and our pushed into a large mass by mechanical scrapers and pumped out the bottom of the tank. Floatable substances like grease and oil will float to the top at this point and are removed by skimmers. STOP HERE. Point out the children that have been removed and what they represent. PROCEED with children walking through secondary portion of plant. Secondary Treatment: Biology at Work. [Have the children walk slowly, single file, into secondary treatment. Explain each process and pull children out according to where they fall out within the treatment process. Those that are pulled out should stand on the outside of the green tarp in the area of secondary treatment. Have several of the bugs recycle through to the aeration tank. Discuss microorganisms and the role they play.] Secondary treatment – major goal is to biologically (with the use of microorganisms) remove contaminants that are dissolved in wastewater. During this treatment, air is supplied to encourage bacteria and other biological organisms to consume most of the waste. The waste is converted to gases and cell tissue. The solids are then removed from
the wastewater. The treated water usually passes through a tank where a small amount of chemical (usually chlorine) is added to disinfect (destroy harmful bacteria and disease germs) the treated water. Solids, usually referred to as sludge, are normally processed in three steps- digestion, dewatering and disposal. Aeration Tank, Sedimentation Tank, Chlorination Basin, Flow and Measurement Testing Wastewater flowing out of primary treatment still contains some suspended solids and other solids that are dissolved in water. These suspended solids are a source of food for protozoa, fungi, algae and hundreds of varieties of bacteria. Secondary treatment promotes the growth of millions of microorganisms, bringing them into close contact with the wastewater on which they feed. The operator of a wastewater treatment plant makes sure that the temperature, oxygen level, and contact time support rapid and complete consumption of the dissolved wastes. The final products are carbon dioxide, water… and more microorganisms. Three common types of secondary treatment include: activated sludge, trickling filters, and lagoons. During the activated sludge process, a portion of settled solids (microorganisms and other solids) is returned to the aeration tank to serve as “seed” organisms. The part not needed for “seed” is commonly called waste activated sludge and is sent to a sludge digester for further treatment. The Bugs that do the Work The bugs that do the work cannot be seen without the aid of a microscope. These tiny organisms include bacteria, protozoa and metazoa. Bacteria- they are the largest group of living organisms. They are the recyclers of natural and human-managed systems. Bacteria are single celled organisms ranging in size from 0.2 um to greater than 100 um. Protozoa- means first animals, typically measuring 5 to 1000 um in size, most are visible only with the aid of a microscope. Metazoa-applies to all animals composed of more than one cell. Rotifers and nematodes are included in this group. [Gather all of the signs. Ask kids to identify one thing they learned. Hand out gummy worms to remaining kids.]
Summary (2 minutes) Wastewater treatment plants purify used water from a community so that it can safely be returned to streams, rivers and lakes. Treating our wastewater helps the rivers, streams and lakes stay healthy so that they are a good place for fish and people. Treating our wastewater is important for us to enjoy activities like swimming, boating and fishing. Microorganisms that can only be seen with the aid of a microscope eat the waste and are truly our clean water heroes, along with the men and women involved in the many aspects of wastewater treatment. [Mention the idea of science projects and our interest to team up with students]
