Creating Mini Wastewater Treatment Plants - Activity

Creating Mini Wastewater Treatment Plants - Activity


Student teams design and then create small-size models of working filter systems to simulate multi-stage wastewater treatment plants. Drawing from assorted provided materials (gravel, pebbles, sand, activated charcoal, algae, coffee filters, cloth) and staying within a (hypothetical) budget, teams create filter systems within 2-liter plastic bottles to clean the teacher-made simulated wastewater (soap, oil, sand, fertilizer, coffee grounds, beads). They aim to remove the water contaminants while reclaiming the waste material as valuable resources. They design and build the filtering systems, redesigning for improvement, and then measuring and comparing results (across teams): reclaimed quantities, water quality tests, costs, experiences and best practices. They conduct common water quality tests (such as turbidity, pH, etc., as determined by the teacher) to check the water quality before and after treatment.

This engineering curriculum aligns to Next Generation Science Standards (NGSS).


A photograph shows a hand drawing of a water treatment plant model composed of a clear plastic bottle, rocks, course sand, fine sand and a coffee filter, through which water is poured.A student design for a wastewater treatment plant model.

Engineering Connection

Environmental engineers design wastewater treatment plants to clean water before discharging into rivers, streams, lakes and seas. They use a variety of stages and processes to remove solids and contaminants from wastewater, including biological and mechanical processes. Filters and settling are common mechanical processes used to remove large particles from raw wastewater. The removal of plastic from a water source is a new challenge for engineers, given the fact that plastic is not soluble nor magnetic and varies in its size and decomposition state.

Learning Objectives

After this activity, students should be able to:

Educational Standards 

 NGSS: Next Generation Science Standards - Science
 Common Core State Standards - Math
 International Technology and Engineering Educators Association - Technology
 State Standards

Suggest an alignment not listed above

Materials List 

Each group needs:

To share with the entire class:

Worksheets and Attachments

Wastewater Design Project Info Sheet (docx)

Wastewater Design Project Info Sheet (pdf)

Making Sense Assessment (docx)

Making Sense Assessment (pdf)

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Pre-Req Knowledge

It is recommended that students complete the associated lesson prior to conducting this activity.


As wastewater is deposited into a river, downstream at the next town, drinking water is being pulled from the same river. So, even though drinking water is treated before it enters our tap, wastewater must also be treated and cleaned before it is returned to a river.


A photograph shows brownish, cloudy dirty water spilling from a clear glass gallon jug lying on its side.How do we clean up dirty water?

Let’s take a look at a sample of river water [or show some of the teacher-made “dirty water] and discuss its cleanliness. (Show students the liter of stream, lake, pond or lagoon water. Give them time to discuss among themselves. Facilitate the discussion with the following prompts.) Would you drink it? Is it safe to drink? How is this dirty water related to your drinking water? Do they come from the same place? How would you clean up the dirty water?

Just like you have been doing, environmental engineers ask themselves these questions when they design wastewater and drinking water treatment plants. How do we clean up the dirty water?

Today, you will work in teams to design a way to clean wastewater. Your  engineering challenge  is to use the engineering design process to clean the water as efficiently and inexpensively as possible while also reclaiming contaminants in the water—such as fertilizer and plastics—for reuse.

Each group gets a (hypothetical) budget of $1,000, which mirrors what real-life engineers encounter. They must design and build their projects within a cost constraint. To help with your overall budget, you can sell back any reclaimed materials! Let’s get started!



Similar to the Earth’s natural water cycle—composed mainly of the evaporation, condensation and precipitation processes—urban water goes through its own water cycle (see Figure 1). Water is withdrawn from surface and groundwater sources and sent to water treatment plants. After purification, the water is distributed to homes, businesses and schools. Then, no longer clean, it flows to centralized wastewater treatment plants. At these plants, contaminants and pollutants are removed from the water before discharging the now-clean water into the environment—where it may be collected by another water treatment plant downstream to serve as another community’s drinking water supply. In this cyclical process, all water is reclaimed water.


A drawing shows the cycle of humans obtaining, using, treating and returning water to the environment. On the water supply side, water is withdrawn from fresh water sources and then purified and delivered. On the water disposal side, wastewater is collected, treated and then discharged into lakes, streams and estuaries.Figure 1. In the urban water cycle, water is cleaned and treated as it drawn from fresh water sources AND cleaned and treated before it is returned to fresh water sources.



Wastewater treatment plants vary in their configuration, depending on the contaminants present in the water and applicable treatment regulations. Typically, most wastewater treatment plants are designed with the steps illustrated in Figure 2.


A flow-chart diagram shows the steps of a wastewater treatment process. Wastewater enters the process, goes through grit removal (via grids), solids removal, pre-treatment, aeration, settler, sand filtration, and disinfection. Sludge is removed at the pre-treatment and settler stages. Some sludge from the settler is returned before the aeration stage. Air is introduced during aeration. Figure 2. The steps of the conventional wastewater treatment process.

Most inorganic larger solids (such as trash from runoff) are removed in the grid and solids removal steps while the pre-treatment stage removes larger organic solids. The aeration zone is a form of biological treatment in which carbon and nutrients such as nitrogen and phosphorus are removed and become solids, which separate from the water in the settler. Sometimes, water goes through an additional sand filtration process before finally being disinfected and released as clean effluent. Sludge from pre-treatment and the settler is collected and dried. The resulting sludge may be reused as fertilizer or sent to a landfill.

In this activity, students are challenged to create filtration systems to clean the provided wastewater sample. They focus on the grid, solids removal, and pre-treatment steps.

Before the Activity

With the Students: Project Kickoff, Research and Design

  1. Lead students through the Introduction/Motivation discussion, which presents the engineering challenge. Provide 5-10 minutes for students to also share and discuss their pre-activity group research findings. Explain that their pre-activity homework was step 2 of the engineering design process: researching the problem. 
  2. Divide the class into groups of three to five students each. Have each team obtain a 2-liter sample of the simulated wastewater.
  3. Hand out a water quality kit/tests to each group. Direct students to test the water using the teacher-chosen water quality tests.
  4. How do we clean the water? Direct the groups to move into step 3 engineering design process: imagine possible solutions for how they might go about cleaning the dirty water. Provide students with information from the Teacher Background and Concepts section. Encourage students to use the Internet and other resources to come up with ideas. Hand out the info sheet, which includes a list of the simulated wastewater contaminants.
  5. Ask students to observe the filter material resources the teacher has made available to purify and extract contaminants from the water. Remind students of the goal:  To clean the water as effectively and inexpensively as possible while also reclaiming contaminants for reuse.
  6. Refer to the budget information on the info sheet and quickly review it as a class. Make sure students understand that each team has a budget ($1,000), each filtering method/material has a cost, and that filtering materials and contaminants also have a post-extraction value for reuse or resale. The costs and resale values are reproduced below.

Filtration Material/Method Costs

fine-grain sand = $400/kg

large gravel = $200/kg

small pebbles = $300/kg

activated charcoal = $1,000/kg

algae = $1/mg

coffee filters = $50 each

cotton mesh/cheese cloth $300/m2

Reuse/Resale Value

clean fine-grain sand = $400/kg

clean large gravel = $200/kg

clean small pebbles = $300/kg

activated charcoal = $400/kg

fertilizer= $20/g

plastic = $10/g

  1. Direct the teams complete step 4 of the engineering design process: to each develop a plan to submit to the instructor in the form of a diagram and budget of how the group intends to clean the water. Expect the plan to stay under the budget set by the instructor and use the provided materials. Remind students to consider how much of the materials can be reused. As students are designing their filters, ask them the Investigating Questions.

With the Students: Step 5, 6, and 7 of the Engineering Design Process: Create, Test, Improve

  1. Based on the approved plan and budget, groups collect materials and construct their water treatment apparatuses. Through at least one build-test-redesign iteration, the aim is  to develop a successful filter for wastewater treatment and resource reclamation .
  2. Once the initial water treatment system is built, students begin running the contaminated water through it. Advise students to take time to discuss their observations and make modifications to their designs, as needed. Remind students that any improvements/redesigns must stay within the budget and that unused materials may be sold back to offset expenses.
  3. Students conduct water quality tests on the filtered water using the same available measures and methods used for the initial contaminated wastewater. They collect and weigh the plastic beads to determine how much of the initial 4 grams they reclaimed. They measure the amount of clean water they reclaimed.
  4. Have teams prepare the reclaimed used materials and pollutants for instructor evaluation (and resale) by making small piles of each material.
  5. Direct students to clean up other supplies and turn them in to the instructor.

With the Students: Results and Evaluation

  1. Have students calculate the reclaimed water and plastic beads as a proportion of the initial amounts put in the simulated wastewater.
  2. As a class, have students compare their results about the reclaimed quantities, water quality tests, final costs and value of remaining resources across groups. Also have them share their experiences and best practices.
  3. To conclude, assign students to reflect on their results via the post-activity assessment, as described in the Assessment section.


dissolved oxygen : The amount of free oxygen in solution in water or wastewater effluent. Adequate concentrations of dissolved oxygen are necessary for fish and other aquatic organisms to live and to prevent offensive odors. Abbreviated as DO.

effluent: The outflowing liquid from a treatment plant to a natural body of water after completion of the treatment process.

eutrophication: The process by which a reservoir, pond or lake becomes enriched with nutrients, especially nitrogen and phosphorus, that support the excess production of algae and other aquatic plant life.

flocculation: The process by which clumps of solids in sewage are made to increase in size by chemical action.

influent: The water, wastewater or other liquid that flows into a reservoir, basin or treatment plant.

organic chemicals: A broad class of compounds that contain carbon. Smaller molecules of this class are primary components of ecological systems. Larger compounds are commonly used to create fuels, solvents, pesticides, plastics and many industrial processes.

pathogen: A disease-causing microorganism, including pathogenic bacteria, viruses, helminths and protozoans.

sedimentation: A water-treatment process during which floating wastes are skimmed off and settled solids are removed for disposal or recycling.

sludge: A thick, soft, wet mud or a similar viscous mixture of liquid and solid components, such as the product of a wastewater treatment, industrial or refining process.

valorization: To give a value to, especially a higher value.

wastewater treatment: When water used by cities or industry is sent through a series of tanks, screens, filters and other treatment actions during which pollutants are removed.

WRRRF: Acronym for water recycling and resource recovery facility. A centralized plant where water used by the people in cities or industrial processes is sent through a series of tanks, screens, filters and other treatment actions for the purpose of removing, valorizing and reusing materials.


Pre-Activity Homework

Wastewater Background:  As a homework assignment, have groups of three to five students each read one section from the EPA Primer for Municipal Wastewater Treatment Systems and recap their findings, which they share with the class to kick off the activity. Recommended distribution of sections:

  1. Requirements, Needs and Challenges (pages 4-6)
  2. Collecting and Treating Wastewater (pages 6-7, 9)
  3. Pollutants (page 8)
  4. Wastewater Treatment (pages 9-16); consider further dividing this section into Primary Treatment and Basic Wastewater Treatment Processes, Secondary Treatment and Land Treatment, and Constructed Wetlands and Disinfection
  5. Pretreatment and Advanced Methods of Wastewater Treatment (pages 16-19)
  6. The Use or Disposal of Wastewater Residuals and Biosolids (pages 19-21)
  7. Decentralized (Onsite or Cluster) Systems (pages 21-24)
  8. Asset Management (pages 24-25)

Activity Embedded Assessment

Design Filters:  Observe student teams as they design successful (!) model filters for wastewater treatment and resource reclamation. Make sure teams remain within the budget and that each student contributes to the design and build.

Post-Activity Assessment

Group/Self Evaluations:  Have students explain the following through discussion and/or writing. The same reflection questions are provided on the Wastewater Design Project Info Sheet.

  1. How effective at cleaning the water is your filter device? Be descriptive!
  2. Provide evidence that your device is cleaning the water. Use test data to back up your claims.
  3. Is this water safe to drink? Why or why not?
  4. How would you change your device to make it more effective?
  5. How could you have worked more effectively as a group to obtain higher-quality products?

Making Sense:  Have students reflect on the science concepts they explored and/or the science and engineering skills they used by completing the Making Sense Assessment.

Investigating Questions

Safety Issues

Activity Extensions

Testing, redesign and revision of student filtration systems could be iterated for improvement over several days. It is up to the instructor to decide how long to carry on the project. Consider implementing a project-based approach in which students research and develop their model devices, build and test them, revise them and test again, and eventually present finished products (model processes) to industry professionals or other expert personnel outside of the school setting.

Activity Scaling

Additional Multimedia Support

Primer for Municipal Wastewater Treatment Systems  by the U.S. Environmental Protection Agency, 2004, at


© 2018 by Regents of the University of Colorado; original © 2017 University of Kansas