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Classroom activity Grade 7 Art & Music

Meet the Microbes: A Wastewater Character Design Studio

A grade 7 art activity where teams design and present characters for the real microbes that clean wastewater at a treatment plant.

Objectives

  1. Students will design a character that shows one wastewater microbe's real job.
  2. Students will write a trait card explaining what their microbe does and why it matters.
  3. Students will present their microbe and explain its place in the treatment process.

Vocabulary

Wastewater
Wastewater is used water from sinks, showers, toilets, and businesses that goes down the drain. It travels through sewer pipes to a treatment plant to be cleaned before returning to nature.

Also: microbe, bacteria, protozoa, trait card

Teacher overview

A wastewater plant does much of its cleaning with living microbes, tiny organisms that eat the waste in dirty water. Secondary treatment removes roughly 85 percent of the organic waste, and bacteria and protozoa do most of that work. This activity is a character-design studio for teams of three to four students. Each team is assigned one real microbe, invents a character that shows what it does, and writes a trait card that explains its job. The characters help students picture a biological process too small to see, and each design choice must match the microbe's real role rather than a made-up one.

Activity Directions

  1. Before class, post the microbe fact sheet where teams can read it. Form teams of three to four and give each team blank cards and markers.
  2. Assign each team one microbe from the fact sheet: waste-eating bacteria that break down organic matter, protozoa that eat loose bacteria and clear the water, or nitrifying bacteria that turn ammonia into a safer form. If you have more teams than microbes, assign a microbe to more than one team.
  3. Explain the rule that connects the art to the science: every design choice must show something true about the microbe. A big mouth might show a waste-eater, and a broom or net might show a protozoan that clears the water.
  4. Teams sketch their character (15 minutes), then write a trait card with four labeled fields: the microbe's name, its real job, what it eats or changes, and why the plant needs it (10 minutes).
  5. Tape the finished characters and cards to a gallery wall in treatment order: waste-eaters first, then protozoa, then nitrifiers.
  6. Run a gallery walk (8 minutes). Each student visits the other teams' cards and finds one fact they did not know.
  7. Have every team present its character in one sentence and confirm that it is in the correct spot on the wall.
  8. Close with the debrief questions below, drawing answers from the whole class.

Microbe fact sheet. Print or post these facts for step 1. All three microbes live together in the aeration tank, where the plant blows in air so they have oxygen.

  • Waste-eating bacteria feed on the dissolved organic matter in wastewater, such as food scraps and human waste. They need oxygen to do this work, and they clump together into small flocs that settle out in the next tank.
  • Protozoa are single-celled organisms much larger than bacteria. They eat loose bacteria that did not join a floc, which leaves the water clearer, and operators look at them under a microscope to judge whether the process is healthy.
  • Nitrifying bacteria change ammonia, which comes from urine and is harmful to fish, into nitrate, a safer form. They grow slowly and do most of their work after the waste-eaters have removed most of the organic matter.

Debrief questions.

  1. Why are the characters placed in this order on the wall?
  2. What makes a character design teach its microbe's real job?
  3. Why does the plant need living microbes after screens and settling?

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: Waste-eating bacteria come first because they break down the bulk of the organic matter; protozoa come next because they eat loose bacteria and clear the water; nitrifying bacteria change ammonia into a safer form. In a real plant all three live together in the aeration tank, so this order follows their work rather than separate tanks: waste-eaters remove most of the organic matter, protozoa graze the loose bacteria, and nitrifiers do most of their work once the organic load has dropped.
  2. Answer: A strong design shows a true trait, such as a waste-eater drawn with a large mouth or a protozoan drawn clearing cloudy water, so the picture teaches the microbe's real job rather than a random feature.
  3. Answer: The plant needs living microbes because they remove waste that screens and settling alone leave behind, which is how secondary treatment reaches roughly 85 percent removal of organic waste.

Differentiation

Support

Give these teams a trait card with the four fields already labeled and one field filled in as a model. Pair them with a fact-sheet excerpt written in shorter sentences.

Extension

Ask teams to design a second character for a condition that harms the microbes, such as a toxic chemical dumped down a drain, and to explain on a card how that character would disrupt the treatment order on the wall.

ELL supports

Provide the microbe fact sheet with a labeled picture for each organism. Allow trait-card fields to be short phrases, and let students rehearse their one-sentence presentation with a partner before the gallery walk.