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Classroom activity Grade 4 Math

Birchwood Cleaning Steps: A Wastewater Plant Station Rotation

A grade 4 station-rotation activity where students move through five steps of a fictional wastewater plant, solving a multiplication card at each stop.

Objectives

  1. Students will multiply multi-digit numbers to find totals at each treatment step.
  2. Students will compare station totals to decide which step handled the most water.

Vocabulary

Aeration
Aeration means mixing air into water. At a wastewater plant, blowers bubble huge amounts of air through tanks so the helpful microbes have the oxygen they need to eat the waste.
Disinfection
Disinfection is the step that kills or disables germs in water so it is safe to drink. Water plants usually disinfect with chlorine, ultraviolet light, or ozone.

Also: screening, grit, settling

Teacher overview

This is a five-station rotation for a class working in small groups of four or five. Each station is one step a fictional wastewater plant, Birchwood, uses to clean used water: screening, grit removal, aeration, settling, and disinfection. Groups move through the steps in the correct order, and at each stop they solve one multiplication problem on their handout. Because students travel through the treatment steps in the same order the water does, the multiplication at each stop describes how much that step handles.

Activity Directions

  1. Before class, post five signs around the room in a loop and in this order: Screening, Grit, Aeration, Settling, Disinfection. Place a copy of the matching handout problem at each sign, or have students read the problem from their own handout.
  2. Explain the order using the signs: used water first passes through screening to catch large items, then grit removal, then aeration, then settling, and finally disinfection before it is clean. Walk the loop once as a class so every group sees the path.
  3. Split the class into five groups and send each group to a different starting station so all stations are busy at once.
  4. At each station, the group reads that station's problem, solves it together on the handout, and shows the multiplication. Give groups about three minutes per station.
  5. Call "rotate" and have every group move to the next station in the loop order. Continue until every group has visited all five stations and solved problems 1 through 5.
  6. After the fifth rotation, gather the class and have groups answer debrief problem 6 together, comparing three of the station totals.
  7. End the activity when every group has completed all five stations and the debrief problem. Close by asking each group to name which treatment step came first and which came last.
Birchwood Cleaning Steps: A Wastewater Plant Station Rotation — Grade 4 Math
Name: ____________________________ Date: ______________

Student Handout

Move through the five stations in order. Solve the problem at each stop. Show your multiplication.

  1. Screening: 6 screens each catch 45 items. How many items do they catch in all?
  2. Grit: grit is pulled for 30 minutes at 25 gallons each minute. How many gallons is that?
  3. Aeration: 4 blowers each push 1,250 gallons of air. How many gallons in all?
  4. Settling: 8 tanks each hold 900 gallons. How many gallons in all?
  5. Disinfection: water is cleaned at 60 gallons each minute for 12 minutes. How many gallons is that?
  6. Which station handled the most gallons: grit, settling, or disinfection?

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: 270 items. 6 × 45 = 270 items.
  2. Answer: 750 gallons. 25 × 30 = 750 gallons.
  3. Answer: 5,000 gallons. 4 × 1,250 = 5,000 gallons.
  4. Answer: 7,200 gallons. 8 × 900 = 7,200 gallons.
  5. Answer: 720 gallons. 60 × 12 = 720 gallons.
  6. Answer: Settling, 7,200 gallons. Settling handled 7,200 gallons, which is more than grit at 750 gallons and disinfection at 720 gallons.

Differentiation

Support

Give supported groups a multiplication chart and pre-drawn area-model grids at each station. Let them start at the Screening and Grit stations, which use smaller numbers, before the larger multiplications at Aeration and Settling.

Extension

Ask early-finishing groups to add the totals from all five stations and write the grand total in gallons and items, then order the five stations from least to greatest.

ELL supports

Add a small picture to each station sign that shows what happens there, such as a screen, a settling tank, and a clean-water drop. Provide a sentence frame at each stop: "At the ___ station, I multiply ___ by ___ to get ___."