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Lesson 4-6: Biological Oxygen Demand Lab (Science)

Page history last edited by mariaelizabethbunn@... 5 years, 8 months ago



Engaging the Student (Entry Task) 

Developing the Ideas--Lesson
Student Handout 
Teacher/Lesson Notes
Materials Checking for Understanding (exit ticket)

1 class period 

 If this lesson is following the sources of pollution jigsaw, have students try and remember what effect fertilizers & "nutrient pollution" had on water bodies. Is an abundance of nutrients necessarily a good thing? Why or why not?


Alternately, have an image of a eutrophic  lake on the overhead. Ask students if they think it's a good habitat for aquatic life; why or why not?



View the teacher version/key here:


Key Concepts

  1. Oxygen levels in Puget Sound (and other waters) affect the kinds and numbers of living plants and animals.
  2. Dissolved oxygen concentrations are affected by factors such as temperature, salinity and dissolved organic matter.


This lab employs a simple model using yeast, powdered milk, and methylene blue, instead of actual sewage, to study the effect of sewage on dissolved oxygen concentrations.


(Given the time and/or desire to go deeper with and challenge advanced students, this lab could be extended by asking students to collect their own water sample and then guiding them through Winkler Method titrations to determine BOD. Additional supplies and preparation would be needed.)



Per Group:

  • 2 50 mL flasks
  • Disposable 1 mL pipettes 
  • Teaspoon 
  • Sharpie
  • Timer 
  • Powdered Milk (2 tsp)
  • Dry Yeast (2 tsp)
  • 3 test tubes
  • Methylene Blue (60 drops)
  • Water 


For "Further investigations" (optional):

  • Cola 
  • Sugar
  • Vinegar
  • Baking soda
  • Honey
  • Karo Syrup 



  1. Based on your laboratory results, what effect did increased sewage have on the dissolved oxygen in the water?
  2. What issues would result from having low dissolved oxygen in a body of water?



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