Chapter 4

Wetlands Module

Listed below are four critical thinking questions posed by the U of M winter 2001 chemical reaction engineering students.  After each question you have the opportunity to rate the questions on their value as a critical thinking question.  Once you rate a question, the student rating it received from winter 2001 students is revealed.  

A company is using a wetland as a wastewater treatment facility. Recently, an employee of the company has observed mutant three-eyed fish swimming in the wetland. This means that the pollution level is too high. However, certain sources have reported that three-eyed fish are delicious. Pollution levels above 0.01 mol/dm³ produce three-eyed fish that are poisonous, and pollution levels under 0.001 mol/dm³ do not produce any delicious three-eyed fish. To maximize the company's production of three-eyed fish, we want to maximize the volume of water such that 0.001 < Cc < 0.01 mol/dm³.Pollutant C is a product of algae metabolism of Pollutants A and B described by the rate law r_c = k_c*Ca*Cb².

a) At what rate should Pollutants A and B be released into the wetland?

b) Do you have any ethical problems with doing this? Phrase your answer in the form of a song.

c) What if these fish were REALLY, REALLY delicious?

Rate the question:

            Excellent                                    Poor

            5            4            3            2            1

Question 2

How would your answer change if the reaction wasn't irreversible?

Rate the question:

            5            4            3            2            1

Question 3

A few years ago, carp infiltrated the wetlands in their brown camouflage scaly bodies. They came in massive numbers and started to stir up the wetlands and increase the TSS levels. This affected the algae and other microorganisms in the wetlands, which in turn affected the effectiveness of the wetlands. Our question is what if the opposite happened and the wetlands were infested with zebra mussels?  Zebra mussels remove toxins and other dissolved substances from the water which lowers the TSS substantially. This happened in Lake Erie in the '80's and had a profound impact on the ecosystem there. How would this affect the wetland's ability to treat waste water?

            5            4            3            2            1

Question 4

How do the seasonal changes (which lead to changes in temperature) lead to changes in the physiology of the microorganisms and the way and rate they react the pollutants.  Also, does this change the organism's life-and-death cycle, thereby changing the number available to degrade the pollutants?

Rate the question:

            5            4            3            2            1

2001 Student Rating

Average:    4.6/5.0

Range:       3 - 5

Question 1

A company is using a wetland as a wastewater treatment facility. Recently, an employee of the company has observed mutant three-eyed fish swimming in the wetland. This means that the pollution level is too high. However, certain sources have reported that three-eyed fish are delicious. Pollution levels above 0.01 mol/dm³ produce three-eyed fish that are poisonous, and pollution levels under 0.001 mol/dm³ do not produce any delicious three-eyed fish. To maximize the company's production of three-eyed fish, we want to maximize the volume of water such that 0.001 < Cc < 0.01 mol/dm³.Pollutant C is a product of algae metabolism of Pollutants A and B described by the rate law r_c = k_c*Ca*Cb².

a) At what rate should Pollutants A and B be released into the wetland?

b) Do you have any ethical problems with doing this? Phrase your answer in the form of a song.

c) What if these fish were REALLY, REALLY delicious?

2001 Student Feedback

"We feel that this question is good because it is very creative and innovative and also brings the ethics of disposing pollutants into wetlands.  Also, we like how they ask us to make a song out of our answer, and how they give limiting conditions, which is quite realistic.  The bad part about this question is that part C is very vague in what they are leading to, or what they are looking for when the fish are REALLY REALLY delicious." 

"It looks like a typical book question.  It doesn't require any creative thought and won't expand what we know about the subject other than what we learned about the book.  On the other hand, this question could be interesting if three-eyed fish did really taste better than regular two-eyed fish."

"This problem was very creative, and provided an interesting expansion to the wetlands problem.  It was not a very practical application, however, it did make students think of the ethical implications that might arise in the engineering field."

"Excellent question, extremely creative.  Adds a new factor.  Probes assumptions from multiple angles and it's funny."

"This is a great question.  It involves critical thinking and a sense of humor.  A good sense of humor is a great quality in a professional engineer.  Also, this question deals with a real-life problem."

Instructor Note

While this problem is cleverly written, it focuses more on creative thinking [c.f. Problem P4-1] than critical thinking.  While the question, "What if the fish are really, really delicious?" probes perspectives and view points, the other questions do not directly relate to Socratic questioning. [see http://www.engin.umich.edu/~cre/probsolv/strategy/crit-n-creat.htm]  A critical question that probes assumptions might be "Would the 3-eyed fish reproduce themselves if transferred to fresh water?"

Question 2

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Question 2 Results

Question 3

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"We liked the question because it followed De Bono's thinking style and not only varies parameters of the problem but makes you think of a related real-life scenario.  However, we are curious about how the monkey affects the problem."

"Group 5 did an excellent job of posing further questions to analyze the wetland module. They connected real world situations with chemical reaction engineering modeling."

"This was a really good question.  It makes us consider a whole other possibility with the zebra mussels.  It takes a real-life situation and asks us to use that information to evaluate this situation.  The only bad thing was the 'Who's the monkey?' question at the end.  What was that all about??"

"This question is very creative.  Interesting ideas, and involves critical thinking."

Instructor Note

This question is also creative, but unlike question 1, it does have better questions on critical thinking.  These questions probe implications and consequences [What if light does not get through algae, or how will zebra mussel filtration contribute to the wetland effectiveness?].  

Question 4

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How do the seasonal changes (which lead to changes in temperature) lead to changes in the physiology of the microorganisms and the way and rate they react the pollutants.  Also, does this change the organism's life-and-death cycle, thereby changing the number available to degrade the pollutants?

2001 Student Feedback  

"Questioning the validity of any assumptions made in a model is always a good practice and can make for good (difficult) problems.  Group 23 hit on these assumptions, namely the amount of microorganisms in the channel with respect to time of year."

"After reading the proposed question submitted by group 23 we believe that the strength of their question was to investigate the novel idea that the number of microorganisms may effect the problem statement.  Their analysis showed weakness though because it did not actually propose any questions to add to the problem."

"This is a good critical thinking question, they make a lot of good points but not easy to follow.  Considering microorganisms is a good example of critical thinking but it focuses a lot on biology.  It brings up good points, about adding modifications/safety features to alter the reactor with different weather conditions (i.e. floods)."

Instructor Note

This question also probes the implications and consequences of how the microorganisms will react with the pollutants.  

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