Teaching TIPS
All students should be encouraged to develop understanding of natural resources , conserving those
resources . They also should be guided to inquire about various chemical processes in nature to achieve a
sustainable environment.
Focus points during discussions :
Guide the discussion towards Oxygen demand , eutrophication, BOD (Biological Oxygen Demand),
hydrological cycle.
Precautions :
● Methylene Blue is colorless in the absence of oxygen and is of blue color in the presence of
oxygen. The amount of biodegradable material decides the time for the color change . Thus
students should be told to observe the reaction carefully in lab.
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It is important to discuss the significance of the decomposers in breaking down the organic
material.
Safety Measures
● Though this is a safe practical activity yet , student needs to be carefully dealing with the
methylene blue - as it can cause irritation and nausea .
● DO(Dissolve Oxygen) capsules should not be consumed and they are be added just at the time to
experiment.
Teachers preparation
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Show pictures and videos of local biological treatment plants.
Distribute the hand out of the presentation before these activities .
Lecture on the concepts of biological treatment and the BOD test.
Encourage class to explain the Explore the concept . The objective of these activities is to
demonstrate the decaying organic matter in Waste Water Treatment Plants . At the end of this
session student should have a clear understanding that dissolved oxygen concentration in the
water samples will decrease because of the microbial activity ,which consumes oxygen.
Encourage students develop a hypothesis - what they expect will happen to the oxygen levels in
the water sample collected from different sources.
Activity plan
Students need to take up the following 3 tasks :Task 1 & 2 are related to detective terry and the third task
involves a research activity.
Task 1: 60 mins to read and respond to the questions.
Task 2: 120 mins to read ,write and discuss the answer's in the class
Task 3: Research activity : Group size : 4 students
Time: 30 mins : Explain the activity and form groups .
120 mins : Let the group perform the experiment ,and write a brief lab report .
60 mins : Discuss the results in class, and then answer the four "thought provoking" questions
Detective Terry
Hello! I am Terry , I have been to the city's water treatment plant. Though I was detailed on the working
of each component there. I am still puzzled about the functioning of some of the water treatment
component. also I want to put a pet fish in the water I had collected from the inlet/outlet of the waste
water treatment plant in two different jars .
Here is the flowchart of what I saw and learned at the waste water treatment plant.
Water from my flush -------------------------------->
They gave me a handout about BOD ,which look like this
BOD (Biological Oxygen Demand) value is used to estimate the amount of
biodegradable organic material in a sample. BOD is a chemical process by
which we can determine the dissolved oxygen required by the microorganisms present in water . It is usually measured as milligrams of oxygen
required per Liter of sample. Usually water sample is preserved in BOD
bottles for 5 days at around 20 degree celcius. During waste water treatment
process the bacteria decomposes the organic matter in the waste water
sample. activated sludge , trickling filters, oxidation ditches are used in
WWTP for the purpose of biological decomposition of organic matter.
Task 1 for you : I forgot some of it !
I need to write a report about the working of the wwtp (waste water treatment plant) .
But unfortunately I forgot about the "biological treatment" in the Waste Water Plant.
Can you help me write about that part of the report ?
I need to summarize this part of the report in not more than 1000 words. I need to
explain the following points .
1. Biochemical general reaction showing decomposition of organic matter ?
2. How aeration in activated sludge treatment plants or in trickling filters, contribute in
the biochemical reaction ?
Task 2. Can you help me with ......
I bought samples from the influent and effluent sewage pipes . Unfortunately I forgot to
label them then. I want to put a pet fish in the clean water, but I really don't know which
jar has the water from effluent and influent stream of the waste water treatment plant .
OR
I don't want my fish to die and thus I decided to calculate the BOD of both the samples
using my school's lab BOD meter.
After the test : results were as follows
Jar 1 has a BOD reading of 740 mg/l
Jar 2 has a BOD reading of 600 mg/l
I really don't understand the significance of this reading . please help me understand
the relation of these values . And also help me decide- in which jar should I pet the fish
(jar 1 or jar 2) ?
Task 3 : Research activity for students
Aim : To know about the effect of biodegradable waste on the Dissolved Oxygen in the water
sample.
Background :When oxygen is present and methylene blue is in its oxidized state, it is blue in
color. When sufficient oxygen is no longer available, methylene blue becomes reduced it and is
colorless.
Methylene blue (oxidized) blue------>methylene blue (reduced) colorless.
Experiment : Take two jars and label them as jar A and Jar B.
In Jar A : In a graduated cylinder add 5 ml water milk 5 ml milk . (hydrate the yeast until just
before the lab. 1 ml of dry yeast dissolved into 10 ml of tap water) . To this mixture ,quickly add
1 ml of yeast mixture . Invert test tube 4 times and place in the test tube rack. There after add 3
drops of methylene blue to the samples ,and let the students note the time taken for the color
change in the test tube.
In Jar B : In another graduated cylinder add 10 ml water add a DO capsule . Plug the test-tube
and shake it well. Then quickly add 3 drops of methylene blue to this mixture. Students should
then be asked to note the time for color change in the test tube.
Task 3.1 : Students need to prepare short lab report .
Task 3.2 : They also need to write answers to the following "thought provoking question"
questions :
1. In which Jar do they think the decomposition took place.
2. Identify the “food” and the “decomposer” present in the decomposition jar.
4. Why do you think the oxygen in the decomposition Jar was all used up?
3.Why do you think the waste water treatment plant ,want to calculate the BOD values of water
flowing out of the effluent streams of their (Waste Water Treatment Plant ) WWTP ?
Grading rubric for these activities is given below :