Student Name:
Lab Partner:
Date of Experiment:
Class Period: NSED-120 (Final Project)
Water Filtration Experiment
Background
Water found in lakes, rivers and other sources often contain impurities that make it appear
undrinkable and smell unpleasant. These water sources may also contain bacteria and other
microorganisms that can inflict disease if not properly treated. Generally, water needs to be
treated before it can be consumed by humans. Generally, water treatment plants clean water
through aeration, coagulation, sedimentation, filtration, and disinfection. Since disinfection
requires significantly more resources and time, we will not include it in our project today.
The first four processes are included in the procedure below.
Pre-Lab Questions
1. Why is it important to filter water?
2. Do you believe that all places in the world have access to clean drinking water?
Explain in your own words.
Objectives
1. Understand procedures that can be used in order to purify water for safe consumption.
2. Consider social issues that prevent access to clean drinking water.
Materials
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4 Liters of lake Yosemite water (alternatively, use 1 cup of soil to 4 liters of water)
3 2 L plastic bottle (two bottles cut in half as shown in Figure 1)
2 2 L (or larger) beakers or another 2 L plastic bottle bottom
20g alum (potassium aluminum sulfate - about 2 tablespoons)
Fine sand (about 800 ml)
Coarse sand (about 800 ml)
Small pebbles (about 400 ml, and may be substituted with natural color aquarium
rocks)
1 large (500 ml or larger) beaker
1 coffee filter
1 rubber band
1 tablespoon (Used to measure alum)
Timer
Procedure
1. Pour about 2 L of Lake Yosemite water into a 2-L plastic bottle. Describe the
appearance and smell of the water.
2. Aeration is the process of adding air to water. Gases trapped inside of the water can
escape, while adding oxygen to the water. Place the cap on the plastic bottle and
shake vigorously for 40 seconds. Continue the aeration process by pouring water from
the plastic bottle into either of the cut off plastic bottles. Pour the water carefully from
one cut off plastic bottle to the other 15 times. Describe any changes that you and
your lab partner observe. Afterwards, take the aerated water and pour it into a beaker
or another 2-L plastic bottle bottom.
3. Coagulation is the process in which dirt and other suspended solid particles in a
mixture are chemically stuck together, so they can be removed from water. Add 20g
alum to the Lake Yosemite water. Slowly stir this mixture for 4 minutes.
4. Sedimentation is the process where gravity pulls particles of alum and sediment to the
bottom of the container. In order for this process to occur, you must leave the mixture
undisturbed in the container for 20 minutes. Record your observations at 5 minute
intervals for a total of 20 minutes based on changes in the water's appearance.
5. Create a filter from the 2L plastic bottle with the top half as follows:
1. Using a rubber band, attach the coffee filter to the outside “neck.” Through the
wider end, pour a layer of pebbles into the bottle, the coffee filter will prevent
the pebbles from falling out. Refer to Figure 2 above for assistance.
2. For the second layer, pour coarse sand on top of the pebbles.
3. For the final layer, pour fine sand on top of the coarse sand.
4. You must clean the filter by slowly and carefully pouring 6L (or more) of
clean tap water. Focus on not disturbing the top layer of sand as you pour the
water through the filter.
6. Filtration removes most of the impurities that remain in water. We can use the filter
that we created in step 5 for the Lake Yosemite water after it has undergone
coagulation and sedimentation. Carefully, without shaking up the sediment, pour
approximately 2/3 of the liquid through the filter. Allow filtered water to collect in a
beaker. The remaining Lake Yosemite water will be poured in a large container in the
front of the classroom to be used as a fertilizer for the school garden. Look at a
sample of the Lake Yosemite water in the front of the classroom and compare the
treated and untreated water. Does this treatment change the appearance and smell of
the water?
7. Disinfection is the process of purifying and killing any harmful organisms. Chemicals
are commonly used and must be handled carefully. For the sake of this experiment,
we will not be using any chemicals to treat the water due to potential effects of using
these chemicals that are not labeled for consumption (such as Clorox). Therefore this
water is unsafe to drink and the microorganisms present in the water can cause
adverse effects.
Observations
Write down some of the observations that you made during the experiment. Focus on what
happened after you poured Lake Yosemite water into the “filter.”
Post-Lab Discussion
We live in a world where we can drink clean water whenever we want. However,
there are less fortunate individuals in the world who lack safe drinking water. Roughly three
people die every ten minutes due to this alone.
The human body contains over 60% water. It is important because it keeps us alive,
and also accessibility to clean water is linked to all kinds of issues ranging from the
environment, gender, class, and race. Access to clean water is a social justice issue that can
be solved by addressing greater structural issues that cause inequality.
In developing countries, access to clean water is only allowed to someone who has
money and power. This creates a situation in which poor people must spend a lot of time and
energy in their pursuit of clean drinking water. If we make water a private good, rather than a
public good in developing countries, we wind up in an unsustainable situation where
economic and other inequalities determine one’s wellbeing.
Stressing this point, we can think of alternative ways to assist those individuals from
developing countries that do not have access to clean water. We utilize materials that we can
easily find anywhere as a way of filtering dirty, otherwise undrinkable water, into clean and
suitable for human consumption.
Post-Lab Questions
1. Even though the water looks clean, why do we need to take the extra step of
disinfecting it?
2. Why do third world governments not provide the clean drinking water that their
citizens need?
3. Distillation is the process of boiling water, collecting the mist and allowing it to cool.
Despite being the most effective way of providing clean drinking water, why do we
not see it more commonly used?
Figure 1: 2 Liter bottle cut in half
Figure 2: Example of a working
filter
References
AGI: American Geological Institute. (2002). AGI Environmental Awareness Series 5.
Retrieved from http://www.agiweb.org/environment/publications/water.pdf
EPA. (2004). Water Filtration Lesson, June 2004. Retrieved from
http://www3.epa.gov/safewater/kids/pdfs/activity_grades_4-8_waterfiltration.pdf
McCaston, M. K., & Rewald, M. (2005). A Conceptual Overview of Underlying Causes of
Poverty. Retrieved from
http://pqdl.care.org/Core%20Library/A%20Conceptual%20Overview%20of%20Unde
rlying%20Causes%20of%20Poverty.pdf/
Images
http://www.thehealthyhomeeconomist.com/wp-content/uploads/2013/07/fly-trap-3.jpg
http://www.hometrainingtools.com/media/images/art/WaterFilt_1.jpg