APES LAB: Water Pollution and Wastewater Treatment Lab Activity

APES LAB: Water Pollution and Wastewater Treatment Lab Activity
Background Information:
Wastewater from domestic and industrial sources must be treated before being discharged back into the environment. In the
U.S., a community of 100,000 persons will produce an average of 1.5 - 2.0 million gallons of wastewater pre day. Modern
sewage treatment processes have evolved over time in response to many disastrous experiences, including outbreaks of water
borne diseases and ecological damage. The World Health Organization estimates that approximately 80% of the sickness,
disease, and deaths of children and infants can be directly linked to contaminated water. One method of testing water for sewage
contamination is called a fecal coliform test. This test detects the presence of E. coli, a bacterium found in the excretory system
of humans and other animals. Water containing no more than one E. coli per 100 mL is considered safe for drinking. Raw
sewage often has E. coli counts in the millions.
Ancient drainage systems were built as early as the 1st Century A.D. in the city of Pompeii and in earlier Minoan sites on the
island of Crete. These early systems simply conveyed wastewater in open conduits to local rivers and streams. By the 3 rd
Century in Rome, the “cloaca maxima” (main sewer) carried storm runoff as well as waste-water from the Roman baths to the
Tiber River in a completely closed system. Elaborate systems, such as the cloaca maxima, were made possible by the central
authority and tax collecting abilities of the Roman Empire and were not widespread. As cities grew in size, the public health
aspects of untreated sewage became apparent. Throughout the Renaissance, human wastes were dumped in street gutters to be
washed away by rainwater. Without any effective means of handling sewage waste, outbreaks of cholera, infectious hepatitis,
and other water borne diseases were common during the Middle Ages in Europe and elsewhere.
Early treatment methods simulated the natural process of purification that was observed in flowing rivers and streams. A
moderate amount of organic waste discharged to a flowing watercourse is exposed to oxygen and natural filtration as it flows
over and through rocks, gravel, and soil. Eventually, the water regains a level of natural purity as it moves downstream. With
the advent of the Industrial Revolution, however, ecological damage to local waterways became a major problem, as populations
and industry grew more concentrated in ever-expanding urban areas. The natural purification process that took place in local
rivers and streams was soon overwhelmed by the amount of discharge. This caused waterways to become badly degraded and
uninhabitable for fish and other aquatic life.
Even today, the sewer systems and treatment methods in parts of many major U.S. cities permits raw, untreated sewage to be
discharged directly into surface waters during times of high runoff after heavy rains. Modern sewage treatment methods simulate
the natural process of aeration and filtration and combine it with biological and chemical treatment. The treatment plant
accomplishes in hours what a river would require weeks to do. Raw sewage entering a sewage treatment plant is separated into
solid and liquid components primarily through screening (filtration), sedimentation (settling), and chemical means (flocculation).
Flocculation is the act or process by which a number of individual, minute, suspended particles are clumped together and loosely
aggregated or precipitated into small lumps or clusters. The sludge is put through the activated sludge process where compressed
air oxidizes and circulates sludge while being “digested” by massive biological action. Natural gas (mostly methane), produced
as a by-product of this process, is used by some treatment plants to heat the facility as well as provide power. After d-watering,
the final product is suitable for land application as a soil conditioner. The liquid component is filtered, aerated, and after final
sedimentation, disinfected with chlorine before discharge back into the environment.
Did you know…?
Most water pollution problems are caused by land-based activities within drainage basins, and not from water-based
activities such as shipping, boating, and swimming.
Prior to 1972, the United States annually discharged over 1 billion pounds of toxic pollutants and 900 million tons of
untreated sewage directly into waterways.
Activated carbon is used in aquariums to bind and remove organic wastes from the water.
Nitrogen and phosphorus, two common by-products of human activities, are considered the limiting nutrients for most
aquatic and marine algae. High levels of these two pollutants can cause ecologically damaging algal blooms that result
in fish kills.
Beginning in 1908, chlorine was added to municipal water supplies in the U.S. before being pumped into water mains.
By the early 1960s, water borne diseases in the U.S. were relatively rare, but still plague the under-developed countries
of the world.
Water purification technicians are responsible for making sure our water is fit to drink by monitoring the chemical and
filtration processes involved in purifying our water. They operate and maintain treatment plant equipment, test for
impurities, and understand and apply the treatment methods required to meet water quality standards.
Materials Needed:
5 Plastic cups, 9 oz
1 Sample of fine gravel, 4-5 oz
Filter paper
air pump and tubing
1 Sample of fine sand, 4-5 oz.
1 Sample of clay soil, 2-3 oz.
1 Ring stand and ring
air stone
1 Sample of coarse sand, 4-5 oz
1 Sample of activated carbon, 2-3 oz 1 Funnel1
Polluted water sample
1. Obtain a plastic cup and label it “control”. Shake the jug of polluted water and pour a sample into the cup.
2. Observe your sample of polluted water. Note the properties of the polluted water including color, odor, clarity,
and the presence of any solids. Record your observations in a table of your own design. (or see sample)
3. As a class, aerate the remainder of the polluted water sample. Connect one end of the airline tubing to an
aquarium pump and the other end of the tubing to an air stone.
4. Lower the air stone into the jug and turn on the aquarium pump. Allow the sample to aerate overnight.
5. After the aeration is complete, remove the air stone from the jug.
6. Label a new plastic cup “Aerated’. Pour a sample of the aerated water into the cup.
7. Observe your sample of aerated water. Note the properties as you did for the sample of polluted water. Record
your observations in the table you designed earlier. (see sample)
8. Have someone from the class add approximately 15 grams of alum (potassium aluminum sulfate) to the jug
containing the aerated water and shake gently. Observe any reaction that takes place.
9. Alum reacts with minerals in an alkaline environment. The result of the reaction is the production of a jelly-like
“floc’. Allow the flocculation procedure to take place for several hours. Overnight is ideal.
10. After the mixture has settled, obtain a new plastic cup and label it ‘Alum’.
11. Carefully pour a sample from the cleared portion (above the floc) of the water in the jug, being sure to leave any
of the floc behind. Pour gently so as not to disturb the floc before every group has
a chance to obtain a sample. This sample will be used for the remainder of your
testing. (we will save the jug of polluted water at this point for another lab coming
12. Record the general appearance of the water, being sure to note the properties
in the table you designed earlier. (see sample).
13. Place a funnel in a ring or clamp attached to a ring stand. (see figure 1)
14. Construct a filter by placing a filter paper in the funnel followed by a layer of
gravel. Next place a layer of coarse sand on top of the gravel and follow this with
a layer of fine sand (see figure 1 at right)
In an actual water treatment plant, the fine sand layer may be several
meters thick. The filter paper is used to simulate the thickness of the fine
sand layer.
15. Rinse your filter several times by running distilled water (not your sample) through it. Run the water through
until it runs clear when leaving the filter.
16. Label an empty cup ‘Sand Filter’ and place it beneath the funnel. Pour the ‘Alum’ sample through the sand
17. Make your observations of the ‘Sand Filter’ sample as you have done previously, and note your observations in
your data table. (see sample)
18. Remove the funnel from the ring stand and dispose of the sand filter in the garbage. Rinse the funnel
thoroughly prior to performing the next step.
19. Place the funnel back in the ring stand and place a new piece of filter paper in it. Add a layer of activated
carbon to the funnel.
20. Label a new cup ‘Carbon Filter’ and place it beneath the funnel. Pour the ‘Sand Filter’ sample through the
carbon filter. Rinse your ‘Sand Filter’ cup and place the carbon-filtered sample back in it. Run the sample through
the carbon filter again. Repeat this process five times.
Carbon filter beds in treatment plants are quite thick. Several passes of the
water through the carbon filter simulates this.
21. Repeat your observations on the ‘Carbon Filter’ sample and record your results in your data table. (see sample)
22. Carefully add a small amount of chlorine bleach (sodium hypochlorite) to the ‘Carbon Filter’ sample. The
amount of bleach to add should be approximately 2% of your remaining volume of filtered sample. (e.g. 50 mL of
filtered water sample x .02 – 1 mL of bleach to be added)
23. Swirl gently for a couple of minutes and observe your sample. Record your observations in your data table. (see
24. Remove the funnel from the ring stand and dispose of the activated charcoal filter. Rinse the funnel thoroughly.
25. Place the funnel back in the ring stand and place a new piece of filter paper in it.
26. Place a new cup under the funnel and pour the ‘Carbon Filter’ sample with bleach through the filter paper. This
is your final effluent
27. Make your final observations and record your results in your data table. (see sample)
Water Sample Properties Data Table (Sample)
Sand Filter
Activated Charcoal
Fine Filter
Analysis Questions:
1. During which stage of the treatment process did the appearance of the water change the most?
2. Which stage of the treatment process was most effective in reducing the odor in the water?
3. What was the biggest observable change after the chlorination process?
4. Thought chlorination produced an observable change in your water sample, what other benefits of the chlorination
process, not tested in this exercise, do you think there are?
5. The filtration and treatment process removed a great deal of rich, organic material from the initial sample of polluted
water. An actual water treatment plant removes tons of organic wastes from water during the treatment process. Do you
think there is any use for this material in other applications?
6. Create a double-bubble thinking map (NOT A VENN DIAGRAM!) comparing and contrasting the water treatment used
in your model with the function of a pool filter. Include at least two similarities and two differences between the two.
7. Water treatment plants are based on many concepts borrowed from natural processes. One of the best systems of natural
water filtration and purification occurs in nature in areas termed wetlands. Using the internet or your school library,
research wetlands and the methods by which water is purified within them. Be sure to define what constitutes a wetland,
how water moves in a wetland, the methods of filtration within wetlands, and why it is important to protect wetlands as a
natural resource.
Study collections