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Grade 12 Maintaining Water Systems Task: 40 Minutes

 

TWELFTH-GRADERS CAN DO DETAILED EXPERIMENTS BUT ARE CHALLENGED TO EXPLAIN THEIR REASONING Watch Maintaining Water Systems. See highlights of students taking the task. Duration: 4.5 minutes.

For this task, grade 12 students were asked to investigate the best site for building a new town based on the quality of a given water supply. Using the provided laboratory equipment and materials, students had to test water samples for levels of specific pollutants and evaluate water treatment processes.

Part A: Selecting the Best Site for a New Town

Step 1 – Students make preliminary recommendation:

In Part A of this hands-on task, twelfth-graders selected the best site for a new town. First, students used a map and a chart of potential pollutants to make a preliminary recommendation for the location of the new town. The students were presented with the following directive:
Before testing the water samples, make a prediction about which potential town site (A or B) you think would have better water quality. Explain why you chose the town site you did and not the other town site. Support your explanation with the information provided on the Map of Water System and Reference Chart 1 only.

The Map of Water System showed a large bay drawn at the bottom of the map with a river and several small tributaries extending north from it. The following locations were indicated on the map:

  • Possible sources of pollution – a farm, a coal mine, a shopping mall, the town of Greenville
  • Town Site A and the location of the drinking water source for Site A
  • Town Site B and the location of the drinking source for Site B

Reference Chart 1 listed the following sources and types of water pollutants:

  • Residential Areas can be a source of nitrates from fertilizers; heavy metals from corroding pipes, such as copper, lead, and iron; vinyl chloride leached from PVC pipes.
  • Industrial Plants and Factories can be a source of barium discharged from metal refineries; dioxin from waste incineration; cyanide discharged from metal, plastic, and fertilizer factories.
  • Agricultural Areas can be a source of nitrate from fertilizers and animal waste.
  • Roads and Parking Lots can be a source of engine oil, which can lead to volatile organic compounds such as benzene; eroded soil particles; garbage; salts.
  • Mines can be a source of acid drainage and heavy metals such as iron and mercury.
  • Other sources can be a source of cadmium runoff from waste batteries and paints; radium from erosion of natural deposits; soil runoff from erosion and road construction; leakage of oil from boats. 

The results showed that 64 percent of twelfth-graders could provide a complete or partial preliminary recommendation with valid support based on the information provided in the map and reference chart.

Try It Yourself: By clicking on onscreen links, users can view enlarged versions of the Map of Water System and Reference Chart 1 and can see a sample, handwritten student response.

Step 2 – Students perform water tests and evaluate data:

Next, students performed tests on water samples and evaluated multiple sources by following these directions:
Use the equipment you have been given to perform your water quality tests on the water samples.

  1. Record each pollutant tested and the level of each pollutant for Site A in columns 1 and 2 of Table 1A.
  2. Now add the test results from the outside laboratory to columns 1 and 2 of Table 1A.
  3. Then complete columns 3 and 4 of Table 1A using the reference materials you have been given in your kit.

Complete the same three steps for Site B and enter the results in Table 1B.
Students were provided with the following materials:

  • Equipment including

  • Water samples from Site A and Site B
  • Test strips for copper, iron, nitrate, and pH
  • Paper towels
  • Safety goggles
  • Safety gloves
  • A stopwatch

  • Test results from an outside laboratory containing data about the sample sites.

  • Town Site A contained these levels of pollutants:
  • Mercury – 0.001 mg/L
  • Turbidity – 2 NTU
  • Lead – 0.000 mg/L
  • Benzene – 0.000 mg/L
  • Total coliform – 6.0 percent

  • Town Site B contained these levels of pollutants:
    • Mercury – 0.000 mg/L
    • Turbidity – 6 NTU
    • Lead – 0.010 mg/L
    • Benzene – 0.003 mg/L
    • Total coliform – 1.0 percent

  • A sample table with spaces for providing the following information:
  • Pollutants tested
  • Level of pollutant
  • Does this exceed the maximum level allowed?
  • Possible sources of pollutant that exceeds maximum level allowed

Results showed that 75 percent of all twelfth-graders could perform detailed scientific experiments and accurately tabulate data. Students who were successful on the first part of the task were more likely to perform at a high level on their experiments. Fifty-three percent of students who provided a complete or partial prediction scored at a high level of performance, while 22 percent of students who provided an unsatisfactory prediction performed at that level.

Try It Yourself: By clicking on onscreen links, users can view enlarged versions of the equipment, the test results, and the table example, as well as an interactive sample student response.

Step 3 – Students make final recommendation:

After completing the tests and recording their results, students evaluated multiple facets of data to make a final recommendation for the new town’s location. They were directed to do the following:  Look at the information you have collected in Table 1A, Table 1B, and Table 2. Which of the potential town sites is a better location for building a new town?

  1. Town Site A
  2. Town Site B
  3. Either Town Site A or Town Site B (neither site would be better than the other)

Support your choice using information from Table 1A, Table 1B, and Table 2.
Results showed that approximately 11 percent of all twelfth-graders scored “Complete” on their final recommendations, while 51 percent scored “Partial” for providing valid information but less specific detail than the students at the “Complete” level. Of the students who provided a complete or partial prediction and scored at a high level of performance, 9 percent provided a final recommendation that was scored “Complete.” Of the students who provided an unsatisfactory prediction but scored at a high level of performance, 1 percent provided a final recommendation that was scored “Complete.” Overall, 38 percent of twelfth-graders provided an unsatisfactory final recommendation.

See Sample Response: By clicking on an onscreen link, users can view a sample, handwritten student response.

Part B: Explaining Water Treatment Processes

Step 4 – Students matched pollutants to water treatment processes:

In Part B of this hands-on task, twelfth-graders demonstrated the depth of their content knowledge. First, students matched specific pollutants to applicable water treatment processes and identified sites where each pollutant exceeded water quality standards using reference chart 2. Students were given the following directions:

Use information from Tables 1A and 1B and your knowledge of physical, chemical, and biological processes to identify the pollutant(s) that could be removed or reduced in each treatment step. Enter in the last column of Table 2 the water samples (Site A, Site B, or Both) where each pollutant you identified exceeds water quality standards.

Students were provided with the following materials:

  • A diagram showing the steps taken in a Water Treatment Plant:

    1. Water to be treated enters the plant. The incoming water is allowed to stand in a settling tank (sedimentation).
    2. The incoming water is treated with chemicals (neutralization, oxidation-reduction, precipitation, and other chemical treatments).
    3. Solid particles and organic matter are removed (filtration, biodegradation).
    4. The water is disinfected (chlorination, irradiation).
    5. The water is sprayed through fountains to remove volatile organic compounds (aeration). The end result is treated drinking water.

  • Reference Chart 2 – National Drinking Water Standards, which lists various pollutants and the maximum level of the pollutant allowed in drinking water:

  • Benzene – 0.005 mg/L
  • Chloride – 250 mg/L
  • Copper – 1.3 mg/L
  • Iron – 0.3 mg/L
  • Lead – 0.015 mg/L
  • Nitrate – 10 mg/L
  • Total Coliforms (including E. coli bacteria) – 5.0 percent
  • Turbidity – 5 NTU
  • Zinc – 5 mg/L
  • pH (measure of acidity) – 6.5-8.5

  • A sample table listing the 5 steps taken in a Water Treatment Plant and spaces in which students needed to enter (A) the pollutants that could be removed or reduced in the step, and (B) the site where the pollutant exceeded standards (Site A, Site B, or Both)

Fourteen percent of twelfth-graders scored at a “High” level on matching specific pollutants to treatment processes; 36 percent of the students scored at a “Medium” level

See Sample Response: By clicking on an onscreen link, users can view a sample, handwritten student response.

Step 5 – Students described processes in a water treatment plant:

In the final step of this hands-on task, students described the processes in a water treatment plant that they would need to use at the site they had chosen. Students were asked to do the following: Describe specific physical, chemical, and biological processes you would need to use in the water treatment plant at the site(s) you chose. Refer to Table 2 in your answer.

Results showed that 28 percent of twelfth-graders scored at a Complete/Partial level.

See Sample Response: By clicking on an onscreen link, users can view a sample, handwritten student response.

SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2009 Science Assessment.