Many people drink treated surface water.
Surface water is cleaned of particulate matter and purified before it is considered safe to drink.

To understand the processes involved in the cleansing and purifying of surface water.

Mathematics:
• Measurement of materials
Social Studies:
• Surface water usage by individuals
Language Arts:
• Communicating information through research
• Discussing various water treatment procedures
• Journaling to record student trials
• Completing data sheet
Art:
• Drawing a model of a filtering system.

Materials:

SAFETY NOTE: It should be recognized that river or pond water may contain contaminants that can be a cause for concern. Proper handling of these water samples should be emphasized at all times.

Per student :
Data Collection Journal
Ugh! We DRINK this Stuff? recording sheet

Per Group:
1 two-liter plastic bottle with cap
1 funnel
2 two-liter plastic bottles prepared as indicated
craft stick
15 grams (11/2 tablespoons) powdered alum
1 liter pond or river water (if not available, add a half cup dirt to the water to approximate
surface water)
ruler water treatment tablets (optional)
800 ml fine sand 5 cm x 5 cm
800 ml course sand
400 ml pebbles
50 ml charcoal (rinsed)
flexible nylon screen
rubber band
permanent marker
clock with a second hand/stopwatch
goggles
latex gloves

Per Class:
1 knife for teacher-use

Procedure:

1. Each group of students prepares the bottles following these directions:
   
   a. Remove the cap from one bottle. Turn it upside down. Using a ruler and a marker, measure 11 cm from the tabletop and mark 2 dots on opposites sides of the bottle. Place the rubber band around the bottle at the dots and draw a ring around the bottle. Mark this bottle with the letters HT (Holding Tank) as illustrated.
   b. Following the same procedure, mark the second bottle as in step 1, but measure this line 26 cm from the tabletop and mark the bottle with the letters FS (Filter System).
   c. The teacher will use a knife to puncture each bottle at the marked rings.
   d. The students will use regular school scissors to cut the bottles all around the rings. Remove the small sections and set aside.

2. Using a funnel, pour one liter of the river water into the remaining uncut bottle.

3. Observe and record the appearance of the water and any odors that may be present.
   

4. Cap the bottle and shake the contents for one minute. Pour the water into the bottle marked HT and continue aerating the water by pouring it from the HT bottle to the FS bottle (with the cap in place) and back at least 10 times, ending with the water in the HT bottle.
   

5. Observe and record any noticeable changes in the odor or appearance of the water.
   
   
6. Measure and pour the alum into the water and stir well with a spoon or craft stick for 5 minutes. After an initial observation (0 min.) record the results of this action at 5 minute intervals for 15 minutes with the bottle remaining absolutely still.
   
   
7. While monitoring is taking place, prepare the FS bottle: remove the cap and place the screen over the end of the bottle and secure it with a rubber band.
   
   
8. Each group discusses how the materials provided can be used to construct a filtering system and records the proposed plan on the group data sheet.
   .
9. Each group constructs a filter system according to their plan and draws the model on the data sheet and in individual journals.
   
   
10. Pour the water in the HT bottle into the uncut bottle using a funnel, being careful not to add any of the sediment that has settled in the bottom. Rinse the HT bottle with clean water.
    
    
11. Place the FS bottle over the HT bottle and pour the water slowly through the filter system. Observe and record results.

Suggested Discussion Questions:

Why do you think students were asked to shake the water and pour it back and forth? Did you notice any changes in the way the water looked or smelled after this procedure? What could have caused these changes? (This is the aeration process that adds oxygen to the water and allows trapped gasses in the water to escape.)
What did the alum do to the water? Did you notice any changes? (The alum causes coagulation to occur. Particulate matter became chemically attracted to each other into floc (particulates) and caused the matter to sink to the bottom as sediment. The remaining water is then free of much of the suspended solid pieces of superfluous matter.)
How did the water look and smell after dripping through the FS bottle? What step in the H2O treatment process did this represent? (This is the filtration step and further cleanses the water of any additional particulate matter. It also simulates what happens to ground-water as it travels through rock and sand layers).
Compare the water filtered through each system. Which system was able to get the water the cleanest? What do you think made the difference? If you could change your system to make it clean the water better, what would you do? (Answers will vary.)