How is clean and accessible drinking water in Philadelphia a civic responsibility?

In most places in the world today, even water from a relatively clean natural source probably needs to be cleaned and tested before it can be consumed.

In Philadelphia, drinking water treatment is a multi-step process that in many cases mimics nature but also is tested every step of the way to comply with  federal regulations and ensure public health.

Start the class by holding up in front of your students two two clear glasses, one filled with tap water and one with rain water. 

Ask them:  Can I drink this water?  How do you know you can trust it to be safe to drink? 

Follow this with the slide deck questions to define the differences POTABLE, GRAY and POLLUTED and discuss the distinctions. 

POTABLE (Safe for human consumption)

GRAY (rain water for watering plants, washing sidewalks/cars/animals etc)

POLLUTED (not good for anybody or anything!)

Ask students to write a reflection.

You will be guiding the students through the building of a model of a water filtration system.

The  slide deck includes the instructions for building the filtration system.

The slide deck linked HERE is a copy of just the filtration system instructions that can be used with your students. It also contains some introductory questions.

Materials needed for each group of 2, 3, or 4 students:

• Plastic 2 Liter bottle (soda or water). Cut off the top third. The top will be inverted to become the funnel. Recommended – Do this prior to handing out materials to the students. 
• Use a piece of duct tape or masking tape around the edge of each section to soften the edges
• Materials for filtering: Sand, Pea Gravel, Other materials they may think of to use (cotton balls? Paper towel? )
• Coffee Filter
• A second container to move the water into to be able to filter it multiple times.

You will also need ‘dirty water.’ You can create dirty water by mixing a pitcher of water with soil, coffee grounds, leaves, plant material, small paper trash, etc.

Students will layer other filtering material into the coffee filter.

Students may test if the order matters. Think about how the large items in the water may be filtered out by the larger filter material (gravel). Layering the sand in first, then the gravel might be the most effective way to filter the water more efficiently. You can have the students test to see if the order the water moves through the filter matters.

Students will filter the water multiple times.

Option 1: Provide students with the materials and they design the solution

Option 2: Guide students through the creation and testing of the filter.

Have students DRAW their filter design and label the order the filter materials were added.

Have them WRITE an explanation of why they put the materials where they did or if they added or removed anything.

Have them then create a PROTOTYPE of their filter using the materials and test to see if it works.

Have students write a description of their observations of the results of their first filtering trial. What does the water look like? Did it filter all the ‘dirty’ elements in the water?

Have the students move the water into the second container and do a second trial. Have students document their observations for this second trial.

Have students conduct a third trial.

If they make any revisions to their design, have them document why and what was the reason for their design revisions.

Use this Filtration Activity Observation worksheet to guide students in their observations.

Have students write or draw a flowchart to describe what is happening during the filtration process.

Note: This learning experience continues on Day 12 looking at the treatment process employed for drinking water.