Instructional Procedures

1. Discuss with the class the difference between a water filtration system and a water filter. Water filters address only the fourth step in the treatment process; a complete system incorporates all five steps. Without the first three steps to remove larger particles, a filter will clog and become ineffective.
2. Use the Problem Solving Process Slides to introduce a deliberate problem-solving method. Students should follow these steps throughout the creation of their filters.
3. Organize the class into groups of 2–3 and have them begin researching methods to filter water.
4. Direct groups to research which materials will work best for their filters.
5. Have students research current EPA drinking water standards. Since you will test for E. coli, they should determine acceptable levels for safe drinking water and note that EPA guidelines, while non-enforceable, are useful safety targets.
6. Groups should develop an idea and materials list to addresses all five processes—aeration, coagulation, sedimentation, filtration, and disinfection—and record it on their Project Planning Worksheet.
7. Have groups begin constructing their filter using the 2-liter bottles and filter materials and document their process (sketches, photos, and/or written steps) on their Project Planning Worksheet.
8. After construction, have groups implement their purification plan. Provide each group with a purification system materials. Use the scale to measure the mass of the input water, filter it, and then measure the mass of the resulting clean water to estimate filter efficiency.
9. Arrange for groups to present their findings to a local expert and obtain feedback on method effectiveness (e.g., wastewater in vs. clean water out, clarity). Consider local utility employees or a Pathful Connect virtual chat.

Instructional Procedures

1. Review the importance of the “evaluate” step of the problem-solving loop. Discuss methods that can improve filter output. Brainstorm solutions to common issues (charcoal in the water, cloudy water, slow filtration, etc.).
2. Ask the groups to evaluate the results of their first attempt and redesign their system. Provide the purification system materials. Using feedback from a local expert or peers, students should improve their filter to produce clearer water through a more efficient filtration process.
3. After groups create Version 2.0 of their filter, have them test again and then disinfect the water.* Direct students to:
   • Evaluate clarity and estimate efficiency (e.g., input vs. output mass using the scale).
   • Apply a disinfection agent following product directions (contact time/concentration).
   • Run a bacteria test (e.g., the E. coli & Coliform Test by Aquavial). If required, place tests in an incubator to speed results; room-temperature development is acceptable but slower.

* Note: Utility-grade water testing is comprehensive and costly; for this class, a small classroom sampling is sufficient to indicate presence/absence of bacteria. Many tests require warm incubation and do not yield instantaneous results. Remind students that results specifically indicate the presence/absence of E. coli/coliforms rather than full potability certification.

Days 8–9 Instructional Procedures

1. Direct the groups to compile all documentation into a presentation detailing the progression of their project. Presentations should include:
   • What research they conducted
   • Their initial plan
   • Feedback received from the local expert
   • How that feedback shaped their second plan
   • How results from the first solution impacted the design of the second filter
   • The result of their bacteria test
   • How their water treatment system addressed each stage of water purification
2. Emphasize that the presentation is twofold: students should show how they progressed through the water purification stages and how they used the problem-solving process.

Day 10 Instructional Procedures

1. Have students present their results and findings to experts who visited the class during the project or to family members who could use the filtration ideas at home.
2. Provide each guest with a copy of the Rubric and Checklist for PBL Presentation for every presentation they will view.
3. Invite experts to offer additional feedback and insights on the final results.
4. All students should complete a Peer Collaboration Evaluation.