Water, water everywhere but not a drop to drink

Did you know that 1/6 of the world does not have access to clean drinking water?  That's over 1.1 billion people!  This week Rieke's 5th graders learned about the microbes all around us and which are the good, the bad, and the ugly.  Located near the school is Stephen's Creek watershed that has had high E. coli pollution over the last 10 years - E. coli is one of our sometimes good but sometimes bad microbes.  For this engineering challenge, the students were asked to purify the water from our creek with the SODIS method - using infrared and ultraviolet radiation from the sun to kill the microbes.  Each team chose a variable to test with their creek water - using baggies vs. glass bottles, black tarp vs. reflective surface, sari filtered water vs. SODIS treated water, aluminum foil boats vs. corrugated roof, ...  We allowed the experiment to run over the weekend and then the students tested their water with a bacterial/coliform petrifilm.  With these plates, bacterial colonies appear as purple dots on the pink plate.  E. coli colonies are purple dots with an air bubbles next to them.

Three days later, they observed the results.

Thankfully, our tap water did not have any detectable bacteria!

Stephen's Creek water - there are 8 E.coli colonies on this plate

From left to right - creek water, sari filtered creek water, SODIS treated creek water

From left to right - creek water, SODIS treated on a black tarp, SODIS treated on reflective surface