Today, we made water filters. It was really satisfying to see that we could filter filthy water into almost clean water.
We began studying this unit after reading a book called Saving Salila’s Turtle about this girl called Salila who lives near the Ganges River which is horribly polluted. When she comes to the river one day, she finds a turtle covered in boat oil crawling around on the beach. She immediately adopts this creature and takes it home. Her father doesn’t like the idea of keeping it but her mother, an environmental engineer, doesn’t mind. So, together they hatch a plan to build their own filter. They make enough water for the turtle to live in and the story has a happy ending.
First, we talked about what was polluting the Ganges, so we listed a bunch of things that could be polluting it. We named oil, people washing their clothes or bathing causing more soap oil to go into the water. We also named that storms could cause sticks and silt to get blown into the river, even though that wasn’t mentioned in the story, it was very likely. Another thing we named was maybe human waste was dumped into the river, and that maybe this is what is creating the brown color.
We then were assigned to actually build filters ourselves to solve the problems Salila had. On the first day of building, we tested out some of the ingredients of our final product. We split into groups, and each group was given a bottle of different types of contaminated water. There were three types. A was mixed with tea, B was mixed with soil, and C was mixed with cornstarch. I felt sorry for the C groups because the cornstarch was permanently dissolved in there. Only like, carbon filters could have separated those two. Thankfully, we got a B and started trying to filter out soil using different materials. Here is a table:
|Sand & Gravel||Check||Check|
We moved on to build our final filter. We were given goals to try to reach. Our teacher brought out 5 bottles filled with different types of water to compare against. There was 5, which was dirty contaminated water, 4, with a lighter color and fewer particles. 3 was even lighter and had fewer particles, 2 was almost clear with a tiny amount of particles, and 1 was perfectly clear and clean water.
I proposed to use a little berry strainer, but my group declined it. In the first design, we used the same upside-down bottle with the bottom cut off as before. We first put a dried out baby wipe on top to get the big particles, then below that, we had another baby wipe inside of 4 stacked coffee filters, then finally a bundled up mosquito screen. Our second design was similar, except instead of the baby wipe on top, we stretched out the screen. And instead of the screen on the bottom, we used sand and gravel. Here is how that went:
With this design, we had very good results as you can see. I liked this unit very much and hope we will come back to studying it in Middle School!
Here are some photos: