It's amazing; My kids have latched onto the idea of water filtration and wont let go. They have tried repeatedly, since the last post, to find some way to clean and filter water. I finaly put a stop to their experimentation when they insisted that I tape two Q-tips together so that they could scoop water with them from one cup to another.
At that point I realized how serious they were so I had them pull out a couple of empty plastic bottles and showed them how to make a sand filter. It actually worked amazingly well considering how little filtering material there was in the upper bottle.
I made sure that they did as much work as possible collecting pebbles and larger rocks. I had to find a source of sand. Fortunately there was a small trickle by some plants near my apartment. After all of the parts were collected I washed them out in the sink, and explained to my daughters that we had to wash out the dirt, because" dirt and water make what?" "Mud!" they replied. And with that they understood that they didn't want to drink mud. So, I washed down the pebbles and sand to get the dirt out, then poured the sand into a coffee filter and set it into the first bottle, which I had already poked holes in the bottom and cut the top off. Then I poured the pebble on top. This collapsed the coffee filter into an envelope shape which is not what I wanted, but it worked out pretty well anyway. Remember; You can do the same thing for real with two large buckets.
Next, I took the whole contraption outside and poured water into the top for my kids to watch it work. It took a couple of rounds for it to run completely clear, but after that it seemed to run fine. I let my kids go with it and didn't see them again for an hour (please remember it been in the upper 90s to low hundreds the last week).
Science, Survivalism, and Raising Kids - Good Times :-)