For this project, you need a large plastic soda bottle, paper towels or napkins, cotton balls, sand, gravel and active carbon if possible. Cut the large plastic soda bottle in half and clean both parts thoroughly. Turn the upper half upside down so that it resembles a funnel, and insert the funnel inside the lower half of the bottle. Place the paper towel, cotton balls, sand, gravel and active carbon inside the funnel in the order given and press a few times to make sure they are compacted. To test out your homemade purifier, try pouring dirty water on top of your assembly and see the results. You can also try putting different layering orders or styles to see what will work best.
Dissolve red food coloring in water and slowly bring it to a boil. Once boiled, place the red solution in a large bowl and add some salt. Place a collecting cup inside the middle of the bowl, making sure the red solution only reaches half of the cup's height. Cover the whole bowl with a clear plastic wrap, allowing the middle of the plastic cover to sag a little in the middle. Put several elastic bands around the edges of the bowl to secure the plastic, and then put a small rock on top of the plastic directly over the collecting cup. Place the setup in direct sunlight and check if the cup inside starts collecting water. The water inside the cup should be colorless and tastes less salty than the original red solution.
Collect some muddy water and let it settle for one whole day in a container. Once the sediment settles, carefully collect the water on top without disturbing the sediments at the bottom. Put the dirty water in another container. Prepare a funnel and a piece of filter paper and mold the filter paper into a cone inside the funnel. Prepare another container and transfer the dirty water from one container to another using the filter. Once done, divide the filtered water into equal amounts. Put some potassium alum on the first half and leave the other half alone for comparison.
Take a square piece of flannel and stitch its opposite ends together to form a conical bag. Do this to three other flannel pieces. Take four O-rings and stitch one into each cone to form the cone lips. Using some nylon string, assemble the cones one above the other so that the bottom of each cone is suspended over the lip of the next one. Hang the assembly through a wooden holder with a hook attached, and position over a receiving vessel. Pour dirty water into the topmost sleeve. The water that is caught should be relatively free of odor and sediment.