As a demonstration, we constructed a prototype sand filter from cheap and easily accessible materia...
As a demonstration, we constructed a prototype sand filter from cheap and easily accessible materials. The filter itself consisted of pool filter sand, medium-sized stones/gravel, and some sponge cut into a disc and placed on top. The grain size of each was graded from largest at the bottom to finest at the top.
The filter was contained by two 5-gallon buckets. The bottom bucket held the actual filter materials, while the top bucket (which is suspended over the bottom bucket by an interior shelf of sorts) contained the water to be filtered. A small hose was attached to the bottom bucket for drainage of the filtered water. The stones mentioned in the first paragraph are placed at the bottom of the bucket and are essential for allowing the filtered water to flow into the hose.
Dirty, soapy "grey" water went in; clear, clean water came out. The final product would still contain pathogens if put to use in a real situation, which means that in the second prototype model there would have to be a stage dedicated to disinfecting the water.