Purifying dampen near layer of rocks, gravel etc. n-e-1 enjoy any devout website on it?? Purifying water beside a bottle. any websites or good methods anyone know...

Purifying water beside a bottle. any websites or good methods anyone know of?
You know of the method of purifying water by putting layer of soil, gravel, sand etc in a bottle? Any info on it (i.e., websites, proposal etc.,) would be greatly appreciated. Thanx!