Sand barrel filters can be used to filter water, making it fit for drinking.
Groundwater drawn from wells and aquifers is renowned for its clarity and clean, refreshing taste. It attains this purity by being filtered through the many feet of rock, sand and soil between the surface (where it first falls as rain) and the underground reservoir from which it is drawn. It is possible to use a barrel filled with sand to simulate this process, along with a little help from a beneficial set of microorganisms collectively called schmutzdecke. This "slow sand filter" is useful in case of natural disasters during which municipal water supplies and well pumps may not be functional.
Instructions
1. Cut a hole in the bottom center of a 50-gallon plastic barrel using a hole saw. This hole will allow you to insert the pipe that will collect the water filtered by the barrel.
2. Drill rings of four to six holes with a diameter of about 1/8 inch around the circumference of a 1- to 2-foot piece of PVC pipe, with a few inches between each ring of holes. Leave the last 4-5 inches of pipe undamaged. The holes will allow water into the pipe from inside the barrel, with the length without holes being the part that extends outside.
3. Insert the pipe into the hole in the barrel until only the part without holes extends outside it. Do this with the barrel on its side, propping up the length of pipe inside the barrel with a piece of scrap wood or whatever is handy. Apply marine caulk around the intersection of the barrel and the pipe both inside and outside the barrel and allow it to dry.
4. Attach a pipe cap and hose fitting to the inside and outside ends of the pipe, respectively, using epoxy as an adhesive. Set two of the cinder blocks down side by side, with about 5 inches between them, and stand barrel up on top of them with the pipe end down. This should be in the place you intend your filter to be used, and should be in partial sunlight to facilitate the growth of the schmutzdecke layer. Do not put it in direct sunlight because that would tend to dry out and kill the organisms.
5. Fill the barrel with sand to a depth of at least 30 inches and layer one or more flat stones on top of it until as much of the sand as possible is covered by stone.
6. Attach 4 to 5 feet of rubber hose to the hose fitting. To fill your filter for the first time, keep the end of the hose above the level of the top of the barrel and use a reservoir or garden hose to fill it. This will fill the barrel from the bottom up, preventing bubbles from forming in the sand that could block water flow. When you are done filling it the first time, attach the nozzle to the hose and close it off.
7. Once the schmutzdecke layer has formed, fill the barrel by pouring water gently in the top and opening the hose to let filtered water out into whatever container you want to store it in.
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