Slow Sand Filter
HOW DIRT CLEANS YOUR WATER
Many of us have made one of the first steps toward water conservation by collecting rain water. But what do you do once you have the water? Have you ever thought to drink it?
Our first thought -- absolutely not! It came off the roof and gutters with all of the other dirty contaminants including dirt and pigeon waste. Not our first choice of water to consume. But surprisingly you can actually turn that filthy water into clean, drinking water by using what you’d least expect -- SAND… which is essentially just another form of dirt. It doesn’t sound very tempting, but surprisingly the process actually works!
How does it work?
The gist of the way it works is water enters the barrel. In the middle of the barrel is a layer of sand and the water above the sand is biologically active called Smutzdecke. The microbes in that layer of sand eat many of the impurities and biological contaminates in the rainwater. The biolayer takes about 2 weeks to form once water is sitting inside the barrel. Several feet of sand do the rest of the work.
Most designs call for a diffuser plate. This is a round plate with holes in it so that when water is pored into the sand filter water will drip down being sure not to disturb the bio layer.
The water slowly trickles through the sand and at the bottom you have clean, drinkable water.
The top layer of water will have to be removed periodically because it is infested with microbes, but otherwise, you've got yourself a home-made rainwater filter that does not require any chemicals or electricity to operate. It’s a cheap and easy way to clean impurities out of your water.
Here at the GreenDesert.org we built our sand filter for less than $100 and we use it to clean debris out of the water before we water our garden.
Although the bio layer takes out living organisms that causes us to get sick, the filter may not take out all chemical pollutants in the water. So if there are any chemical contaminants in your original source of water… there will be a chance they are still there.
Bottom-line, a sand filter does a good job of cleaning your water. But always test your water before drinking it… don’t just assume it’s safe simply because it went through the sand filter.