Surthrival Trailer Mark 1 Update 38 Creating a Biosand Pre-Filter for Water Purification

Hello my fellow Steemians!

Sorry its taken me a while to create a proper post, but I've finally got to a point where I can get back to my primary focus which is on the trailer project. Today I worked to create a biosand water filtration system that can be integrated into the water collection/storage system for the Surthrival Trailer.

I learned about biosand filtration several years ago during some research into low cost water filtration techniques. Biosand filtration has been used for many years in remote areas as a way to create sustainable clean drinking water sources. There have been many studies done on these types of systems used in remote locations around the world which report that biosand filtration does a pretty good job as a low cost water filtration device. The following is one such source. https://www.wsp.org/sites/wsp.org/files/publications/WSP_biosand_cambodia.pdf

I am incorporating this filter into the trailer as a means to provide a pre-filter for collected water, and generated water via a dehumidifier. The final filtration of drinking water will be handled using a high quality gravity Alexa-Pure water filtration system.

Here is the view of the biosand filter created from a 3" schedule 40 pvc pipe cut to 4' with endcap.

The biosand filter consists of 3 layers : Top-Fine Sand, Middle-Small Pea Gravel, Bottom-Large Pea Gravel. As can be seen in the image below.

A standard 3/4 garden hose valve was used. A hole was drilled into the approximate center of the 3" pvc endcap using a step drill bit. The bit stopped around the 1" diameter mark. It's important to get close to this value so the valve may thread properly into the hole.

Teflon thread tape was applied to the threads of the valve.

The valve was tightened into the endcap with some channel lock pliers. Its optional, but the endcap may be glued on with pvc glue if desired. I would recommend gluing if you will be moving the filter around a lot.

I started by adding my largest size of pea gravel which was approximately 7 handfuls just enough to cover a volume above the endcap of the pipe. You can add more or less of the larger size gravel as you desire. Its purpose is to allow the water to easily flow after it has seeped through the sand in the filter. The sand is doing the majority of the work for the filter.

The next step is to add the small pea gravel on top of the larger gravel. This layer should be about the same, and you can error on adding slightly more of this gravel. The purpose of this layer is to keep the particles of sand separated from seeping down into the larger gravel area, but still allowing the water to seep through to that section.

The final step is to add a column of fine sand. The sand does all the work in the system as it give a tremendous area for competing bacteria to thrive. These bacteria are the magic ingredient in biosand water filtration as they are in charge of breaking down the harmful pathogens that may exist in contaminated water. The longer the system is established the better the filter becomes.

I want to caveat this by saying, I would not completely rely on this type of filter for my drinking water unless I had no other secondary option for a final filtration.

You should leave a space at the top of the filter to allow for pouring a larger amount of water to keep from splashing over and giving you the ability to filter a larger amount of water.

Thank you for your time if you checked out my update for my Surthrival Trailer project.

P.S. If you understand the principle, this type of filter can be built many different ways, using any kind of container you have on hand.

Yours in liberty toward a brighter future, may the great creator bring peace and joy within your hearts, Greg @makinstuff