Open Sourcing Plans for “Low-Tech, High-Thinking” Water Filters

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Open Sourcing Plans for “Low-Tech, High-Thinking” Water Filters

Everyone deserves reliable access to safe water. All too often efforts to create water systems in developing countries are stymied by a lack of community insight and context appropriate solutions. Some studies have shown that 35-50% of these water systems become inoperable after five years. OHorizons, a non-profit organization currently tackling water safety, is working on ways to make safe drinking water available. They’re doing this by focusing on “Low-Tech, High-Thinking” solutions that are easy to implement and maintain, and by providing communities with the knowledge and skills to build and maintain this solution for themselves.


BioSand Filters are a great example of a “Low-Tech, High-Thinking” device. Developed in the ’90s by Dr. David Manz of the University of Calgary, these filters work by passing unclean water through layers of sand and gravel. Microbes get trapped in the sand and eventually resort to eating other microbes in the water in order to survive. This biological layer (or “biolayer”) takes about a month to develop naturally, and once it does the BioSand Filter can effectively remove up to 98% of bacteria, up to 99% of viruses and protozoa, and up to 100% of worms. The design also makes use of a natural siphon effect, which means no water pump is needed to get clean water out and there is always just enough standing water to maintain an effective biolayer.


The structure that holds all the layers together is basically a concrete box with an embedded tube for the siphon. Because its design is relatively simple, it’s easy to quickly train the beneficiaries of this technology to build and maintain them. The BioSand Filters can last up to 20 years and treat 3–12 gallons of water a day, all without electricity or the use of high tech equipment.

To make constructing these filters more accessible, OHorizons has created an open source plan for making the concrete bodies for these filters out of wood, as an alternative to relying on steel molds. The difference between a steel mold and a wood mold may seem subtle, but, unlike steel molds, wood molds are cheaper up front, can be built with local materials and (if necessary) without electricity, and don’t require special skills to make. You can find these plans, along with a number of additional resources, on the OHorizons website. Watch how the mold is put together and used to create a BioSand Filter in the playlist below.

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An important facet of the OHorizons mission is partnering with local organizations to help spread knowledge about BioSand Filters to those who stand to benefit most directly from using one in their home. They’ve partnered with LEDARS Bangladesh, the Daho Foundation in Kenya, and Agua Limpia Ecuador, to name a few. “Beneficiaries should be involved in projects. They should know how a technology is made and how it works. They should know how to source a replacement part and they should have the means to fix it on their own.” This credo  is the cornerstone of OHorizons’ outreach. The philosophy is that with the knowledge gained, people will be empowered to help themselves and others in their community long the after the volunteers training them have left.

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Their first outreach efforts in Bangladesh and Ecuador involved small teams on the ground to train individuals in-person. Executive Director Natalie Relich recalls, “In those settings, our team actually provided little formal ‘training,’ we were mainly ensuring that safety precautions were being taken and answering any questions as they came up.” (This was thanks in part to their thorough step-by-step manual.)

Later in 2014, OHorizons was contacted by a group who, working to bring BioSand Filters to Mali, had arrived on site only to discover that their steel mold hadn’t been built correctly. By providing this group with the OHorizons wood mold manuals, technical resources, and some very minimal instruction, OHorizons was able to help them build three BioSand Filter molds in a few short days without traveling to Mali themselves. This spurred the decision to make their technical resources fully open source and available in multiple languages, and it also encouraged them to work via virtual partnerships with organizations working on improving water safety within their own communities. Their mold making manual and exhaustive appendix are currently available in English, Spanish, and Portuguese, and they are currently looking for a volunteer to translate their work into French as well.


Since beginning their BioSand Filter implementation in 2014, OHorizons has helped communities with unclean water build over 1,530 BioSand Filters, providing approximately 7,650 people with access to clean water right in their homes. Dylan Lunney, the OHorizons Director of Communications, talked to me about their plans to provide clean water access to 1.1 million people worldwide by the end of 2021. “A lot will need to happen to make this a reality,” Lunney says, “Our top goals right now are to prove via our Bangladesh BioSand Filter project that this is a high quality solution for providing families with safe drinking water and to spread awareness about our organization and unique approach so that we can connect with financial sponsors and new implementation partners around the world. Everyone deserves reliable access to safe water!” Working with LEDARS, their goal is to distribute 200,000 BioSand Filters in Bangladesh alone over the next six years. Their wood mold plans will continue to be made available at no charge online, and they are working to make more translations of their manual available.

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A typical day for Lisa includes: getting up to see the sunrise, bicycling, interning at Make:, reading and writing short stories, and listening to audiobooks and podcasts for hours while working on projects or chores.

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