Slow sand filtration was once a common treatment method for drinking water in developed countries such as the United States and Japan until more advanced technologies emerged.  However, the last few decades have seen a rebound in slow sand filtration in the developing world such as Haiti, Cambodia and Guatemala.  The process is a simple one, making slow sand filtration an effective solution to help provide clean water around the world.

The main process behind slow sand filters is not the sand filtering out contaminants like a traditional filter, but rather the top layer of sand developing a biologically active layer that consumes harmful pathogens and bacteria such as Escherichia Coli (E. Coli), Giardia, Enteric Viruses, heavy metals and many other contaminants.  Traditionally this layer is known as a schmutzdecke but is more commonly known as a bio-layer, giving slow sand filters their nickname of bio-filters.

EWB-UCF will be purchasing already made bio-filters from an organization named Pure Water for Haiti, which has been producing the filters for several years and has been an instrument in bringing clean water to Port Au Prince following the earthquake.  The filters have proven successful in and around Port Au Prince and we plan to bring this technology to the remote community of Mare Brignol. 

Intermittent bio-filters differ from traditional slow sand filters in that they do not require replacement of sand, which can be both costly and unsustainable. Cleaning the filter occurs when the biolayer grows too much whereby flow is restricted, when this happens the top layer of sand is stirred and the suspended particles removed until flow resumes.  The filters are solely constructed of concrete and PVC pipe, making them simple and durable.  If managed properly the filters require no outside replacement parts, thus enabling the user the independence of providing clean drinking water for themselves.  

Bio-filters, like any biological system, require maintenance and knowledge of how the filters work.  This includes proper cleaning of the bio-layer and proper filter usage.  Without the proper education in maintaining the filters, many have found them to not work properly.  That is why EWB-UCF is partnering with Pure Water for Haiti in bringing filter trainers to the community of Mare Brignol prior to installation.  With each filter installation bringing  a face-to-face training course in proper use and maintenance of the filter, enabling a community member to take water treatment on their own.  Along with full community involvement in decision making processes, such as filter introduction and education, EWB-UCF sees this as the most effective and sustainable solution for Mare Brignol.

So far five filters have been installed during the December 2009 trip.  The filters were part of a pilot study to see how effective the filters worked within the community.  Based on the success of the pilot, we plan to install 30 more concrete slow sand filters in December 2010, and more in May 2010.  We look forward to continue working on this project to enrich the lives of Mare Brignol!