On August 19th we installed our first "slow sand filtration" unit in the Ngobe community of Bahia Honda on Isla Bastimentos. College volunteers Madison Busker of Emory University, Michelle Quan of the University of California at San Diego, and volunteer Mike Swigert, assisted in the creation and installation of the unit. The community is in an area where there are no wells. Their drinking water comes from small streams on adjacent properties and captured rain water. Rain water alone does not meet their needs, due to its seasonality and their lack of adequate storage devices. Ground water is typically contaminated at the source or after collection through the use of contaminated containers or hand contact. Water borne disease affects most community members with its greatest toll on the young and the old (which sometimes die). Believing that "the simplest system is the best system", we chose the slow sand flirtation method based on a recommendation by Eric Nyman of Greenlines, Inc. Slow sand filtration is a very simple system which has been in use for hundreds of years. This unit utilized a 70 gal. water tank and was fitted with PVC piping to provide a bottom output of filtered water. The water is poured into the top and passes down through 4 inches of fine sand, 30 inches of medium grade sand, and a bottom 3 inch layer of pea gravel. A fine plastic mesh was laid over the upper level to capture large trash from the water to be filtered. This can be taken out and shook off as required. Water initially added to the system stands for 2-3 days (not used) and creates its own set of bacteria on the surfaces and spaces between the sand and rock. After the 3 days, any additional water must pass through these bacterially active layers and it has been reported through laboratory tests that up 98% of the harmful bacteria are removed. Engineers without Borders have found units still in operation after 4 years with only minor maintenance required. We gathered biographical data of the families to use the unit and established a follow-up schedule to monitor their health progress. At the installation we noted some design changes which could improve the unit. For example, a cover over the outflow to prevent children and animals from making contact with this area and contaminating it would be very beneficial.
