Undergraduate Thesis

Improving slow sand filters for communities with low incomes and limited water

Angélica Erazo-Oliveras


Indigenous people in Mexican southern communities do not have the infrastructure for potable water systems, causing the adoption of practices that increase contamination events, resulting in serious public health problems, most of them associated with gastrointestinal diseases. Slow Sand Filtration (SSF) is an inexpensive and efficient way to obtain potable water, but there are aspects of the filter's construction and function that needs to be improved (e.g., preparation of the sand, water flow rate) so that it can be used in communities with low incomes and limited water access.

In this study, we improved the construction of these filters at El Verde Field Station (EVFS) in Luquillo, Puerto Rico, we intend to apply the improved SSF system to the water of an indigenous community in Chiapas, Mexico. The cleaning process of the sand was improved in such a way that a of pail of sand can be cleaned in a reasonable amount of time (45 minutes), without the need of a lot of water. The operation of the three filters at EVFS using three different water flow rates (0.015, 0.03, 0.06 liters/minute/ m2) showed a better efficiency with a rate of 0.03 liters/minute/m2. The filter with this water flow removed 97% of the turbidity, 100% of ammonia and 100% of fecal coliforms of the raw water. The use of this technology by people with no technical or academic preparation was improved by providing educational materials appropriate to their skill levels. As part of this thesis a workshop was done in Chiapas, Mexico to present the slow sand filters to four integrants of the indigenous community of Saclum. It is vital that studies such as this continue so that SSF technology can be improved and the implementation of this technology can reach other communities with potable water problems.