Field evaluation of a horizontal gravel prefilter coupled to a slow sand filter for the production of potable water from a surface water source in Puerto Rico

The purpose of this thesis is to evaluate the effectiveness of the Horizontal Flow Gravel Prefilter (HFGP) coupled by the Slow Sand Filter (SSF) to produce safe drinking water in Puerto Rico. The surface water treated had a problem of chronic fecal contamination. Results showed that the coupled system can consistently produce water below 1 NTU of turbidity according to the water quality compliance requirements. The HFGP brings an additional help to reduce fecal contamination. The prefilter removed 50% of turbidity, 85% of suspended solids but it can not guarantee removal of turbidities below to 25 NTU all of the time. However, simulations of extreme turbidity events showed that SSF managed influents up to of 150 NTU and consistently produce turbidities below 1.0 NTU. The coupled system is adequate to produce drinking water and can be used by other rural communities in Puerto Rico and in other tropical environments.