The use of polymeric membranes that do not require electricity and cleaning is an attractive technology for use in the point-of-use (POU) treatment of water in areas where access to drinking water is limited. This study sought to evaluate the performance of a biofilm-controlled gravity-driven membrane (GDM) in the treatment of well water contaminated with fecal microorganisms and to validate the operating and maintenance concepts described in the literature. The effects of different pressures (50, 70, and 100 mbar) were tested using a 100,000 Da ultrafiltration (UF) membrane across 129 days of continuous filtration. After stabilization, the system achieved average permeate fluxes of 4.4 ± 0.2 L m−2 h−1, 4.7 ± 0.3 L m−2 h−1, and 6.5 ± 0.4 L m−2 h−1, and total membrane resistances of 4.2 × 1012 m−1, 5.4 × 1012 m−1, and 5.5 × 1012 m−1 for the hydraulic loads of 50, 70, and 100 mbar, respectively. An analysis of the filtrates showed a 3-log removal efficiencies for E. coli in all filters, producing water that was in compliance with potability standards. The average turbidity removal efficiencies were 72 %, 74 %, and 50 % for hydraulic loads of 50, 70, and 100 mbar, respectively. The total organic carbon content and the ultraviolet absorption at 254 nm were reduced by 7–17 % and 10–30 %, respectively. The membrane did not affect the removal of chlorides and sulfates. The biofilm, developed in an oligotrophic environment, contributed to the filtration of a constant amount of water (flux stabilization) but did not improve the quality of the filtrate. The results of this study suggest that the GDM filtration system can be considered as a potential alternative to produce POU decentralized drinking water in terms of both quantity and quality. The constant permeate flux and the complete removal of E. coli without the need for backwashing or cleaning make the technology attractive for application in developing countries to treat well water at low cost and minimum maintenance.