The study aims at validating the point-of-use investigations on long-term gravity-driven ultrafiltration for a scaled-up system, which could produce drinking water for a community of 100-200 inhabitants using natural surface water. Eawag, KWB and Opalium conceived a membrane-based small-scale system (SSS) which can operate without crossflow, backflush, aeration or chemical cleaning. Equipped with a biosand filter as pretreatment, it is designed to be robust, energy-sufficient (gravity-driven) and run with restricted chemical intervention (only residual chlorine). The containerised unit (10’) requires to be fed with raw water at a 2 m-height (energy-equivalent to ~8Wh/m3). As sole operational requirement, the membrane reactor is simply to be drained (i.e. emptied) on daily to weekly basis to superficially remove the material retained by the membrane and accumulated in the module. Otherwise, the system, which is only driven by a 40 cm differential pressure head (i.e. 40 mbar), is totally self-determined and autonomous. This report details the validation tests performed at Veolia Water Research Center in Annet-sur-Marne (France) from January to August 2009 : the gravity-driven UF compact unit showed promising results in regards to flux stabilization and flow capacity. Although early investigations take place in winter, an initial flux stabilization to 2.5 lmh is observed, which is below the reference results from the Eawag lab tests (i.e. 7-10 lmh, at 20 ± 2°C). However, the “scaled-up” system can benefit from a weekly drainage which seems to enhance the flux to 4-5 lmh, and thereby, the unit is to produce more than 4 m3/d, which is consistent with the design target of 5 m3/d. Moreover, the increase of the drainage frequency (to 3 times/week) along with warmer temperatures – leading to a better membrane permeability and biological activity - contribute to a further enhancement to 5-7 lmh. This is particularly relevant for South Africa, for which decentralized water supply is a burning issue and where the unit is to be further tested from November 2009. The investigations also highlighted the critical performance of the biosand filter as pretreatment. More than the UF step – whose membrane integrity was confirmed with bacterial analyses, the pretreatment step needed more frequent (i.e. monthly) O&M requirements. Therefore, the pretreatment necessity will be further assessed in South Africa where high turbidity peaks could represent an extra challenge for the unit.