Because of intense regulatory activity and recent microbial outbreaks, low-pressure membrane technologies are recognized by the water industry as very attractive processes for producing drinking water. Today, more than 2 millions m(3)/d (750 mgd) of drinking water is being produced worldwide using low pressure membranes, including microfiltration (MF) and ultrafiltration (UF). UF technology has been found to exceed current water regulation for turbidity, Giardia, and also virus removal. It should be noted that now out of the low-pressure membrane full-scale plants identified worldwide, UF applications represent about 74% of the total installed capacity. Today, UF technology is being used worldwide for treating various water sources. It is reported that 50% of the Aquasource UF membrane plants have being applied on surface waters, including river, reservoir, and lake source waters. This technology has been used in municipal drinking water application for more than 10 years. It should be noted that the oldest plant (October 1988), Amoncourt, France is still running with its original Aquasource membrane modules. The expected membrane life of 5 years estimated from laboratory experiments has been verified. The technology has now been optimized and is becoming competitive as compared to conventional processes for larger scale plant capacities. Projects with capacities greater than 100,000 m(3)/d (30 mgd) are being implemented. It should be emphasized that due to the rapid development of this fairly new technology, capital and O&M costs of UF membrane technology are still expected to decrease. The different types of treatment combination with Aquasource UF can ensure a treated water quality which meet current and future regulations for various source waters (groundwater or surface water with higher organic content). UF is perfectly suited to clarifying groundwater, mainly to eliminate particles (suspended solids or micro-organisms). For example, coupled with PAC (CRISTAL((R))), UF can be used equally well to treat groundwater contaminated by micropollutants such as pesticides or surface water with a high organic matter load. In addition, for surface water of high organic matter level and with fairly variable quality, a coagulation/ sedimentation step prior to UF should also be considered.