When wells are placed sufficiently close to a river and pumped on a consistent basis, a portion of the river flow is drawn into the wells. This process is often called riverbank filtration (RBF). As the river water travels through the riverbed sediments and aquifer materials most suspended and dissolved contaminants are removed. This process can be termed as "natural" filtration as it is similar to the water filtration process. RBF has been used extensively for drinking water supply in many large and medium-sized cities in Europe and the United States. It is also gaining popularity in many recently industrialized countries such as Korea, and developing countries such as India. In order for RBF to work, a source water of dependable flow and reasonable quality must be present, and there must be hydraulic connection between the river and the aquifer where the wells are screened. Both horizontal collector and vertical wells are used for RBF. While the European countries prefer vertical wells (longer travel time), American water utilities prefer large-capacity horizontal collector wells because many of these utilities use the existing treatment facilities to treat the filtrate produced from the RBF wells.

The RBF process lowers turbidity of surface water significantly. When vertical wells are used, turbidity of the filtrate is similar to that of ground water. For horizontal collector wells, turbidity levels are generally less than 0.1 NTU. Additional filtration may not be needed. The filtrate from RBF systems is significantly lower in dissolved organic carbon, anthropogenic chemicals (pesticides, pharmaceuticals, etc.), and pathogens. If the RBF water is to be disinfected with chlorine, the potential for trihalomethane formation is reduced. The US Environmental Protection Agency provides "filtration credit" to water utilities that employ RBF at the front end of their treatment plants. This credit ranges from 05. to 1.0 log for protozoa Cryptosporidia depending on the hydrogeologic setting and well type. It is possible to conduct a demonstration study and based on the results request additional filtration credit. RBF water has the potential to become an important component of supply for cities located on riverbanks, particularly in developing countries. The surface waters in these countries are often polluted with microbes and chemicals due to inadequate waste treatment facilities. RBF is generally able to remove most of these contaminants.