Worldwide potential of riverbank filtration

As the demand for piped drinking water is increasing in developing economies, water utilities are facing the challenge of treating surface water that is often polluted. Furthermore, many cities in developing countries are examining the feasibility of providing a continuous pressurized supply on a 24 h basis to reduce cross contamination. This practice is adding further stresses to treatment capacities in many cities. Riverbank filtration (RBF) is considered to be an excellent treatment (or pretreatment) technology for drinking water production. When wells are placed sufficiently close to a river and pumped, a part of the pumpage is induced infiltration water from the river. In the case of a lake, the process is called lake-bank filtration. As the induced surface water filters through the riverbed sediments and aquifer materials, most suspended and dissolved contaminants, including pathogenic bacteria and viruses are filtered out. RBF has been used in Europe for more than a century to supply drinking water to communities along the Rhine, Elbe, Danube, and Seine rivers. RBF systems have also been supplying drinking water to several communities in the US for nearly half a century. In post-World War II Europe, when the rivers were significantly polluted with municipal and industrial effluents, RBF was the most efficient method of producing high quality drinking water. Pollution in the Rhine in 1960s and 1970s was so severe that the river was termed the ‘‘Sewer of Europe’’ in the Netherlands. At that time, RBF and filtration of river water through dune sand provided drinking water to many communities in the Netherlands. Many of these systems are still functioning well. As late as 1980s, rivers such as the Elbe that passed through the former Czechoslovakia, East Germany, and West Germany contained significant amounts of industrial waste, particularly from the pulp and paper industry. Water quality was poor. RBF systems on the Elbe around the City of Dresden were able to remove most of the surface water contaminants. Recent studies show that RBF is capable of removing many pharmaceutical compounds, pesticides, and endocrine disrupting chemicals that are present in surface water. Removal of natural organic carbon also reduces the formation of disinfection byproducts during chlorination. Some of the most densely populated countries are located in Asia. Drinking water supplies in large cities in those countries mostly come from surface sources. For example, in India and China, a large number of cities are located along rivers, and provide potable water to hundreds of millions of people. In the Ganges Plains, many rivers are perennial, fed by snow and ice-melt waters from the Himalayan mountains. The major rivers of China also receive snow-melt runoff. The perennial nature of these rivers attracted the development of cities along their banks. Many of these cities are large with millions of people living in them. Subsequently, irrigation systems were developed to produce crops during the summer months. Reduction of flow due to irrigation diversion, and discharge of municipal and industrial effluent (often receiving only primary treatment) have caused tremendous water quality degradation in these rivers. For example, the City of Kanpur, India, located on the bank of the Ganges, has a metropolitan population of about 5 million. Before the construction of a new barrage and treatment plant, a diversion canal brought water to the treatment plant. The main industries in Kanpur are textiles and leather tanning. Often blood-red dyes can be seen in the river from the railway bridges. The treatment C. Ray (&) Faculty of Engineering, Driftmier Engineering Center, University of Georgia, Athens, GA 30602, USA e-mail: cray@engr.uga.edu