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Managing cyanotoxin risks at the drinking-water offtake
Published in Ingrid Chorus, Martin Welker, Toxic Cyanobacteria in Water, 2021
Justin Brookes, Mike Burch, Gesche Grützmacher, Sondra Klitzke
Bank filtration is characterised by drinking-water wells in the vicinity of a lake or river that are fed mainly by water infiltrating from the surface water supply (Figure 9.3). For other types of MAR, surface water is first conveyed into infiltration ponds, trenches or wells from which it infiltrates into the subsurface aquifer and is reclaimed in nearby wells. Due to different hydrogeological settings, residence times may vary between a few days to several months. The decisive parameters for the residence time are the hydraulic conductivity of the aquifer (governed by the grain size distribution as well as the existence of a clogging layer) and the distance between point of infiltration and well. Usually, infiltrated surface water blends in the well with ambient groundwater, diluting possible contaminants originating from the surface water (and vice versa; however, groundwater contaminants may also be diluted by uncontaminated surface water).
Problems and promise of managed recharge in karstified aquifers: the example of Lebanon
Published in Water International, 2020
Wisam M. Khadra, Pieter J. Stuyfzand
River bank filtration is associated with induced subsurface infiltration from nearby groundwater extraction, which creates a hydraulic preference for groundwater flow towards pumping wells. This constrains the flow and reduces the random losses expected in karst. Bank filtration is recommended nowadays as a superior alternative to surface water abstraction, to avoid the problems of turbidity, pathogens and pollution. It is widely spread in the world, and has had high success, for instance in Germany, Netherlands, Slovakia, Hungary, Switzerland, India, Egypt and the US (Dillon & Stuyfzand, 2019). This option can easily gain public support because of its easy implementation, low cost, good investment of surface water that is lost otherwise, and natural attenuation of river water during aquifer passage, resulting in lower concentrations of suspended material, pathogens and various chemical pollutants (Dillon, Miller, Fallowfield, & Hutson, 2002; Medema & Stuyfzand, 2002; Stuyfzand, 1998).