Bank filtration
River Bank filtration is a type of filtration that works by passing water to be purified for use as drinking water through the banks of a river or lake. It is then drawn off by extraction wells some distance away from the water body. The process may directly yield drinkable water, or be a relatively uncomplicated way of pre-treating water for further purification.[1]
Usage
The process has been in use in Europe, especially in Germany along the Rhine and later in Berlin, since the 1870s. Major facilities also exist in many other countries, including the United States, where Nebraska is leading in the use of such facilities.[1][2]
Procedure
Three filtration mechanisms are possible. Physical filtration or straining takes places when suspended particulates are too large to pass through interstitial spaces between
Chemical filtration or ion exchange may take place when aquifer soils react with soluble chemicals in the water.[3] Most 'normal' contaminants (microbial organisms and inorganic or organic pollutants) will be removed by bank filtration, either because they get filtered out by the sand/earth of the bank, or because the passage time (which may be days or potentially weeks) is sufficient to render them inactive.[2] Research has also shown that the removal efficiency depends not only on the contaminant, but also on the "hydraulic and chemical characteristics of the bottom sediment and the aquifer, the local recharge-discharge conditions, and biochemical processes".[1]
Limitations
There have been indications that some pharmaceutical compounds (medical drug traces from human use) may not always be sufficiently removed by bank filtration, and that in areas with substantial contamination of this type, additional treatment may be needed.[1]
Wastewater applications
See also
References
- ^ a b c d Occurrence and fate of pharmaceuticals during bank filtration Archived 2008-08-29 at the Wayback Machine - Heberer, Thomas et al.; Technical University of Berlin / United States Geological Survey, ca 2001
- ^ University of Hawaii, Manoa, bulletin, 2000/08. Accessed 2008-03-24.)
- ^ Metcalf & Eddy (1972). Wastewater Engineering. McGraw-Hill. p. 644.
- ^ Polar, Jose A. (June 2007). "The Fate of Pharmaceuticals After Wastewater Treatment". Florida Water Resources Journal.
- ISBN 0-471-92435-0.
- ^ Fair, Gordon Maskew; Geyer, John Charles & Okun, Daniel Alexander (1968). Water and Wastewater Engineering, Volume 2. John Wiley & Sons. pp. 34–4&5.