page_title: Bank filtration
section_title: Procedure
hierarchical_section_title: Bank filtration / Procedure
caption_attribution_description: V popředí zatravněný pás se studněmi přirozené infiltrace. V úpravně vod v Káraném se tyto studně nachází ve vzdálenosti 200-300 m od řeky Jizery. Využívají faktu, že voda přirozeně prosakuje skrz okolní písky a tak se čistí. Takovýchto úseků je v okolí Jizery 7 v celkové délce 30 km. Každá sběrná studna je tvořená kameninovou rourou, která je ve spodní části po obvodu perforovaná. Uprostřed je trubka na čerpání vody, která je spojena s násoskou. Ta vytváří podtlak a tak dochází k čerpání vody. Voda z násosky teče potrubím do sběrné studny a poté přes načerpací stanici do úpravny v Káraném, kde je ošetřena chlórem. Na fotografii je pak vidět pásmo hygienické ochrany vod I. Stupně v bezprostřední blízkosti studní. V okolí, kde je umožněna zemědělská činnost v omezené míře se pak nachází pásmo hygienické ochrany vod II. stupně. Tento systém je v provozu od roku 1914 a jeho kapacita je 900-1000 l/s. Doba zdržení je asi 1 měsíc. Mocnost zdejších štěrkopísků je 8-12 m. Zdroje: Křivánek, Oldřich a Kněžek, Miroslav. 2001. Zdroje pitné vody v Káraném. Principy získávání vody v oblasti káranské vodárny. Pražské vodovody a kanalizace a.s.
context_page_description: 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.
context_section_description: Three filtration mechanisms are possible.  Physical filtration or straining takes places when suspended particulates are too large to pass through interstitial spaces between alluvial soil particles.  Biological filtration occurs when soil microorganisms remove and digest dissolved or suspended organic material and chemical nutrients.  Chemical filtration or ion exchange may take place when aquifer soils react with soluble chemicals in the water.  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. 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".
  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.
caption: Well line bank infiltration at Jizera river, Czech Republic.
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