Decision support tool

Background information

Drinking water abstraction

The type of raw water abstraction and raw water quality determine which further treatment steps are necessary. If surface water is directly abstracted the intake of cyanobacteria should be avoided if possible; otherwise it shall be necessary to assure that the treatment used is able to eliminate cyanotoxins.

Water abstraction after sediment passage (bank filtration [1], artificial recharge [2]) is a near-natural technique for combined drinking water abstraction and treatment. Water abstraction via bank filtration or artificial recharge does not necessarily require a further drinking water treatment step as these techniques are able to remove cyanotoxins in the case of a suitable subsurface and retention times.

Further information on drinking water abstraction and cyanotoxins can be found in the following.

Direct abstraction

Sediment passage

[1] Bank filtration

Bank filtration is water abstraction from wells which are largely fed with water from a nearby river or lake and purified by travelling through the bank (i.e. subsurface, mostly with sand or gravel). Retention times in the subsurface are typically between about 3 days and six months, depending on the distance of the shoreline, river level, local geology, and the construction and maximum flow rate of the wells.

[2] Artificial groundwater recharge

Artificial groundwater recharge is achieved by the infiltration of surface water or purified waste water via e.g. infiltration ponds or soakaway ditches in the subsurface to employ this purification potential and increase ground water quantities for abstraction. Artificial recharge is usually used if the natural amount of groundwater is not sufficient to cover water demand.