Ochering

Ocher drainage canal in the Lausitz

When clogging is called precipitation of ferric hydroxides, and manganese (IV) oxide in water production plants. In oxygen-free water with a low pH value, large amounts of divalent iron ions can be dissolved (up to 100 mg / l). If such water comes into contact with atmospheric oxygen, divalent iron oxidizes to brown, trivalent iron hydroxide ("iron ocher"). This falls out and is deposited. Manganese ions dissolved in the water precipitate as black manganese oxide .

These soft deposits (incrustations) of iron ocher represent a major problem in water extraction, as they clog all parts of the system such as wells , pumps or pipelines.

In the case of well filters in particular, the clogging of the well can lead to the water pumping drying up. Drainage and injection wells are also affected . Especially if the fed-in water has come into contact with air and its oxygen content has increased as a result.

Since the composition of the groundwater cannot be changed, only the deposition process can be delayed or moved to another location. Airtight well heads reduce the entry of oxygen into the water and thus the oxidation of dissolved iron and manganese.

In addition to chemical-physical causes, biological causes are also suggested for the clogging. Iron and manganese bacteria are able to oxidize Fe ²⁺ and Mn ²⁺ to insoluble Fe (III) and Mn (IV) oxide hydrates.

Groundwater is partially de-iced so that it can be used as drinking water.

Deposits that are based on the precipitation of lime in the form of carbonates are called sintering .

Individual evidence

↑ Basics of iron removal and manganese removal. Retrieved on April 13, 2019 (encyclopedia entry in trinkwasserspezi.de).
↑ ocher formation. Retrieved on April 13, 2019 (encyclopedia entry in wasser.de).
^ ^A ^b Bernhard Odenwald, Uwe Hekel, Henning Thormann: Groundwater flow - groundwater management . In: Karl Josef Witt (Hrsg.): Grundbau-Taschenbuch . Volume 2: Geotechnical Methods. 7th edition. ISBN 978-3-433-01845-3 , pp. 615 f .
↑ ocher formation. Retrieved on April 13, 2019 (Spektrum.de).
^ Stefan Wilhelm: Water treatment: chemistry and chemical process engineering . 7th edition. Springer Verlag, ISBN 978-3-540-25163-7 , pp. 142 .

[1] Basics of iron removal and manganese removal. Retrieved on April 13, 2019 (encyclopedia entry in trinkwasserspezi.de).

[2] ocher formation. Retrieved on April 13, 2019 (encyclopedia entry in wasser.de).

[Grundbau-Taschenbuch_2-3] A ^b Bernhard Odenwald, Uwe Hekel, Henning Thormann: Groundwater flow - groundwater management . In: Karl Josef Witt (Hrsg.): Grundbau-Taschenbuch . Volume 2: Geotechnical Methods. 7th edition. ISBN 978-3-433-01845-3 , pp. 615 f .

[4] ocher formation. Retrieved on April 13, 2019 (Spektrum.de).

[5] Stefan Wilhelm: Water treatment: chemistry and chemical process engineering . 7th edition. Springer Verlag, ISBN 978-3-540-25163-7 , pp. 142 .