Well regeneration

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Schematic representation of the filter gravel filling of a well

Under well rehabilitation is meant removing performance-reducing deposits from a drilling or horizontal filter wells , to increase its yield.

In the case of a new well (1) the piping, the well sump and the filter material bed (material surrounding the filter in the annulus; usually gravel, sand or glass balls) should be completely free of deposits. As a well's service life increases, wells and, above all, their filter material embankments age.

Aging processes

The deposits formed by aging processes are divided into inner (2) and outer (3) deposits.

Sanding up (silting up)

Silting up often occurs in wells that are not completely sanded during the construction phase. This process is aided by an incorrect selection of the filter material. An unfavorable installation location of the well pump can also cause the well to silt up. Many soils contain fine sands, which are mobilized by the changed hydraulic conditions and can then clog the pores in the filter material. By discharging the fine grain fraction of the soil, suffosion can lead to subsidence of the soil and thus to further damage to the well.

Incrustations

Encrustations can appear as ocher or sintering .

Ocher deposits are usually caused by iron or manganese precipitation . In the groundwater there are mostly low oxygen concentrations, which means that iron and manganese are mainly in dissolved form. These compounds can be oxidized by the ingress of oxygen at the filter slots or in the filter material. This leads to a precipitation of the metal oxides which are sparingly soluble and adhere to the surrounding material. Over time, the growth of these layers leads to a reduction in the pore space or to a closure of the filter slots.

Sintering usually consists of calcium carbonate precipitated from the groundwater . This precipitation can be caused, for example, by the outgassing of carbon dioxide from the groundwater. Changes in the pH value in the groundwater can also lead to sintering of the well.

Mucilage

If there are increased amounts of nitrogen compounds or organic substances in the extracted groundwater, fungi and bacteria can increase the build-up of slime in the well. Mucilage in wells can also be caused by sulfur-processing bacteria if sulfur- and oxygen-rich water is mixed with one another in the well.

Deposits of aluminum compounds

If groundwater with different pH values ​​mixes in the well, aluminum compounds can precipitate and deposit on the system components.

corrosion

Corrosion occurs in wells with metallic materials at low pH values, through contact corrosion (contact with more noble metal parts in the water) or through stray currents.

Regeneration process

The purpose of a well regeneration is not only to remove the optically visible internal deposits, but above all the external deposits behind the piping in order to achieve sustainable cleaning success and thus an increase in the performance of the well. There are many different mechanical and mechanical- chemical regeneration processes available, which work according to the following principle:

  • Separation: breaking the bond between deposits and filter gravel or filter pipe
  • Discharge: In parallel to the separation, it is necessary to simultaneously pump out the (detached) deposits from the well
  • Control: Monitoring of the regeneration progress

See also

literature

  • Klaus-Dieter Balke, Ulrich Beims, Franz Wilhelm Heers, Bernward Hölting, Reiner Hormighausen and Georg Matthess: Textbook of Hydrogeology, Volume 4, Groundwater Development - Basics, Well Construction, Groundwater Protection , Water Law . Borntraeger brothers, Berlin - Stuttgart 2000, ISBN 3-443-01014-8 . Pp. 479-505
  • DVGW e. V .: Technical rule worksheet W 130, well regeneration . DVGW German Association of the Gas and Water Industry e. V., Bonn 2007, ISSN  0176-3504 .