Professional rehabilitation of wells and filters
The well lives
The compaction of well filters has usually biological causes. Water bacteria protect themselves against adverse environmental conditions with slimy, protein-rich substances. They form microscopic and macroscopic biofilms, i.e. they cover the surfaces in the filter and well casing as well as in the downstream water systems with more or less thick “living” protein layers. These provide favourable living conditions for specialised bacteria and fungi that convert and separate organic and inorganic substances which are dissolved in the water.
This leads to grain growth in the filter and thus causes changes in the grain and gap distributions originally used in the filter. In extreme cases, the gravel grains grow together to form solid concretions, the filter function is disturbed or simply does no longer exist.
CARELA® rehabilitation agents dissolve iron-, manganese- and, of course, all types of limestone-containing deposits. Incrustations, sintering and slime are also reliably removed. Iron-, manganese- and sulphur-reducing bacteria and fungi are exposed and safely killed.
The aim of well rehabilitation is to treat aging wells in such a way that they regain or even exceed their original capacity.
CARELA’s innovative research and development led to new products that solve global problems of water supply in an effective, environmentally friendly and material friendly way.
Filter cleaning and filter rehabilitation
Gravel filtration is a process used for deferrization and demanganization in potable water treatment. Both open filter basins and closed filter vessels are used. The filters are designed as single- and multi-layer filters. Various filter materials such as quartz gravel of different classifications, but also activated carbon, hydroanthracite, pumice and plastic materials (bio balls) are used.
After prior aeration the iron contained in the water is retained in the filter as Iron(III) hydroxide. Manganese is oxidised by biological or chemical processes and forms firmly adhering coating on the filter gravel.
When the filter is backwashed, only the iron hydroxide is removed from the filter bed but often it is not removed completely. With increasing operating time of the filter, solid iron and manganese coatings form on the gravel grains. This leads to grain growth and a change in the originally calculated grain size distribution and the gap volume. The filter resistance increases, the filter runtime between backwashes is shortened and the required amount of backwash water increases. Overall, this increases both the operating costs and the iron and manganese contents in the filtered water – the filter loses its performance!
Consequence: The filter material must be replaced at great expense! The more efficient alternative is to rehabilitate the filter!
Filter gravel with firmly adhering deposits
Filter gravel after rehabilitation