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Mineral Scale
 
Slime Bacteria

 

Declining specific capacity is usually the result of:
  • Mineral scale
  • Slime bacteria
  • Silt or sand buildup in the screen or the well itself
  • Physical obstruction of the screen or borehole
  • Changes in the aquifer or the geological area around the well site
  • Limitations of the aquifer
 
Mineral scale
Groundwater often contains significant levels of minerals. The type of minerals and their concentration depend on the well's location and the local geology. In groundwater, naturally occurring carbonic acid, produced from carbon dioxide in the water, keeps the minerals in solution. When the water is pumped, carbon dioxide is lost through depressurization as the water is drawn from the formation into the well. The minerals separate from solution and precipitate on the well screen and formation as hard scale. In areas where sulfates, iron, manganese and carbonates are present, mineral scale can build up in layers. Slippery blistering or bubbling nodules may appear on the pump, pump column or well as a result of electrochemical or bacterial activities.
 
Slime bacteria or iron bacteria

The naturally occurring heterotrophic bacteria present in every aquifer can produce slime. Water velocity constantly draws these bacteria in, increasing their numbers in the well. The iron bacteria present in upper-surface soil can be transported into a well during drilling or well/pump maintenance. These bacteria have a life span of only about 30 minutes. When dead, any slime produced will slowly harden into an oxide of iron, manganese or whatever other nutrient is processed. Chlorine is not effective at penetrating this biological mass and won't kill these bacteria. It only retards their growth for a short period of time. Any attempt to kill live bacteria will only partially succeed and will leave oxides in place as a nutrient base for future bacteria. The growth then expands exponentially and plugging continues. If slime is present in a well, three conditions may exist:

  • Slime
  • Oxides from decaying bacteria
  • The potential for mineral scale
Any chemical treatment, in conjunction with a good development process, should deal with all three conditions.
 
Other well problems
Sand, silt and other fine-grained particles can accumulate at the bottom of the well, contributing to declining capacity. With the right equipment and techniques, these can easily be removed from the well. Other problems, such as large physical obstructions, extensive damage to the well screen, or changes in the aquifer due to such natural events as earthquakes may not be so easily resolved.
 

To determine if hydro-fracturing is right for
your well
, contact us today!

13812 W Lincoln Rd. • Spokane, WA 99224-9100
509-466-5078 • 800-368-0998
Fax: 509-467-2012
 
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