Geothermal water treatment

Geothermal wells harness energy from hot magma beneath the earth's crust by transferring it to subsurface water. At certain key locations near the junctions of the earth's subsurface plates, hot water and steam return upward by convection. Such sites are sometimes identified by hot springs and geysers. Geothermal fields are often located in these areas. Locations where geothermal energy has been harnessed include California, New Zealand, Italy, Japan and Iceland.

One of the chief problems in exploiting water-dominated fields is undoubtedly caused by scale formation. Many of these waters (or brines) contain high mineral loadings and often high concentrations of dissolved carbon dioxide. As the brine rises through the wellhead the pressure is lowered, carbon dioxide flashes off and the pH of the water increases. The tendency to produce calcium carbonate scale can become quite severe. The problem becomes even worse in surface equipment where the water pressure is lowered to flash off steam. (The steam generally is routed to turbines for the production of electricity).

One way of controlling calcium carbonate scaling is through the use of Dequest® phosphonates and polymers. They are also used against some other commonly encountered scales, such as strontium salts and silica.