Decarbonation of the geothermal watersof Chott El Fejjej in an open double partition reactor without chemcial additions

摘要

A softening process of the geothermal waters of Chott El Fejjej(Tunisia) performed during air bubbling in an opened bouble partition reactor (ODPR) by seeding of calcium carbonate recovered onsite constitutes a first and an interesting exampleof simple and clean technology.The water is treated in conditinuous flow without chemical additions,so the increase of pH is minimised.Consequently,there is no homogeneous nucleation and Mg(OH)_2 precipitation that would disturb the CaCO_3 crystallisation.Thus,large production of wastesludge is avoided.A secondary set-off of precipitation takes place on seed grains in the ODPR.The conical part,where the sludge is collected by sedimentation and purged continuously,makes ODPR a simple technology.Our attentinis focused on the effect of water flow rate,amount of added seed and first tank temperature of the reactor on CaCO_3 crystallisation.