Iron in thermal waters in Bulgaria – state and problems

Abstract

The chemical composition of thermal waters has an important role in their use as a shallow geothemal source. One of the chemical components that may have a negative impact is iron. Its presence in the water can lead to both chemical and biocorrosion, as well as filling of the wells and facilities associated with the use of thermal waters. The aim of the study is to characterize the iron content and its present forms in thermal waters in Bulgaria. More than 250 samples of water sources revealing thermal waters are summarized and analyzed. In most cases iron concentrations are between 0.01 and 0.05 mg/l and in only 10% – it is above 0.1 mg/l. The forms of iron found in the water, the mineral phases, which can be formed, as well as their changes that occur with decreasing of temperature and increasing of the oxidation-reduction potential of the waters, are determined. It makes possible to predict the occurrence of undesirable processes (scaling and/or corrosion) for their exploitation after reaching the surface.