In Sijarinska spa, there are some 15 mineral and thermomineral springs, that are already being used for therapeutic purposes. For the exploitation of heat energy boring B-4 is very interesting. It is a boring of a closed type, with the water temperature of about 78?C and a flow rate of about 33 l/s. Waters with the flow rate of about 6 l/s are currently used for heating of the Gejzer hotel, and waters of the flow rate of about 0,121 l/s for the pilot drying plant. The paper presents this pilot plant. .

In this paper we have examined the effect of variable frequency electromagnetic field generated with a homemade device on deposit formation in installations with geothermal water from Sijarinjska Spa. The frequency alteration of the electromagnetic field in time was made by means of the sinusoidal and saw-tooth function. In laboratory conditions, with the flow of geothermal water at 0.015 l/s and temperature of 60 °C for 6 hours through a zig-zag glass pipe, a multiple decrease of total deposit has been achieved. By applying the saw-tooth and sinusoidal function, the decrease in contents of calcium and deposit has been achieved by 8 and 6 times, respectively. A device was also used on geothermal water installation in Sijarinjska Spa (Serbia), with the water flow through a 1'' diameter non-magnetic prochrome pipe at 0.15 l/s and temperature of 75 °C in a ten-day period. A significant decrease in total deposit and calcium in the deposit has also been achieved

A comprehensive analysis of physicochemical parameters in geothermal waters from the sites in Sijarinska spa (drill hole B-4) and Vranjska spa (drill hole VG-2) in order to investigate their tendency to form deposits in the pipe installation is presented. Both drill holes, B-4 and VG-2 possess utilization capacity of 30/27 L s-1 with water temperatures 75-90 °C. VG-2 water does not show any tendency of (or shows very little) sedimentation compared to the B-4 water. The behavior of the geothermal water from the B-4 hole was examined in real conditions of water flow through the pipe installation in Sijarinska spa. The results of geochemical analysis of B-4 water show that aragonite is the predominant mineral in the sediment (98%) with small amount of calcite, vaterite and anhydrite.

Geochemical and physicochemical characteristics of geothermal water from A-2 well are investigated in order to estimate its tendency towards the formation of scale in the pipe installation. Based on the geochemiocal analysis of major elements and groups, as well as triangular plots, this geothermal water can be classified as Na-Alk•SO4 type. The ternary diagram classifies it as steamheated-peripheral water. A-2 has a good utilization capacity of 1 L s-1 at the water temperature of 84 °C. Regarding this, SI values are determined as the measure of tendency to form deposits. A positive SI value of calcite (0.14) and aragonite (0.03) at the temperature of 84 °C suggests a very low tendency to form scale, as well as the possible occurrence of a minor proportion of carbonate minerals. XRD mineralogical and SEM analyses of the scale have confirmed its calcite composition. SI values for the temperature of 25 °C indicate the safe silicate minerals deposition due to the positive temperature coefficient. The obtained SI values indicate that the A-2 geothermal water in Vranjska Banja is suitable for use in piping installations because it shows poorly pronounced tendency to form deposits.