Geothermal Water Quality in Oued R hir Valley (Southeast Algeria).Scaling Problem and Hardness Treatment

The conducts of drinking water supply in Oued R hir valley, have been for a long time jeopardized by encrusting. Geothermal water, the only source of drinking water, has a high capacity tendency to form scale is the origin of this phenomenon. This water is highly mineralized (2.5 g L 1) and of a very high degree of hardness (1120 mg L 1 as CaCO3). The maximum scaling rate (1.4 cm y 1) is observed in the conducts located at the first kilometer of the water source, where the water temperature and pressure are very favorable. The calcareous mass produced is estimated at 1.6 g L 1, or 2243 t y 1. The treatment results show that hydrated lime process has very low efficiency (11.5%) facing water hardness, compared with that obtained by the sodium carbonate (61%). They, thus testify that water hardness dominated is the permanent hardness. Yet the process with Na2CO3 added to produced water 255 mg L 1 of the sodium with the initial water content (323 mg L 1) for each 682 mg L 1 as CaCO3 of water hardness removed.