Geothermal energy is known as an environmentally friendly, reliable, and safe source of energy produced from renewable sources. In order to ensure the sustainable operation of geothermal power plants, it is necessary to recharge geothermal fluids back into the reservoirs. It is worth mentioning that the accidental release of geothermal brines or the accumulation of salts and silica from geothermal power facilities can lead to significant environmental issues. Geothermal fluids brought to the surface for any application must be treated in the most practical and feasible way before discharge to the any receiving body or back to the reservoirs. The objective of this chapter was therefore to study the hydrogeochemical properties of geothermal fluids in different regions and propose some scientific approached for the treatment of spent geothermal fluid prior to its use as an alternative water source, especially in agriculture applications.