Geothermal power production: accidental fluid releases, waste disposal, and water use

Abstract

Environmental problems related to the use and disposal of fluids can accompany the operation of geothermal power plants using hot water resources (temperature > 150/sup 0/C). More than 100 kg of fluids must be extracted, processed, and disposed for each kW.h of electricity generated from a facility relying on a geothermal reservoir with fluids of 150/sup 0/C. The low thermal efficiencies of geothermal power plants result in large requirements for cooling water - over 7.4 x 10/sup 4/ m/sup 3//MW.y compared with 1.7 x 10/sup 4/ m/sup 3//MW.y for coal-fired plants. Geothermal fluids can contain as much as 250,000 mg/1 total dissolved solids. Toxic substances like boron and NH/sub 3/ are often present in fluids. This paper focuses on impacts associated with accidental releases of geothermal fluids as well as the disposal of liquid and solid wastes. The consequences of consuming alternative sources of cooling water are also addressed. Inadvertent discharges of fluids are of concern because they could contaminate soils and surface waters, adversely affecting crops and aquatic organisms. The pretreatment of fluids before subsurface injection could lead to solid waste problems - especially when toxic substances are produced. The consumption of alternative cooling waters can pose problems involving the disposal of blowdown from cooling towers. In addition, the toxicity of drift emitted from cooling towers depends on the kind of cooling water used