HYDROGEN PEROXIDE AS A GEOTHERMAL COOLING WATER BIOCIDE

Abstract

Evaporative cooling water systems in geothermal power plants can pose a number of challenges for geothermal operators. The challenges of corrosion, deposition and biological control can be magnified in systems utilising direct contact condensers due to the presence of hydrogen sulphide in the cooling water. The presence of hydrogen sulphide results in the formation of elemental sulphur that can deposit throughout the cooling water system and restrict flow in pipe work, impact fill reliability and plant efficiency. Perhaps the most challenging aspect of the presence of hydrogen sulphide in the cooling water system is the limitations this places on biocide selection, and the resultant difficulties faced by some plants of maintaining effective cooling water control when faced with sulphur oxidising bacteria. This paper discusses the methods utilised by Mercury to monitor and control cooling water pH excursions as a result of sulphur oxidising bacteria in its geothermal cooling water systems, including the use of hydrogen peroxide to control sulphur oxidising bacterial activity.