A Review on Waste Water Disposal at the Nesjavellir Geothermal Power Plant

Abstract

Three types of waste waters are produced at the Nesjavellir geothermal power plant. They consist of condensate water and separate water derived from high enthalpy wells, and heated fresh groundwater derived from shallow cold water wells. These three different types of fluids all represent a potential source of pollution, either chemical and/or thermal pollution. Release of these fluids into surface streams or into shallow sink wells is today considered to be unacceptable as it can cause irreversible environmental problems. At the Nesjavellir geothermal field, surface springs in the Nesjahraun lava and lake water from Lake Thingavallavatn are sampled two times a year at ten locations and analyzed for major chemical components, as well as temperature and pH. Temperature loggers are also in place at various locations, including at various depths in shallow research wells for temperature profiling. This paper describes monitoring work done on waste water from the Nesjavellir geothermal power plant. It reviews chemical and thermal monitoring efforts for the last 30 years and describes the various methods used to prevent chemical and thermal pollution. This includes the use of cooling towers and reinjection wells. Finally suggestions are presented to fulfil both environmental standards and to prevent operational disruptions.