Geothermal Energy Applications in Wastewater Treatment

Abstract

An evaluation was conducted on the use of geothermal energy in wastewater treatment in the Canadian Prairie Provinces. The assessment included an analysis of geothermal energy costs, an examination of the effects of using elevated temperatures in wastewater treatment, a selection of suitable uses of the low‐grade energy in wastewater treatment, and a preliminary assessment of costs and benefits. By heating the wastewater influent to 30° C on a year‐round basis, performance (as measured by BOD removal) of an activated sludge plant might be increased by 10–15%. There may be much less benefit in the case of long‐detention aerated lagoons. The benefit may be significant (approximately 30%) for trickling filter plants, but such systems are generally not considered for use in the harsh western Canadian climate. The economics of using geothermal energy to improve wastewater treatment‐plant efficiency is not particularly attractive. An additional investment of 33–50% of the cost of the treatment plant is generally required for the installation of a geothermal energy system so that any enhanced efficiency of the treatment plant is obtained.