Applicability of ground source heat pumps as a bioremediation-enhancing technology for monoaromatic hydrocarbon contaminants

Abstract

Geothermal or ground source heat pumps (GSHPs) are among the highest growing renewable energy technologies used for heating and cooling of buildings. However, despite being a well-established technology, their geo-environmental effects such as impact of the heat on the biosphere is still not thoroughly understood. This study uses FEFLOW software, to simulate heat and mass transport of a vertical closed-loop GSHP system. Transient flow and heat transport results for a multiple borehole system are presented which indicate long-term effects on subsurface temperature. Moreover, the impact of temperature change in a contaminated granular porous subsurface during remediation applications is examined. In particular, as subsurface temperatures are elevated due to geothermal heating, sorption will decrease and biodegradation rates will increase. These effects are examined in the context of contaminant transport, to evaluate the possibility of utilizing geothermal heating as a remediation strategy. The results revealed that temperature changes caused by GSHP operation can significantly enhance biodegradation of hydrocarbon contaminants. For instance, elevated subsurface temperature resulted in 97% reduction in benzene total mass, after one year of GSHP operation for a typical office building in Toronto.