Role of Temperature and Flow in Biomass Transporting in Porous Media

Abstract

Underground water source heat pumps system is an underground geothermal technology that extracts underground water as a lower temperature heat source, and recharged into the same aquifer after heat exchanger. During the recharging process, not only external microorganisms such as bacteria but also a variety of contaminants ( for example carbon sources, nitrogen sources, the growth inhibitors/promoters and so on) would get into the aquifer to affect the aquifer's living environment for microbial, which would affect the quality of underground water directly or indirectly. Not only that, the extraction and injection of underground hot water would cause the redistribution of temperature, which would then affect the growth of microorganisms as a key affecter. And the biomass would be transported by seepage flow in way of advection and conduction mainly. Based on the background of underground water source heat pumps system, the coupling of three-field (temperature-hydraulic-microbial) is analyzed, and a corresponding coupled THB model is obtained. Taking Escherichia coli as target organisms in the aquifer, the distribution of biomass various with time and space are obtained respectively. The temperature and advection sensitivity of microbial concentration is also acquired. It is showed that the growth of microbial plays a great role in the process of its transportation, and the concentration of microbial would increase significantly when the local temperature increased or the convection strength decreased while other effects stay the same.