Kinetic study on clogging of a geothermal pumping well triggered by mixing-induced biogeochemical reactions

Luc Burte; Charles A. Cravotta; Lorine Bethencourt; Julien Farasin; Mathieu Pedrot; Alexis Dufresne; Marie-Francoise Gerard; Catherine Baranger; Tanguy Le Borgne; Luc Aquilina

doi:10.1021/acs.est.9b00453

USGS · 70203992

Kinetic study on clogging of a geothermal pumping well triggered by mixing-induced biogeochemical reactions

Luc Burte·Charles A. Cravotta·Lorine Bethencourt·Julien Farasin·Mathieu Pedrot·Alexis Dufresne·Marie-Francoise Gerard·Catherine Baranger·Tanguy Le Borgne·Luc Aquilina

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Abstract

The sustainability of ground-source geothermal systems can be severely impacted by microbially mediated clogging processes. Biofouling of water wells by hydrous ferric oxide is a widespread problem. Although the mechanisms and critical environmental factors associated with clogging development are widely recognized, effects of mixing processes within the wells and time scales for clogging processes are not well characterized. Here we report insights from a joint hydrological, geochemical, and metagenomics characterization of a geothermal doublet in which hydrous ferric oxide and hydrous manganese oxide deposits had formed as a consequence of mixing shallow groundwater containing dissolved oxygen and nitrate with deeper, anoxic groundwater containing dissolved iron (Fe II ) and manganese (Mn II ). Metagenomics identify distinct bacteria consortia in the pumping well oxic and anoxic zones, including autotrophic iron-oxidizing bacteria. Batch mixing experiments and geochemical kinetics modeling of the associated reactions indicate that Fe II and Mn II oxidation are slow compared to the residence time of water in the pumping well; however, adsorption of Fe II and Mn II by accumulated hydrous ferric oxide and hydrous manganese oxide in the well bore and pump riser provides “infinite” time for surface-catalyzed oxidation and a convenient source of energy for iron-oxidizing bacteria, which colonize the surfaces and also catalyze oxidation. Thus, rapid clogging is caused by mixing-induced redox reactions and is exacerbated by microbial activity on accumulated hydrous oxide surfaces.

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Luc Burte, Charles A. Cravotta, Lorine Bethencourt, Julien Farasin, Mathieu Pedrot, Alexis Dufresne, Marie-Francoise Gerard, Catherine Baranger, Tanguy Le Borgne, Luc Aquilina. 2019-04-30. Kinetic study on clogging of a geothermal pumping well triggered by mixing-induced biogeochemical reactions. https://doi.org/10.1021/acs.est.9b00453

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