Groundwater microbiology of an urban open‐loop ground source heat pump with high methane

Barnett, Megan J.; Farr, Gareth J.; Shen, Jianxun; Gregory, Simon P.. 2023 Groundwater microbiology of an urban open‐loop ground source heat pump with high methane. Groundwater, 61 (2). 274-287. 10.1111/gwat.13291

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Text (Open Access Paper) Groundwater - 2023 - J Barnett - Groundwater Microbiology of an Urban Open‐Loop Ground Source Heat Pump with High Methane.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (1MB) | Preview

Abstract/Summary

Ground source heat pumps (GSHPs) are low carbon alternatives to gas boilers for decarbonising heating. Open-loop GSHP systems abstract groundwater, pass it though a heat exchanger and return it to ground or surface water. Groundwater samples from the top and base of an abstraction and a recharge borehole of an open-loop GSHP system in Cardiff, UK were assessed, and compared to two local boreholes in the same aquifer. Groundwater samples were taken when the GSHP system was active (once) and inactive (twice) and analysed for changes in geochemistry, viable cell counts and microbial community (16S rRNA gene sequencing). The GSHP had a distinct geochemistry and microbial community compared to the control boreholes, and the abstraction borehole showed greater variability than the recharge borehole. The microbial community of the GSHP system showed an increase in relative abundance of genera involved in oxidation of methane and methylated compounds, of which Methylotenera was the most abundant (up to 83.9% of 16S rRNA gene sequences). There were also changes in genera associated with nitrification (Nitrospira, Nitrosomonas) and those with potential for sulphur and iron cycling (Rhodoferax). Methane concentration was analysed out after identification of methylotrophs and found that methane concentrations were up to 2855 μg L-1, likely having had a significant impact on the bacterial communities present. Understanding the microbiology and biogeochemisty of GSHP systems provides insight into potential issues with local infrastructure and long-term system performance, and support modelling to maximise efficient and sustainable use of the subsurface.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1111/gwat.13291
ISSN:	0017-467X
Date made live:	07 Feb 2023 10:49 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/533974

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