Biogeochemical clogging in groundwater energy wells
The inherent heating/cooling potential energy in groundwater is a growing, renewable resource in Norway, and an important contribution towards the green shift in energy consumption patterns. Groundwater in shallow aquifers maintains a near-constant temperature throughout the year (ca. 10 C in the Oslo area), and thus can provide cooling during summer months, and heating during winter, by pumping water from wells through heat exchangers. Aquifers can also be utilized for storing energy, e.g. reusing hot water produced during cooling in summer, for heating in winter.
So-called open systems, with direct extraction and injection of water in shallow aquifers, are much more energy-efficient compared to closed-loop systems (where a liquid for heating/cooling is circulated inside pipes or tubes and exchanging heat/cold indirectly with aquifers). Part of the reason for this is that there is a risk of biogeochemical clogging in open wells, meaning that when we impose changes in pressure, temperature as well as water chemistry, and especially if anoxic /anoxic groundwater is mixed, chemical reactions occur, with precipitates clogging and reducing the efficiency of injection/production wells. Many of these processes (e.g. redox-reactions, carbonate precipitation) are bacterially mediated and/or catalyzed.
Understanding the control parameters, for example, the effect of geological heterogeneity and substrate mineralogy, and how the bacteria play a role in the kinetics is a central research topic in improving the efficiency towards green energy solutions.
Aims (research questions):
- Are the clogging reactions and microbe communities the same in fractured aquifers and porous aquifers, given that the mineralogy and water chemistry is similar?
- Which controlling parameters are the most important? And how can we address these in planning remediation or improving well efficiency?
- Fieldwork: sample biosludge and mineral precipitates from geothermal wells in the Oslo area.
- X-ray diffraction - mineralogy analysis
- Scanning electron microscopy – characterization of coating
- Ion chromatography – water chemistry
- Bacterial characterization at NORCE research centre
- The student should follow GEO9900/5900 – Chemical Processes in Soil and Ground Water in spring 2021 as preparation and have completed GEO4190 - Hydrogeology in fall 2020.