The effects of river water infiltration on sub-surface microbiology and physico-chemical water characteristics in a pristine aquifer
Hagelin, Titta (2012)
Hagelin, Titta
2012
Ympäristö- ja energiatekniikan koulutusohjelma
Luonnontieteiden ja ympäristötekniikan tiedekunta - Faculty of Science and Environmental Engineering
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Hyväksymispäivämäärä
2012-04-04
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201205151115
https://urn.fi/URN:NBN:fi:tty-201205151115
Tiivistelmä
Artificial groundwater recharge (AGR) and bank filtration (BF) are old, widely applied methods to produce drinking water by the infiltration of surface water through soil. These methods are increasingly used because they are considered to offer a relatively inexpensive and sustainable way to increase the water quality by physical, chemical and biological processes. One of the primary goals of AGR and BF is the removal of natural organic matter (NOM) that has several indirect adverse effects. Pollutants possibly existing in aquatic environments may pose a risk of aquifer contamination and have harmful effects for human health. Biodegradation has an important role in sustainable removal of NOM and pollutants in AGR and BF. However, the mechanisms affecting the natural removal processes are still poorly understood, and therefore more knowledge of underlying biogeochemical processes is needed.
A research project TEVA (Improving artificial groundwater recharge by the development of on-line monitoring and control) was established to improve the understanding of the removal mechanisms of NOM during AGR and to enhance the AGR process control by on-line monitoring. As a part of the TEVA-project, the aim of this thesis was to study the effects of surface water infiltration on a pristine aquifer by monitoring physico-chemical water and bacterial community changes in Virttaankangas AGR site, southwest Finland, during experimental river water infiltration. In addition, the feasibility of biofilm collector slides for aquifer biofilm sampling was evaluated.
The progress of infiltrated water in the aquifer was evident from increased dissolved organic carbon (DOC) concentrations. Compared to the initial infiltrated water concentration, DOC removal was observed along the soil passage. However, no preferential removal of any molecular fraction of DOC could be demonstrated.
Due to infiltration, the native groundwater bacterial community profile changed significantly towards the community composition of infiltrated water. Attached bacterial community composition was not strongly influenced by water infiltration. Leucine incorporation method confirmed bacterial activity in the subsurface, whilst the RNA-based community analysis indicated that only a minor part of the attached and unattached communities were responsible for the activity in the aquifer.
Differences in the minor bacterial groups between soil and biofilm collector community compositions were observed. However, the biofilm collectors accumulated dominating soil bacterial groups and therefore the collectors reliably collected the dominant soil bacteria.
A research project TEVA (Improving artificial groundwater recharge by the development of on-line monitoring and control) was established to improve the understanding of the removal mechanisms of NOM during AGR and to enhance the AGR process control by on-line monitoring. As a part of the TEVA-project, the aim of this thesis was to study the effects of surface water infiltration on a pristine aquifer by monitoring physico-chemical water and bacterial community changes in Virttaankangas AGR site, southwest Finland, during experimental river water infiltration. In addition, the feasibility of biofilm collector slides for aquifer biofilm sampling was evaluated.
The progress of infiltrated water in the aquifer was evident from increased dissolved organic carbon (DOC) concentrations. Compared to the initial infiltrated water concentration, DOC removal was observed along the soil passage. However, no preferential removal of any molecular fraction of DOC could be demonstrated.
Due to infiltration, the native groundwater bacterial community profile changed significantly towards the community composition of infiltrated water. Attached bacterial community composition was not strongly influenced by water infiltration. Leucine incorporation method confirmed bacterial activity in the subsurface, whilst the RNA-based community analysis indicated that only a minor part of the attached and unattached communities were responsible for the activity in the aquifer.
Differences in the minor bacterial groups between soil and biofilm collector community compositions were observed. However, the biofilm collectors accumulated dominating soil bacterial groups and therefore the collectors reliably collected the dominant soil bacteria.