Dissolved Fe and Mn are found in acid and anaerobic groundwater, but they have traditionally not been considered a health concern, but more a problem connected with discolouration and taste. Manganese is often hard to remove and may stay in solution to cause impacts on taste and staining of laundry. Furthermore, there is new evidence that high manganese in drinking water may have an adverse impact on learning capacity in young children, although there remain many uncertainties.
For groundwater, subsurface iron and manganese removal by oxidation is a good alternative to traditional methods. Today there are several techniques to remove Fe & Mn from groundwater and a number of waterworks in Europe are using in situ methods. In Norway, one such technique, the Vyredox method is used in Grindalsmoen waterworks, Elverum.
Here, groundwater is filtered through an aerated zone around the producing well, resulting in the removal of iron and manganese by oxidation/precipitation. However, the exact geochemical mechanism involved is not clear.
It is generally believed to be a combined sorption and oxidation process, where iron-oxide/hydroxide precipitates on mineral grain surfaces, and further promote sorption of Fe2+, Mn2+ and also other heavy metals. The adsorbed Fe2+ & Mn2+ ions are easily oxidized (catalytic oxidation). The literature on Fe/Mn oxidation demonstrates that it can take place under both biotic and abiotic conditions.
In this master thesis, the main objective is to identify if the main oxidation pathway is abiotic or biotic in the groundwater treatment by the Vyredox method.
Aims
This master thesis aims at:
- establishing what bacterial consortia are present in groundwater where Fe/Mn oxidation/precipitation takes place
- performing laboratory experiments to study bacterial Mn oxidation on field samples representative for the conditions at Elverum under purely abiotic and mixed (abiotic + biotic) conditions
- integrating laboratory and literature data in geochemical modelling of the treatment plant at Elverum
This knowledge may furthermore be used to enhance removal technology.
The MSc study will apply both field and laboratory work as well as reactive transport calculations. This will give the student good experience with methods commonly used in environmental geology and geochemistry.
Laboratory studies will apply relevant aquifer material and use both batch and column experiments, where aqueous concentrations and solid characteristics will be determined. The results will be analyzed and simulated by geochemical tools.
Requirements:
- Basic knowledge of chemistry and biology
- Basic programming skills
- Students who want to work with this thesis are required to take GEO5900 – Chemical processes in soil and groundwater
