Background
Elevated concentrations of iron (Fe) and manganese (Mn) are a well-known challenge at drinking-water treatment plants supplied by groundwater. These elements occur naturally in bedrock and unconsolidated sediments. However, their mobility in groundwater is largely controlled by redox conditions. In Norway, groundwater abstraction wells are often established close to surface-water bodies, potentially inducing groundwater – surface water mixing, affecting redox conditions by introducing oxygen.
Rambøll consulting agency holds data from three such waterworks—Koppang, Berkåk, and Strømbo—providing an opportunity to investigate controlling factors for Fe and Mn occurrence. Available datasets vary in duration and quality among sites, but include borehole records, well depths and dimensions, lithological descriptions, grain-size distributions, long-term water-chemistry data, geophysical measurements, and groundwater-level observations from production and monitoring wells.
Research
This MSc project will assess Fe and Mn content in groundwater at two or three waterworks in similar geological settings and evaluate principal processes responsible for the observed concentrations.
Some key questions are: How do Fe and Mn concentrations vary with the distance between abstraction wells and nearby surface-water sources? To what extent are concentrations related to well depth, sediment characteristics, and hydraulic conductivity? How is the chemical quality of the surface-water source compared to the groundwater chemistry observed in production wells? Furthermore, how have well-operation practices—including pumping regimes, drawdown, and abstraction rates—affected the historical development of water quality?
By comparing two or three sites, the study will distinguish site-specific controls from more general hydrogeological mechanisms relevant to aquifer recharge and groundwater supply. The student may choose to focus more on chemical OR physical controls, depending on their interest.
Methods:
Compare hydrogeological data from 2-3 water works in Trøndelag, analyse time series of chemical composition in relation to geology and well placement. The student will consider groundwater – surface water mixing.
Methods may include mineral analysis in sediment (Figure 1), water chemistry and environmental tracers (e.g. Radon, Helium) OR study of pumping rates and groundwater modelling (Figure 3). The student may visit the water works and include field work if interested.
.png)
.png)
.png)
