Groundwater, together with glaciers and polar icecaps, are the main reservoirs of freshwater in the world. In the Netherlands, more than half of the drinking water is being produced by using groundwater. Recent studies have shown that despite the lower exposure of the groundwater, some contaminants such as pesticides, are present in groundwater systems at micropollutant concentrations. Bioremediation is an environmentally friendly technology that relies on living organisms to biodegrade contaminants. Biodegradation processes in groundwater can be limited by the oligotrophic environmental conditions in combination with the low pesticides concentration. Bioremediation technologies have been presented as a possible solution to remove pesticides from groundwater, making clear that more research is necessary before safe and effective application. The main goal of this thesis was to better understand the biological and environmental factors playing a role in the biodegradation of pesticides at micropollutants concentration in drinking water aquifers in the Netherlands.