Bioremediation of pesticides: unravelling the anaerobic microbiological potential of oligotrophic drinking water aquifers

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. In-situ micropollutants remediation represents a very promising but also delicate measure, because drinking water sources need to be protected from any activity that could represent a risk for drinking water production. Bioremediation processes in groundwater can be limited by the oligotrophic environmental conditions in combination with the low pesticides concentration. Bioremediation technologies that rely on pesticides biodegradation have previously been presented as a possible solution to remove pesticides from groundwater systems, 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 groundwater systems used for drinking water production in the Netherlands. The different chapters of this book contributed to: (a) create an overview of molecular tools that facilitate anaerobic pesticide monitored natural attenuation, (b) determine which groundwater microbial communities are present in the field and what are the environmental factors exerting selective pressure on them, (c) discover the metabolic potential for the biodegradation of pesticides of microbial communities in the field, (d) understand which environmental factors can facilitate pesticides biodegradation by indigenous microorganisms present in natural groundwater systems, (e) comprehend the fate of an added degrading inoculum to an stable groundwater column system. Finally, a general discussion is presented as well as some recommendations and further research lines are proposed to continue exploring the potential of microbial communities for the biodegradation of pesticides at micropollutants in groundwater systems used for drinking water production.