BayCEER Workshop 2025

Lab-scale and in-situ trials of hydrogen and methane driven chemolithoautotrophic nitrate reduction as a potential nitrate mitigation strategy for shallow porous drinking water aquifers

Nitrate pollution in groundwater is a persistent challenge for drinking water production across Europe. Preventing accumulation requires sustainable management, particularly in shallow aquifers with limited attenuation potential. Elevated concentrations often persist long after nitrogen inputs are reduced. Especially in oligotrophic shallow systems, there is an urgent need for innovative, cost-effective technologies to lower nitrate loads and secure drinking water supplies.

This project develops a novel strategy for nitrate remediation in shallow groundwater. By injecting reduced gaseous electron donors (H₂ and CH₄), autotrophic denitrification is stimulated directly upstream of production wells. This avoids enrichment of heterotrophic microbiota, some of which may pose hygienic risks.

Laboratory microcosm experiments under varying aquifer conditions enabled enrichment of a stable hydrogen-driven microbial community from sediments, with metabolic processes and kinetics characterized. Enrichment cultures of autotrophic denitrifiers were successfully reintroduced into sediment matrices in a bioreactor. Inoculating non-denitrifying aquifer material with these cultures reestablished denitrification in the presence of hydrogen. Current isotopic labelling experiments aim to clarify the roles of specific microorganisms in nitrate reduction.

In a mesoscale pilot flume system, methane-driven nitrate reduction was achieved. Further microcosm studies will isolate and characterize the responsible microbial populations. Finally, the approach is being tested in a shallow porous aquifer in a proof-of-concept field experiment.

In conclusion, harnessing the intrinsic capacity of autotrophic microorganisms and employing gases producible by green biotechnology may provide a local, robust, and sustainable solution to persistent nitrate contamination of groundwater and drinking water.