Global nitrate pollution in groundwater poses a great challenge. In Europe, groundwater is crucial for drinking water, necessitating sustainable management for shallow aquifers with high recharge. However, their attenuation potential against pollutants like nitrate is often limited. High nitrate levels persist in many aquifers even long after reducing nitrogen inputs. Persistent high nitrate levels in oligotrophic shallow groundwater systems call for urgent development of innovative and cost-effective technologies to eliminate nitrate loading and ensure a sustainable water supply, meeting the growing demand.

In this BMBF-funded project under the "LURCH – Nachhaltige Grundwasserbewirtschaftung" initiative, we aim to implement a novel approach for nitrate removal from shallow groundwater. Via the injection of reduced gaseous electron donors (H₂/CH₄), we aim to stimulate autotrophic denitrification directly upstream of burdened drinking water wells. In lab scale microcosms, we are currently simulating in situ conditions for a range of aquifer materials and amendments, while enrichment cultures of autotrophic denitrifying communities are established for potential stimulation within natural aquifers. A mesoscale flume experiment tests gas injection principles and monitors stimulation effects. The final aim is to implement this approach at a field-scale pilot plant, eliminating nitrate in an actual drinking water production system.

Preliminary data is suggesting that injecting H₂/CH₄ can effectively eliminate nitrate from groundwater aquifers without adversely impacting water quality or hydraulic characteristics through secondary reactions, like mineral dissolution or biofilm clogging. Current techniques for nitrate elimination mostly involve post-treatment of pumped groundwater with methods like osmosis, anion exchange, electrodialysis, or water treatment in bioreactors. Here, we want to harness autotrophic microbial potentials intrinsic to groundwater systems for a new and sustainable solution to a notorious problem. A more precise understanding of the microbiology involved in autotrophic denitrification in drinking water aquifers will support these developments.