Treatment by enhanced denitrification of forecasted nitrate concentrations under different climate change scenarios

Abstract

Climate change has a decisive influence on future water resources and, consequently, on future nitrate (NO₃^-) concentrations. Due to decreasing water resources, in addition to decreasing and finite NO₃^- degradation capacities of the aquifers, higher NO₃^- concentrations are expected in the future. Likewise, NO₃^- pollution is expected to become more frequent. However, enhanced denitrification by addition of organic carbon (C) as an electron donor is a promising treatment method. This study describes the first model using NO₃^- projections based on climate projections, combined with the treatment method of enhanced denitrification. The exemplary study area is the Lodshof water catchment which is located in the Lower Rhine Embayment. The model illustrates the considerable potential of enhanced denitrification as an effective treatment. The expected increase in NO₃^- concentrations by the end of the 21^st century, resulting from climate chance and a decreasing water resource, can be reduced by 38-58% in this model. In all projections, the limit value of 50 mg/L can be complied by this treatment. A projection with 20% lower NO₃^- input and the described treatment highlights the effectivity of combining measures to be able to manage the NO₃^- problem. Furthermore, this publication critically discusses the transfer of denitrification rates from laboratory experiments to the field scale and finally into models like this.

Keywords: Climate change; Groundwater pollution; Modelling; Nitrate; Organic carbon; Water balance projection.