Comparison of Denitrification Induced by Various Organic Substances—Reaction Rates, Microbiology, and Temperature Effect

Ortmeyer, F. ORCIDiD
Begerow, D. ORCIDiD
Guerreiro, M. A. ORCIDiD
Wohnlich, S. ORCIDiD
Banning, A. ORCIDiD

DOI: https://doi.org/10.1029/2021WR029793
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/9799
Ortmeyer, F.; Begerow, D.; Guerreiro, M. A.; Wohnlich, S.; Banning, A., 2021: Comparison of Denitrification Induced by Various Organic Substances—Reaction Rates, Microbiology, and Temperature Effect. In: Water Resources Research, 57, 11, DOI: https://doi.org/10.1029/2021WR029793. 
 
Begerow, D.; 2 Department of Evolution of Plants and Fungi Ruhr‐Universität Bochum Bochum Germany
Guerreiro, M. A.; 2 Department of Evolution of Plants and Fungi Ruhr‐Universität Bochum Bochum Germany
Wohnlich, S.; 1 Ruhr‐Universität Bochum Hydrogeology Department Bochum Germany
Banning, A.; 3 School of Biological, Earth and Environmental Sciences (BEES) University College Cork Cork Ireland

Abstract

Widespread groundwater pollution with nitrate (NO3−) and the finite and decreasing geogenic NO3− degradation capacity in aquifers require a better understanding of potential treatment methods. This project aimed at exploring and comparing the efficiency of four organic substances as electron donors for heterotrophic denitrification. Circulation column experiments using sediment without NO3− degradation capacity and high agricultural NO3− groundwater were conducted. Acetate, glucose, ascorbic acid, and ethanol were added to these columns in three concentration steps to induce biological denitrification, whereby also temperature dependence of denitrification rates (room temperature and typical groundwater temperature of 10°C) was taken into account. Results show denitrification with all four carbon (C) sources with intensities varying considerably between electron donors. Comparison of the two temperature approaches shows substantial differences between applied organic substances and indicates T as an important variable for denitrification. Ethanol is clearly the most effective electron donor for biodenitrification in groundwater investigated in this study, with a stronger and more effective NO3− degradation at 10°C than at room temperature. In contrast, much higher reaction rates are achieved with glucose at room temperature, compared to 10°C. Denitrification with ascorbic acid is very low at both temperatures; its addition produces biomass which repeatedly led to column clogging. In the entire test series, nitrite (NO2−) accumulation occurred more frequently and in higher concentrations at 10°C. Analysis of microorganisms shows a strong modification in microbial community in reaction to the addition of different organic C as well as between the two temperature approaches.


Key Points:

Higher denitrification rate with ethanol at 10°C, consequently, reaction kinetics does not generally increase with rising temperature.

Addition of organic substances and temperature strongly modify the denitrifying microbial community.

Electron donor selection for induced nitrate reduction depends on the groundwater temperature of the region.