Microbial diversity in denitrification beds

The use of drainages in agricultural fields near to aquatic systems can lead to extensive eutrophication through high concentrations of nitrogen and other nutrients present in fertilizers. One approach to reduce these nitrate loads in ecosystems involves denitrification beds, which provide decentralized wastewater treatment.In this study, laboratory denitrification reactors with wood chips as carbon source were developed and inoculated with agricultural drainage water from a study area. Objectives were 1) to investigate the denitrification potential and the development of side products like nitrite, ammonium and methane under different nitrate concentrations and 2) to analyze the microbial community structure and activity within these reactors and compare it between low and high nitrate concentration.Wood chips allover select for the development of a diverse microbial community that is especially suited to the removal of low nitrate concentrations. Interestingly, higher nitrate concentrations can lead to an activity switch from denitrification to dissimilatory reduction of nitrate to ammonium (DNRA). Metatranscriptome results let hypothesize that members of the order Ignavibacteriales seem to play an important role in this ammonium production.