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Nitrogen
Published in Robert H. Kadlec, Treatment Marshes for Runoff and Polishing, 2019
The removal of oxidized nitrogen in marshes is the result of a complex set of processes that is often termed “denitrification.” Nitrate disappearance occurs via many pathways that potentially remove nitrate (Burgin and Hamilton, 2007). The list includes: Denitrification is respiratory denitrification, in which organic matter is oxidized by nitrate in sediments and biofilms. Typically, most of the nitrate is converted to N2, but a variable fraction is converted to nitrous oxide (N2O).Dissimilatory nitrate reduction to ammonium (DNRA) is a heterotrophic process that utilizes organic matter as the energy source to reduce nitrate via fermentation.Sulfur-driven autotrophic denitrification couples the reduction of nitrate to the oxidation of reduced sulfur forms, including free sulfide (H2S and S2–) and elemental sulfur.Anammox (anaerobic ammonium oxidation) is an autotrophic process by which ammonium is combined with nitrite under anaerobic conditions, producing N2. The nitrite is derived from the reduction of nitrate.
Molecular Methods for Assessing Microbial Corrosion and Souring Potential in Oilfield Operations
Published in Kenneth Wunch, Marko Stipaničev, Max Frenzel, Microbial Bioinformatics in the Oil and Gas Industry, 2021
Gloria N. Okpala, Rita Eresia-Eke, Lisa M. Gieg
One of the mechanisms supporting the injection of nitrate into oil reservoirs for souring control is the inhibition of sulfide production in SRM by nitrite (Voordouw et al. 2009). However, in most low-temperature reservoirs, nitrite production is transient as it is further reduced to N2 via the denitrification pathway (Agrawal et al. 2012). This pathway involves nitrite reductase encoded by the nirS (heme c- and heme d1-containing nitrite reductase) and nirK (copper- and heme d1-containing nitrite reductase) gene, or via the dissimilatory nitrate reduction to ammonium (DNRA) pathway (Zumft 1997; Fida et al. 2016). However, at higher temperatures, nitrite had been reported to accumulate in some oilfield-derived tNRB enrichments (Reinsel et al. 1996; Agrawal et al. 2014). Using the MMM approaches of 16S rRNA sequencing and qPCR to enumerate nitrite reduction genes, Fida et al. (2016) investigated the temperature limit of nitrite reduction by oilfield-derived thermophilic nitrate reducers, and the effect of temperature on the nitrite reductase genes. Produced water samples from a low temperature oil field that were continuously treated with nitrate (2 mM) to prevent souring were used for establishing laboratory microcosms at 40 to 70°C. 16S rRNA gene sequencing data revealed that temperature caused a shift in microbial community composition. At 50–70°C, Geobacillus and Petrobacter were the dominant nitrate-reducers, while Pseudomonas and Thauera were most abundant at lower temperatures (40–45°C). Thauera, Petrobacter, and Geobacillus strains were isolated from the enrichments and the abundance of the nitrite reductase genes nirS and nirK were quantified using qPCR at different temperatures. At lower temperatures of 40–45°C, the nirS gene was abundant in Thauera but was in comparatively low abundance in the thermophilic Petrobacter and Geobacillus spp. However, at higher incubation temperatures, where nitrite accumulated, the nirS and nirK genes could not be amplified/quantified from Petrobacter and Geobacillus spp. A further probe into the distribution of nitrite reductase genes revealed that the nirS gene was not active at high temperatures. Thus, using MMM in combination with culturing, this study suggested that nitrite accumulation at high temperatures is effective, due to the fact that nitrite reductase is not active at higher temperatures (Fida et al. 2016).
Coupling anammox with heterotrophic denitrification for enhanced nitrogen removal: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Anammox is an autotrophic process using CO2 as the sole carbon source (van de Graaf et al., 1997). Nevertheless, there are studies showing that anammox bacteria display a versatile metabolism beyond our realization. Hu et al. (2019) reported Kuenenia stuttgartiensis can couple ammonium oxidation with nitric oxide reduction to produce only N2 in the absence of nitrite. Some anammox bacteria species can also reduce nitrate to ammonium with the oxidation of volatile fatty acid (VFA), i.e., acetate and propionate (Güven et al., 2005; Kartal, Rattray et al., 2007; Liang, Li, Zhang, Zeng, Yang, Zhang, 2015). This dissimilatory nitrate reduction to ammonium (DNRA) process proceeds in two steps: NO3--N is firstly reduced to NO2--N, and then NO2--N is further reduced to NH4+-N. The produced NH4+-N and NO2--N is finally converted to N2 via anammox pathway when VFA is not available (Kartal, Kuypers et al., 2007). The DNRA process was found in many field studies, i.e. the anoxic zones in waterbody, sediments. This finding is of great significance for the application of anammox-based biotechnology, as NO3--N can be further removed in-situ. However, DNRA is sensitive and influenced by various environmental parameters, which reduces its feasibility in the engineering systems (van den Berg et al., 2015). It seems other bioprocess is required to solve the nitrate problem.
Nutrient processes and modeling in urban stormwater ponds and constructed wetlands
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2019
Brendan Troitsky, David Z. Zhu, Mark Loewen, Bert van Duin, Khizar Mahmood
Dissimilatory nitrate reduction to ammonium (DNRA) is a reduction reaction that directly competes with denitrification. While both DNRA and denitrification result in lower nitrate levels, DNRA converts the available nitrate to ammonium, rather than gaseous N2 (Matheson et al. 2002). Organic carbon often serves as an electron donator for DNRA and so anoxic locations with high organic carbon and low nitrate – either in water or sediment – often serve as the prime location for DNRA bacteria (Kraft et al. 2011; van den Berg et al. 2015).