Inhibition by free nitrous acid (FNA) and the electron competition of nitrite in nitrous oxide (N2O) reduction during hydrogenotrophic denitrification

et al. 2021

Environ. Sci. Technol.

Chemical absorption–biological reduction based on Fe(II)EDTA is a promising technology to remove nitric oxide (NO) from flue gases. However, limited effort has been made to enable direct energy recovery from NO through production of nitrous oxide (N2O) as a potential renewable energy rather than greenhouse gas. In this work, the enhanced energy recovery in the form of N2O via biological NO reduction was investigated by conducting short-term and long-term experiments at different Fe(II)EDTA–NO and organic carbon levels. The results showed both NO reductase and N2O reductase were inhibited at Fe(II)EDTA–NO concentration up to 20 mM, with the latter being inhibited more significantly, thus facilitating N2O accumulation. Furthermore, N2O accumulation was enhanced under carbon-limiting conditions because of electron competition during short-term experiments. Up to 47.5% of NO–N could be converted to gaseous N2O–N, representing efficient N2O recovery. Fe(II)EDTA–NO reduced microbial diversity and altered the community structure toward Fe(II)EDTA–NO-reducing bacteria-dominated culture during long-term experiments. The most abundant bacterial genus Pseudomonas, which was able to resist the toxicity of Fe(II)EDTA–NO, was significantly enriched, with its relative abundance increased from 1.0 to 70.3%, suggesting Pseudomonas could be the typical microbe for the energy recovery technology in NO-based denitrification.

Section: Discussionsupporting

confidence: 91%

Biological Reduction of Nitric Oxide for Efficient Recovery of Nitrous Oxide as an Energy Source

Wang

Chen

et al. 2021

Environ. Sci. Technol.

“…In denitrification process, the electrons were originally devoted by organic carbon compounds and then transferred to the nitrogen oxide reductases, including nitrate reductase (NAR), nitrite reductase (NIR), nitric oxide reductase (NOR) and nitrous oxide reductase (N 2 OR), to reduce the corresponding nitrogen oxides. Nevertheless, N 2 O could accumulate and emit to atmosphere due to the incomplete denitrification caused by inadequate operational conditions (Wang et al, 2018). The mechanisms of N 2 O emissions from nitrifying activated sludge have been widely investigated, while little information could be found in the heterotrophic denitrification biofilm under anoxic conditions.…”

Section: Eps Smp Extraction and Fluorescent Spectramentioning

confidence: 99%

Biological denitrification in an anoxic sequencing batch biofilm reactor: Performance evaluation, nitrous oxide emission and microbial community

Ding

Guo

et al. 2019

Bioresource Technology

The present study evaluated the performance of biological denitrification in an anoxic sequencing batch biofilm reactor (ASBBR) and its nitrous oxide (N 2 O) emission. After 90 days operation, the effluent chemical oxygen demand and total nitrogen removal efficiencies high of 94.8% and 95.0%, respectively. Both polysaccharides and protein contents were reduced in bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) after biofilm formation. According to typical cycle, N 2 O release rate was related to the free nitrous acid (FNA) concentration with the maximum value of 3.88 μg/min and total conversion rate of 1.27%. Two components were identified from EEM-PARAFAC model in soluble microbial products (SMP). Protein-like substances for component 1 changed significantly in denitrification process, whereas humic-like and fulvic acid-like substances for component 2 remained relatively stable. High-throughput sequencing results showed that Lysobacter, Tolumonas and Thauera were the dominant genera, indicating the co-existence of autotrophic and heterotrophic denitrifiers in ASBBR.

“…Compared with other soluble organics or dissolved sulfur electron donors, the solid element sulfur obtains lower bioavailability and electron supply capability due to its limited aqueous solubility, which would cause electron competition between the key enzymes such as NOR and N 2 OR subsequently (Di Capua et al, 2016; Oberoi et al, 2021; Sahinkaya & Kilic, 2014; S. S. Wang, Cheng, et al, 2021). Hence, based on the limited electron supply from sulfur and the lower affinity of N 2 OR than that of NOR for electron equivalents (J. Chen et al, 2015; Pan et al, 2012; Pan, Ye, et al, 2013; Ribera‐Guardia et al, 2014; Richardson et al, 2009; Y. Wang et al, 2018), N 2 O could efficiently accumulate and be recovered in sulfur‐driven NO‐based denitrification system accordingly.…”

Section: Resultsmentioning

confidence: 99%

Sulfur‐driven autotrophic denitrification of nitric oxide for efficient nitrous oxide recovery

Wang

Biotech & Bioengineering

et al. 2021

Nitrous oxide (N2O) was previously deemed as a potent greenhouse gas but is actually an untapped energy source, which can accumulate during the microbial denitrification of nitric oxide (NO). Compared with the organic electron donor required in heterotrophic denitrification, elemental sulfur (S0) is a promising electron donor alternative due to its cheap cost and low biomass yield in sulfur‐driven autotrophic denitrification. However, no effort has been made to test N2O recovery from sulfur‐driven denitrification of NO so far. Therefore, in this study, batch and continuous experiments were carried out to investigate the NO removal performance and N2O recovery potential via sulfur‐driven NO‐based denitrification under various Fe(II)EDTA‐NO concentrations. Efficient energy recovery was achieved, as up to 35.5%–40.9% of NO was converted to N2O under various NO concentrations. N2O recovery from Fe(II)EDTA‐NO could be enhanced by the low bioavailability of sulfur and the acid environment caused by sulfur oxidation. The NO reductase (NOR) and N2O reductase (N2OR) were inhibited distinctively at relatively low NO levels, leading to efficient N2O accumulation, but were suppressed irreversibly at NO level beyond 15 mM in continuous experiments. Such results indicated that the regulation of NO at a relatively low level would benefit the system stability and NO removal capacity during long‐term system operation. The continuous operation of the sulfur‐driven Fe(II)EDTA‐NO‐based denitrification reduced the overall microbial diversity but enriched several key microbial community. Thauera, Thermomonas, and Arenimonas that are able to carry out sulfur‐driven autotrophic denitrification became the dominant organisms with their relative abundance increased from 25.8% to 68.3%, collectively.