Effect of H₂S on N₂O Reduction and Accumulation during Denitrification by Methanol Utilizing Denitrifiers

Abstract

Sulfide is produced in sewer networks, and previous studies suggest that sulfide in sewage could alter the activity of heterotrophic denitrification and lead to N2O accumulation during biological wastewater treatment. However, the details of this phenomenon are poorly understood. In this study, the potential inhibitory effects of sulfide on nitrate, nitrite, and N2O reduction were assessed with a methanol-utilizing denitrifying culture both prior to and after its exposure and adaptation to sulfide. Hydrogen sulfide was found to be strongly inhibitory to N2O reduction, with 50% inhibition observed at H2S concentrations of 0.04 mg H2S-S/L and 0.1 mg H2S-S/L for the unadapted and adapted cultures, respectively. In comparison, both nitrate and nitrite reduction was more tolerant to H2S. A 50% inhibition of nitrite reduction was observed at approximately 2.0 mg H2S-S/L for both unadapted and adapted cultures, while no inhibition of nitrate reduction occurred at the highest H2S concentrations applied (2.0 mg H2S-S/L) to either culture. N2O accumulation was observed during nitrate and nitrite reduction by the adapted culture when H2S concentrations were above 0.5 and 0.2 mg H2S-S/L, respectively. Additionally, we reveal that hydrogen sulfide (H2S), rather than sulfide, was likely the true inhibitor of N2O reduction, and the inhibitory effect was reversible. These findings suggest that sulfide management in sewers could potentially have a significant impact on N2O emission from wastewater treatment plants.

Mitigating Global Warming Potential and Greenhouse Gas Intensities by Applying Composted Manure in Cornfield: A 3-Year Field Study in an Andosol Soil

“…Soil pH was a major factor controlling annual N 2 O emissions and this agrees with previous reports [72,73]. The N 2 O reductase enzyme is reported to be more active at low soil pH relative to activities of NO 3 − and NO 2 − reductase enzymes [73], which could have resulted in the reduced N 2 O reduction to N 2 during denitrification and consequently higher fluxes at low soil pH.…”

“…The N 2 O reductase enzyme is reported to be more active at low soil pH relative to activities of NO 3 − and NO 2 − reductase enzymes [73], which could have resulted in the reduced N 2 O reduction to N 2 during denitrification and consequently higher fluxes at low soil pH. The most important factors controlling CH 4 emission in this study were soil moisture and temperature.…”

Influence of copper on expression of nirS, norB and nosZ and the transcription and activity of NIR, NOR and N2OR in the denitrifying soil bacteria Pseudomonas stutzeri

“…However in these studies, the Cu concentration at which N 2 OR maintained an optimum activity and where the lowest proportion of N 2 O to N 2 levels were generated, were not evaluated in further detail. Additionally, the presence of sulfide, especially H 2 S in a Cu‐deficient environment has been known to affect the reduction of N 2 O to N 2 (Manconi et al ., ; Pan et al ., ). Given that in our study, S 2 − and H 2 S could have been generated during anaerobic incubation of the broth from CuSO 4 (source of the Cu) and cysteine, this may have also contributed to the accumulation of N 2 O.…”

Measurement and understanding of methane emission from sewers

“…In addition to sulfide control, these chemicals can simultaneously induce inhibitory effects on methanogens in sewers, thus leading to possible methane elimination , Gutierrez et al, 2014, Jiang et al, 2013b, Zhang et al, 2009. For example, a recent study conducted by Mohanakrishnan et al (2009a) (Pan et al, 2013). …”

“…It is expected that penetration of nitrate into the sediment would be very limited. Additionally, nitrate addition to gravity sewers could potentially lead to N 2 O emission due to denitrification and the known inhibitory effects of hydrogen sulfide on N 2 O reduction (Pan et al, 2013).…”