Evaluating the Role of Microbial Internal Storage Turnover on Nitrous Oxide Accumulation During Denitrification

Abstract

Biological wastewater treatment processes under a dynamic regime with respect to carbon substrate can result in microbial storage of internal polymers (e.g., polyhydroxybutyrate (PHB)) and their subsequent utilizations. These storage turnovers play important roles in nitrous oxide (N2O) accumulation during heterotrophic denitrification in biological wastewater treatment. In this work, a mathematical model is developed to evaluate the key role of PHB storage turnovers on N2O accumulation during denitrification for the first time, aiming to establish the key relationship between N2O accumulation and PHB storage production. The model is successfully calibrated and validated using N2O data from two independent experimental systems with PHB storage turnovers. The model satisfactorily describes nitrogen reductions, PHB storage/utilization, and N2O accumulation from both systems. The results reveal a linear relationship between N2O accumulation and PHB production, suggesting a substantial effect of PHB storage on N2O accumulation during denitrification. Application of the model to simulate long-term operations of a denitrifying sequencing batch reactor and a denitrifying continuous system indicates the feeding pattern and sludge retention time would alter PHB turnovers and thus affect N2O accumulation. Increasing PHB utilization could substantially raise N2O accumulation due to the relatively low N2O reduction rate when using PHB as carbon source.

Assessment of Heterotrophic Growth Supported by Soluble Microbial Products in Anammox Biofilm using Multidimensional Modeling

“…Mathematical modeling has been proven to be a powerful tool for comprehensively understanding complex microbial processes in biological wastewater treatment 19 29 30 31 32 33 34 35 36 . In this work, 1-D and 2-D mathematical modeling were applied to assess the heterotrophic bacterial growth on three types of microbial products (UAP, BAP, and decay released substrate) from anammox bacteria in anammox biofilm, during the biotransformation of nitrogen compounds.…”

Modulation of Nitrous Oxide (N2O) Accumulation by Primary Metabolites in Denitrifying Cultures Adapting to Changes in Environmental C and N

“…This balance can be disturbed via either a decrease in the production rate of electron equivalents or an increase in reducible N oxides. The amount and degradability of intracellular carbon affects the rate of production of electron equivalents. ,, For example, oxidation of intracellular carbon storage compounds (i.e., poly-β-hydroxybutyrate (PHB)) have been shown to influence the rate of electron-equivalent generation and N 2 O accumulation. − The consumption of electron equivalents is governed by the type and amount of nitrogen oxide. For example, NO 3 – concentration governs the overall denitrification rate, but NO 2 – and FNA can lower NO 3 – metabolism and increase N 2 O accumulation by inhibiting N 2 O reductase (Nos) in a dose-dependent manner. , An investigation into the interactions between multiple carbon oxidation pathways and nitrite reduction has not been previously reported.…”

Novel insights into the taxonomic diversity and molecular mechanisms of bacterial Mn(III) reduction

“…Active synthesis of storage polymers suggested that 'Ca. D. occultata' was experiencing electron acceptor starvation at the time of harvesting, consistent with Mn(III) depletion in the bottles (Liu et al, 2015;Guanghuan et al, 2018). Polyphosphate-related proteins, including phosphate transporters, polyphosphate kinase, polyphosphatase and poly-3-hydroxybutyrate synthesis machinery were detected in the proteome (Table S4).…”