Labile carbon release from oxic–anoxic cycling in woodchip bioreactors enhances nitrate removal without increasing nitrous oxide accumulation

McGuire, Philip M.; Dai, Valentina; Walter, M. Todd; Reid, Matthew C.

doi:10.1039/d1ew00446h

Cited by 9 publications

(18 citation statements)

References 66 publications

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“…The N 2 O yield also varied considerably, initially increasing as the reactor transitioned to hypoxic conditions, and then decreasing and stabilizing once the system became anoxic. NH 4 + concentrations in the reactor pore water were negligible, suggesting that DNRA was not a major process in this system (McGuire et al, 2021).…”

Section: Resultsmentioning

confidence: 95%

“…There were no systematic changes in denitrification gene abundances between the beginning and end of experiments, or between CS and DRW reactors. Wet chemical and dissolved gas measurements reported in McGuire et al (McGuire et al, 2021) showed that the DRW reactor had significantly faster NO 3 − removal rates than the CS reactor. In replicate 1, DRW conditions also led to a decrease in the effective N 2 O yield from 8.1 × 10 −3 ± 2.1 × 10 −3 mg N 2 ON/mg NO 3 − ‐ N in the CS reactor to 1.4 × 10 −4 ± 6.4 × 10 −4 mg N 2 O−N/mg NO 3 − −N in the DRW reactor.…”

Section: Resultsmentioning

confidence: 97%

“…This hypothesis has yet to be confirmed, however. DOC released from woodchips under oxic–anoxic cycling also had lower aromaticity (McGuire et al, 2021), strengthening links between oxic–anoxic cycling and transformations of aromatic lignin or lignin‐derived molecules.…”

Section: Introductionmentioning

confidence: 97%

“…This practice increased the release of dissolved organic C (DOC) from wood and achieved significant and sustained increases in NO 3 − removal efficiencies compared to permanently flooded conditions (Maxwell et al, 2019), though the microbial drivers for these observations were not characterized. We recently employed drying/re‐flooding in laboratory‐scale WBRs to show that this approach can also decrease production of the potent greenhouse gas N 2 O in the aftermath of reactors being re‐flooded (McGuire et al, 2021). This was an unexpected but promising result, given the notion that nosZ expression can be inhibited by O 2 exposure (Qu et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Oxic–anoxic cycling promotes coupling between complex carbon metabolism and denitrification in woodchip bioreactors

McGuire

Butkevich

Saksena

et al. 2023

Environmental Microbiology

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Denitrifying woodchip bioreactors (WBRs) are increasingly used to manage the release of non‐point source nitrogen (N) by stimulating microbial denitrification. Woodchips serve as a renewable organic carbon (C) source, yet the recalcitrance of organic C in lignocellulosic biomass causes many WBRs to be C‐limited. Prior studies have observed that oxic–anoxic cycling increased the mobilization of organic C, increased nitrate (NO3−) removal rates, and attenuated production of nitrous oxide (N2O). Here, we use multi‐omics approaches and amplicon sequencing of fungal 5.8S‐ITS2 and prokaryotic 16S rRNA genes to elucidate the microbial drivers for enhanced NO3− removal and attenuated N2O production under redox‐dynamic conditions. Transient oxic periods stimulated the expression of fungal ligninolytic enzymes, increasing the bioavailability of woodchip‐derived C and stimulating the expression of denitrification genes. Nitrous oxide reductase (nosZ) genes were primarily clade II, and the ratio of clade II/clade I nosZ transcripts during the oxic–anoxic transition was strongly correlated with the N2O yield. Analysis of metagenome‐assembled genomes revealed that many of the denitrifying microorganisms also have a genotypic ability to degrade complex polysaccharides like cellulose and hemicellulose, highlighting the adaptation of the WBR microbiome to the ecophysiological niche of the woodchip matrix.

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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Oxic–anoxic cycling promotes coupling between complex carbon metabolism and denitrification in woodchip bioreactors

McGuire

Butkevich

Saksena

et al. 2023

Environmental Microbiology

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“…Efforts have been made to optimize process performance and bioreactor design, by considering reactor hydrology (Hoover et al, 2016;Martin et al, 2019;Nordström and Herbert, 2017;Schaefer et al, 2021), substrates for the denitrifying microorganisms (Cameron and Schipper, 2010;Hellman et al, 2021;McGuire et al, 2021;Wang and Chu, 2016) and choice of inoculum (Lefèvre et al, 2013). However, it is not until recently interest has been drawn to the microbial communities in the bioreactors.…”

Section: Introductionmentioning

confidence: 99%

Spatial and temporal changes in microbial communities and greenhouse gas emissions in a denitrifying woodchip bioreactor at low water temperatures

Hellman

Juhanson

Herbert

et al. 2023

Preprint

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Nitrogen (N) pollution is a major threat to ecosystems and a driver of climate change through emissions of the greenhouse gas nitrous oxide (N2O). Mining activities are increasingly recognized for contributing to N pollution due to undetonated, N-based explosives. A woodchip denitrifying bioreactor, installed to treat nitrate-rich leachate from waste rock dumps in northern Sweden, was monitored for two years to determine the spatial and temporal distribution of microbial communities in pore water and woodchips and their genetic potential for different N transformation processes, and how this affected the N removal capacity and possible production of undesired N species, like ammonium, nitrite and N2O. About 80 and 65 % of the nitrate was removed from the leachate the first and second operational year, respectively, which agreed with a decrease in dissolved organic carbon in the outlet water. There was a succession in the microbial community over time and in space along the reactor length in both pore water and woodchips, which was reflected in the genetic potential for N cycling and ultimately also reactor performance. We conclude that DNRA had minimal impact on the overall N removal efficiency due to the low relative abundance of the key gene nrfA involved in DNRA and the low production of ammonium. However, nitrite, ammonium, and N2O were formed in the bioreactor and released in the effluent water, although direct emissions of N2O from the surface was low. The N2O production in the reactor might be explained by the ratio between the genetic potential for overall denitrification and N2O reduction in the woodchip and pore water communities, as indicated by the low ratio between the abundance of nir and nosZ genes. Altogether, the results indicate that the denitrification pathway was temporally as well as spatially separated along the reactor length, and that unwanted reactive N species were produced at different time points and locations in the reactor. Thus, the succession of microbial communities in woodchip denitrifying bioreactors treating mining impacted water develops slowly at low temperature, which impacts the reactor performance.

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Enhanced nitrate removal and side effects of methanol dosing in denitrifying bioreactors

Moghaddam

Torres-Rojas

Schipper

2022

Ecological Engineering

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Labile carbon release from oxic–anoxic cycling in woodchip bioreactors enhances nitrate removal without increasing nitrous oxide accumulation

Abstract: Denitrification in woodchip bioreactors (WBRs) treating agricultural drainage and runoff is frequently carbon-limited due to the recalcitrance of carbon (C) in lignocellulosic woodchip biomass. Recent research has shown that redox...

Cited by 9 publications

References 66 publications

Oxic–anoxic cycling promotes coupling between complex carbon metabolism and denitrification in woodchip bioreactors

Oxic–anoxic cycling promotes coupling between complex carbon metabolism and denitrification in woodchip bioreactors

Spatial and temporal changes in microbial communities and greenhouse gas emissions in a denitrifying woodchip bioreactor at low water temperatures

Enhanced nitrate removal and side effects of methanol dosing in denitrifying bioreactors

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