More Like this

1. Sensor‐mediated granular sludge reactor for nitrogen removal and reduced aeration demand using a dilute wastewater

   https://doi.org/10.1002/wer.1296  

   Bekele, Zerihun A. ; Delgado Vela, Jeseth ; Bott, Charles B. ; Love, Nancy G. ( February 2020 , Water Environment Research)

   A sensor‐mediated strategy was applied to a laboratory‐scale granular sludge reactor (GSR) to demonstrate that energy‐efficient inorganic nitrogen removal is possible with a dilute mainstream wastewater. The GSR was fed a dilute wastewater designed to simulate an A‐stage mainstream anaerobic treatment process. DO, pH, and ammonia/nitrate sensors measured water quality as part of a real‐time control strategy that resulted in low‐energy nitrogen removal. At a low COD (0.2 kg m⁻³ day⁻¹) and ammonia (0.1 kg‐N m⁻³ day⁻¹) load, the average degree of ammonia oxidation was 86.2 ± 3.2% and total inorganic nitrogen removal was 56.7 ± 2.9% over the entire reactor operation. Aeration was controlled using a DO setpoint, with and without residual ammonia control. Under both strategies, maintaining a low bulk oxygen level (0.5 mg/L) and alternating aerobic/anoxic cycles resulted in a higher level of nitrite accumulation and supported shortcut inorganic nitrogen removal by suppressing nitrite oxidizing bacteria. Furthermore, coupling a DO setpoint aeration strategy with residual ammonia control resulted in more stable nitritation and improved aeration efficiency. The results show that sensor‐mediated controls, especially coupled with a DO setpoint and residual ammonia controls, are beneficial for maintaining stable aerobic granular sludge.

   Tight sensor‐mediated aeration control is need for better PN/A.

   Low DO intermittent aeration with minimum ammonium residual results in a stable N removal.

   Low DO aeration results in a stable NOB suppression.

   Using sensor‐mediated aeration control in a granular sludge reactor reduces aeration cost.

    

   more » « less
2. Ammonia-oxidizing archaea are integral to nitrogen cycling in a highly fertile agricultural soil

   https://doi.org/10.1038/s43705-021-00020-4  

   Huang, Laibin ; Chakrabarti, Seemanti ; Cooper, Jennifer ; Perez, Ana ; John, Sophia M. ; Daroub, Samira H. ; Martens-Habbena, Willm ( December 2021 , ISME Communications)

   null (Ed.)

   Abstract Nitrification is a central process in the global nitrogen cycle, carried out by a complex network of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), complete ammonia-oxidizing (comammox) bacteria, and nitrite-oxidizing bacteria (NOB). Nitrification is responsible for significant nitrogen leaching and N 2 O emissions and thought to impede plant nitrogen use efficiency in agricultural systems. However, the actual contribution of each nitrifier group to net rates and N 2 O emissions remain poorly understood. We hypothesized that highly fertile agricultural soils with high organic matter mineralization rates could allow a detailed characterization of N cycling in these soils. Using a combination of molecular and activity measurements, we show that in a mixed AOA, AOB, and comammox community, AOA outnumbered low diversity assemblages of AOB and comammox 50- to 430-fold, and strongly dominated net nitrification activities with low N 2 O yields between 0.18 and 0.41 ng N 2 O–N per µg NO x –N in cropped, fallow, as well as native soil. Nitrification rates were not significantly different in plant-covered and fallow plots. Mass balance calculations indicated that plants relied heavily on nitrate, and not ammonium as primary nitrogen source in these soils. Together, these results imply AOA as integral part of the nitrogen cycle in a highly fertile agricultural soil. 

   more » « less
3. Out of sight, but not out of season: Nitrifier distributions and population dynamics in a large oligotrophic lake

   https://doi.org/10.1111/1462-2920.16616  

   Peoples, Logan M. ; Seixas, Miranda H. ; Evans, Kate A. ; Bilbrey, Evan M. ; Ranieri, John R. ; Tappenbeck, Tyler H. ; Dore, John E. ; Baumann, Adam ; Church, Matthew J. ( March 2024 , Environmental Microbiology)

   Nitrification is an important control on the form and distribution of nitrogen in freshwater ecosystems. However, the seasonality of nitrogen pools and the diversity of organisms catalyzing this process have not been well documented in oligotrophic lakes. Here, we show that nitrogen pools and nitrifying organisms in Flathead Lake are temporally and vertically dynamic, with nitrifiers displaying specific preferences depending on the season. While the ammonia‐oxidizing bacteria (AOB) Nitrosomonadaceae and nitrite‐oxidizing bacteria (NOB)Nitrotogadominate at depth in the summer, the ammonia‐oxidizing archaea (AOA) Nitrososphaerota and NOB Nitrospirota become abundant in the winter. Given clear seasonality in ammonium, with higher concentrations during the summer, we hypothesize that the succession between these two nitrifying groups may be due to nitrogen affinity, with AOB more competitive when ammonia concentrations are higher and AOA when they are lower. Nitrifiers in Flathead Lake share more than 99% average nucleotide identity with those reported in other North American lakes but are distinct from those in Europe and Asia, indicating a role for geographic isolation as a factor controlling speciation among nitrifiers. Our study shows there are seasonal shifts in nitrogen pools and nitrifying populations, highlighting the dynamic spatial and temporal nature of nitrogen cycling in freshwater ecosystems.

    

   more » « less
4. Controls on nitrite oxidation in the upper Southern Ocean: insights from winter kinetics experiments in the Indian sector

   https://doi.org/10.5194/bg-19-3425-2022  

   Mdutyana, Mhlangabezi ; Marshall, Tanya ; Sun, Xin ; Burger, Jessica M. ; Thomalla, Sandy J. ; Ward, Bess B. ; Fawcett, Sarah E. ( January 2022 , Biogeosciences)

   Abstract. Across the Southern Ocean in winter, nitrification is the dominantmixed-layer nitrogen cycle process, with some of the nitrate producedtherefrom persisting to fuel productivity during the subsequent growingseason. Because this nitrate constitutes a regenerated rather than a newnutrient source to phytoplankton, it will not support the net removal ofatmospheric CO2. To better understand the controls on Southern Oceannitrification, we conducted nitrite oxidation kinetics experiments insurface waters across the western Indian sector in winter. While allexperiments (seven in total) yielded a Michaelis–Menten relationship withsubstrate concentration, the nitrite oxidation rates only increasedsubstantially once the nitrite concentration exceeded 115±2.3 to245±18 nM, suggesting that nitrite-oxidizing bacteria (NOB) require aminimum (i.e., “threshold”) nitrite concentration to produce nitrate. Thehalf-saturation constant for nitrite oxidation ranged from 134±8 to403±24 nM, indicating a relatively high affinity of Southern OceanNOB for nitrite, in contrast to results from culture experiments. Despitethe high affinity of NOB for nitrite, its concentration rarely declinesbelow 150 nM in the Southern Ocean's mixed layer, regardless of season. Inthe upper mixed layer, we measured ammonium oxidation rates that were two-to seven-fold higher than the coincident rates of nitrite oxidation,indicating that nitrite oxidation is the rate-limiting step fornitrification in the winter Southern Ocean. The decoupling of ammonium andnitrite oxidation, combined with a possible nitrite concentration thresholdfor NOB, may explain the non-zero nitrite that persists throughout theSouthern Ocean's mixed layer year-round. Additionally, nitrite oxidation maybe limited by dissolved iron, the availability of which is low across theupper Southern Ocean. Our findings have implications for understanding thecontrols on nitrification and ammonium and nitrite distributions, both inthe Southern Ocean and elsewhere.

    

   more » « less
5. Fate and Transport of the Biologically Treated Landfill Leachate Induced Dissolved Organic Nitrogen (DON)

   Md Ashik Ahmed*, Md Redowan ( June 2023 , AEESP Research and Education Conference, Northeastern University, June 20-23, 2023)

   This study evaluated the performance of sequencing batch reactors (SBR) in the fate and transport of dissolved organic nitrogen (DON) using a blend of wastewater and landfill leachate. Most nitrogen removal methods concentrate on inorganic nitrogen, whereas some biological processes add DON to the effluent. Two reactors were introduced with wastewater and landfill leachate of high and low organic carbon and compared them to a reactor without leachate. DON transformation, characterization, and microbial community dispersion were examined to understand the effects of leachate-induced effluent DON on the biological nitrogen removal process. The ammonium removal efficiencies were found 96, 97, and 98%; COD removal efficiencies were 75, 59, and 63%; and total nitrogen (TN) removal efficiencies were 83, 86, and 88%, for R1, R2, and R3, respectively. The effluent nitrate concentrations were found 1.67 ± 0.89 (R1), 3.05 ± 2.08 (R2), and 1.31 ± 1.30 (R3) mg/L and DON went down from 9.67 ± 2.5 to 6.02 ± 2.8 mg/L (R1), 9.29 ± 3.4 to 7.49 ± 3.6 mg/L (R2), and 3.59 ± 1.6 to 2.08 ± 1.1 mg/L (R3). Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and excitation-emission matrices (EEMs) with parallel factor (PARAFAC) analysis were used to characterize DON. Microbial community analysis was also conducted. Leachate-induced DON discharge's environmental effects were assessed using in-situ aquatic ecosystem algal bioassay. SBR system removed most inorganic nitrogen species and a small amount of leachate-induced DON. The study emphasizes the need for independent investigations to assess their effects on receiving water bodies. 

   more » « less