Acidic nitrification is attracting wide attention because it can enable robust suppression of nitrite-oxidizing bacteria (NOB) in wastewater treatment. This study reports a comprehensive assessment of the novel acidic nitrification process to identify the key factors that govern stable nitrite accumulation. A laboratory-scale moving-bed biofilm reactor receiving low-alkalinity wastewater was continuously operated under acidic conditions (pH < 6) for around two years, including nine stages varying influent and operational conditions. The results revealed that nitrite accumulation was related to three factors, i.e., influent ammonium concentration, operating pH, and ammonia-oxidizing microbial community. These three factors impact nitrite accumulation by altering the concentration of free nitrous acid (FNA), which is a potent inhibitor of NOB. The critical FNA concentration is approximately one part per million (ppm, ∼1 mg HNO-N/L), above which nitrite accumulation is stably maintained in an acidic nitrifying system. The findings of this study suggest that stable nitrite accumulation via acidic ammonia oxidation can be maintained under a range of influent and operational conditions, as long as a ppm-level of FNA is established. Taking low-strength mainstream wastewater (40-50 mg NH-N/L) with limited alkalinity as an example, stable nitrite accumulation was experimentally demonstrated at a pH of 4.35, under which an FNA of 2.3 ± 0.6 mg HNO-N/L was attained. Under these conditions, Nitrosoglobus became the only ammonia oxidizer detectable by 16S rRNA gene sequencing. The results of this study deepen our understanding of acidic nitrifying systems, informing further development of novel wastewater treatment technologies.
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http://dx.doi.org/10.1021/acs.est.1c07522 | DOI Listing |
Redox Biol
January 2025
Department of Pediatrics, Division of Neonatology, Loma Linda University School of Medicine, Loma Linda, CA, USA; Lawrence D. Longo, MD Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, CA, USA. Electronic address:
Repeated use of nitroglycerin results in a loss of its vasodilatory efficacy which limits its clinical use for the treatment of angina pectoris. This tolerance phenomenon is a defining characteristic of all compounds classified as nitrodilators, which includes NTG as well as S-nitrosothiols and dinitrosyl iron complexes. These compounds vasodilate via activation of soluble guanylate cyclase, although they do not release requisite amounts of free nitric oxide (NO) and some do not even cross the plasma membrane.
View Article and Find Full Text PDFJ Environ Manage
January 2025
Biological Processes Laboratory (LPB), São Carlos School of Engineering (EESC), University of São Paulo (USP), Av. João Dagnone, 1100, Santa Angelina, São Carlos, São Paulo, 13563-120, Brazil.
Water Environ Res
January 2025
College of Urban Construction, Wuhan University of Science and Technology, Wuhan, China.
Microalgae-bacteria systems present a promising approach for CO reduction in wastewater treatment. The effect of inoculation bacteria-algae ratio on performance was investigated in this study. Different inoculation ratios (bacteria: algae 1:2, 1:1, 1:0.
View Article and Find Full Text PDFTheriogenology
January 2025
Grupo de Química Orgánica Medicinal, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400, Montevideo, Uruguay; Área de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la República, Mataojo 2055, 11400, Montevideo, Uruguay. Electronic address:
The aim was to study the effect of 4-phenylfuroxan-3-carbonitrile (Fx), a NO-releasing agent, and carbetocin, an oxytocin receptor agonist, on matrix metalloproteinases-2 (MMP-2) activity and PGE2 production in cervix from cycling sheep. Cervical explants were incubated during 12 h with MEM supplemented with increasing concentrations of Fx in DMSO (2 %) (0 to 300 μg/mL) with Cb (100 ng/mL) (Experiment 1, n = 15) and DMSO (2 %), DMSO + Cb (100 ng/mL) or DMSO + Fx (30 μg/mL) (Experiment 2, n = 10), and their respective controls. In the supernatants, activated (A) and latent (L) MMP-2 activities were determined by a SDS-PAGE zymography, PGE2 concentration by immunoassay and NO production indirectly as nitrites by spectrophotometry.
View Article and Find Full Text PDFJ Exp Bot
January 2025
Morden Research and Development Centre, Agriculture and Agri-Food Canada, Morden, MB, Canada.
Alternative oxidase (AOX) regulates the level of reactive oxygen species and nitric oxide (NO) in plants. While under normoxic conditions it alleviates NO formation, there are several indications that in the conditions of low oxygen such as during seed germination before radicle protrusion, in meristematic stem cells, and in flooded roots AOX can be involved in the production of NO from nitrite. Whereas the first reports considered this role as indirect, more evidence is accumulated that AOX can act as a nitrite: NO reductase.
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