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Biotechnology and Bioengineering Dec 2020Aerobic granular sludge (AGS) technology allows simultaneous nitrogen, phosphorus, and carbon removal in compact wastewater treatment processes. To operate, design, and...
Aerobic granular sludge (AGS) technology allows simultaneous nitrogen, phosphorus, and carbon removal in compact wastewater treatment processes. To operate, design, and model AGS reactors, it is essential to properly understand the diffusive transport within the granules. In this study, diffusive mass transfer within full-scale and lab-scale AGS was characterized with nuclear magnetic resonance (NMR) methods. Self-diffusion coefficients of water inside the granules were determined with pulsed-field gradient NMR, while the granule structure was visualized with NMR imaging. A reaction-diffusion granule-scale model was set up to evaluate the impact of heterogeneous diffusion on granule performance. The self-diffusion coefficient of water in AGS was ∼70% of the self-diffusion coefficient of free water. There was no significant difference between self-diffusion in AGS from full-scale treatment plants and from lab-scale reactors. The results of the model showed that diffusional heterogeneity did not lead to a major change of flux into the granule (<1%). This study shows that differences between granular sludges and heterogeneity within granules have little impact on the kinetic properties of AGS. Thus, a relatively simple approach is sufficient to describe mass transport by diffusion into the granules.
Topics: Aerobiosis; Sewage; Waste Disposal, Fluid; Water Purification
PubMed: 32725888
DOI: 10.1002/bit.27522 -
Free Radical Biology & Medicine Aug 2019For well over a hundred years, members of the bacterial phylum Cyanobacteria have been considered strictly photosynthetic microorganisms, reflected in their... (Review)
Review
For well over a hundred years, members of the bacterial phylum Cyanobacteria have been considered strictly photosynthetic microorganisms, reflected in their classification as "blue-green algae" in the botanical code. Recently, genomes recovered from environmental sequencing surveys representing two major uncultured basal lineages (classes) of Cyanobacteria have been found to completely lack photosynthetic and CO fixation genes. The most likely explanation for this finding is that oxygenic photosynthesis was not an ancestral feature of the Cyanobacteria, and rather originated following divergence of the primary lines of descent. Here we describe recent findings on the evolution of aerobic respiration in the non-photosynthetic cyanobacterial classes, and how this has been interpreted by researchers interested in the evolution of oxygenic photosynthesis.
Topics: Aerobiosis; Biological Evolution; Cell Respiration; Cyanobacteria; Oxygen; Photosynthesis
PubMed: 30930297
DOI: 10.1016/j.freeradbiomed.2019.03.029 -
Chemosphere Feb 2023The widespread use of perfluorooctanoic acid (PFOA) has rendered its frequent detection in wastewater. The tolerance and recovery of aerobic granular sludge (AGS) to...
The widespread use of perfluorooctanoic acid (PFOA) has rendered its frequent detection in wastewater. The tolerance and recovery of aerobic granular sludge (AGS) to PFOA were investigated in short-term (Phase Ⅰ) and long-term (Phase Ⅱ, operation strategy adjustment: shortening aeration time and prolonging anaerobic and anoxic time). Results showed that in Phase Ⅰ, the performance of R2 reactor (0.05 mg/L PFOA) was slightly negatively affected, while 0.5 and 2.0 mg/L PFOA in R3 and R4 reactors significantly damaged the key enzyme activities of AGS, leading to deterioration of nutrients removal. TN and TP removal efficiencies decreased correspondingly from 79.32% to 78.41% on day 0 to 74.66% and 74.14% in R2 and 68.57% and 67.80% in R3 and 56.94% and 57.47% in R4 on day 7, respectively. In Phase Ⅱ, the key enzyme activities of AGS were obviously renewed dependent on operation strategy adjustment and AGS self-regulation. The performance of AGS in R2 (continuously dosing 0.05 mg/L PFOA) and R4 (stopping dosing PFOA) recovered quite good, while the long-term adverse effects of 0.5 mg/L PFOA on AGS in R3 were still more difficult to be alleviated. In end of Phase Ⅱ (69-97days), the average TN and TP removal efficiencies correspondingly reached 83.31% and 82.09% in R1 (control), 80.67% and 79.62% in R2, 76.38% and 74.27% in R3, and 79.01% and 78.25% in R4, respectively. Further analysis revealed that the effect of PFOA on proteins in extracellular polymeric substances (EPS) was greater than that on polysaccharides. Specifically, short-term dosage of PFOA mainly affected loosely bound EPS, while long-term dosage of PFOA affected tightly bound EPS. Although AGS is severely inhibited by short exposure to 2.0 mg/L PFOA (in R4), after the operation strategy adjustment, EPS content decreased, nutrient and oxygen transport channels of AGS were re-established, which contributed to the recovery of AGS.
Topics: Sewage; Waste Disposal, Fluid; Bioreactors; Nitrogen; Aerobiosis
PubMed: 36460153
DOI: 10.1016/j.chemosphere.2022.137430 -
Genes Jul 2019Steroids are perhydro-1,2-cyclopentanophenanthrene derivatives that are almost exclusively synthesised by eukaryotic organisms. Since the start of the Anthropocene, the... (Review)
Review
Steroids are perhydro-1,2-cyclopentanophenanthrene derivatives that are almost exclusively synthesised by eukaryotic organisms. Since the start of the Anthropocene, the presence of these molecules, as well as related synthetic compounds (ethinylestradiol, dexamethasone, and others), has increased in different habitats due to farm and municipal effluents and discharge from the pharmaceutical industry. In addition, the highly hydrophobic nature of these molecules, as well as the absence of functional groups, makes them highly resistant to biodegradation. However, some environmental bacteria are able to modify or mineralise these compounds. Although steroid-metabolising bacteria have been isolated since the beginning of the 20th century, the genetics and catabolic pathways used have only been characterised in model organisms in the last few decades. Here, the metabolic alternatives used by different bacteria to metabolise steroids (e.g., cholesterol, bile acids, testosterone, and other steroid hormones), as well as the organisation and conservation of the genes involved, are reviewed.
Topics: Aerobiosis; Anaerobiosis; Bacteria; Biodegradation, Environmental; Environmental Pollutants; Metabolic Networks and Pathways; Steroids
PubMed: 31284586
DOI: 10.3390/genes10070512 -
The Science of the Total Environment Jun 2023Aerobic granular sludge (AGS) is promising for water resource recovery. Despite the mature granulation strategies in sequencing batch reactor (SBR), the application of... (Review)
Review
Aerobic granular sludge (AGS) is promising for water resource recovery. Despite the mature granulation strategies in sequencing batch reactor (SBR), the application of AGS-SBR in wastewater treatment is usually costly as it requires extensive infrastructure conversion (e.g., from continuous-flow reactor to SBR). In contrast, continuous-flow AGS (CAGS) that does not require such infrastructure conversion is a more cost-effective strategy to retrofit existing wastewater treatment plants (WWTPs). Formation of aerobic granules in both batch and continuous-flow mode depends on many factors, including selection pressure, feast/famine conditions, extracellular polymeric substances (EPS), and environmental conditions. Compared with AGS in SBR, creating proper conditions to facilitate granulation in continuous-flow mode is challenging. Researchers have been seeking to tackle this bottleneck by studying the impacts of selection pressure, feast/famine conditions, and operating parameters on granulation and granule stability in CAGS. This review paper summarizes the state-of-the-art knowledge regarding CAGS for wastewater treatment. Firstly, we discuss the CAGS granulation process and effective parameters (i.e., selection pressure, feast/famine conditions, hydrodynamic shear force, reactor configuration, the role of EPS, and other operating factors). Then, we evaluate CAGS performance in removing COD, nitrogen, phosphorus, emerging pollutants, and heavy metals from wastewater. Finally, the applicability of the hybrid CAGS systems is presented. At last, we suggest that integrating CAGS with other treatment methods such as membrane bioreactor (MBR) or advanced oxidation processes (AOP) can benefit the performance and stability of granules. However, future research should address unknowns including the relationship between feast/famine ratio and stability of the granules, the effectiveness of applying particle size-based selection pressure, and the CAGS performance at low temperatures.
Topics: Sewage; Waste Disposal, Fluid; Aerobiosis; Wastewater; Bioreactors
PubMed: 36889385
DOI: 10.1016/j.scitotenv.2023.162633 -
The ISME Journal Jan 2024Genome-scale metabolic models (GEMs) are valuable tools serving systems biology and metabolic engineering. However, GEMs are still an underestimated tool in informing... (Review)
Review
Genome-scale metabolic models (GEMs) are valuable tools serving systems biology and metabolic engineering. However, GEMs are still an underestimated tool in informing microbial ecology. Since their first application for aerobic gammaproteobacterial methane oxidizers less than a decade ago, GEMs have substantially increased our understanding of the metabolism of methanotrophs, a microbial guild of high relevance for the natural and biotechnological mitigation of methane efflux to the atmosphere. Particularly, GEMs helped to elucidate critical metabolic and regulatory pathways of several methanotrophic strains, predicted microbial responses to environmental perturbations, and were used to model metabolic interactions in cocultures. Here, we conducted a systematic review of GEMs exploring aerobic methanotrophy, summarizing recent advances, pointing out weaknesses, and drawing out probable future uses of GEMs to improve our understanding of the ecology of methane oxidizers. We also focus on their potential to unravel causes and consequences when studying interactions of methane-oxidizing bacteria with other methanotrophs or members of microbial communities in general. This review aims to bridge the gap between applied sciences and microbial ecology research on methane oxidizers as model organisms and to provide an outlook for future studies.
Topics: Methane; Oxidation-Reduction; Aerobiosis; Metabolic Networks and Pathways; Models, Biological
PubMed: 38861460
DOI: 10.1093/ismejo/wrae102 -
Comparative Biochemistry and... Feb 2021The aerobic dive limit (ADL) and the hypothesis that most dives are aerobic in nature have become fundamental to the understanding of diving physiology and to the... (Review)
Review
The aerobic dive limit (ADL) and the hypothesis that most dives are aerobic in nature have become fundamental to the understanding of diving physiology and to the interpretation of diving behavior and foraging ecology of marine mammals and seabirds. An ADL, the dive duration associated with the onset of post-dive blood lactate accumulation, has only been documented with blood lactate analyses in five species. Applications to other species have involved behavioral estimates or use of an oxygen store / metabolic rate formula. Both approaches have limitations, but have proved useful to the evaluation of the dive behavior and ecology of many species.
Topics: Aerobiosis; Animals; Behavior, Animal; Diving
PubMed: 33186706
DOI: 10.1016/j.cbpa.2020.110841 -
Environmental Research May 2023Composite pollutants are prevalent in wastewater, whereas, the simultaneous accomplishment of efficient nitrogen removal and resources recovery remains a challenge. In...
Simultaneous removal of ammonia nitrogen, recovery of phosphate, and immobilization of nickel in a polyester fiber with shell powder and iron carbon spheres bioreactor: Optimization and pathways mechanism.
Composite pollutants are prevalent in wastewater, whereas, the simultaneous accomplishment of efficient nitrogen removal and resources recovery remains a challenge. In this study, a bioreactor was constructed to contain Pseudomonas sp. Y1 using polyester fiber wrapped with shell powder and iron carbon spheres, achieving ammonia nitrogen (NH-N) removal, phosphate (PO-P) recovery, and nickel (Ni) immobilization. The optimal performance of bioreactor was average removal efficiencies of NH-N, PO-P, calcium (Ca), and Ni as 82.42, 96.67, 76.13, and 98.29% at a hydraulic retention time (HRT) of 6 h, pH of 7.0, and influent Ca and Ni concentrations of 100.0 and 3.0 mg L, respectively. The bioreactor could remove PO-P, Ca, and Ni by biomineralization, co-precipitation, adsorption, and lattice substitution. Moreover, microbial community analysis suggested that Pseudomonas was the predominant genus and had possessed tolerance to Ni toxicity in wastewater. This study presented an effective method to synchronously remove NH-N, recover PO-P, and fix heavy metals through microbially induced carbonate precipitation (MICP) and heterotrophic nitrification and aerobic denitrification (HNAD) technology.
Topics: Wastewater; Ammonia; Phosphates; Denitrification; Nickel; Powders; Iron; Carbon; Nitrogen; Bioreactors; Aerobiosis
PubMed: 36805352
DOI: 10.1016/j.envres.2023.115476 -
The Science of the Total Environment Jan 2024The evolution of emerging contaminants (ECs) has caused greater requirements and challenges to the current biological wastewater treatment technology. As one of the most... (Review)
Review
The evolution of emerging contaminants (ECs) has caused greater requirements and challenges to the current biological wastewater treatment technology. As one of the most promising biological treatment technologies, the aerobic granular sludge (AGS) process also faces the challenge of ECs. This study summarizes the recent progress and characteristics of several representative ECs (persistent organic pollutants, endocrine disrupting chemicals, antibiotics, and microplastics) in AGS systems that have garnered widespread attention. Additionally, the biodegradation and adsorption mechanisms of ECs were discussed, and the interactions between various ECs and AGS was elucidated. The importance of extracellular polymeric substances for the stabilization of AGS and the removal of ECs is also discussed. Knowledge gaps and future research directions that may enable the practical application of AGS are highlighted. Overall, AGS processes show great application potential and this review provides guidance for the future implementation of AGS technology as well as elucidating the mechanism of its interaction with ECs.
Topics: Sewage; Waste Disposal, Fluid; Plastics; Bioreactors; Wastewater; Aerobiosis
PubMed: 37838059
DOI: 10.1016/j.scitotenv.2023.167792 -
Journal of Animal Science Jul 2021We evaluated the effects of different types of additives on the fermentation and aerobic stability of alfalfa (Medicago sativa) ensiled at 2 dry matters (DM). Alfalfa...
Effect of microbial and chemical additives on the fermentation and aerobic stability of alfalfa silage ensiled at 2 dry matters and subjected to air stress during storage.
We evaluated the effects of different types of additives on the fermentation and aerobic stability of alfalfa (Medicago sativa) ensiled at 2 dry matters (DM). Alfalfa was untreated (CTRL) or treated with sodium benzoate, potassium sorbate, and sodium nitrite (SFE), or microbial inoculants (Lactobacillus plantarum MTD1 [LP] or L. buchneri 40788 and Pediococcus pentocaseus 12455 [LBPP]) at a moderate (38%) and high (46%) DM using a completely randomized design with a 2 × 4 factorial arrangement of treatments. High DM silage was higher (P < 0.01) in pH, had less lactic and acetic acid (P < 0.01) and had more yeasts (P < 0.05) and molds (P < 0.01) than moderate DM silage. Recovery of DM declined (P < 0.01) for CTRL and LP treated silages with increasing DM but was not different between LBPP and SFE treatments. Compared to CTRL, LBPP had a lower (P < 0.01) DM recovery at the moderate DM, but SFE had the greatest (P < 0.01) recovery of all treatments at the high DM. Treatment with LBPP increased (P < 0.05) the concentrations of acetic acid and 1,2 propanediol (PD) compared with other treatments (P < 0.01). Numerically, fewer yeasts were found in additive treated silages compared with CTRL, but they were statistically (P < 0.01) lower only when treated with SFE. Treatment with LP resulted in a small improvement in aerobic stability at the moderate but not high DM. In contrast, treatment with SFE and LBPP markedly improved (P < 0.01) the aerobic stability of alfalfa silage at both DM. Whereas SFE and LBPP were similar in their improvements in aerobic stability at the DM, LBPP was better (P < 0.01) than SFE at the high DM. A higher (P < 0.01) concentration of acetic acid in LBPP compared with other treatments was most likely responsible for better stability. This study showed that LBPP and SFE resulted in increases in the aerobic stability of alfalfa silage and it is the first study showing SFE, can markedly improve the aerobic stability of alfalfa silage.
Topics: Aerobiosis; Animals; Fermentation; Lactobacillus; Medicago sativa; Silage; Zea mays
PubMed: 34051076
DOI: 10.1093/jas/skab174