The granulation of anaerobic ammonium oxidation (Anammox) biomass plays a key role in high rate performance of upflow-type Anammox reactors. However, the formation of cavitation inside granules may ...result in sludge flotation problem, which negatively affects the operation stability. For quantitative evaluation of the Anammox granules flotation in upflow reactors, an integrated mathematical model was formulated based on the principles that the limitation of substrate diffusion would result in bacterial starvation, lysis and subsequently aiding the formation of cavitation in the inner zone of granules. The proposed model is used to investigate the possible mechanism of cavitation formation and granules flotation. The combined modelling and experimental results showed that the model predictions matched well with the actual floating behavior of granules (R2 = 0.83 for settled sludge and 0.76 for floating sludge). Based on the model results, the granule flotation could be divided into three zones namely (i) no-flotation zone (no flotation occurrence), (ii) transition zone (flotation with a part of granules), and (iii) flotation zone (inevitable flotation occurrence). The floating behavior of granules was mainly influenced by granule diameter (2.5–4.5 mm) and substrate concentration (NO2–N, 50–250 mg/L) in the transition zone. The optimum granule diameter to avoid flotation but with excellent settling performance was identified around 2.5 mm. Additionally, the granule size is more sensitivity to flotation than substrate concentration. Hence, controlling the size of granules is more important to alleviate granule flotation in Anammox reactors’ operation.
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•A novel model on Anammox granule flotation was developed based on cell lysis and cavitation.•Granule floating behavior can be assessed by substrate concentration and diameter.•Reactor operating conditions must be kept in no-flotation and transition zones.•Flotation potential increases with the rise in cavitation inside Anammox granules.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
Advanced oxidation processes (AOPs) based on formation of free radicals at ambient temperature and pressure are effective for treating endocrine disrupting chemicals (EDCs) in waters. In this study, ...we systematically investigated the degradation kinetics of bisphenol A (BPA), a representative EDC by hydroxyl radical (OH) with a combination of experimental and theoretical approaches. The second–order rate constant (k) of BPA with OH was experimentally determined to be 7.2 ± 0.34 × 109 M−1 s−1 at pH 7.55. We also calculated the thermodynamic and kinetic behaviors for the bimolecular reactions by density functional theory (DFT) using the M05–2X method with 6–311++G** basis set and solvation model based on density (SMD). The results revealed that H–abstraction on the phenol group is the most favorable pathway for OH. The theoretical k value corrected by the Collins–Kimball approach was determined to be 1.03 × 1010 M−1 s−1, which is in reasonable agreement with the experimental observation. These results are of fundamental and practical importance in understanding the chemical interactions between OH and BPA, and aid further AOPs design in treating EDCs during wastewater treatment processes.
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•Experimental and theoretical methods were used to investigate OH oxidation of BPA.•The theoretical result is in good agreement with the experimental observation.•The reaction mechanism has been elucidated on the molecular level.•Our results aid AOTs design in removal of BPA during water treatment processes.
The experimental and theoretical k values for the reaction of BPA and OH were in agreement, and H–abstraction on the phenol group is the most favorable pathway.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
N6-methyladenosine (m6A) represents one of the most common RNA modifications in eukaryotes. Specific m6A writer, eraser, and reader proteins have been identified. As an m6A eraser, ALKBH5 ...specifically removes m6A from target mRNAs and inactivation of Alkbh5 leads to male infertility in mice. However, the underlying molecular mechanism remains unknown. Here, we report that ALKBH5-mediated m6A erasure in the nuclei of spermatocytes and round spermatids is essential for correct splicing and the production of longer 3′-UTR mRNAs, and failure to do so leads to aberrant splicing and production of shorter transcripts with elevated levels of m6A that are rapidly degraded. Our study identified reversible m6A modification as a critical mechanism of posttranscriptional control of mRNA fate in late meiotic and haploid spermatogenic cells.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Semantic segmentation of human images is a research hotspot in the field of computer vision. At present, the semantic segmentation models based on U-net generally lack the ability to capture the ...spatial information of images. At the same time, semantic incompatibility exists because the feature maps of encoder and decoder are directly connected in the skip connection stage. In addition, in low light scenes such as at night, it is easy for false segmentation and segmentation accuracy to appear. To solve the above problems, a portrait semantic segmentation method based on dual-modal information complementarity is proposed. The encoder adopts a double branch structure, and uses a SK-ASSP module that can adaptively adjust the convolution weights of different receptor fields to extract features in RGB and gray image modes respectively, and carries out cross-modal information complementarity and feature fusion. A hybrid attention mechanism is used in the jump connection phase to capture both the channel and coordinate context information of the image. Experiments on human matting dataset show that the PA and MIoU coefficients of this algorithm model reach 96.58% and 94.48% respectively, which is better than U-net benchmark model and other mainstream semantic segmentation models.
The performance of high-loaded anaerobic ammonium oxidizing (ANAMMOX) upflow anaerobic sludge bed (UASB) reactors was investigated. Two ANAMMOX reactors (R1 with and R2 without effluent recycling, ...respectively) were fed with relatively low nitrite concentration of 240 mg-N L
−1 with subsequent progressive increase in the nitrogen loading rate (NLR) by shortening the hydraulic retention time (HRT) till the end of the experiment. A super high-rate performance with nitrogen removal rate (NRR) of 74.3–76.7 kg-N m
−3 day
−1 was accomplished in the lab-scale ANAMMOX UASB reactors, which was 3 times of the highest reported value. The biomass concentrations in the reactors were as high as 42.0–57.7 g-VSS L
−1 with the specific ANAMMOX activity (SAA) approaching to 5.6 kg-N kg-VSS
−1 day
−1. The high SAA and high biomass concentration were regarded as the key factors for the super high-rate performance. ANAMMOX granules were observed in the reactors with settling velocities of 73–88 m h
−1. The ANAMMOX granules were found to contain a plenty of extracellular polymers (ECPs) such as 71.8–112.1 mg g-VSS
−1 of polysaccharides (PS) and 164.4–298.2 mg g-VSS
−1 of proteins (PN). High content of hemachrome (6.8–10.3 μmol g-VSS
−1) was detected in the ANAMMOX granules, which is supposed to be attributed to their unique carmine color.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
The study reported one concept for fabrication of honeycomb block AC@Ti-Cu-Ni-Zn-Sb-Mn particles serving as packed bed particle electrodes for the degradation of PAP in wastewater. The proposed ...three-dimensional electrochemical systems exhibit excellent removal efficiency toward PAP. The particle electrodes activated O2 to generate H2O2 further forming OH. The pathway study suggested that the quinoneimine is the major intermediate and OH radicals play important roles in the reaction.
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•Honeycomb block particle electrodes were synthesized through a facile method.•Ti-Cu-Ni-Zn-Sb-Mn were in-situ loaded on particle electrodes as catalysts.•The AC@Ti-Cu-Ni-Zn-Sb-Mn activated O2 to generate H2O2 further forming OH.•PAP is mainly degraded by indirect oxidation of OH radical.
Emerging contaminants such as pharmaceuticals has been one of the most challenging environmental problems. In this work, we developed a one-step facile sol–gel method of loading TiO2, CuO, NiO, ZnO, Sb2O3 and MnO onto honeycomb block activated carbon (AC@Ti-Cu-Ni-Zn-Sb-Mn), further applying as particle electrodes in a three-dimensional electrochemical system for the efficient degradation of p-aminophenol (PAP). Factors associated with the preparation of AC@Ti-Cu-Ni-Zn-Sb-Mn particle electrodes were investigated. The AC@Ti-Cu-Ni-Zn-Sb-Mn particle electrodes were analyzed by scanning electron microscope (SEM), energy dispersive spectrum analysis (EDX), X-Ray Diffraction analysis (XRD), Brunner-Emmet-Teller (BET) and X-ray Photoelectron spectroscopy (XPS). The effects of conductivity, pH value, aeration intensity, current density, conductivity and initial concentration on PAP degradation were also studied. Importantly, the PAP degradation results show that the activity of the particle electrodes supported by block honeycomb activated carbon is much better than that of the particle electrodes supported by granular activated carbon. The removal efficiency of PAP achieved approximately 99.87% under the optimized condition. The pathway study suggested that the quinoneimine is the major intermediate during the three-dimensional electrochemical degradation and OH radicals play important roles in the reaction. Overall, its facile fabrication and efficient electrochemical degradation performance indicate that the proposed honeycomb block particle electrodes have potential for practical applications of refractory organic pollutants.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
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•The copper ammonia complex ratio in aqueous solution was determined.•Copper mainly exists in the form of copper tetraamine.•Complex components were identified by infrared derivative ...spectroscopy.•Integration of PCR and UV–vis spectroscopy allows the quantification of copper ammonia complex.
Ammonia can form stable chemical complexes with heavy metal ions, which significantly affect the treatment efficiency of these wastewaters. Thus, accurately determining the concentration of heavy metal ammonia complex ions is crucial to understanding the complex decomposition mechanism. The current study predicted the composition of copper ammonia solution through thermodynamic calculations. The mid-infrared first derivative spectra obtained from density functional theory (DFT) calculation and measurements of the simulated solutions were compared, which indicated that Cu(NH3)42+ was the primary form of complexes in solution. The acquired FTIR spectra and UV–vis spectra demonstrated a strong correlation with the Cu(NH3)42+ concentrations; whereas a principal component regression (PCR) model was implemented for concentration computation. The UV–vis-PCR model was found to be a fast and accurate method for quantification of copper-ammonia complex concentration, and its detection limit and quantification limit could reach 5 mg·L−1 and 10 mg·L−1, respectively, in the 5–200 mg·L−1 range. This study established qualitative and quantitative methods for analyzing copper ammonia complex in water, which provided the feasibility for rapid real-time monitoring of copper ammonia complex.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The role of soluble microbial products (SMP), the most important component of effluent organic matter from municipal wastewater treatment plants, in sulfate radical (SO4 •–)-based advanced oxidation ...technologies (AOTs) remains substantially unclear. In this study, we first utilized a suite of macro- and microanalytical techniques to characterize the SMP from a membrane bioreactor for its fundamental molecular, spectroscopic, and reactivity properties. The degradation kinetics of three representative pharmaceuticals (i.e., naproxen, gemfibrozil, and sulfadiazine) in the presence of SMP was significantly reduced as compared to in its absence. Possible mechanisms for the interference by SMP in degrading these target compounds (TCs) were investigated. The low percentage of bound TCs to SMP ruled out the cage effect. The measurement of steady-state 1O2 concentration indicated that formation of 1O2 upon UV irradiation on SMP was not primarily responsible for the degradation of TCs. However, the comparative and quenching results reveal that SMP absorbs UV light acting as an inner filter toward the TCs, and meanwhile scavenges SO4 •– with a high second-order rate constant of 2.48 × 108 MC –1 s–1.
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IJS, KILJ, NUK, PNG, UL, UM
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