RESUMEN
Despite the promising potential of elemental sulfur-based denitrification (ESDeN) packed-bed progresses, challenges such as excessive biofilm growth and gas entrapment persist, leading to denitrification deterioration. Water flush (WF) is recognized as an effective strategy, yet its effects remain underexplored. To address this knowledge gap, this study systematically investigated WF effects on ESDeN packed-bed denitrification. Results demonstrated that controlling WF effectively regulated denitrification, achieving superior and stable rates. Compared to no WF (0.45 kgN·m-3·d-1), rates improved by 1.20 â¼ 1.56 times under low-frequency (weekly WF, 0.54 kgN·m-3·d-1) and low-intensity WF (0.54 â¼ 0.70 kgN·m-3·d-1). High-frequency (hours WF) and high-intensity WF (30 & 50 m/h) further amplified denitrification rates by 1.73 â¼ 2.29 times. The enhanced denitrifications under low-frequency/intensity WF were mainly attributed to prolonged actual hydraulic retention time (AHRT), while high-frequency/intensity WF improved both AHRT prolonging and biofilm thinning, facilitating mass transfer. This study offers a promising avenue for fine-tuning denitrification rates via strategic WF adjustments.
Asunto(s)
Biopelículas , Desnitrificación , Azufre , Agua/química , Reactores Biológicos , Purificación del Agua/métodos , Eliminación de Residuos Líquidos/métodosRESUMEN
Micromovements of the eye during visual fixations provide clues about how our visual system acquires information. The analysis of fixational eye movements can thus serve as a noninvasive means to detect age-related or pathological changes in visual processing, which can in turn reflect associated cognitive or neurological disorders. However, the utility of such diagnostic approaches relies on the quality and usability of detection methods applied for the eye movement analysis. Here, we propose a novel method for (micro)saccade detection that is resistant to high-frequency recording noise, a frequent problem in video-based eye tracking in either aged subjects or subjects suffering from a vision-related pathology. The method is fast, it does not require manual noise removal, and it can work with position, velocity, or acceleration features, or a combination thereof. The detection accuracy of the proposed method is assessed on a new dataset of manually labeled recordings acquired from 14 subjects of advanced age (69-81 years old), performing an ocular fixation task. It is demonstrated that the detection accuracy of the new method compares favorably to that of two frequently used reference methods and that it is comparable to the best of the two algorithms when tested on an existing low-noise eye-tracking dataset.
Asunto(s)
Fijación Ocular/fisiología , Ruido , Movimientos Sacádicos/fisiología , Percepción Visual/fisiología , Anciano , Anciano de 80 o más Años , Algoritmos , Femenino , Humanos , Masculino , Vías Visuales/fisiologíaRESUMEN
China had a large production capacity of chlorobenzenes. An extensive investigation was conducted to understand the occurrence and characteristics of PCDD/Fs from four chlorobenzene production plants. The concentrations of PCDD/Fs in mono-CB production and in a new di-CB production routine were revealed. Concentrations of PCDD/Fs in residues, byproducts, products and wastewater varied between 8.4*103-4.0*106 ng TEQ/kg, 1.5-5.0*104 ng TEQ/kg, NDâ¼0.12 ng TEQ/kg and 6.0*104-9.1*104â¯pg TEQ/L, respectively. OCDF, 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, and 2,3,7,8-TeCDF were the most abundant congeners of the 17 2,3,7,8-substituted PCDD/Fs. In most samples, PCDFs contributed more than 99% of the total TEQs of PCDD/Fs, in which 2,3,4,7,8-PeCDF was the dominating contributor. It is inferred PCDFs were mainly formed in the chlorination reactions. The emission factors were suggested and the amount of PCDD/Fs formed in CB production was estimated to be 450â¯g TEQ in 2012. Residue, byproduct and wastewater were potentially the main pathways of PCDD/Fs to the environmental releases.
Asunto(s)
Clorobencenos/química , Dibenzofuranos Policlorados/análisis , Dibenzodioxinas Policloradas/análisis , China , Dibenzofuranos Policlorados/química , Dibenzodioxinas Policloradas/químicaRESUMEN
According to the Stockholm Convention, polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) are classified into unintentionally produced persistent organic pollutants (UP-POPs), and named dioxins. Coke production as a thermal process contains organic matters, metal and chlorine, is considered to be a potential source of dioxins. Intensive studies on the emission of dioxins from coking industry are still very scarce. In order to estimate the emission properties of dioxins through coke production, isotope dilution HRGC/HRMS technique was used to determine the concentration of dioxins through flue gas during heating of coal. Three results were obtained. First, total toxic equivalents at each stationary emission source were in the range of 3.9-30.0 pg x m(-3) (at WHO-TEQ) for dioxins which was lower than other thermal processes such as municipal solid waste incineration. Second, higher chlorinated PCDD/Fs were the dominant congeners. Third, emissions of dioxins were dependent on coking pattern. Stamping coking and higher coking chamber may lead to lower emission.
Asunto(s)
Contaminantes Atmosféricos/análisis , Benzofuranos/análisis , Coque , Bifenilos Policlorados/análisis , Dibenzodioxinas Policloradas/análogos & derivados , Polímeros/análisis , China , Monitoreo del Ambiente , Incineración , Dibenzodioxinas Policloradas/análisisRESUMEN
Based on the requirement of National Implementation Plan for the Stockholm Convention on Persistent Organic Pollutants (NIP), six industries including pulp and paper industry have been set as the priority key sectors to implement the best available technology and best environmental practice (BAT/BEP) within a specific time for UPOPs reduction. Non-wood pulping has always played important role in virgin pulp production in China, its elemental chlorinated bleaching process has been confirmed as main source of Dioxin emission for the sector. As the signature party of Stockholm Convention and long time existing country of non-wood pulping, identification of Dioxin emission situation is significant importance to China to committee the obligation of Stockholm Convention. The Dioxin concentrations in outflow water of bamboo, straw, reed, and bagasse pulping processes (chlorination alkaline extraction hypochlorite, CEH) are 41.8 pg x L(-1), 72.7 pg x L(-1), 7.46 pg x L(-1), and 19.7 pg x L(-1) respectively, which are all around the national waste water discharge standard (30 pg x L(-1)). But relevant data will easily exceed national standard while the limitation of unit water consumption for pulp making is decreased. So the application of best available techniques/best environmental practices (BAT/BEP) is very necessary to improve relevant mills up to the above standard, and proceed the sector meeting the national and international requirements for Dioxin emission. At the same time, the text calculates emission factors on bamboo, straw, reed and bagasse pulp making process through whole process monitoring, which will provide meaningful reference for increasing relevant factors in UNEP Toolkit.