活性污泥耗氧速率的测定及其影响因素试验分析

本文首先介绍了活性污泥净化能力判别指标——耗氧速率的原电池氧测定法,继而通过试验研究了一些相关的影响因素同比耗氧速率的关系,最后分析说明了比耗氧速率在监控活性污泥系统运行中所起的作用。     

Defect-enhanced photocatalytic removal of dimethylarsinic acid over mixed-phase mesoporous TiO2

Much attention has been paid to the pollutant dimethylarsenic acid(DMA),because of its high toxicity even at very low doses.Although TiO_2 photocatalytic oxidation(PCO) is one of the few effective methods for treating DMA-containing water,the efficient decomposition of DMA and simultaneous removal of toxic arsenic species remains a significant but challenging task.Here,defective mesoporous TiO_2 with mixed-phase structure was synthesized and used as both photocatalyst and adsorbent for DMA removal.Due to the reduced band-gap and enhanced separation of photogenerated charge carriers, the oxygen-deficient TiO_2 nanostructures exhibited 4.2 times higher PCO efficiency than commercial TiO_2(P25).More importantly,the high surface area of the mesoporous TiO_2 provided sufficient active sites for in-situ adsorption and reaction,resulting in the efficient removal of as-formed As(V).Combining the experimental and characterization results,the different roles of reactive species during PCO reactions were clarified.In the presence of hole(h~+) as the dominant oxidation species,DMA was demethylated and transformed into MMA.Thereafter,MMA was subsequently reduced to As(Ⅲ) by photo-generated electrons.Superoxide radicals(O_2~(·-)) played a significant role in oxidizing As(Ⅲ) into As(Ⅴ),which was finally adsorptively removed by the mesoporous TiO_2.     

Safety parameters for oxygen-enriched flames

The utilization of low-quality gaseous fuel from biomass gasification and the abundance of oxygen-rich streams obtained as a by-product of nitrogen-air separation by membrane technology has incentivized the development of sustainable oxygen-enriched combustion technologies in the last decades. However, a dearth of experimental and numerical analysis addressing the reactivity and safety aspects of these mixtures at initial low temperatures can be observed in the current literature.In this work, the heat flux burner was adopted for the measurement of the laminar burning velocity of methane in oxygen enriched air at different equivalence ratios. Results were compared with numerical data obtained by means of detailed kinetic mechanisms developed at the University of Bologna and the Gas Research Institute (GriMech3.0). Simplified correlations for the estimation of the laminar burning velocity with respect to the oxygen content at any equivalence ratio were developed, tested and evaluated.An elemental reaction-based function was found appropriate for the estimation of the overall reactivity of the investigated mixtures. Besides, numerical analyses were performed to characterize the flame structures in terms of temperature and product distribution under several initial conditions. These results gave further insights into the reaction mechanisms of gaseous fuels in the case of oxygen-enriched air, highlighting potential bottlenecks for kinetic model refinements. Eventually, relevant safety parameters were estimated, in particular the flammability range of the fuel/oxidant mixture, in terms of lower and upper flammability limits.     

Evaluation of laboratory-scale in-vessel co-composting of tobacco and apple waste

Efficient composting process requires set of adequate parameters among which physical–chemical properties of the composting substrate play the key-role. Combining different types of biodegradable solid waste it is possible to obtain a substrate eligible to microorganisms in the composting process. In this work the composting of apple and tobacco solid waste mixture (1:7, dry weight) was explored. The aim of the work was to investigate an efficiency of biodegradation of the given mixture and to characterize incurred raw compost. Composting was conducted in 24 L thermally insulated column reactor at airflow rate of 1.1 L min^?1. During 22 days several parameters were closely monitored: temperature and mass of the substrate, volatile solids content, C/N ratio and pH-value of the mixture and oxygen consumption. The composting of the apple and tobacco waste resulted with high degradation of the volatile solids (53.1%). During the experiment 1.76 kg of oxygen was consumed and the C/N ratio of the product was 11.6. The obtained temperature curve was almost a “mirror image” of the oxygen concentration curve while the peak values of the temperature were occurred 9.5 h after the peak oxygen consumption.     

Tuning of activated sludge in winter based on respirogram profiles under standard and site temperatures

Respirograms of activated sludge OUR_ x~Tand OUR_x~(20)were measured under site(T) and standard(20°C) temperatures, respectively, and the predicted standard temperature respirogram OUR_( x,cal)~(20)was also calculated using the Arrhenius equation. These respirogram profiles reveal more information than effluent quality. A decrease of OUR_ x ~(20)is a critical alarm signal for the loss of pollutant removal capacity, and a sudden increase of the predicted value OUR_( x,cal)~(20)is an alarm signal for the unrecoverable deterioration of biomass. The sign of OUR_x~(20)–OUR_(x,cal)~(20)can be used for selection of tuning strategies. For example, a negative value of OUR_x~(20)–OUR_( x,cal)~(20)indicates that doubling biomass is difficult,thus strategies such as extending the reaction time with limited available biomass is preferred. The findings in this study elucidated the respiration profile of activated sludge under changes of temperature and can be effectively used for the stable operation of Wastewater Treatment Plants under cold temperatures and seasonal variations.     

Photocatalytic defluorination of perfluorooctanoic acid by surface defective BiOCl: Fast microwave solvothermal synthesis and photocatalytic mechanisms

There is an urgent need for developing cost-effective methods for the treatment of perfluorooctanoic acid(PFOA)due to its global emergence and potential risks.In this study,taking surface-defective BiOCl as an example,a strategy of surface oxygen vacancy modulation was used to promote the photocatalytic defluorination efficiency of PFOA under simulated sunlight irradiation.The defective BiOCl was fabricated by a fast microwave solvothermal method,which was found to induce more surface oxygen vacancies than conventional solvothermal and precipitation methods.As a result,the asprepared BiOCl showed significantly enhanced defluorination efficiency,which was 2.7 and33.8 times higher than that of BiOCl fabricated by conventional solvothermal and precipitation methods,respectively.Mechanistic studies indicated that the defluorination of PFOA follows a direct hole(h~+)oxidation pathway with the aid of·OH,while the oxygen vacancies not only promote charge separation but also facilitate the intimate contact between the photocatalyst surface and PFOA by coordinating with its terminal carboxylate group in a bidentate or bridging mode.This work will provide a general strategy of oxygen vacancy modulation by microwave-assisted methods for efficient photocatalytic defluorination of PFOA in the environment using sunlight as the energy source.     

Effects of oxidizing environment on digestate humification and identification of substances governing the dissolved organic matter (DOM) transformation process

• Liquid digestate humification was investigated under different oxidizing environment. • Tryptophan-like substances dominated the transformation of the liquid digestate DOM. • The humification sequence of the liquid digestate DOM was identified. • UV₃₂₅ was first identified as a pre-humus intermediate during humification reaction. The formation of humic-like acids (HLAs) is an essential process for converting liquid digestate into organic soil amendments to enhance agricultural sustainability. The aim of this study was to investigate the impact of oxygen and/or MnO₂ on the production of HLAs. Herein, abiotic humification performance of the digestate dissolved organic matter (DOM) is investigated with fluxes of air and N₂ in the absence and presence of MnO₂. Our results demonstrated that the fate of digestate DOM greatly depends on the oxidizing environment, the MnO₂ enhanced nitrogen involved in the formation of HLAs. The synergistic effects of MnO₂ and oxygen effectively improved the production of HLAs, and the corresponding component evolution was analyzed using spectroscopic evidence. The two-dimensional correlation spectroscopy results demonstrated that the reaction sequence of digestate DOM followed the order of protein-like substances, substances with an absorbance at 325 nm, substances with UV absorbance at 254 nm and HLAs. Additionally, excitation emission matrix fluorescence combined with parallel factor analysis (EEM-PARAFAC) showed that tryptophan-like C3 was more prone to transformation than tyrosine-like C2 and was responsible for the humification process. The substance with an absorbance at 325 nm was a reaction intermediate in the transformation process of protein-like substances to HLAs. The above findings can be used to promote the production of liquid fertilizer associated with carbon sequestration as well as the sustainable development of biogas production.     

Effects of synthesis methods on catalytic activities of CoOx–TiO2 for low-temperature NH3-SCR of NO

A series of cobalt doped TiO_2(Co-TiO_2) and Co Oxloaded TiO_2(Co/TiO_2) catalysts prepared by sol–gel and impregnation methods respectively were investigated on selective catalytic reduction with NH_3(NH_3-SCR) of NO. It was found that Co-TiO_2 catalyst showed more preferable catalytic activity at low temperature range. From characterization results of XRD,TEM, Raman and FT-IR, Co species were proved to be doped into TiO_2 lattice by replaced Ti atoms. After being characterized and analyzed by NH_3-TPD, PL, XPS, EPR and DRIFTS, it was found that the better NH_3-SCR activities of Co-TiO_2 catalysts, compared with Co/TiO_2 catalyst, were ascribed to the formation of more oxygen vacancies which further promoted the production of more superoxide ions(O-2). The superoxide ions were crucial for the formation of low temperature SCR reaction intermediates(NO-3) by reacting with adsorbed NO molecule. Therefore, these aspects were responsible for the higher low temperature NH_3-SCR activity of Co-TiO_2 catalysts.     

The O₂-enriched air gasification of coal, plastics and wood in a fluidized bed reactor

The effect of oxygen-enriched air during fluidized bed co-gasification of a mixture of coal, plastics and wood has been investigated. The main components of the obtained syngas were measured by means of on-line analyzers and a gas chromatograph while those of the condensate phase were off-line analysed by means of a gas chromatography-mass spectrometer (GC-MS). The characterization of condensate phase as well as that of the water used as scrubbing medium completed the performed diagnostics. The experimental results were further elaborated in order to provide material and substances flow analyses inside the plant boundaries. These analyses allowed to obtain the main substance distribution between solid, gaseous and condensate phases and to estimate the conversion efficiency of carbon and hydrogen but also to easily visualise the waste streams produced by the process. The process performance was then evaluated on the basis of parameters related to the conversion efficiency of fuels into valuable products (i.e. by considering tar and particulate as process losses) as well as those related to the energy recovery.     

一台延期报废的氧气储罐的监控使用

通过对一台储氧卧罐检验结果的分析及对历次检验情况的比较,建议对这台容器进行判废处理。但由于生产需要,该容器不能立即更新,专家们根据实际情况提出了用声发射仪监控,延长使用期一年的意见。