Abstract ：

The organic compound composition of wastewater, serves as a crucial indicator for the operational performance of activated sludge processes and has a major influence on the development of filamentous bulking in activated sludge. This study focused on the impact of typical soluble and slowly-biodegradable organic compounds, investigating the pathways through which these substrates affect the occurrence of filamentous bulking in systems operated under both high- and low-oxygen conditions. Results showed that slowly-biodegradable organic compounds lead to a concentrated distribution of microorganisms within flocs, with inward growth of filamentous bacteria. Both Tween-80 and granular starch treated systems exhibited a significant increase in protein content. The glucose system, utilizing soluble substrates, exhibited a markedly higher total polysaccharide content. Microbial communities in the Tween-80 and granular starch treated systems were characterized by a higher abundance of bacteria known to enhance sludge flocculation and settling, such as Competibacter, Xanthomonadaceae and Zoogloea. These findings are of high significance for controlling the operational performance and stability of activated sludge systems, deepening our understanding and providing a novel perspective for the improvement of wastewater treatment processes. © 2024

Keyword ：

EPS Microbial community Slowly biodegradable organic compounds Sludge bulking Sludge morphology

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Abstract ：

As an energy and carbon saving process for nitrogen removal from wastewater, the partial nitrification and denitrification process (PN/D) has been extensively researched. However, achieving stable PN in municipal wastewater has always been challenging. In this study, a gel immobilized PN/D nitrogen removal process (GI-PN/D) was established. A 94d pilot-scale experiment was conducted using real municipal wastewater with an ammonia concentration of 43.5 ± 5.3 mg N/L at a temperature range of 11.3–28.7℃. The nitrogen removal performance and associated pathways, shifts in the microbial community as well as sludge yield were investigated. The results were as follows: the effluent TN and COD were 0.6 ± 0.4 mg/L and 31.1 ± 3.8 mg/L respectively, and the NAR exceeding 95 %. GI-PN/D achieved deep nitrogen removal of municipal wastewater through stable PN without taking any other measures. The primary pathways for nitrogen removal were identified as denitrification, simultaneous nitrification-denitrification, and aerobic denitrification. High-throughput sequencing analysis revealed that the immobilized fillers facilitated the autonomous enrichment of functional bacteria in each reactor, effectively promoting the dominance and stability of the microbial communities. In addition, GI-PN/D had the characteristic of low sludge yield, with an average sludge yield of 0.029 kg SS/kg COD. This study provides an effective technical for nitrogen removal from municipal wastewater through PN. © 2024

Keyword ：

Gel immobilization Sludge yield Autonomous enrichment Deep nitrogen removal Partial nitrification

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Abstract ：

Friction rolling additive manufacturing (FRAM) is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head. The thermal efficiency of FRAM, which depends only on friction to generate heat, is low, and the thermal-accumulation effect of the deposition process must be addressed. An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling (PC-FRAM) is devised in this study, and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head. Additionally, 2195-T87 Al-Li alloy is used as the feed material, and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated. The results show that water cooling significantly improves heat accumulation during the deposition process. The cooling rate increases by 11.7 times, and the high-temperature residence time decreases by more than 50 %. The grain size of the PC-FRAM sample is the smallest, i.e., 3.77±1.03 μm, its dislocation density is the highest, and the number density of precipitates is the highest, the size of precipitates is the smallest, which shows the best precipitation-strengthening effect. The hardness test results are consistent with the precipitation distribution. The ultimate tensile strength, yield strength and elongation of the PC-FRAM samples are the highest (351±15.6 MPa, 251.3 ± 15.8 MPa and 16.25 %±1.25 %, respectively) among the samples investigated. The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples. The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect. © 2024

Keyword ：

Friction rolling additive manufacturing Plasma preheating Heat accumulation Al-Li alloy Microstructure Instant cooling

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Abstract ：

The expandable graphite (EG) modified TiO2 nanocomposites were prepared by the high shear method using the TiO2 nanoparticles (NPs) and EG as precursors, in which the amount of EG doped in TiO2 was 10 wt.%. Followed by the impregnation method, adjusting the pH of the solution to 10, and using the electrostatic adsorption to achieve spatial confinement, the Pt elements were mainly distributed on the exposed TiO2, thus generating the Pt/10EG-TiO2–10 catalyst. The best CO oxidation activity with the excellent resistance to H2O and SO2 was obtained over the Pt/10EG-TiO2–10 catalyst: CO conversion after 36 hr of the reaction was ca. 85% under the harsh condition of 10 vol.% H2O and 100 ppm SO2 at a high gaseous hourly space velocity (GHSV) of 400,000 hr−1. Physicochemical properties of the catalysts were characterized by various techniques. The results showed that the electrostatic adsorption, which riveted the Pt elements mainly on the exposed TiO2 of the support surface, reduced the dispersion of Pt NPs on EG and achieved the effective dispersion of Pt NPs, hence significantly improving CO oxidation activity over the Pt/10EG-TiO2–10 catalyst. The 10 wt.% EG doped in TiO2 caused the TiO2 support to form a more hydrophobic surface, which reduced the adsorption of H2O and SO2 on the catalyst, greatly inhibited deposition of the TiOSO4 and formation of the PtSO4 species as well as suppressed the oxidation of SO2, thus resulting in an improvement in the resistance to H2O and SO2 of the Pt/10EG-TiO2–10 catalyst. © 2023

Keyword ：

Titania supported platinum Electrostatic adsorption CO oxidation Resistance to H2O and SO2 Expandable graphite

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Abstract ：

The manganese-cobalt mixed oxide nanorods were fabricated using a hydrothermal method with different metal precursors (KMnO4 and MnSO4·H2O for MnOx and Co(NO3)2⋅6H2O and CoCl2⋅6H2O for Co3O4). Bamboo-like MnO2⋅Co3O4 (B-MnO2⋅Co3O4 (S)) was derived from repeated hydrothermal treatments with Co3O4@MnO2 and MnSO4⋅H2O, whereas Co3O4@MnO2 nanorods were derived from hydrothermal treatment with Co3O4 nanorods and KMnO4. The study shows that manganese oxide was tetragonal, while the cobalt oxide was found to be cubic in the crystalline arrangement. Mn surface ions were present in multiple oxidation states (e.g., Mn4+ and Mn3+) and surface oxygen deficiencies. The content of adsorbed oxygen species and reducibility at low temperature declined in the sequence of B-MnO2⋅Co3O4 (S) > Co3O4@MnO2 > MnO2 > Co3O4, matching the changing trend in activity. Among all the samples, B-MnO2⋅Co3O4 (S) showed the preeminent catalytic performance for the oxidation of toluene (T10% = 187°C, T50% = 276°C, and T90% = 339°C). In addition, the B-MnO2⋅Co3O4 (S) sample also exhibited good H2O-, CO2-, and SO2-resistant performance. The good catalytic performance of B-MnO2⋅Co3O4 (S) is due to the high concentration of adsorbed oxygen species and good reducibility at low temperature. Toluene oxidation over B-MnO2⋅Co3O4 (S) proceeds through the adsorption of O2 and toluene to form O*, OH*, and H2C(C6H5)* species, which then react to produce benzyl alcohol, benzoic acid, and benzaldehyde, ultimately converting to CO2 and H2O. The findings suggest that B-MnO2⋅Co3O4 (S) has promising potential for use as an effective catalyst in practical applications. © 2023

Keyword ：

Bamboo-like morphology Hydrothermal method Manganese-cobalt mixed oxide Nanorod Toluene oxidation

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Abstract ：

Previous air pollution control strategies didn't pay enough attention to regional collaboration and the spatial response sensitivities, resulting in limited control effects in China. This study proposed an effective PM2.5 and O3 control strategy scheme with the integration of Self-Organizing Map (SOM), Genetic Algorithm (GA) and WRF-CAMx, emphasizing regional collaborative control and the strengthening of control in sensitive areas. This scheme embodies the idea of hierarchical management and spatial-temporally differentiated management, with SOM identifying the collaborative subregions, GA providing the optimized subregion-level priority of precursor emission reductions, and WRF-CAMx providing response sensitivities for grid-level priority of precursor emission reductions. With Beijing-Tianjin-Hebei and the surrounding area (BTHSA, “2 + 26” cities) as the case study area, the optimized strategy required that regions along Taihang Mountains strengthen the emission reductions of all precursors in PM2.5-dominant seasons, and strengthen VOCs reductions but moderate NOx reductions in O3-dominant season. The spatiotemporally differentiated control strategy, without additional emission reduction burdens than the 14th Five-Year Plan proposed, reduced the average annual PM2.5 and MDA8 O3 concentrations in 28 cities by 3.2%–8.2% and 3.9%–9.7% respectively in comparison with non-differential control strategies, with the most prominent optimization effects occurring in the heavily polluted seasons (6.9%–18.0% for PM2.5 and 3.3%–14.2% for MDA8 O3, respectively). This study proposed an effective scheme for the collaborative control of PM2.5 and O3 in BTHSA, and shows important methodological implications for other regions suffering from similar air quality problems. © 2023

Keyword ：

SOM WRF-CAMx PM2.5 and O3 control GA Machine learning Bionic algorithm

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Abstract ：

A study was conducted on aerosol-radiation interactions over six cities in this region within the 2015–2019 period. WRF-Chem simulations on 2017 showed that based on the six-city average, the aerosol load (PM2.5 concentrations) of 121.9, 49.6, 43.3, and 66.3 µg/m3 in January, April, July, and October, mainly lowered the level of downward shortwave radiation by 38.9, 24.0, 59.1, and 24.4 W/m2 and reduced the boundary layer height by 79.9, 40.8, 87.4, and 31.0 m, via scattering and absorbing solar radiation. The sensitivity of meteorological changes to identical aerosol loads varied in the order July > January > October and April. Then, the cooling and stabilizing effects of aerosols further led to increases in PM2.5, by 23.0, 3.4, 4.6, and 7.3 µg/m3 respectively in the four months. The sensitivity of the effect of aerosols on PM2.5 was greatest in January rather than in July, contrary to the effect on meteorology. Moreover, a negative linear relation was observed between daily BLH reductions and aerosol loads in fall and winter, and between PM2.5 increases and aerosol loads in all seasons. With the PM2.5 pollution improvements in this region, the aerosol radiative forcing was effectively reduced. This should result in daily BLH increases of 10–24 m in fall and winter, and the estimates in Beijing agreed well with the corresponding results based on AMDAR data. Additionally, the reduction in aerosol radiation effects brought about daily PM2.5 decreases of 1.6-2.8 µg/m3, accounting for 7.0%–17.7% in PM2.5 improvements. © 2022

Keyword ：

Boundary layer height (BLH) PM2.5 Radiative forcing Aerosol North China

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Abstract ：

An evidence-based control strategy for emission reduction of VOC sources can effectively solve the regional PM2.5 and O3 compound pollution in China. We estimated the anthropogenic VOC emission inventory in China in 2018 and established a source profile database containing 129 sources based on localized detection and the latest research results. Then, the distribution of the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) for emission sources was analyzed. Moreover, priority control routes for VOC emission sources were proposed for different periods. Anthropogenic VOC emissions in China reached 27,211.8 Gg in 2018, and small passenger cars, industrial protective coatings, biomass burning, heavy trucks, printing, asphalt paving, oil storage and transportation, coking, and oil refining were the main contributors. Industrial protective coatings, small passenger cars, and biomass burning all contributed significantly to OFP and SOAFP. Priority in emission reduction control should be given to industrial protective coatings, small passenger cars, heavy trucks, coking, printing, asphalt paving, chemical fibers, and basic organic chemical sources over the medium and long term in China. In addition, the priority control route for VOC emission sources should be adjusted according to the variations in VOC emission characteristics and regional differences, so as to obtain the maximum environmental benefits. © 2022

Keyword ：

Reactivity Volatile organic compounds Anthropogenic emission inventory Emission projection Priority control route

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This study employed multispectral techniques to evaluate fulvic acid (FA) compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation (PN) process. Results showed that FA removal efficiency (FRE) decreased from 90.22 to 23.11% when FA concentrations in the reactor were increased from 0 to 162.30 mg/L, and that molecular size, degree of aromatization and humification of the effluent FA macromolecules all increased after treatment. Microbial population analysis indicated that the proliferation of the Comamonas, OLB12 and Thauera exhibit high FA utilization capacity in lower concentrations (<50.59 mg/L), promoting the degradation and removal of macromolecular FA. In addition, the sustained increase in external FA may decrease the abundance of above functional microorganisms, resulting in a rapid drop in FRE. Furthermore, from the genetic perspective, the elevated FA levels restricted carbohydrate (ko00620, ko00010 and ko00020) and nitrogen (HAO, AMO, NIR and NOR) metabolism-related pathways, thereby impeding FA removal and total nitrogen loss associated with N2O emissions. © 2022

Keyword ：

Partial nitritation UV/Vis 3DEEM-PARAFAC Fulvic acid Microbially driven mechanism

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Abstract ：

The PdPtVOx/CeO2−ZrO2 (PdPtVOx/CZO) catalysts were obtained by using different approaches, and their physical and chemical properties were determined by various techniques. Catalytic activities of these materials in the presence of H2O or SO2 were evaluated for the oxidation of ethylbenzene (EB). The PdPtVOx/CZO sample exhibited high catalytic activity, good hydrothermal stability, and reversible sulfur dioxide-poisoning performance, over which the specific reaction rate at 160°C, turnover frequency at 160°C (TOFPd or Pt), and apparent activation energy were 72.6 mmol/(gPt⋅sec) or 124.2 mmol/(gPd⋅sec), 14.2 sec−1 (TOFPt) or 13.1 sec−1 (TOFPd), and 58 kJ/mol, respectively. The large EB adsorption capacity, good reducibility, and strong acidity contributed to the good catalytic performance of PdPtVOx/CZO. Catalytic activity of PdPtVOx/CZO decreased when 50 ppm SO2 or (1.0 vol.% H2O + 50 ppm SO2) was added to the feedstock, but was gradually restored to its initial level after the SO2 was cut off. The good reversible sulfur dioxide-resistant performance of PdPtVOx/CZO was associated with the facts: (i) the introduction of SO2 leads to an increase in surface acidity; (ii) V can adsorb and activate SO2, thus accelerating formation of the SOx2− (x = 3 or 4) species at the V and CZO sites, weakening the adsorption of sulfur species at the PdPt active sites, and hence protecting the PdPt active sites to be not poisoned by SO2. EB oxidation over PdPtVOx/CZO might take place via the route of EB → styrene → phenyl methyl ketone → benzaldehyde → benzoic acid → maleic anhydride → CO2 and H2O. © 2023

Keyword ：

Sulfur dioxide resistance Volatile organic compound Supported palladium−platinum−vanadium catalyst Ceria−zirconia Ethylbenzene oxidation

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