Potassium ferrate pretreatment promotes short chain fatty acids yield and antibiotics reduction in acidogenic fermentation of sewage sludge

During the acidogenic fermentation converting waste activated sludge (WAS) into short-chain fatty acids (SCFA), hydrolysis of complex organic polymers is a limiting step and the transformation of harmful substances (such as antibiotics) during acidogenic fermentation is unknown. In this study, potassium ferrate (K₂FeO₄) oxidation was used as a pretreatment strategy for WAS acidogenic fermentation to increase the hydrolysis of sludge and destruct the harmful antibiotics. Pretreatment with K₂FeO₄ can effectively increase the SCFA production during acidogenic fermentation and change the distribution of SCFA components. With the dosage of 0.2 g/g TS, the maximum SCFA yield was 4823 mg COD/L, which is 28.3 times that of the control group; acetic acid accounts for more than 90% of the total SCFA. The higher dosage (0.5 g/g TS) can further increase the proportion of acetic acid, but inhibit the overall performance of SCFA production. Apart from the promotion of hydrolysis and acidogenesis, K₂FeO₄ pretreatment can also simultaneously oxidizes and degrades part of the antibiotics in the sludge. When the dosage is 0.5 g/g TS, the degradation efficacy of antibiotics is the most significant, and the contents of ofloxacin, azithromycin, and tetracycline in the sludge are reduced by 69%, 42%, and 50%, respectively. In addition, K₂FeO₄ pretreatment can also promote the release of antibiotics from sludge flocs, which is conducive to the simultaneous degradation of antibiotics in the subsequent biological treatment process.     

Chemical characterization and source identification of PM2.5 in Luoyang after the clean air actions

Luoyang is a typical heavy industrial city in China, with a coal-dominated energy structure and serious air pollution. Following the implementation of the clean air actions, the physicochemical characteristics and sources of PM_2.5 have changed. A comprehensive study of PM_2.5 was conducted from October 16, 2019 to January 23, 2020 to evaluate the effectiveness of previous control measures and further to provide theory basis for more effective policies in the future. Results showed that the aerosol pollution in Luoyang in autumn and winter is still serious with the average concentration of 91.1 μg/m³, although a large reduction (46.9%) since 2014. With the contribution of nitrate increased from 12.5% to 25.1% and sulfate decreased from 16.7% to 11.2%, aerosol pollution has changed from sulfate-dominate to nitrate-dominate. High NO₃⁻/SO₄²⁻ ratio and the increasing of NO₃⁻/SO₄²⁻ ratio with the aggravation of pollution indicating vehicle exhaust playing an increasingly important role in PM_2.5 pollution in Luoyang, especially in the haze processes. Secondary inorganic ions contributed significantly to the enhancement of PM_2.5 during the pollution period. The high value of Cl⁻/Na⁺ and EC concentration indicate coal combustion in Luoyang is still serious. The top three contributor sources were secondary inorganic aerosols (33.3%), coal combustion (13.6%), and industrial emissions (13.4%). Close-range transport from the western and northeastern directions were more important factors in air pollution in Luoyang during the sampling period. It is necessary to strengthen the control of coal combustion and reduce vehicle emissions in future policies.     

Wall losses of oxygenated volatile organic compounds from oxidation of toluene: Effects of chamber volume and relative humidity

Vapor wall losses can affect the yields of secondary organic aerosol. The effects of surface-to-volume (S/V) ratio and relative humidity (RH) on the vapor-wall interactions were investigated in this study. The oxygenated volatile organic compounds (OVOCs) were generated from toluene-H₂O₂ irradiations. The average gas to wall loss rate constant (k_gw) of OVOCs in a 400 L reactor (S/V = 7.5 m⁻¹) is 2.47 (2.41 under humid conditions) times higher than that in a 5000 L reactor (S/V = 3.6 m⁻¹) under dry conditions. In contrast, the average desorption rate constant (k_wg) of OVOCs in 400 L reactor is only 1.37 (1.20 under humid conditions) times higher than that in 5000 L reactor under dry conditions. It shows that increasing the S/V ratio can promote the wall losses of OVOCs. By contrast, the RH effect on k_gw is not prominent. The average k_gw value under humid conditions is almost the same as under dry conditions in the 400 L (5000 L) reactor. However, increasing RH can decrease the desorption rates. The average k_wg value under dry conditions is 1.45 (1.27) times higher than that under humid conditions in the 400 L (5000 L) reactor. The high RH can increase the partitioning equilibrium timescales and enhance the wall losses of OVOCs.     

环境约束下长江经济带全要素能源效率的时空分异研究——基于超效率DEA模型和ML指数法

基于超效率DEA模型和ML指数法,考察长江经济带1999~2013年全要素能源效率。实证研究结果显示:研究期内,环境约束下的长江经济带全要素能源效率年均下降2.9%,而不考虑环境因素的全要素能源效率年均下降幅度仅为0.4%,污染是导致能源效率损失的重要因素;长江经济带整体层面全要素能源效率的发展演变基本呈"双峰一谷"的"M"形分布,表现为两个"上升—下降"周期,而省际和上中下游全要素能源效率的演变特征迥异;从空间差异看,省际全要素能源效率差异远远大于上中下游差异,但近年来这种差异均有不同程度的缩小。未来长江经济带发展必须践行生态文明发展战略,保证发展的可持续性,同时加强能源、环保等领域的合作,促进长江经济带全要素能源效率发展的协同进步。     

西部横断山区强降温气候条件下桥塔温度效应及抗裂性能优化研究∗

在强降温极端气候条件下,桥塔混凝土表面存在开裂风险。为此,以我国西部横断山脉地区某大跨悬索桥为工程背景,开展了强降温气候条件下桥塔温度效应及抗裂性能优化研究。首先,提出了桥址区极端天气的识别与模拟方法,并验证了所提模拟方法的有效性。随后,建立桥塔节段的 3D 有限元模型,分析了强降温极端天气下混凝土桥塔的温度场以及温度应力分布特征。最后,针对强降温极端天气下混凝土桥塔外表面存在开裂风险的问题,提出了两种桥塔混凝土表面抗裂优化方法,并通过参数分析给出了本例桥塔的最优参数。研究结果表明：在强降温天气下,当不考虑任何抗裂优化措施前,桥塔表面拉应力极值为 2.06 MPa,存在较大开裂风险;当采用抗裂优化措施后,提出的两种措施均能有效降低混凝土桥塔表面的拉应力极值。通过参数分析发现,采用有机涂料涂装桥塔表面的优化方法时,白色有机涂料的优化效果最佳;当采用桥塔表面覆盖 UHPC 的优化方法时,其厚度为 0.04 m 时优化效果最佳。     

对新形势下发展环保产业措施的探讨

论述了我国环保产业发展的现状和发展前景,并对发展环保产业的主要措施进行了探讨。     

Low-reactive circulating fluidized bed combustion (CFBC) fly ashes as source material for geopolymer synthesis

In this contribution, low-reactive circulating fluidized bed combustion (CFBC) fly ashes (CFAs) have firstly been utilized as a source material for geopolymer synthesis. An alkali fusion process was employed to promote the dissolution of Si and Al species from the CFAs, and thus to enhance the reactivity of the ashes. A high-reactive metakaolin (MK) was also used to consume the excess alkali needed for the fusion. Reactivities of the CFAs and MK were examined by a series of dissolution tests in sodium hydroxide solutions. Geopolymer samples were prepared by alkali activation of the source materials using a sodium silicate solution as the activator. The synthesized products were characterized by mechanical testing, scanning electron microscopy (SEM), X-ray diffractography (XRD), as well as Fourier transform infrared spectroscopy (FTIR). The results of this study indicate that, via enhancing the reactivity by alkali fusion and balancing the Na/Al ratio by additional aluminosilicate source, low-reactive CFAs could also be recycled as an alternative source material for geopolymer production.