污水生物处理中生物膜传质特性的研究进展

生物膜法处理污水,起主要作用的是附着于填料表面形成的生物膜,因此研究生物膜的传质特性对于提高处理效率、探究处理机理具有重要意义.本文综述了生物膜传质特性在污水生物处理中的研究进展,包括生物膜结构模型、传质微环境,以三相传质体系为研究重点的传质特性,以及影响生物膜传质的因素包括生物膜结构和水力条件等,并对以后应着重开展的...     

Heterogeneous uptake of NO2 on soils under variable temperature and relative humidity conditions

Heterogeneous reactions of nitrogen dioxide (NO₂) on soils collected from Dalian (S1) and Changsha (S2) were investigated over the relative humidity (RH) range of 5%-80% and temperature range of 278-328 K using a horizontal coated-wall flow tube. The initial uptake coefficients of NO₂ on S2 exhibited a decreasing trend from (10 ± 1.3) × 10^-8 to (3.1 ± 0.5) × 10^-8 with the relative humidity increasing from 5% to 80%. In the temperature effect studies, the initial uptake coefficients of S1 and S2 decreased from (10 ± 1.2) × 10^-8 to (3.8 ± 0.5) × 10^-8 and from (16 ± 2.2) × 10^-8 to (3.8 ± 0.4) × 10^-8 when temperature increased from 278 to 288 K for S1 and from 278 to 308 K for S2, respectively. As the temperature continued to increase, the initial uptake coefficients of S1 and S2 returned to (7.9 ± 1.1) × 10^-8 and (20 ± 3.1) × 10^-8 at 313 and 328 K, respectively. This study shows that relative humidity could influence the uptake kinetics of NO₂ on soil and temperature would impact the heterogeneous chemistry of NO₂.     

Chemical characteristics of haze particles in Xi'an during Chinese Spring Festival: Impact of fireworks burning

Fireworks burning releases massive fine particles and gaseous pollutants, significantly deteriorating air quality during Chinese Lunar New Year(LNY) period. To investigate the impact of the fireworks burning on the atmospheric aerosol chemistry, 1-hr time resolution of PM_(2.5) samples in Xi'an during the winter of 2016 including the LNY were collected and detected for inorganic ions, acidity and liquid water content(LWC) of the fine aerosols. PM_(2.5) during the LNY was 167 ± 87 μg/m~3, two times higher than the China National Ambient Air Quality Standard(75 μg/m~3). K~+(28 wt.% of the total ion mass) was the most abundant ion in the LNY period, followed by SO_4~(2-)(25 wt.%) and Cl-(18 wt.%). In contrast, NO_3~-(34 wt.%) was the most abundant species in the haze periods(hourly PM32-2.5 75 μg/m), followed by SO_4(29.2 wt.%) and NH_4~+(16.3 wt.%), while SO_4~(2-)(35 wt.%) was the most abundant species in the clean periods(hourly PM_(2.5) 75 μg/m~3), followed by NO_3~-(23.1 wt.%) and NH_4~+(11 wt.%). Being different from the acidic nature in the non-LNY periods, aerosol in the LNY period presented an alkaline nature with a pH value of 7.8 ± 1.3. LWC during the LNY period showed a robust linear correlation with K_2SO_4 and KCl, suggesting that aerosol hygroscopicity was dominated by inorganic salts derived from fireworks burning. Analysis of correlations between the ratios of NO--3/SO_4~(2-) and NH_4~+/SO_4~(2-) indicated that heterogeneous reaction of HNO_3 with NH_3 was an important formation pathway of particulate nitrate and ammonium during the LNY period.     

Light absorption properties and potential sources of brown carbon in Fenwei Plain during winter 2018–2019

A distinctive kind of organic carbon aerosol that could absorb ultraviolet-visible radiation is called brown carbon (BrC), which has an important positive influence on radiative budget and climate change. In this work, we reported the absorption properties and potential source of BrC based on a seven-wavelength aethalometer in the winter of 2018–2019 at an urban site of Sanmenxia in Fenwei Plain in central China. Specifically, the mean value of BrC absorption coefficient was 59.6 ± 36.0 Mm^?1 at 370 nm and contributed 37.7% to total absorption, which made a significant impact on visibility and regional environment. Absorption coefficients of BrC showed double-peak pattern, and BrC had shown small fluctuations under haze days compared with clean days. As for the sources of BrC, BrC absorption coefficients expressed strong correlations with element carbon aerosols and primary organic carbon aerosols, indicating that most of BrC originated from primary emissions. The linear correlations between trace metal elements (K, As, Fe, Mn, Zn, and Pb) and BrC absorption coefficients further referred that the major sources of BrC were primary emissions, like coal burning, biomass burning, and vehicle emissions. The moderate relationship between BrC absorption coefficients and secondary organic aerosols suggested that secondary production of BrC also played an important role. The 120 hr backward air mass trajectories analysis and concentration-weighted trajectories analysis were also used to investigate potential sources of BrC in and around this area, which inferred most parts of BrC were derived from local emissions.     

平江县生态弹性度定量分析评价研究

根据生态弹性力的概念,体会其深刻内涵及意义,根据区域实际情况,科学合理的构建平江县生态系统弹性力评价指标体系,运用综合评价的方法计算分析平江县生态系统弹性力,结果显示从2008年至2013年间,平江县生态系统弹性力呈下降趋势,主要原因是水资源总量下降,并对之后生态系统可持续发展和经济发展提出建议.     

中国十大流域近40多年降水量时空变化特征

利用中国1956～2000年月降水量资料,按流域将全国划分为10个区域,分析了各流域年、季降水量的多年平均状况和年代际变化特征以及长期变化趋势。分析结果进一步证实,中国北方流域降水量少,年际变化大,水资源缺乏且不稳定;南方流域降水较多,年际变化较小,水资源相对充足且比较稳定。分析结果还表明,近45年来,北方外流河流域年降水量一般趋于减少,特别是20世纪90年代以来降水明显减少;南方流域以降水增加为主,90年代降水均较80年代增多,特别是长江流域以南地区更为明显。季节降水减少主要出现在夏秋季,冬春季降水有微弱增加趋势。近20年来,中国绝大多数流域降水的增减趋势与近45年长序列的变化趋势基本一致。北方大部分外流河流域年降水量减少,南方流域多为增加。夏、秋季,大部流域降水较前20年减少,冬春季则相反。中国西北诸河流域是十大流域中惟一四季降水均有增加的流域。     

模块化填料人工湿地处理农村生活污水

构建美人蕉(Canna indicate L.)潜流人工湿地系统,对比研究基于模块化填料的人工湿地系统(MS-C-S)和基于普通碎石填料的人工湿地系统(GS-C-S)对农村生活污水的处理效果。结果表明,模块化填料对氨氮和总磷的去除率明显高于碎石填料。在MS-C-S和GS-C-S系统运行5 d后,MS-C-S系统对氨氮的去除率高达54.2%~69.4%,而GS-C-S系统仅为13%~28%;MS-C-S系统对总磷去除率77.7%~83.5%,而GS-C-S仅为54.5%。MS-C-S系统对氨氮和COD的去除率比 MS-U-S分别高出约23%和11%;而MS-C-S和MS-C-L系统对氨氮、总磷和COD的去除趋势和去除效果都几乎相近。模块化填料及以其为基质的人工湿地系统可以很好地去除氨氮、总磷和COD,有一定的应用前景。     

粉煤灰替代石灰进行污泥深度脱水的中试研究

采用板框压滤机在中试规模下,以粉煤灰替代工业石灰,对污泥进行调质脱水实验研究,从而考察粉煤灰替代石灰进行污泥调质脱水的可行性。结果表明：粉煤灰投加后可降低污泥pH,降低其二次污染危害,但污泥进料量却降低14.3%~15.2%,脱水能力下降;针对不同有机质含量的污泥,粉煤灰的替代性并不相同,对于低有机质含量污泥,采用粉煤灰替代工业石灰具有一定可行性,且随着粉煤灰投加量的加大,污泥热值逐步上升,而对于高有机质含量污泥,粉煤灰并不适用于其深度脱水过程。     

秸秆粉煤灰基颗粒填料生物膜特性的比较

为提高曝气生物滤池处理效率、研发新型具有结构和功能优势的颗粒填料,采用间歇式完全混合循环流态化反应器,探究了自制复合颗粒A、自制复合颗粒B、中劲陶粒及石英砂颗粒填料在4个水力停留时间下的挂膜性能、动力学参数及生物膜活性等生物膜特性,建立了生物膜微生物动力学参数实验测定的新方法。结果表明：当水力停留时间为8~12 h时,自制复合颗粒A、B挂膜性能优于石英砂和中劲陶粒,生物膜增殖速率分别为95.83 、63.75 mg·(L·h)⁻¹(以COD去除率标准评价)和54.13、29.23 mg·(L·h)⁻¹(以氨氮降解率标准评价);装填复合颗粒A的完全混合循环流态化反应器氨氮降解效率最高,相应生物膜表观产率系数最低,剩余污泥量最少;当水力停留时间超过8 h后,复合颗粒附着生长生物膜的脱氢酶活性、表面蛋白质、多糖含量最高。由此可知,以自制复合颗粒A、B为颗粒填料能优化曝气生物滤池的处理效率。本研究结果可为新型生物滤池技术的发展提供参考。     

针铁矿-腐殖酸的复合物对泰乐菌素的吸附

针铁矿与腐殖酸共存于环境中时,会通过一定的相互作用形成有机矿质复合体,这种复合体会对抗生素在环境中的吸附产生一定的影响。研究了针铁矿与腐殖酸的复合物对泰乐菌素的吸附特性。结果表明:针铁矿与腐殖酸的复合是通过化学作用进行结合的;针铁矿与腐殖酸复合之后,其对泰乐菌素的吸附能力明显增强;针铁矿及其与腐殖酸的复合物对泰乐菌素的吸附动力学可以用二级动力学模型和扩散模型较好的拟合,吸附具有明显的非线性,吸附等温线可以用Freundlich模型较好地拟合;针铁矿及其与腐殖酸的复合物对泰乐菌素的吸附受溶液pH值和离子强度的影响,且吸附机制主要以疏水性分配作用、氢键作用、离子交换和表面络合机制为主。