Fouling of nanofiltration membrane by e uent organic matter: Characterization using di erent organic fractions in wastewater

The UF membrane with molecular weight cuto (MWCO) ranging from 2 to 100 kDa and XAD-8 resin were employed to identify the characteristic of molecular weight (MW) distribution of wastewater e uent organic matter (EfOM) in terms of TOC and UV254, as well as the amounts of the hydrophilic/hydrophobic organic fractions in di erent MW ranges. Then, the nanofiltration (NF) membrane fouling experiments were carried out using the above fractionated water to investigate the e ect of MW distribution and hydrophilic/hydrophobic characteristics of EfOM on the membrane flux decline using the fractionated water samples. The experimental results have shown that 45.61% of the total organics belongs to the low MW one, among which the percentage of the hydrophilic organics with low MW (less than 2 kDa) was up to 28.07%, while that of the hydrophobic organics was 17.54%. In particular, the hydrophilic fraction was found to be the most abundant fraction in the e uents. MW distribution has a significant e ect on the membrane fouling. When the MWwas less than 30 kDa, the lower the MW, the larger was the specific flux decline, while in the case of MW higher than 30 kDa, the higher the MW, the larger was the specific flux decline, and the decline degree of low MW organics was larger than the high MW one. With the same MW distribution range, specific flux decline of the hydrophilic organic was considerably slower than that of the hydrophobic organic, which indicated that the hydrophobic organic fractions dominantly contribute to the flux decline.     

Desulfurization of dibenzothiophene（DBT） by a novel strain Lysinibacillus sphaericus DMT-7 isolated from diesel contaminated soil

A new bacterial strain DMT-7 capable of selectively desulfurizing dibenzothiophene (DBT) was isolated from diesel contaminated soil. The DMT-7 was characterized and identified as Lysinibacillus sphaericus DMT-7 (NCBI GenBank Accession No. GQ496620) using 16S rDNA gene sequence analysis. The desulfurized product of DBT, 2-hydroxybiphenyl (2HBP), was identified and confirmed by high performance liquid chromatography analysis and gas chromatography-mass spectroscopy analysis respectively. The desulfurization kinetics revealed that DMT-7 started desulfurization of DBT into 2HBP after the lag phase of 24 hr, exponentially increasing the accumulation of 2HBP up to 15 days leading to approximately 60% desulfurization of the DBT. However, further growth resulted into DBT degradation. The induced culture of DMT-7 showed shorter lag phase of 6 hr and early onset of stationary phase within 10 days for desulfurization as compared to that of non-induced culture clearly indicating the inducibility of the desulfurization pathway of DMT-7. In addition, Lysinibacillus sphaericus DMT-7 also possess the ability to utilize broad range of substrates as sole source of sulfur such as benzothiophene, 3,4-benzo DBT, 4,6-dimethyl DBT, and 4,6-dibutyl DBT. Therefore, Lysinibacillus sphaericus DMT-7 could serve as model system for efficient biodesulfurization of diesel and petrol.     

太湖原水中膜污染物质的确定与表征

采用混凝沉淀和浸没式微滤膜联用技术处理太湖原水,考察组合工艺中的有机物亲疏水性和分子量分布变化,并分析化学清洗水的有机物组分,以期确定造成膜污染的主要物质成分.结果表明,混凝预处理可有效去除大分子的亲水性有机物,这类有机物仅能导致可逆污染,而中等和小分子的有机物会导致不可逆污染.此外,三维荧光光谱表明与膜污染关系最密切的2个区域为:λex=230nm/λem=330~350nm (区域Ⅰ)和λex=280nm/λem=300~350nm (区域Ⅳ),其对应的胞外蛋白质类有机物和溶解性微生物产物(SMP)是造成微滤膜不可逆污染的主要物质.     

A comparison of two methods to observe the effects of dual metal exposure to the chironomus larvae

A study was conducted to investigate the effects of metal mixtures on the Chironomus plumosus. Two methods of preparing the mixtures were used, the Toxic Unit (TU) method and the parts per million (PPM) + PPM method. A comparison was undertaken between the two methods to observe the ease with which (1) experiment could be conducted and (2) whether LC₅₀ values could be obtained. In this study, it was noted that the PPM + PPM method was an easier method to conduct metal mixture experiments as the LC₅₀ values could be easily calculated for individual metals and compared with the LC₅₀ values of metals obtained from single metal experiments. The findings showed that the LC₅₀ value for zinc (Zn) was more toxic for chromium (Cr) when it was reduced from 9.6 to 0.3 mg L^?1, with silver the LC₅₀ value became 3.6 mg L^?1, 4.5 mg L^?1 with nickel (Ni). In the PPM + PPM method, the LC₅₀ value for Zn was observed to be 10.2 mg L^?1 when in mixture with chromium, 23.8 mg L^?1 with silver, and 13.4 mg L^?1 with Ni. Changes in the 96 h LC₅₀ value were found to be significant for all metals.     

A numerical investigation of fluid-structure coupling of 3 MW wind turbine blades

In this paper, computational modeling is created for 3 MW wind turbine blade using the software Solidworks, and the computations are carried out using Workbench for the fluid–structure interaction of blades due to both the rated and the extreme wind load. The methods developed are applied to the simulation of the NREL Phase VI wind turbine blades, and validation against published data is presented. Moreover, the static structural analysis for wind turbine rotor is performed using Mechanical APDL. The results show that the maximum values of stress reach 458 MPa and 76.9 MPa due to the rated and extreme wind load, respectively, which are lower than 78.3 MPa, the flexural strength of Swancor 2511-A epoxy resin for blade material.     

600 MW机组除尘器升级改造及效益评价

元宝山发电有限责任公司2号600 MW机组配套电除尘器由于设计效率低、燃烧煤种变化、设备老化等多方面原因,除尘效率下降,除尘器出口烟尘排放浓度超标严重。为了满足新的《火电厂大气污染物排放标准》的要求,对元宝山发电有限责任公司2号机组配套电除尘器进行升级改造,将原有的4台四电场静电除尘器增效改造为4台电袋复合式除尘器。通过电除尘器的改造,降低了除尘器出口粉尘排放浓度,提高了除尘效率,保证了2号机组电除尘器的安全稳定运行。     

基于自然生态单元的中国城乡建设用地空间格局特征分析

基于经济和社会视角的国家尺度城市空间格局研究取得重要进展,而全国城市空间格局的自然生态关联性呈现新的研究需求。由此通过自然生态单元等级划分并与城乡建设用地叠加,揭示了全国城乡建设用地在自然生态单元的空间格局特征及其主要问题:在一级生态功能区中,生态调节区面积最广,主要分布在我国西北、西南和东北等生态脆弱地区,但其内部城乡建设用地占比最小仅为0.69%,产品提供区城乡建设用地的占比为2.74%,人居保障区面积最小且集中分布在我国东部沿海地区,但其城乡建设用地占比最大,高达11.20%;城乡建设用地在自然生态单元的分布差异总体由自然地貌与大河流域特征决定,城镇群区、农产品提供区和土壤保持区占据79.54%的城乡建设用地,位于平原水网、丘陵、喀斯特和丹霞等地貌特征为主的胡焕庸线东南部;城乡建设用地分布格局也表现为东多西少,与我国三大阶梯的地势格局分布较为一致;上述格局关联性体现了人和环境之间的相互依存关系,但近些年来在开发需求膨胀和工程技术进步等人为因素驱动下,城乡建设用地呈现向较高海拔地区的扩张趋势。这为新型城镇化背景下城乡可持续发展和生态安全格局构建提供基础信息,也为辨识中国城市空间组织和演化机理提供技术支撑。     

既有线200 km/h提速客货共线直线段轨道的动力特性

既有线提速是高速铁路发展的重要方向之一。本文主要对轨道路基在列车荷载作用下的动力响应规律进行了研究。首先,建立轨道系统在移动荷载作用下的动力响应理论分析模型,该模型将轨道结构视为连续支承欧拉梁,对ANSYS软件进行二次开发,实现了模型的数值分析;然后,建立直线段轨道数值分析模型,利用该模型分析了荷载速度、载重、不平顺波长、不平顺波深对既有线路提速200 km/h客货共线直线段钢轨、轨枕的竖向位移及竖向加速度的影响。可为制定新的铁路养护技术规范提供技术参考。     

起落架落震试验环境温度模拟技术研究

目的验证某型飞机从万米高空俯冲降落直至着陆滑跑过程中,在经历了环境温度从-55℃到常温快速剧烈变化后起落架性能的改变。方法依据起落架落震试验要求,进行起落架高低温环境模拟技术研究。结果综合考虑试验技术指标、试验件结构尺寸和试验场地限制,成功研制了专用的起落架高低温环境模拟设备。结论为研究起落架缓冲器内敏感参数与温度的变化规律和起落架结构性能提供了验证手段。     

太湖及辽河流域表层沉积物中拟除虫菊酯的浓度水平及毒性评估

对辽河和太湖流域表层沉积物中8种常见的拟除虫菊酯:联苯菊酯、高效氯氟氰菊酯、氯菊酯、甲氰菊酯、氟氯氰菊酯、氯氰菊酯、氰戊菊酯、溴氰菊酯进行分析测定.结果显示,太湖流域中拟除虫菊酯含量范围为0.02～2.91ng·g-1(干重,下同),平均含量为0.63ng.g-1,处于相对较低的水平;辽河流域中的含量相对较高,其范围是0.14～19.6ng·g-1,平均含量为6.20ng·g-1.采用毒性单元TU(选用钩虾Hyallela Azteca的LC50)对拟除虫菊酯毒性风险进行估算,太湖流域∑TU值范围是0～0.40,相比之下,辽河流域的∑TU值高出很多,范围在0.10～1.73之间,其中有3个点位的∑TU值大于1,表明其具有一定的生态风险,其毒性主要来源于氯氰菊酯和氰戊菊酯.