旋流分离器油水分离效率的模拟研究

采用计算流体力学的方法,探讨了操作条件和物料特性对旋流分离器分离油水效率的影响。旋流器为单锥双入口,其主直径为50 mm,锥角为5.5°。模拟过程中,采用商业用软件‘Fluent 6.3’中的雷诺应力模型和欧拉多相流模型来模拟不同条件下油水旋流分离器的分离性能。模拟结果表明,对于本研究的油水旋流分离器,最佳的分流比是10%,最佳的油滴浓度是0.5%(V/V)。在最佳的分流比和油滴浓度下,当进口流速为10.46 m/s时,油水旋流分离器可将15μm的油滴去除80%以上,油滴的分离界限粒径d50(50%的分离效率)为9.2μm。在模拟的基础上,用统计软件STATISTICA6.0对分离效率与操作条件和物料特性之间的关系进行拟合。通过拟合式预测的分离效率与实测值相吻合,误差小于15%。     

杭州市环保系统人才发展现状与对策

对杭州市环保系统的人才总量、学历结构、专业结构、职称结构和年龄结构等方面作了较详细的分析；针对杭州市环保系统存在的人才总量不足、结构分布不合理和高层次人才匮乏等问题，提出了引进高层次人才、加强教育培训、壮大基层队伍等对策。     

循环流化床锅炉燃煤技术热电厂生命周期评价

运用生命周期评价方法,应用Gabi5.0软件对采用循环流化床锅炉燃煤技术的热电企业进行资源耗竭和环境影响分析,计算各生产单元生命周期清单的全球变暖潜值、酸化效应潜值、富营养化潜值、非生物资源耗竭潜值、人体毒性潜值以及光化学烟雾和臭氧生成潜值等主要环境影响类型,对燃煤发电过程进行生命周期评价。结果表明,全球变暖和非生物资源耗竭为发电运行过程中主要的环境影响因素,分别占53%和15.05%;锅炉燃烧阶段的环境影响最重,占整个生命周期影响值的77.12%,并且除生物耗竭潜值外的其他5项指标均为发电运行阶段各个单元中最高。采用SNCR脱硝技术减少燃烧过程中NOx的排放量,并对该技术方案进行生命周期评价,比较方案实施前后的环境影响。     

基于两级拓扑优化的振动台扩展台面设计与试验验证

根据拓扑优化基本原理,利用OptiStruct进行振动台扩展台面的结构最优化设计,通过两级拓扑优化完成结构的拓扑寻优。首先利用整体级拓扑优化,找到结构的整体最佳构造。然后利用局部级拓扑优化,对局部结构进行拓扑寻优,最终完成产品的结构设计。试验结果与仿真结果对比表明,误差在5%以内,表明方法的有效性和实用性。     

Infrastructure development through PPPs in India: criteria for sustainability assessment

Public private partnerships (PPPs) allow the Indian Government to leverage private capital for meeting the widening demand-supply gap in the provision of infrastructure services. The private sector, however, prefers to limit the participation to financially attractive projects only, thereby resulting in patterns of infrastructure creation impeding the progress towards sustainable development. In order to promote sustainable development, the PPP procurement process should focus on incentivising the private sector for sustainable infrastructure development rather than concentrating on ensuring financial sustainability only. This paper discusses the principles-based PPP-specific framework that has been developed to facilitate assessment of PPP projects' progress towards sustainable development. The framework development was based on a holistic approach to sustainability assessment and subsequently validated through questionnaire survey with key stakeholders in the Indian PPP programme. This framework will provide the decision makers with appropriate decision aid for integration of sustainable development principles in the PPP procurement process.     

Recent Changes in Stream Flashiness and Flooding,and Effects of Flood Management in North Carolina and Virginia

The southeastern United States has undergone anthropogenic changes in landscape structure, with the potential to increase (e.g., urbanization) and decrease (e.g., reservoir construction) stream flashiness and flooding. Assessment of the outcome of such change can provide insight into the efficacy of current strategies and policies to manage water resources. We (1) examined trends in precipitation, floods, and stream flashiness and (2) assessed the relative influence of land cover and flow‐regulating features (e.g., best management practices and artificial water bodies) on stream flashiness from 1991 to 2013. We found mean annual precipitation decreased, which coincided with decreasing trends in floods. In contrast, stream flashiness, overall, showed an increasing trend during the period of study. However, upon closer examination, 20 watersheds showed stable stream flashiness, whereas 5 increased and 6 decreased in flashiness. Urban watersheds were among those that increased or decreased in flashiness. Watersheds that increased in stream flashiness gained more urban cover, lost more forested cover and had fewer best management practices installed than urban watersheds that decreased in stream flashiness. We found best management practices are more effective than artificial water bodies in regulating flashy floods. Flashiness index is a valuable and straightforward metric to characterize changes in streamflow and help to assess the efficacy of management interventions.     

城市道路沉积物氮、磷溶出特性

国内外众多研究表明,城市不透水表面沉积物是雨水径流中污染物的重要来源。以北京市某道路沉积物为研究对象,对城市道路沉积物的粒径分布进行了分析,并通过批量实验,研究了不同粒径道路沉积物中氮、磷营养物及有机物(COD)的溶出特性。实验结果表明,粒径较大的沉积物中氮含量较高,而粒径较小的沉积物中磷含量较高;虽然TP、PO3-4、TN、NO-3、NH+4、COD的溶出浓度、溶出速率变化特征各不相同,但总体趋势是粒径越小氮、磷及COD溶出浓度和溶出速率越大,且最大溶出速率都出现在前5 min。因此,为实现对城市雨水径流污染的有效控制,应采用源头控制措施对小粒径道路沉积物和初期雨水进行有效控制。     

集中式饮用水源地邻苯二甲酸酯类物质分布特征与健康风险评估

以某地区7个集中式饮用水源地为研究对象,采用固相萃取气相色谱-质谱法(SPE-GC-MS)对水体中16种邻苯二甲酸酯的分布特征和溯源进行了研究,并利用健康风险评估模型对水体PAEs进行了健康风险评价。结果表明:邻苯二甲酸二正丁酯、邻苯二甲酸二(2-乙基己基)酯、邻苯二甲酸二异丁酯和邻苯二甲酸二正辛酯在所有PAEs同系物中含量丰富,而所有样品均无邻苯二甲酸二(2-甲氧基)乙酯和邻苯二甲酸二戊酯的检出;二水厂和亨达水务断面Σ_(16)PAEs浓度最高,四水厂和五水厂断面Σ_(16)PAEs浓度最低;水体12种PAEs共提出3个主成分,揭示了91%的影响因子;层次聚类分析表明:7个采样断面聚为2类,分别代表了内河和长江水体。水体中PAEs的致癌风险值和非致癌风险值均远低于参考值,说明研究水体PAEs不会对居民构成致癌风险或其他明显的健康风险,但需加强该地区PAEs使用的规范与监管,强化末端处理,以规避风险。     

3种短链脂肪酸对活性污泥储存PHA的影响

采用经乙酸钠驯化培养具有一定聚羟基烷酸酯(PHA)储存能力的活性污泥,考察乙酸、丙酸和丁酸3种短链脂肪酸,以及乙酸、丁酸分别与丙酸按1∶1、1∶2、2∶1比例组合成的6种混合酸作为碳源时对活性污泥中PHA的储存和转化的影响。实验结果表明,在3种短链脂肪酸中,以丁酸为碳源得到活性污泥PHA储存量最高,为40.53 mg/g;在混合酸中,乙酸与丙酸按1∶2组合时,系统PHA储存量最高,为773.4 mg/g。混合酸相对于单一的脂肪酸碳源更有利于活性污泥储存PHA。在混合酸总量一定的条件下,随着丙酸比例的增加,乙酸与丙酸混合比丁酸与丙酸混合更有利于微生物的PHA储存。     

Gold Mining: Is It Worth Its Weight?

Gold (Au) accounts for only 0.004 g/ton of the earth's crust and is the most desired element. With an average annual world production of approximately 2,500 tons, the current methods of Au mining in developing countries cause major environmental issues. These issues vary from deforestation to cyanide and mercury (Hg) contamination. This article presents several cases of environmental catastrophes caused by Au mining in different regions of the world (Africa, the Middle East, Eastern Europe, and South America). It discusses the currently available processes for the large-scale extraction of metallic Au grains and supports the need for an alternative sustainable process.