Efficiency and effectiveness of systems for the treatment of domestic wastewater based on subsurface flow constructed wetlands in Jarabacoa, Dominican Republic

Constructed wetlands(CwW)are well known nature-based systems for water treatment.This study evaluated the efficiency and effectiveness of seven domestic wastewater treatment systems based on horizontal flow CWs in Jarabacoa,the Dominican Republic.The results showed that the CWs were efficient in reducing the degree of contamination of wastewater to levels below the Dominican wastewater discharge standards for parameters such as the 5-day biochemical oxygen demand(BOD5)and chemical oxygen demand,but not for the removal of phosphorus and fecal coliforms.In addition,a horizontal flow subsurface wetland in the peri-urban area El Dorado was evaluated in terms of the performance of wastewater treatment in tropical climatic conditions.The concentrations of heavy metals,such as zinc,copper,chromium,and iron,were found to decrease in the effluent of the wetland,and the concentrations for nickel and manganese tended to increase.The levels of heavy metals in the effluent were lower than the limit values of the Dominican wastewater discharge standards.The construction cost of these facilities was around 200 USD per population equivalent,similar to the cost in other countries in the same region.This study suggested some solutions to the improved performance of CWs:selection of a microbial flora that guarantees the reduction of nitrates and nitrites to molecular nitrogen,use of endemic plants that bioaccumulate heavy metals,combination of constructed wetlands with filtration on activated carbon,and inclusion of water purification processes that allow to evaluate the reuse of treated water.

Adsorption characteristics of construction waste for heavy metals from urban stormwater runoff

Stormwater runoff has become an important source of surface water pollution. Bioretention, a low impact development measure in urban stormwater management, has been proven to be effective in the removal of pollutants from stormwater runoff, with appropriate bioretention media. In this study, construction wastes were selected as bioretention media to remove heavy metals from stormwater runoff. Static and dynamic adsorption batch experiments were carried out to investigate the adsorption of heavy metals in simulated stormwater runoff system with construction wastes in different particle sizes. The experimental results show that the pseudo-secondorder kinetic model characterizes the adsorption process and the adsorption equilibrium data are well described by Freundlich isotherm model. The construction wastes used can remove heavy metals from stormwater runoff effectively, with their average removal rates all more than 90%. The particle size of construction wastes greatly influences the equilibrium time, rate and adsorption capacity for heavy metals.

Adsorption characteristics of Pb from urban stormwater runoff by construction wastes

Construction wastes were selected as the adsorbents and static and dynamic adsorption batch experiments were carried out to investigate the adsorption of Pb to construction wastes with different particle size gradations in the simulated stormwater runoff system.The experimental results show that the pseudo-second-order kinetics model can better characterize the adsorption process of Pb than the pseudo-first-order kinetics model.The adsorption equilibrium data can be well fitted by the Freundlich isotherm model. The construction wastes with different tested size gradations can greatly remove Pb from stormwater runoff and their average removal rate can reach up to 99%.The construction wastes with narrow size distribution can better remove Pb but with worse permeability than those with wide size distribution. The particle size gradation of construction wastes greatly influences the equilibrium time rate and the capacity of Pb adsorption.The equilibrium adsorption rate and capacity are 18.1 μg/min and 5.5 μg/g respectively for the construction wastes with the size of 2.36 to 4.75 mm which are the greatest among the different size gradations.The present study provides a scientific basis for effectively controlling Pb pollution from stormwater runoff and the construction wastes resource utilization.

Heavy Metals Removal from Swine Wastewater Using Constructed Wetlands with Horizontal Sub-Surface Flow

The removal efficiency of Cu and Zn from swine wastewater was evaluated as effected by three variables: the hydraulic retention time (HRT) (24, 48, 72 and 96 hours), two different plant species (Typha domingensis Pers. and Eleocharis cellulosa) and two different sizes of filter media (5 and 15 mm) using a horizontal sub-surface flow constructed wetland. From the results, a significant difference was observed in the removal efficiency of Cu and Zn with respect to different hydraulic retention times. The best results were obtained in the HRT of 96 hours for Zn where 96% removal of Zn with Typha domingensis Pers. specie with gravel of 15 mm (experimental unit 6) was achieved. For Cu, at 72 hours of HRT, the efficiency was nearly 100% in five of the six study units (1, 2, 3, 5 and 6). In contrast, in experimental unit 4 with gravel of 15 mm and without plants, only 86% Cu removal was achieved.

A Review on Constructed Wetlands Components and Heavy Metal Removal from Wastewater

Constructed wetlands are man-made complex of substrates, emergent/submergent vegetation, and water. Constructed wetlands have been known as an efficient and low-cost treatment process. Constructed wetland is a natural treatment system that physical, chemical, and biological processes occur when water, soil, plants, and microorganisms interact. They are considered as natural treatment ecosystems that are designed to take advantages of the natural processes to provide wastewater treatment. Constructed wetlands treat different types of wastewaters such as municipal, industrial, agricultural, and storm water. The removal of heavy metals within wetlands is performed generally by plant uptake and by adsorption onto sediments. Heavy metal treatment examples and some specifications and regulations are finally discussed.

Study on the Heavy Metals Removal Efficiencies of Constructed Wetlands with Different Substrates

In this study constructed wetlands (CWs) were used to remove three heavy metals (Zn, Cu and Pb). The two tested substrates were made of coke and gravel, respectively. First order dynamic model was appropriate to describe removing of Zn and Cu. The experimental results showed that first dynamic removal rate constants of Zn in CWs with coke and gravel were 0.2326 h-1 and 0.1222 h-1, respectively. And those of Cu in CWs with coke and gravel were 0.2017 h-1 and 0.3739 h-1. However, removal efficiencies of Pb in the coke system and the gravel system were within 95-99%, so the first order dynamic model failed to fit the experimental data because the hydraulic resident times of Pb did not affect outlet concentration of Pb. From the removal rate constants, it is found that the coke and gravel system have different absorption efficiencies of heavy metal pollutants. Therefore, it is suggested that the removal efficiencies of heavy metals are influenced by the choice of substrates to some extent.

Project Construction and Important Technical Innovation for Qinshan Phase Ⅲ (PHWR) Nuclear Power Plant

Qinshan Phase Ⅲ(PHWR)Nuclear Power Plant,the first commercial heavy water reactor nuclear power plant in China,was the biggest trade project performed between the governments of China and Canada.As the owner,the Third Qinshan Nuclear Power Company(TQNPC)persisted in independent innovation management during the project construction,commissioning and self-dependent operation,efficiently realizing the three controls of the project,i.e.quality control,schedule control and investment control,and persisted in technical improvement on the basis of digestion and absorption of CANDU-6 technology to improve the unit safety and reliability.The project construction practice has helped China's nuclear power project management to becomeprogrammed,computerized,standardized and internationalized management from the existing basis.After completion of the project,with unit safe and steady operation as the prerequisite,TQNPC performed several technical modifications and innovations to continuously improve the unit performance.In the area of staff development,TQNPC paid much attention to cultivation of corporate culture,strengthed staff training and built up a good circulating mechanism with staff training and project construction promoting each other.Further to "Zero Breakthrough" and a new step forward of locolization successfully realized in Qinshan Nuclear Power Plant and Nuclear Power Qinshan Joint Venture Company,the improvement and developemnt of nuclear power project management level in Qinshan Phase Ⅲ(PHWR)Nuclear Power Plant provided reference for promotion of nuclear power development in China and standardized management of introducing large imported project.

Synthesis of Geopolymers Using Local Resources for Construction and Water Purification

Large deposits of impure kaolins exist in Jordan and many parts of the world;geoplymers can reduce environmental impacts and have multi-application in many fields, such as water purification, waste treatment, fire proof construction, etc. The aim of this research is to investigate the use of alkali activated zeolitic tuff and low purity metakaolin as precursors for the production of functional geoplymers exhibiting proper mechanical properties and high potential for water storage and decontamination of polluted solutions. The results confirmed that this type of geopolymers showed superior mechanical characteristics and higher adsorption capacity towards heavy metals such as Cu(II) ions, which was similar to natural zeolite. X-ray diffraction analysis showed that phillipsite, a major zeolite mineral, disappeared upon geopolymerization, while scanning electron microscopy analysis showed that geopolymers exhibit a porous matrix of nano-particles. The geopolymers have also displayed high compressive strength and tensile bending strength of about 7.8 MPa and 45 MPa respectively, compared to reference geopolymers. This functional-geopolymers indicate that they are efficient, cost effective and have a potential for number of applications including construction, water storage and wastewater treatment.

重型施工机械安拆吊装作业视觉可达性BIM仿真分析

为提高重型施工机械安拆吊装作业安全工效,改善安拆作业过程中人员的可视性,提出基于可视锥法的多主体视觉可达性建筑信息模型(BIM)仿真方法。首先,通过重型施工机械视觉任务分解,得到重型施工机械多主体视觉任务;其次,以wk-35型电铲安拆作业为研究对象,分析起重驾驶司机-信号工-司索工多主体视觉任务,运用计算机辅助三维交互应用(CATIA)人因仿真模块,构建安拆吊装作业多主体视觉的BIM仿真场景;然后,采用可视锥法,计算安拆吊装作业过程多主体视觉可达性量值,测度多主体视觉可达性水平,构建重型机械施工机械多主体视觉评价模型;最后,调节BIM模型的过程参数,推演多主体视觉变化趋势,评价安拆吊装作业多主体视觉可达性。结果表明:安拆作业中起重司机在起升下降过程中视觉可达性较差,在平移过程中视觉可达性较好;信号工和司索工的位置与其视觉可达性联系紧密,当信号工处于视野刚好覆盖起重司机和司索工的位置时,其视觉可达性最好,而司索工需不断调整位置,使其视觉可达性达到最佳。

确保民族自决的新中国工业化(1949—1973)

从新中国成立以来至1973年“四三方案”的提出,我国工业化的主要任务一直是确保民族独立和民族自决,即从做好经济建设、提高国防能力、完成战略腹地产业备份等多个方面入手,保障国家安全、确保民族独立。这是通过一系列的战略部署和重大事件来实现的:第一,通过社会主义改造建立社会主义经济制度,为确立国家工业化的社会主义性质奠定基础。第二,做好经济建设,以发展来保安全、保自决,包括确定中国推进工业化是走优先发展重工业的道路,通过以“156项工程”为代表的项目建设、借助技术引进来快速奠定工业体系基础,促进以钢铁工业为代表的基础工业快速发展等。第三,“两弹一星”国防尖端科技产业的突破,一方面从国防实力上真正确保了民族独立;另一方面通过国防尖端产业的引领,带动了整个工业的发展、促进了工业体系的建设。第四,三线建设这个巨大的社会经济工程,一方面通过战略大后方的建设极大地增强了我国面对战争威胁的博弈力量,加大了对国家安全和民族独立的保障能力;另一方面,通过优化地区工业布局推动了区域协调,推进了我国工业化的发展。以上都为下一阶段的发展打下了制度、物质、国际环境的基础。

重离子医学中心建设工程造价控制的要点分析

重离子医学中心的建设和重离子治疗系统装置的购置费用较为高昂,如何在确保工程质量和效率的前提下,做好重离子医学中心的基本建设和成本管理,科学、合理、有效地控制建设工程造价,成为每一位医院基本建设管理者需要思考的问题。本文以医院建设者的视角,介绍了重离子医学中心建设工程中造价控制的难点,对做好造价控制的关键要素进行分析并提出了建议,可以为其他重离子医学中心建设项目的工程造价控制提供参考。

湿地植物对镉和抗生素单一及复合污染物的去除机制

本文对镉和抗生素残留的湿地植物体内体外2条去除途径、镉-抗生素复合污染的湿地植物去除研究进展进行综述。湿地植物根系是植物去除镉的主要部位——镉在湿地植物根际微环境的迁移转化受根际分泌物有机酸、土壤理化性质、微生物群落等影响,植物体内螯合素的螯合/络合作用对镉的植物体内去除起重要影响,而植物根表铁膜是重要的植物体外螯合物,是植物根际-微生物共同体发挥去除效应的场所。湿地植物-微生物协同效应能有效去除抗生素残留污染,但抗生素残留对根际微生物群落组成和结构影响显著,存在产生抗生素抗性细菌和抗性基因的风险。镉和抗生素复合污染因污染物母体种类、浓度不同而表现出不同的络合物行为特征,进而影响对湿地植物的毒性作用;也同时带有污染物母体的毒性特征,呈现复杂的毒性机制。相较于环境中的综合性污染现状,目前仅对少数种类重金属和抗生素复合污染的湿地植物去除进行研究。结合近年来国内外研究进展,我们提出湿地植物去除抗生素及其重金属抗生素复合污染物现有研究的不足及未来发展方向,以期为重金属和抗生素复合污染的湿地植物修复技术提供理论支撑。

南昌文体中心大跨度重型钢结构桁架设计关键问题分析

南昌文体中心项目采用大跨度重型钢结构桁架实现了最大99m的无柱空间。为了阐述大跨度重型钢结构桁架的设计思路,考察设计、施工中各因素的影响,通过理论分析和数值模拟细致地讨论了涉及的关键问题,包括杆件布置、支承条件、关键节点构造、施工过程的影响等。结果表明:腹杆布置形式对弦杆内力的影响较小;重型桁架两支承端的连接处理至关重要,应注意保证弦杆轴力在极限承载状态下的有效传递,并弱化弯矩的影响;整体提升施工方案对结构内力分布影响较大,“后激活”部分杆件的方法可以考虑提升过程中桁架端面的转动效果,更为准确地体现施工过程的影响。

南海及邻域砂矿资源分布特征及成矿模式

南海及邻域具有多样的地形地貌和丰富的物源,为海洋固体矿产资源的形成和分布提供了物质来源和堆积环境。为系统查明南海及邻域砂矿资源分布情况,本文通过对南海及邻域2606个站位表层沉积物样品进行粒度测试、碎屑矿物鉴定,以及重矿物的品位计算,分析了南海及邻域有用矿物砂矿资源以及建筑用砂资源分布特征并预测了远景区,总结了砂矿成矿模式。结果表明,南海及邻域具有远景的矿种主要有锆石、钛铁矿、金红石、锐钛矿、独居石和石榴子石等;重矿物高品位矿点主要集中在南海东北陆架、菲律宾海盆、南部陆架,重矿物异常区主要位于周缘陆架浅水区以及越东外陆架浅水海域、菲律宾海盆。锆石品位异常区的范围最大,达到工业品位的面积也最大;其次是磁铁矿、钛铁矿、独居石的异常区;锐钛矿、金红石异常区的面积相当;石榴子石品位异常范围最小。根据砂矿的分布规律、大地构造背景、成矿条件以及成矿元素特征,圈定了24个有用重矿物砂矿成矿远景区和6个成矿带。沉积物中砂(0.063~2 mm)含量大于50%的建筑用砂的远景区9个,主要分布于海南岛西南面到台湾海峡南部一线以北海域,其次为南海南部礼乐滩、万安滩、曾母暗沙附近海域,其余海域极为罕见。基于南海砂矿资源分布特征,初步建立了近岸型、潮流砂脊型、古河道埋藏型、峡口型、陆架坡折带型等五种砂矿成矿模式,为海砂资源进一步勘查提供方向和建议。

基于载重飞艇的整体立塔技术仿真研究

在输电铁塔的施工中,悬浮抱杆组塔和整体起吊组塔是目前应用广泛的两种组塔方式。针对这些组塔方式存在人员高空作业风险和大重型装备无法到达山区施工现场等问题,提出一种基于载重飞艇的整体立塔方案。该方案在地面完成整个输电铁塔的组装后,利用载重飞艇提供牵引力,使输电铁塔绕铰接式结构旋转直至竖立。针对立塔全过程,根据飞艇的牵引方式、飞行速度、飞艇牵引力与铁塔所形成的夹角对铁塔应力和应变的影响等,分为三种方案进行仿真研究。仿真结果表明,该整体立塔技术方案安全可靠,避免了人员高空作业的危险性,且能使大重型设备到达山区作业现场。

双层大跨重型钢梁受限空间内逆序施工技术

基于丽水国际会展中心项目政务方厅钢结构施工策划实践,介绍双层交错式大跨重型钢梁在受限空间内采用逆序施工技术的具体应用情况。采用先上后下的逆序吊装施工顺序,并结合原有结构支撑反顶、楼板钢筋加密、双机抬吊等施工工艺措施,使得在多种受限工况下的双层交错式重型钢梁仍可以经地面拼装后进行整体吊装,避免因大型机械上楼板造成的楼板开裂以及重型钢梁高空对接导致的精度不足、焊接质量不合格等一系列严重质量问题,最终达到减少安装措施费用、保护成品结构、缩短工期的施工目标,实现工程施工效益最大化。

中国企业海外重化工投资项目配套码头选址原则

中国企业的大型海外重化工投资项目通常需要自建码头以完成物料运输,因此项目的选址很大程度取决于码头的建设位置。分析归纳此类项目码头选址具有空间跨度大、明确约束少、研究深度深等特征,筛选影响该类项目码头选址的主要因素有波浪条件、水深条件、泥沙条件、地质地震情况、陆域场地条件、港口依托条件、运输里程等,提出以建设成本和运营成本总和最低为评判标准的选址准则目标,总结从初选的宏观研究到终选的方案微观研究的选址思路和流程,并以中国企业在马来西亚的某投资项目为例,演绎整个选址的过程,可供类似项目选址参考。

新时期某重载铁路路堑穿越大型滑坡体施工技术应用

通过细致的地质勘察与滑坡体评估,研究制订有针对性的施工方案,旨在优化重载铁路路堑工程设计并确保施工安全与效率,涵盖具体施工步骤、安全控制及环境保护,案例分析展示了技术应用的成效,证明先进施工技术在提升工程安全、减轻环境影响及促进生态修复方面的有效性,为类似工程提供了宝贵经验,展示了工程技术环保理念的结合。

基于重交通条件下曲线桥梁施工关键技术

重交通条件下,曲线桥梁施工难度进一步增加。为了给重交通条件下的曲线桥梁施工提供一些参考,利用案例分析法,以一个曲线桥梁施工工程为例,分析了重交通条件下的曲线桥梁施工问题,并提出了几条针对性解决技术。得出:重交通条件下,曲线桥梁偏心风险较大,可以利用下行线移动模架外侧加固+上行线顶推复位技术进行调整,有效解决桥梁偏心问题。

超高重型大跨度室内滑雪场钢屋盖建造技术

网架作为一种空间杆系结构,因其具有整体性和稳定性好、空间刚度大和抗震性能好的优点而被广泛应用在大跨度结构中。常规的网架安装方法主要有整体提升法、高空滑移法、分条吊装法及高空散装法等。但超高重型焊接球网架不同于一般螺栓球网架,其跨度及可承受的荷载更大,对应的施工安装难度及安全风险更高,如果仅采用单种常规安装方法,很难高效、顺利地实现结构成型。以上海临港冰雪之星项目室内滑雪场钢屋盖为背景,着重介绍“原位原姿态拼装后分块整体提升”的安装技术路线及对应施工过程分析和改进措施,并通过对胎架拼装、提升控制及卸载等关键工序的研究,为今后类似大跨度钢结构屋盖安装的施工方案提供参考。