Modeling iron release from cast iron pipes in an urban water distribution system caused by source water switch

Significant iron release from cast iron pipes in water distribution systems (WDSs), which usually occurs during the source water switch period, is a great concern of water utilities because of the potential occurrence of “red water” and customer complaints. This study developed a new method which combined in-situ water stagnation experiments with mathematical models and numerical simulations to predict the iron release caused by source water switch. In-situ water stagnation experiments were conducted to determine the total iron accumulation in nine cast iron pipes in-service in Beijing when switching the local water to treated Danjiangkou Reservior water. Results showed that the difference in the concentration increment of total iron in 24 hr (ΔCI_TI,24), i.e. short-term iron release, caused by source water switch was mainly dependent on the difference in the key quality parameters (pH, hardness, nitrate, Larson Ratio and dissolved oxygen (DO)) between the two source waters. The iron release rate (R_Fe) after switch, i.e. long-term iron release, was closely related to the pipe properties as well as the DO and total residual chlorine (TRC) concentrations. Mathematical models of ΔCI_TI,24 and R_Fe were developed to quantitatively reveal the relationship between iron release and the key quality parameters. The R_Fe model could successfully combine with EPANET-MSX, a numerical simulator of water quality for WDSs to extend the iron release modeling from pipe level to network level. The new method is applicable to predicting iron release during source water switch, thus facilitating water utilities to take preventive actions to avoid “red water”.     

障碍物条件下纳米SiO2粉体抑制瓦斯爆炸特性

为了研究障碍物条件下纳米SiO_2粉体对瓦斯爆炸的抑制特性,采用自行搭建的150 mm×150 mm×500 mm可视化瓦斯爆炸试验系统,分别对不同质量浓度和粒径的纳米SiO_2粉体抑爆特性进行了试验研究。结果表明:在障碍物条件下,纳米SiO_2粉体对瓦斯爆炸具有良好的抑制效果,0.10 g/L的30 nm SiO_2粉体可使9.5%瓦斯气体的最大火焰传播速度降低35%,爆炸超压降低34%;然而,纳米SiO_2粉体并非质量浓度越大抑爆效果越好,而是存在最佳抑爆质量浓度,即随纳米SiO_2粉体质量浓度上升,其抑爆性能先增大后减小,最佳抑爆质量浓度约为0.10 g/L;此外,纳米SiO_2粉体的抑爆性能与其粒径相关,且存在最佳抑爆粒径,相同质量浓度下30 nm SiO_2粉体比15nm和50 nm SiO_2粉体的抑爆效果好。     

浅谈蒸气锅炉的水位事故

通过分析锅炉缺水、满水和汽水共腾三种锅炉水位事故的原因 ,有针对性地提出了预防措施及发生锅炉水位事故的处理方法     

Analyzing injury severity of bus passengers with different movements

Objective: Though public transport vehicles are rarely involved in mass casualty accidents, when they are, the number of injuries and fatalities is usually high due to the high passenger capacity. Of the few studies that have been conducted on bus safety, the majority focused on vehicle safety features, road environmental factors, as well as driver characteristics. Nevertheless, few studies have attempted to investigate the underlying risk factors related to bus occupants. This article presents an investigation aimed at identifying the risk factors affecting injury severity of bus passengers with different movements.

Method: Three different passenger movement types including standing, seated, and boarding/alighting were analyzed individually using classification and regression tree (CART) method based on publicly available accident database of Great Britain.

Results: According to the results of exploratory analyses, passenger age and vehicle maneuver are associated with passenger injury severity in all 3 types of accidents. Moreover, the variable “skidding and overturning” is associated with injury severity of seated passengers and driver age is correlated with injury severity of standing and boarding/alighting passengers.

Conclusions: The CART method shows its ability to identify and easily explain the complicated patterns affecting passenger injury severity. Several countermeasures to reduce bus passenger injury severity are recommended.     

舟山市排污废水和附近海水的细菌学研究

对舟山市两大排污口的污水和附近海水中细菌的数量和种类进行了详细的研究。结果表明：排污水中的细菌数量相当高，平均为８．２＊１０＾５个／ｍｌ，粪大肠杆菌数量高达３．５＊１０＾８个／Ｌ。细菌的种类组成隶属２０个属、２５种。污水细菌中主要优势菌为Ｘａｎｔｈｏｍｏｎａｓｍａｌｔｏｐｈｉｌｉａ、Ｓｐｈｉｎｇｏｍｏｎａｓｐａｕｃｉｍｏｂｉｌｉｓ、Ｐｓｅｕｄｏｍｏｎｓａｃｅｐａｃｉａ等。海水中优势菌为Ｐｓｅｕｄｏ     

人与自然的和谐,先从法之间的"和谐"开始

自1979年《中华人民共和国环境保护法(试行)》颁布以来,针对大气污染、水污染、噪声污染、固体废物污染、放射性污染等污染类型和森林、草原、水、土地、野生动物等环境要素以及环境影响评价、清洁生产等环境管理制度,国家立法机关均制定了相应的法律法规,形成了较为完善的环境法律体系,环保有法可依的目标已初步实现。     

真菌对微量元素铁、锌、硒生物富集作用的研究

研究了在不同培养基成分和同一培养基成分中 ,三株酵母菌和三株食用菌对Fe ,Zn ,Se的富集作用 .结果表明 :培养基成分、微量元素浓度和不同的菌株会影响六株真菌的生物富集作用 .提高培养基中蛋白质、脂肪和Fe ,Zn ,Se的浓度 ,有利于它们对Fe ,Zn ,Se的富集 ,较高浓度的Fe ,Zn ,Se盐能促进香菇菌丝的生长     

种植业面源污染防控技术发展历程分析及趋势预测

种植业对农业面源污染贡献不容小觑.已有治理技术并不在少数,但受技术参数模糊和技术应用效果不明朗等因素的影响,现阶段技术应用和污染治理效果不理想.对此,本研究基于近20年国内外种植业面源污染防控的发表论文,明确种植业面源污染防治技术的体系框架,梳理技术的发展历程,比较不同方向技术对生产投入、产量及污染物排放的作用效果,对新时期下我国植业面源污染防控的发展前沿趋势作出预判.本研究构建了源头削减、过程拦截和养分回用这3个领域以及栽培、生态沟渠和尾/废水等14个方向的技术体系.结果发现,源头削减领域获得了最高关注度,研究方向多且热度仍在不断提升;我国对其中肥料方向技术的研究集中度较高.相比之下,过程拦截和养分回用领域的技术较为单一和欠缺.养分利用效率提升、转运过程调控和土壤添加剂使用将是种植业面源污染防控未来的主要着力点和抓手.农田基础设施的配套及后端净化体系的构建,将有助于集成、耦合多领域技术,进一步确保种植业面源污染防控的作用效果.     

一体化活化硅藻土反应器应用于污水深度处理的中试研究

开发了一种新型的污水深度处理反应器--一体化活化硅藻土反应器,并对其性能和净水效果进行了研究.结果表明:与常用的混凝剂PAC、硫酸铝相比,活化硅藻土对污水厂尾水中的SS、NH3-N、COD、BOD5、TP、TN、UV254等污染物指标的去除效果更好且其处理成本也较低;当原水流量和水质变化时,一体化活化硅藻土反应器具有一...     

粉煤灰／膨润土-聚丙烯酸盐聚合化学固沙材料的研究

文章利用粉煤灰／膨润土一聚丙烯酸盐聚合研制了一种化学固沙材料,通过大量的实验研究,确定了该固沙材料的最优配比,粉煤灰、膨润土和水玻璃的含量分别为60％、32％和16％,此条件下的固沙材料抗压强度及吸水、保水能力最佳。综合考虑到抗压强度、吸水率、失水率和经济成本,最佳配比确定为：粉煤灰、膨润土、水玻璃、聚丙烯酰胺与聚乙烯醇分别为50．4％、33．6％、8％、3％和5％,经核算每千克化学固沙剂的成本3．6元,说明了该固沙材料固沙的可行性及经济性。探讨了该膨润土粉煤灰水玻璃的固结机理、化学固沙机理及化学固沙材料的应用。