An alternate approach for transient flow modeling in urban drainage systems

Implementing control structures such as gates at suitable locations in the urban drainage network enables its improved utility by actively controlling and optimizing the flow during a flood event. The successful operation of the control structure is fully governed by the suitability and efficiency of the control strategy adopted, which in turn depends on the response characteristics of the urban drainage system under different flow conditions. For an extreme rainfall event, it is necessary to model the transient flow in the urban drainage system. However, such an exercise is mostly restricted by the limited data and lack of in-depth survey of urban drainage systems in most of the developing countries like India. Taking this into consideration, an alternate approach has been presented in this paper for modeling the transient flow in the urban drainage system under limited data availability. The results obtained have also been compared with the finite difference model using four-point implicit scheme in time domain. The developed model can be used for the computation of temporal distribution of water surface profile with special consideration of lateral inflow. The application has been demonstrated by applying it to a representative catchment in Mumbai, India.     

An integrated modeling approach to predict flooding on urban basin.

Correct prediction of flood extents in urban catchments has become a challenging issue. The traditional urban drainage models that consider only the sewerage-network are able to simulate the drainage system correctly until there is no overflow from the network inlet or manhole. When such overflows exist due to insufficient drainage capacity of downstream pipes or channels, it becomes difficult to reproduce the actual flood extents using these traditional one-phase simulation techniques. On the other hand, the traditional 2D models that simulate the surface flooding resulting from rainfall and/or levee break do not consider the sewerage network. As a result, the correct flooding situation is rarely addressed from those available traditional 1D and 2D models. This paper presents an integrated model that simultaneously simulates the sewerage network, river network and 2D mesh network to get correct flood extents. The model has been successfully applied into the Tenpaku basin (Nagoya, Japan), which experienced severe flooding with a maximum flood depth more than 1.5 m on September 11, 2000 when heavy rainfall, 580 mm in 28 hrs (return period > 100 yr), occurred over the catchments. Close agreements between the simulated flood depths and observed data ensure that the present integrated modeling approach is able to reproduce the urban flooding situation accurately, which rarely can be obtained through the traditional 1D and 2D modeling approaches.     

An integrated approach for solving urban water and wastewater crises in the Arabian Gulf States.

Various environmental and economic aspects of urban water and wastewater crises in a number of the Arabian Gulf States are discussed. An integrated approach, which considers simultaneously the problems of urban waters (shortage of water supply and problems associated with urban drainage) and those in connection with wastewater (i.e. environmental impact) is proposed. The feasible link between the main factors affecting these problems and the anticipated results encourage the implementation of the proposed approach. The conclusions suggest immediate municipal legislation.     

An integrated approach for improving the wastewater discharge and treatment systems

Since treatment plants have been built all over Germany during the last decades, the water quality of receiving streams has been improved remarkably. But there are still a lot of quality problems left, which are caused e.g. by combined sewer overflows (CSO), treatment plant effluents or rainwater discharges from separate sewer systems. At present different efforts are undertaken to control sewer systems in order to improve the operation of urban drainage systems or more generally, design processes. The Emschergenossenschaft and Lippeverband (EG/LV) are carrying out research studies, which are focusing on a minimization of total emissions from sewer systems both from wastewater treatment plant (WWTP) effluents and from CSO. They consider dynamic interactions between rainfall, resultant wastewater, combined sewers, WWTP and receiving streams. Therefore, in an advanced wastewater treatment, a model-based improvement of WWTP operation becomes more and more essential, and consequently a highly qualified operational staff is needed. Some aspects of the current research studies are presented in this report. The need and the use of an integrated approach to combine existing model components in order to optimize dynamic management of combined sewer systems (CSS) with a benefit for nature are outlined.     

基于GIS的城市排水管网模型拓扑规则检查和处理

构建城市排水管网模型可以辅助解决与城市排水系统相关的水量与水质问题。城市排水系统各要素间存在复杂的拓扑关系,通常构建城市排水系统模拟模型需要对排水系统要素之间的拓扑关系进行检查和修正。对于较大规模的城市排水系统建模,检查和修正排水系统要素之间的拓扑关系将是一项繁琐的工作。以城市排水系统模拟中常用的SWMM模型为例,借助GIS的空间分析功能开发了城市排水系统模拟中基于规则的拓扑检查和处理的方法,并在澳门半岛排水系统建模中得到了应用。该方法利用GIS可视化表达要素之间的拓扑关系并可快速对拓扑错误进行定位和修正,保证了模型中空间数据的完整性、一致性和连通性,同时通过系统集成可以提高排水模型构建的效率和模拟的准确性。     

城市排水系统集成模拟研究进展

在回顾城市排水系统集成模拟研究发展和现状的基础上,结合可持续性城市排水系统理论,分析了现阶段城市排水系统集成模拟研究的局限和面临的问题。为了适应城市排水系统结构和功能的演变,实现系统的可持续性,今后城市排水系统集成模拟的研究应当完善对系统结构的描述,在集成模拟的过程中考虑不确定性因素对系统的影响,并构建高效能计算平台,解决城市排水系统大规模计算问题。     

Performance indicators for the efficiency analysis of urban drainage systems.

Performance indicators implemented in a decision support system (DSS) for the technical, managerial and economic evaluation of urban drainage systems (UDS), called MOMA FD, are presented. Several kinds of information are collected and processed by MOMA FD to evaluate both present situation and future scenarios of development and enhancement. Particular interest is focused on the evaluation of the environmental impact, which is considered a very relevant factor in the decision making process to identify the priorities for UDS improvements.     

城市生活污水回用适宜条件和途径

城市污水回用是城市水资源利用的重要方式。分散处理是目前污水处理的新方向。提出了符合上述原则的城市居民小区生活污水回用的适宜条件和途径,即处理回用除粪便污水和厨房用水以外的较"清洁"的废水。宜于采用占地较少、操作简便的膜处理方法,最好是超滤膜,以彻底除去病毒和细菌。既不影响城市小区优美的居住环境,为居民所接受,又易于实施,从而达到水资源可持续利用的目的。     

On the use of an ontology for the identification of degrees of freedom in urban wastewater systems.

The management of Urban Wastewater Systems (UWS) requires a comprehensive understanding of the interactions of processes and substances in the system. This leads to complex numerical models which can be applied to predict management actions or understand misconduction of the system. Nevertheless, for the communication between stakeholders in the process of optimizing a UWS these models are far too sophisticated. In this paper the use of an ontology is described serving as a conceptual model of the UWS which can be used for dissemination or as a preliminary stage to numerical models. The ontology therefore is part of a dissemination tool describing potential measures which can be applied to optimize a UWS.     

SWMM模型在城市雨水排除系统分析中的应用

采用暴雨管理模型(Storm Water Management Model,SWMM),结合Huff方法生成的典型降雨情景对清华大学校园内的一个独立雨水排除系统进行了模拟计算,并对地表产流、排水口排水状况和管道负荷情况进行了分析讨论.基于真实测绘数据构建雨水管网模型,并利用实测流量数据进行参数验证,保证了计算和分析结果的可靠性.利用SwMM模型模拟和分析的方法,可全面反映研究区域雨水排除系统的服务性能,为区域防洪排涝和雨水管网的更新、改造与维护提供决策支持.     

Normalising impacts in an environmental systems analysis of wastewater systems.

In an environmental systems analysis of four wasterwater systems, the environmental aspects were prioritised by normalisation of predicted impacts from the studied systems to the total impacts from society. Priority Group 1 (highest priority) consisted of discharges (flows) of nitrogen, cadmium, lead and mercury to water, recycling of nitrogen and phosphorus to arable land and flows of heavy metals to arable land. A conventional wastewater system (A) was compared to irrigation of energy forest with biologically treated wastewater (B), liquid composting of toilet wastewater (C) and a conventional system supplemented with urine separation (D). Analysing the aspects in priority group one, systems B-D improved the management of plant nutrients and decreased the flow of heavy metals to water, while the flow to arable land increased, especially for system B. The suggested method is useful in municipal environmental planning and when choosing a wastewater system.     

城市给水排水管网系统专用GIS平台开发与应用

运用地理信息系统进行城市给水排水管网数据管理,有助于提高企业管理的质量和效率。但是目前采用的GIS软件平台都是覆盖电信、电力、国土资源、煤气、交通、水利、水务运营等多个专业的通用GIS平台,应用于城市给水排水行业有较多冗余功能,既浪费资源也降低系统的运行效率。一般不能直接满足行业的特殊需求,需进行二次开发。以华东地区某市给水管网地理信息系统应用为例,对城市给水排水管网专用GIS平台的开发与应用进行一次尝试。     

The effect of climate change on urban drainage: an evaluation based on regional climate model simulation.

That we are in a period of extraordinary rates of climate change is today evident. These climate changes are likely to impact local weather conditions with direct impacts on precipitation patterns and urban drainage. In recent years several studies have focused on revealing the nature, extent and consequences of climate change on urban drainage and urban runoff pollution issues. This study uses predictions from a regional climate model to look at the effects of climate change on extreme precipitation events. Results are presented in terms of point rainfall extremes. The analysis involves three steps: Firstly, hourly rainfall intensities from 16 point rain gauges are averaged to create a rain gauge equivalent intensity for a 25 x 25 km square corresponding to one grid cell in the climate model. Secondly, the differences between present and future in the climate model is used to project the hourly extreme statistics of the rain gauge surface into the future. Thirdly, the future extremes of the square surface area are downscaled to give point rainfall extremes of the future. The results and conclusions rely heavily on the regional model's suitability in describing extremes at timescales relevant to urban drainage. However, in spite of these uncertainties, and others raised in the discussion, the tendency is clear: extreme precipitation events effecting urban drainage and causing flooding will become more frequent as a result of climate change.     

基于SWMM的城市排涝措施研究及应用

针对南方大多数老城区排涝措施不足、一到汛期就出现积水的问题,为了优选合理经济的排涝措施方案,采用SWMM模型研究某片老城区在不同重现期降雨的影响,分析现有排水管网的排水能力,对超载管道及积水区域提出了两个初步排涝方案。其中方案一为增大溢流段管径20%～50%,方案二为20%汇水面积布设LID措施,模拟结果表明两个方案在降雨重现期P≥10a时,都有部分区域出现积水现象。为此提出两个优化排水方案,即调整溢流区域管径大小、又调整布设LID措施比例的方案。其中方案三将管网管径改造比例调整为方案一的50%,LID措施占研究区域面积比例为方案二的50%;方案四中管网管径改造比例调整为方案一的100%,LID措施占研究区域面积比例为方案二的25%。通过排涝效果和经济效益综合分析,当防涝设计重现期P20a时,应选择方案三,重LID措施比例、轻管道改造比例;当防涝设计重现期P≤20a时,应选择方案四,重管道改造比例、轻LID措施比例。研究区排水防涝设计标准为30a一遇暴雨不成灾,建议选择方案三。研究成果对选择城市进行管网改造比例和LID措施比例有着一定的借鉴和指导意义,但由于受到其他参考指标的影响,最优比例仍有待深入研究。     

深圳市城市污水资源化分析

在分析深圳市自有水资源极少,与经济持续高速发展和人口高度集中的矛盾的基础上,提出了高质量水高功能使用,低质量水低功能使用的观点。将城市污水经深度处理后,以环境用水为主,市政杂用水为辅作再生利用,其使用量占平均日污水量的56％;并结合污水处理厂布局,就近回用污水,逐一分配到30条河流,使之保持平水期径流量,可较好地实施深圳市污水资源化。     

Knowledge-based fuzzy system for diagnosis and control of an integrated biological wastewater treatment process.

A supervisory expert system based on fuzzy logic rules was developed for diagnosis and control of a laboratory- scale plant comprising anaerobic digestion and anoxic/aerobic modules for combined high rate biological N and C removal. The design and implementation of a computational environment in LabVIEW for data acquisition, plant operation and distributed equipment control is described. A step increase in ammonia concentration from 20 to 60 mg N/L was applied during a trial period of 73 h. Recycle flow rate from the aerobic to the anoxic module and bypass flow rate from the influent directly to the anoxic reactor were the output variables of the fuzzy system. They were automatically changed (from 34 to 111 L/day and from 8 to 13 L/day, respectively), when new plant conditions were recognised by the expert system. Denitrification efficiency higher than 85% was achieved 30 h after the disturbance and 15 h after the system response at an HRT as low as 1.5 h. Nitrification efficiency gradually increased from 12 to 50% at an HRT of 3 h. The system proved to react properly in order to set adequate operating conditions that led to timely and efficient recovery of N and C removal rates.     

Evaluation of water security: an integrated approach applied in Wuhan urban agglomeration, China

To evaluate water security, the Water Resources Sustainability Evaluation Model has been developed. The model employs four criteria (economic development, flood control security, water supply security, and water environment security) and has 22 indicators, integrating them using their relative weights. The model is applied to evaluate the water security of Wuhan urban agglomeration, China. The values of the indicators are normalized using the exponential efficacy functions based on the law of diminishing marginal utility. The evaluation results show that, overall, the state of water security in Wuhan urban agglomeration is good, which is in good agreement with the true situation. The comparison between the results of the model and other three evaluation methods by the Spearman coefficient of rank correlation verifies the science and reliability of the developed model. Consequently, it is concluded that the model can be an effective tool for evaluating the states of water security and provide a basis on which to create policies for improving inadequacies in water security.     

Estimation of reduced and increasing health risks by installation of urban wastewater systems.

This paper aims to propose a methodological framework for quantifying the reduction and increase of health risks associated with urban wastewater systems. A risk assessment model was used to quantify reduction in disease burden while a life cycle assessment approach was used to quantify increasing risks by environmental loading. Disability adjusted life years (DALYs) was used to quantify health risks. This framework was applied to a hypothetical watershed to evaluate health risks by installation of wastewater treatment systems. In this hypothetical case, 55 DALYs per year of health risk would be reduced for 200,000 people in the downstream community by constructing wastewater systems for 200,000 people, while a range from 1.9 to 22 DALYs per year of health risks would be generated by materials and energy consumption for construction and operation of wastewater systems. However, this result would significantly change, depending on the parameters used in this analysis. The proposed methodology should be improved to obtain more precise results, but it will suggest useful information to discuss the overall effects due to the installation of various types of urban wastewater systems.     

城市防洪排涝工程设计

在分析我国城市特点和城市排涝理论研究现状的基础上,对城市防洪排涝工程设计的标准、堤顶高程的确定、堤防工程与城市规划的关系、河道及河口整治等进行了探讨,指出城市防洪工程的设计在保证防洪安全功能的条件下,应向多功能建设发展。     

基于SWMM的城市排水系统改造优化研究

为了解决城市排水系统改造优化时系统淤积的问题,采用SWMM(Storm Water Management Model)模拟技术进行排水系统改造优化研究。以柳州中心城区为例,构建包含淤积设置的排水系统现状模型进行现状评估,并构建清淤工况模型来评估清淤措施的效果。在清淤模型基础上,针对p=5年情景分析系统溢流原因并进行改造,将过水能力不足的管段增加断面尺寸,使得系统能够抵御5年一遇降雨,并运用模型验证其可行性。结果表明:现状排水系统在p=2年情景下溢流量为9 083 m3,排水能力较弱,其原因是设计标准较低且存在一定的淤积现象;将系统进行清淤措施后在p=2年情景下溢流量为2 616 m~3,减少了71.2%,有明显改善但还存在较大的溢流现象;以5年一遇为目标对系统15%的管段进行改造,改造后在p=2年、p=3年情景下均无溢流现象,在p=5年下溢流量为238 m~3,不足以形成内涝灾害。改造方案可以有效地解决城市内涝现象,并为城市排水系统改造优化提供参考依据。