The scope of integrated modelling: system boundaries, sub-systems, scales and disciplines.

Integrated modelling has become an urgent issue of urban drainage and wastewater treatment planning. The scope of integrated modelling, system boundaries and disciplines to be involved are addressed in view of future developments and new paradigms in urban drainage, demanding the inclusion of the full urban water cycle. A system analysis is demonstrated to identify relevant sub-systems and components, processes and interactions within the urban water system. The permissibility to exclude subsystems or neglect interactions is evaluated. Integrated modelling of urban water system is characterised as an ambitious task in regard to system complexity, heterogeneous scales and interface problems. The methodical status quo is characterised in preliminary approaches towards integrated modelling. It is concluded that it does not seem promising to create and apply one entity model for the scope of integrated urban water modelling. Instead, the development of adequate and efficient IT frameworks is identified as the key issue of integrated modelling. Harmonising interfaces to facilitate the linking of existing models is presented as the objective of a European research project HarmonlT and the U.S. EPA Multimedia Integrated Modelling System project MIMS.     

Frequency analysis of river water quality using integrated urban wastewater models

In recent years integrated models have been developed to simulate the entire urban wastewater system, including urban drainage systems, wastewater treatment plants, and receiving waterbodies. This paper uses such an integrated urban wastewater model to analyze the frequency of receiving water quality in an urban wastewater system with the aim of assessing the overall system performance during rainfall events. The receiving water quality is represented by two indicators: event mean dissolved oxygen (DO) concentration and event mean ammonium concentration. The compliance probability of the water quality indicators satisfying a specific threshold is used to represent the system performance, and is derived using the rainfall events from a series of 10 years' rainfall data. A strong correlation between the depth of each rainfall event and the associated volume of combined sewer overflow (CSO) discharges is revealed for the case study catchment, while there is a low correlation between the intensity/duration of the rainfall event and the volume of the CSO discharges. The frequency analysis results obtained suggest that the event mean DO and ammonium concentrations have very different characteristics in terms of compliance probabilities at two discharging points for CSO and wastewater treatment plant effluent, respectively. In general, the simulation results provide an understanding of the performance of the integrated urban wastewater system and can provide useful information to support water quality management.     

河流水质模型(RWQM1)介绍及实例分析

以河流水质为目标对城市污水系统进行集成管理,是改善河流水质、保护生态环境的有效途径。介绍了国际水协会河流水质1号模型(RWQM1),该模型采用与标准活性污泥模型类似的描述方式,用化学需氧量作为有机物度量描述有机物与营养物,选择表征碳、氢、氧、氮、磷循环的水质成分和模型状态变量,描述河流中好氧与缺氧条件下物质的循环变化过程。该模型可直接与活性污泥模型相连接,用于集成城市污水处理系统的设计规划与监视控制。     

Analysis of scenarios for wastewater and urban drainage systems in Brazil based on an integrated modeling approach.

Brazil is currently facing widespread problems in the urban environment associated with inadequate wastewater and urban drainage systems, particularly for low-income communities. These problems are promoted by the rapid and often unplanned urbanization process in developing cities and are compounded by a lack of funding, absence of planning, ineffective institutional arrangements, and inappropriate policies to provide the framework for integrated wastewater and stormwater management. Because planning for the provision of wastewater and urban drainage systems is a complex task, an integrated-modeling approach is proposed to provide a practical methodology for sanitation and urban drainage planning in Brazilian cities. In the model development, as well as technical aspects, other aspects related to institutional, financial, socio-economic, environmental and public health issues were also taken into account.     

南通市河网格局特征及水环境响应

对南通市河网景观格局与地表水污染的关系进行探讨。在对南通市的河网景观格局进行定性分析的基础上,设计并定量计算了南通市河网景观格局指标,据此分析了不同排污功能河流的景观格局特点:①就污染程度来说,工业排污河流最为严重,生活排污河流次之,农业排污河流水质最好;②就河流污染物分布来说,工业排污河流最不均匀,生活排污河流次之,农业排污河流最为均匀。这与实测分析结果基本一致,说明城市河网景观格局是影响污染物分布、运移的主要因素之一。     

An integrated approach for urban water quality assessment

This paper introduces an integrated approach for the assessment of receiving water quality and the relative contribution of the urban drainage system to perceived receiving water quality problems. The approach combines mass balances with relatively simple receiving water impact models. The research project has learned that the urban drainage system is only one of the determining factors with respect to receiving urban water quality problems. The morphology of the receiving waters and the non-sewer sources of pollution, such as waterbirds, dogs, or inflow of external surface water might be equally important. This conclusion underlines the necessity to changes today's emission based approach and adopt an integral and immission based approach. The integrated approach is illustrated on a case study in Arnhem, where the receiving water quality remained unsatisfactory even after retrofitting a combined sewer system into a separated sewer system.     

Assessment of data and parameter uncertainties in integrated water-quality model

In integrated urban drainage water quality models, due to the fact that integrated approaches are basically a cascade of sub-models (simulating sewer system, wastewater treatment plant and receiving water body), uncertainty produced in one sub-model propagates to the following ones depending on the model structure, the estimation of parameters and the availability and uncertainty of measurements in the different parts of the system. Uncertainty basically propagates throughout a chain of models in which simulation output from upstream models is transferred to the downstream ones as input. The overall uncertainty can differ from the simple sum of uncertainties generated in each sub-model, depending on well-known uncertainty accumulation problems. The present paper aims to study the uncertainty propagation throughout an integrated urban water-quality model. At this scope, a parsimonious bespoke integrated model has been used allowing analysis of the combinative effect between different sub-models. Particularly, the data and parameter uncertainty have been assessed and compared by means of the variance decomposition concept. The integrated model and the methodology for the uncertainty decomposition have been applied to a complex integrated catchment: the Nocella basin (Italy). The results show that uncertainty contribution due to the model structure is higher with respect to the other sources of uncertainty.     

Integrated assessment of urban drainage system under the framework of uncertainty analysis.

Due to a rapid urbanization as well as the presence of large number of aging urban infrastructures in China, the urban drainage system is facing a dual pressure of construction and renovation nationwide. This leads to the need for an integrated assessment when an urban drainage system is under planning or re-design. In this paper, an integrated assessment methodology is proposed based upon the approaches of analytic hierarchy process (AHP), uncertainty analysis, mathematical simulation of urban drainage system and fuzzy assessment. To illustrate this methodology, a case study in Shenzhen City of south China has been implemented to evaluate and compare two different urban drainage system renovation plans, i.e., the distributed plan and the centralized plan. By comparing their water quality impacts, ecological impacts, technological feasibility and economic costs, the integrated performance of the distributed plan is found to be both better and robust. The proposed methodology is also found to be both effective and practical.     

Random number generator or sewer water quality model?

Integrated urban drainage modelling and environmental impact assessment require sewer emission models to be linked with submodels for treatment infrastructure and receiving rivers. The uncertainty in current water quality modelling is, however, huge, and environmental impact assessment looses more and more credibility. Based on an integrated modelling case for a combined sewer-WWTP-river system, it is shown in the paper that the integrated model does not produce more accurate results in comparison with the random simulation of emission concentrations from a frequency distribution. This should, however, not pose a serious problem as in most applications of impact assessment, model results are not needed in real time but in statistical terms. Further investigation makes clear that detail/sophistication in water quality modelling is not so important, but that more focus has to be given to long-term simulations, the use of parsimonious models and model validation based on concentration frequencies.     

Model-based knowledge acquisition in environmental decision support system for wastewater integrated management

The main goal of the Water Framework Directive is to achieve good chemical and ecological status of water bodies by 2015. The implementation of integrated river basin management, including sewer systems, wastewater treatment plants and receiving water bodies, is essential to accomplishing this objective. Integrated management is complex and therefore the implementation of control systems and the development of decision support systems are needed to facilitate the work of urban wastewater system (UWS) managers. Within this context, the objective of this paper is to apply integrated modelling of an UWS to simulate and analyse the behaviour of the 'Congost' UWS in Spain, and to optimize its performance against different types of perturbations. This analysis results in optimal operating set-points for each perturbation, improves river water quality, minimizes combined sewer overflows and optimizes flow lamination from storm water tanks. This is achieved by running Monte Carlo simulations and applying global sensitivity analysis. The set-points will become part of the knowledge base composed of a set of IF-THEN rules of the environmental decision support system being developed for this case study.     

不同取样法设计暴雨标准关系初探

我国城市排水工程由建设部门主管,排水工程规划设计与水利部门管辖的防洪排涝体系有所脱节,给城市防洪排涝体系的统一规划带来困扰,标准即是关键问题之一。以石家庄市为例,分析年最大值法和年多个样法两种不同取样方法计算设计暴雨标准的相互关系,在城区相关水利工程规划设计中当涉及城乡洪（涝）沥水组合时可作为参考。     

Integrated operation of sewer system and WWTP by simulation-based control of the WWTP inflow.

In recent years numerical modelling became a standard procedure to optimise urban wastewater systems design and operation by integration. For dynamic control of the wastewater teatment plant (WWTP) inflow, a model-based predictive concept is introduced aiming at improving the receiving water quality. An on-line simulator running parallel to the real WWTP operation reflects the actual state of operation and provides this model information to a prognosis tool which determines the best option for the WWTP inflow. The investigations showed that it is possible to reduce the NH4-N peak concentrations in the receiving water by dynamic WWTP inflow control based on predictive scenario analysis.     

Integrated modelling for the evaluation of infiltration effects.

The objective of the present study is the estimation of the potential benefits of sewer pipe rehabilitation for the performance of the drainage system and the wastewater treatment plant (WWTP) as well as for the receiving water quality. The relation of sewer system status and the infiltration rate is assessed based on statistical analysis of 470 km of CCTV (Closed Circuit Television) inspected sewers of the city of Dresden. The potential reduction of infiltration rates and the consequent performance improvements of the urban wastewater system are simulated as a function of rehabilitation activities in the network. The integrated model is applied to an artificial system with input from a real sewer network. In this paper, the general design of the integrated model and its data requirements are presented. For an exemplary study, the consequences of the simulations are discussed with respect to the prioritisation of rehabilitation activities in the network.     

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.     

污水处理系统的集成控制策略研究

以实现河流水质目标为前提,充分利用河流纳污能力,根据不同环境与气候条件调节污水处理厂运行状况和排水管网的污水排放量,可有效保护河流生态质量。基于城市污水处理系统集成仿真平台,提出了4种以河流水质为目标的城市污水处理系统集成控制方案,通过对排水管网和污水处理厂的协调控制,实现了河流水质的改善。仿真结果验证了集成控制策略的有效性。     

Klimawandel und Urbanisierung – wie soll die Wasserinfrastruktur angepasst werden?

Conventional urban water servicing has successfully provided cities with clean water, sanitation and flood protection. Traditional approaches are unsuited to address future challenges like climate change and modern urban development trends (e.g. migration, aging population, densification). As well as increased risks of water scarcity and flooding, society's demands for urban amenity and healthy waterways in metropolitan areas also challenge these traditional principles of urban water management. It is increasingly recognized that solutions to these challenges will not be purely technological in nature; the socio-institutional contexts will also be critical. However modelling tools to support medium and long-term strategic planning of integrated social and infrastructural dimensions are lacking, leaving decision-makers with untested policy ideas. To identify possible transition strategies to a resilient city, the development of the DAnCE4Water (Dynamic Adaptation for eNabling City Evolution for Water) within the EU FP7 project “PREPARED: Enabling Change” as a strategic planning and decision-support tool is thus proposed. DAnCE4Water allows ‘What-if’ experiments by investigating possible consequences of policies and strategic actions, taking into consideration urban development, climate change, biophysical environment and societal dynamics. This paper presents the concept of the DAnCE4Water tool and its application to an example city's evolution 20 years into the future.     

An integrated urban drainage system model for assessing renovation scheme

Due to sustained economic growth in China over the last three decades, urbanization has been on a rapidly expanding track. In recent years, regional industrial relocations were also accelerated across the country from the east coast to the west inland. These changes have led to a large-scale redesign of urban infrastructures, including the drainage system. To help the reconstructed infrastructures towards a better sustainability, a tool is required for assessing the efficiency and environmental performance of different renovation schemes. This paper developed an integrated dynamic modeling tool, which consisted of three models for describing the sewer, the wastewater treatment plant (WWTP) and the receiving water body respectively. Three auxiliary modules were also incorporated to conceptualize the model, calibrate the simulations, and analyze the results. The developed integrated modeling tool was applied to a case study in Shenzhen City, which is one of the most dynamic cities and facing considerable challenges for environmental degradation. The renovation scheme proposed to improve the environmental performance of Shenzhen City's urban drainage system was modeled and evaluated. The simulation results supplied some suggestions for the further improvement of the renovation scheme.     

Integrated Resource Planning for Water and Wastewater

Abstract

This paper describes the use of integrated resource planning for water and wastewater service provision by a major urban water utility. This methodology aims to meet the water and sewerage needs of the community at the least cost and includes an explicit analysis of the costs and benefits of measures that reduce the demand for water and the discharge of wastewater effluent. It therefore requires disaggregation of the demand for water into end-uses and a consideration of the linkages between the water supply and sewerage components of the business. This approach has significant advantages in economic, environmental, and social terms. The case study results indicate that significant investments in water efficiency programs are justified on economic grounds, particularly where augmentation of water and sewerage infrastructure is planned. Three studies undertaken as part of Sydney Water's efforts to integrate supply- and demand-side planning are described in this paper: first, a major integrated resource planning exercise designed to reduce demand for water by up to 35 percent, costing more than AU$25 million; second, a case study in a series of small towns where the benefits arise from reducing the capacity of sewage treatment plants by reducing wastewater flow; and third, in a major industrial region where water efficiency measures integrated with reuse measures reduce overall costs.