Urban Water最新文献

An application of stochastic simulation for the reliability analysis of single and multiquality water distribution systems (MWDS) is formulated and demonstrated. MWDS refers to systems in which waters of different qualities are taken from sources, possibly treated, mixed in the system, and supplied as a blend. The stochastic simulation framework was cast in a reliability analysis program (RAP), based on EPANET, and quantifying three reliability measures: the fraction of delivered volume (FDV), the fraction of delivered demand (FDD), and the fraction of delivered quality (FDQ). RAP is demonstrated on two example applications: a simple illustrative, and a more “real-life” complex one. The results quantify the reliability of the systems and provide lower bounds for the reliability measures adopted.

To improve the efficiency of storm drainage networks, many local authorities have invested in network upgrading projects. Many upgrading alternatives can be generated for a given problem. It is the designer's responsibility to choose among the available alternatives. The main objective of the upgrade designs is to reduce flooding of urban areas during extreme storm events. This paper presents an expert system based on fuzzy inference to evaluate the sensitivity of urban areas to network failure. The produced results allow the designer to classify various network upgrading alternatives according to their impacts on urban areas and to introduce this order in a multi-criteria method. A practical application of the expert system is given and its applicability is discussed.

There is an increased attention on integrated analysis of sewer network, wastewater treatment plant (WWTP) and receiving waters. Its objective is to derive new strategies for an ecologically and economically optimised protection of receiving waters. Simultaneous numerical simulation of discharges from the sewer network and the WWTP is necessary if interactions between the subsystems are important and/or if integrated control is to be investigated. This paper presents an application of numerical models running under MATLAB™/SIMULINK™ for an integrated analysis of sewer network and WWTP in Odenthal, Germany. The simulation tool is a combination of the modules PLASKI for wastewater production, SIMBA^® sewer for transport processes in the sewer system and SIMBA^® for biological wastewater treatment. Results of the study show that the application of this tool is suitable for testing control strategies in real urban wastewater systems. The application of control strategies offers ways to reduce the pollutant load to receiving waters especially by eliminating small discharge events and giving priority to most polluted water for treatment and storage.

Results of a material balance for nitrogen and phosphorus for Austria will be shown as one example for the use of regional material balances in water quality management. Nutrients in wastewater stem from food and thus from agricultural production to a high extent. The use of sewage sludge from wastewater treatment plants recirculates a part of these nutrients into agriculture. Phosphorus removal at treatment plants is an important step for the improvement of sludge quality. Problems with the reuse of sewage sludge are related to the content of potentially hazardous substances (e.g., heavy metals) in the sludge. Strategies for reduction of heavy metal loadings of sewage sludge have to consider all different sources. As shown in a second example diffuse sources (e.g., corrosion of roofings) highly influence the heavy metal contents of sewage sludge. Additionally, the input of heavy metals via coagulants for phosphorus precipitation must be considered.

The composition of grey wastewater depends on sources and installations from where the water is drawn, e.g. kitchen, bathroom or laundry. The chemical compounds present originate from household chemicals, cooking, washing and the piping. In general grey wastewater contains lower levels of organic matter and nutrients compared to ordinary wastewater, since urine, faeces and toilet paper are not included. The levels of heavy metals are however in the same concentration range. The information regarding the content of xenobiotic organic compounds (XOCs) is limited. From this study, 900 different XOCs were identified as potentially present in grey wastewater by the use of tables of contents of household chemical products.

The occurrence of two herbicides (diuron and simazine) in receiving surface waters is related to their seasonal applications within an urban catchment. Comparisons of herbicide concentrations within baseflow and during rainfall conditions provide an insight into pollutant transport processes following application to urban surfaces. Two storm events, with different hydrological characteristics, are described. The maximum recorded herbicide concentrations reached 238.4 and $\text{2.23}\text{μg}\text{/}\text{l}$ for diuron and simazine, respectively, with the former corresponding to an application loss of 45.1% with respect to the diuron recently applied to the urban catchment. The factors influencing the extent of application losses to receiving waters of herbicides applied to urban substrates are discussed.

Many of the wastewater collection systems in the USA were developed in the early part of the last century. Maintenance, retrofits, and rehabilitations since then have resulted in patchwork systems consisting of technologies from different eras. More advanced and cost-effective methods to properly rehabilitate these systems must be considered to guarantee sustainability into the future. Achieving sustainable development presents a challenge to deliver new and innovative infrastructure and facilities needed to serve society while protecting the environment. In the context of this paper, sustainable development would provide new and improved solutions to existing and emerging problems associated with wastewater collection system infrastructure. Such solutions would, for example, include consideration of innovative approaches and practices for identifying and rehabilitating problems in existing systems and ways of preventing these problems in new construction. The paper focuses on technical issues and research needs in three major areas: (1) assessment of system integrity; (2) operation, maintenance, and rehabilitation; and (3) new construction. Many of the issues and needs discussed were identified at a USEPA sponsored experts workshop on infrastructure problems associated with wastewater collection systems.

The effect of source control measures on the design of combined sewer systems can in most cases only be correctly assessed using the intrinsic temporal rainfall variability, because long antecedent periods can have an important influence. A conceptual model was built to assess the effect of rainwater tanks on the rainfall runoff using long term historical rainfall series. The outflow of the rainwater tank model is converted to equivalent rainfall series. Based on intensity/duration/frequency-relationships (IDF-relationships) for this equivalent flattened rainfall, modified design storms are developed.

Environmental costs and benefits are increasingly required to be integrated within economic analyses of project options in the water industry in the UK and elsewhere. This paper considers the inclusion of environmental valuations within economic level of leakage (ELL) calculations. It reviews how valuation methodologies have been incorporated in the ELL in the UK, and discusses ways in which this process may be improved in practice.

For urban water supplies, many a times water often has to be conveyed to great heights over a relatively short distance. On account of development of large pressure heads, pumping cannot be done in a single stage, and one has to resort to multistage pumping. In the present design practice the number of pumping stages are decided on an ad hoc basis and the pumping main in the intervening stages is designed as a single pumping main. Such a design is a suboptimal design. Presented herein are the explicit equations for the optimal number of pumping stages, the pumping main diameter, and the corresponding cost. It is hoped that the equations are useful to a design engineer.