Urban Water最新文献

The in-service strength degradation, as a result of corrosion, of cast iron water distribution pipes has been investigated. The strengths of 1 m lengths of pipe extracted from the ground have been measured in either 3- or 4-point bending and the size of the controlling defect has been estimated by visual examination of the fracture surface. The application of Weibull statistics to the bend test data demonstrates that there is bimodal behaviour which suggests that there are two populations of flaws present. It is postulated that the larger flaw size population is associated with corrosion pits that form during the process of graphitisation, while the smaller flaw size population is associated with the inherent flaws within the (brittle) cast iron pipe material. A critical pit depth is identified at the transition between the two competing flaw populations, where there is a change in slope on the Weibull plot. It is shown also that the residual strength/pit depth data are described equally well by either of the two conventional analyses, i.e. loss of section and fracture mechanics.

Recent environmental regulations imply the need for optimisation of wastewater treatment and, therefore, a need for tools providing quantitative and qualitative information about urban wastewater characterisation and evolution. This work presents simple methods developed for UV spectra exploitation, namely direct comparison, spectra differences and normalisation. Simple comparisons of spectra helped understand the UV physical response of total suspended solids and enabled to check wastewater quality conservation. The investigation of the various size range fractions of samples from different origins enables the proposal of a typology of these fractions taking into account organic matter origin, its stability, the part of inorganic particles and weather conditions.

Combined sewer systems in Slovakia were evaluated during a three-year joint research project of the Water Research Institute and the Department of Sanitary Engineering of the Slovak University of Technology. First results of the comprehensive assessment are presented in the paper. Over 300 combined sewer overflows (CSOs) were visited and their structural condition evaluated. Samples of overflowing water were taken from eight overflows and analysed for common constituents. A water quality database was prepared from the CSO pollution data. The first flush of organic pollution was not confirmed in any of the events.

This paper describes conceptual and practical aspects of urban storm drainage performance indicators, based on the authors' experience in developing countries, particularly India. The paper begins by presenting a general framework of objectives and performance indicators as logical intermediate steps between values and the decisions taken to reflect them. The paper then considers practical approaches to performance and indicator measurement, based on field experience in India. General conclusions about drainage performance indicators are then presented, stressing the challenge of finding indicators which are (1) valid indicators of performance, (2) relatively easy to measure, and (3) helpful to the decision-maker.

Sustainability challenges us to reflect on wastewater treatment differently. Instead of focussing on end-of-pipe-treatment for emission prevention, attention shifts towards optimal resource utilisation, favouring the development of decentralised systems. But are these systems more sustainable than centralised wastewater treatment systems? What aspects determine sustainability? In an extensive literature review we give an overview of sustainability assessment methods and currently used indicators. Based on this we propose a general assessment methodology that builds on multi-objective optimisation and a complete set of sustainability indicators, yielding insight into the trade-offs made when selecting sustainable wastewater treatment systems.

The Department of Public Works for the city of Rotterdam manages a complex urban drainage system. The system consists of 30 catchments, collects wastewater discharged by 30 pumping stations, to a total of five treatment plants (1.1 million equivalent population). At present control of all these pumping stations is being centralised. To assess the benefits of central control, a performance index (PI) was developed to classify the actual performance of the system under control, during dry weather conditions and during storm events. The PI is composed of deterministic and heuristic indicators that reflect the quality of the control with respect to different objectives set for the entire water system.

In a case study the PI was computed for several historic events and showed encouraging results in different modes of control for both dry weather and storm conditions. From the results it can be concluded that the technology described in this paper can help to identify points that need performance improvement in the urban water system in general and in the way it is controlled specifically.

Environmental sustainability is a concern and stated objective for municipalities and organisations, but is often vaguely defined and clear measurement procedures are lacking. An iterative procedure for the selection of indicators, which reflects the environmental sustainability of urban water systems, is presented. The analytical basis for selecting indicators is life cycle assessment (LCA), which provides a stringent assessment of environmental sustainability. The indicators were evaluated in Case Studies in a developed and a developing region. The iterative procedure allows refinement/replacement of indicators through Case Studies and further LCA.

Performance indicators play an increasing role in the design and the operation of urban drainage systems. However, uncertainties linked to both calculation of performance indicators and their use in decision-aid tools and methods have been rarely accounted for. Two case studies concerning stormwater facilities are presented in this paper. The first one concerns the effect of sampling and analytical uncertainties on the evaluation of a single performance indicator defined as the annual interception efficiency of a stormwater storage and settling tank. The second one is related to the effect of modelling uncertainties on the evaluation of several performance indicators and on their impact as regards the choice of maintenance strategy of a stormwater infiltration tank. Both cases show that uncertainties are very significant and shall be accounted for in the calculation and the use of performance indicators.