Urban Water最新文献

This work presents a review of applicable sewer rehabilitation options using trenchless technology in Malaysia. The typical problems faced in wastewater collection systems are analysed and factors that determine the selection method are outlined. This study also highlights the necessary steps to be taken prior to the rehabilitation work. The trenchless technology reviewed here comprises repair, renovation and replacement options. The cost-effectiveness of different rehabilitation methods was identified to assess the economic viability of various options in the Malaysian context. This study reveals that not all the trenchless technologies available in the market are suitable for use in Malaysia, mainly due to incompatibility of the rehabilitation materials used. Furthermore, as trenchless rehabilitation generally involves higher capital outlay than open-cut methods, the choice of rehabilitation method has to be made on a case-to-case basis.

The raw sewage volume potentially discharged from a sewer network to the environment arising from its component failures is proposed as a measure of overall system reliability. This paper presents a simple method for quickly and properly calculating this volume. The basis for this method is a representation of the sewer network by a combination of Y-like fragments named here as structure-forming elements. Each such element is formally substituted by a fictitious equivalent sewer with a failure rate leading to the same output for the same input. A sequential application of this approach reduces the problem of estimating the discharged sewage volume to elementary subproblems for which the solution is simple. Examples are used to demonstrate the possibilities of this method.

Land cover information suitable for urban drainage modelling is acquired by airborne remote sensing. The scanner used is a line scanner that scans continuously while the aircraft flies forward recording 11 bands of the electromagnetic spectrum. This is classified by first segmenting the image into approximately homogeneous polygons using a Marr–Hidreth edge detector. These polygons are then classified into roofs, paved areas and permeable land. Rigorous accuracy tests are applied to the classified imagery, which shows that this method gives better results than any of those currently used. Dawn thermal imagery was not used in this study.

Reliability analysis of water distribution systems is a complex task. A review of the literature reveals that there is currently no universally acceptable definition or measure for the reliability of water distribution systems as it requires both the quantification of reliability measures and criteria that are meaningful and appropriate, while still computationally feasible. This paper focuses on a tailor-made reliability methodology for the reliability assessment of regional water distribution systems in general, and its application to the regional water supply system of Nazareth, in particular. The methodology is comprised of two interconnected stages: (1) analysis of the storage–conveyance properties of the system, and (2) implementation of stochastic simulation through use of the US Air Force Rapid Availability Prototyping for Testing Operational Readiness (RAPTOR) software.

This paper describes a statistical analysis of the structural condition of rigid sewer pipes. The aim of the study was to identify the factors that have most influence on a sewer's structural condition. A statistical investigation, in the form of a logistic regression analysis, was performed on an extensive data set that combined a number of previously disparate data sources. The study would suggest that there are a large number of variables which are significant in assessing the risk of a sewer collapsing or deteriorating to such an extent that collapse is likely. The analysis described contributes significantly to the small amount of work of this nature previously completed.

During a survey of the contamination of soils receiving sewer water/industrial wastewaters, we identified two sites, one with limited plant growth and containing 2290 mg Ni and 40 mg Cd kg⁻¹ (contaminated soil) and another with good plant growth and containing 26 mg Ni and 2 mg Cd kg⁻¹ soil (uncontaminated soil). Various Ni levels ranging from 26 to 2290 mg kg⁻¹ were created by mixing contaminated and uncontaminated soils in different proportions to study the influence of Ni content of soil on microbial biomass, urea hydrolysis and nitrogen transformations. Soil microbial biomass decreased with increasing levels of Ni and Cd in soil. Urea hydrolysis was faster in uncontaminated soil (65% within 12 h in soil containing 26 mg Ni $\text{kg}{}^{\mathrm{-1}}$) compared to contaminated ones (41% within 12 h in soil containing 2290 mg Ni kg⁻¹). The values of first-order rate constant for urea hydrolysis (k) were higher in uncontaminated soil as compared to Ni contaminated soil. The NH₄⁺–N content increased up to 14 days of incubation in soil containing Ni >1230 $\text{mg}\text{kg}{}^{\mathrm{-1}}$ and decreased thereafter, however, in other soils it decreased with increasing incubation period. The NO₃⁻–N content increased with increasing incubation period irrespective of the Ni content of the soil. These results indicate that soils containing excessive concentration of toxic metals (Ni, Cd) may decrease the microbial biomass and also lead to leaching losses of urea owing to delayed hydrolysis.

The efficiency of real time control (RTC) to decrease storm overflows from combined sewers to receiving waters was demonstrated in several case studies. Global predictive control (GPC), an effective strategy to perform real time management of sewers, requires simulation models to anticipate the future state of the system (flow rates and water levels). To compute these predictions, a hydraulic model using an implicit discretization scheme to solve simplified continuity and momentum equations was developed. The performance of the model is evaluated by comparison with the USEPA EXTRAN model results. This comparison shows that the model gives results similar to those of the EXTRAN model, with the advantage of producing faster and more stable results regardless of space and time steps used. Additional validation with the SUPERLINK model is also presented.

This paper presents an overview of the US Environmental Protection Agency's (EPA's) wet-weather flow (WWF) research program. Research priorities for 2001 are presented. In 1996, EPA issued the “Risk Management Research Plan for Wet Weather Flows”, a plan that presents specific WWF problems and anticipated research approaches to solve them. Within each area, the state-of-the-art knowledge is presented and the unknowns cited; research questions to address the unknown are also posed. In the time since November 1996, other organizations, notably the Water Environment Research Foundation (WERF), have reviewed WWF research programs and developed associated research needs reports.

Municipal activities continuously change soil properties and hydrology yet direct destructive sampling to monitor these changes is troublesome in urban areas. Electrical geophysical methods provide the means to investigate hydrological conditions and subsurface properties without soil disturbance. Methods of self-potential, electrical profiling, vertical electrical sounding, and non-contacting electromagnetic profiling were applied to urban soils in Astrakhan', Russia, and Kiev, Ukraine. Depth to the groundwater table, salinity of soils and groundwater, and soil profile organization were estimated with the methods. The methods ensure quick yet non-destructive estimation of soil and hydrological conditions in cities assisting with successful restoration and preservation of municipal constructions.