Showing papers in "Urban Water Journal in 2005"
TL;DR: In this paper, the authors present a literature review on different types of impermeable surface and their relative impacts on landscape hydrology, and describe the manner in which these surfaces are assessed for their putative impacts.
Abstract: Increased impervious surface area is a consequence of urbanization, with correspondent and significant effects on the hydrologic cycle. It is intuitive that an increased proportion of impervious surface brings with it shorter lag times between onset of precipitation and subsequently higher runoff peaks and total volume of runoff in receiving waters. Yet, documentation on quantitative relationships between the extent and type of impervious area and these hydrologic factors remains dispersed across several disciplines. We present a literature review on this subject to better understand and synthesize distinctions among different types of impermeable surface and their relative impacts, and describe the manner in which these surfaces are assessed for their putative impacts on landscape hydrology.
696 citations
TL;DR: In this article, an integrated approach to control of quantity and quality in water supply and distribution systems is proposed, which consists in optimising the operational cost, meeting a demand on water of desired quality and maintaining the system constraints.
Abstract: An integrated approach to control of quantity and quality in water supply and distribution systems is proposed. The integrated control consists in optimising the operational cost, meeting a demand on water of desired quality and maintaining the system constraints. This constrained optimising control problem is complex due to nonlinearities, large dimension, output constraints, mixed-integer structure of the variables involved, at least two time scales in the system dynamics and an uncertainty. A sub-optimal two-level hierarchical control structure is proposed that allows incorporating the desired controller functions and yet making the synthesis of these functions possible. The algorithms for implementing the functionalities are proposed and discussed. Detail design of the lower level controller is presented and investigated. The controller performance is validated by simulation.
47 citations
TL;DR: In this paper, a WSP was developed for the Kampala piped water supply in Uganda by the National Water and Sewerage Corporation (NWC) using risk maps.
Abstract: The World Health Organisation (WHO) promote the use of water safety plans (WSPs) in the 3rd edition of the Guidelines for Drinking-Water Quality (2004). WSPs place an emphasis on risk assessment coupled with risk management, with simple indicators to monitor process control and periodic verification through audit and microbial indicators. A WSP was developed for the Kampala piped water supply in Uganda by the National Water and Sewerage Corporation. The use of risk maps was found to greatly aid the identification of hazardous events in the distribution system. A validation exercise was performed that showed the WSP was properly designed. The study shows WSPs can be successfully developed for utilities in developing countries and offer significant cost savings in water quality control. Senior management endorsement was found to be essential to provide the authority to develop and implement the activities required for effective water safety management.
35 citations
TL;DR: In this paper, the authors synthesize the operational and structural barriers encountered across a diversity of sites, provide an understanding of how and why those barriers arose and propose a set of strategies through which those barriers can be addressed.
Abstract: Centralized waterborne sanitation faces serious social, economic and environmental sustainability challenges. Dry sanitation (DS) may ease some of those, but it is not known whether DS can be a viable solution at large scales and in urban settings. We assessed DS viability in a broad range of large scale and urban contexts in Mexico. Here, we synthesize the operational and structural barriers encountered across a diversity of sites, provide an understanding of how and why those barriers arose and propose a set of strategies through which those barriers can be addressed. We include reference to other large-scale and urban experiences outside Mexico.
32 citations
TL;DR: The development of such an SDSS based on fuzzy inference is discussed and techniques enabling the incorporation of both expert judgement and field evidence are described in an effort to address one of the main criticisms of linguistic (fuzzy) modelling: that of subjectivity.
Abstract: Spatial Decision Support Systems (SDSS) represent an attempt to assist in the decision making process by a set of intelligent, knowledge-based techniques and as such have an increasingly important role to play as the data required for spatially sensitive decisions become more available in a wide range of problem areas. The urban environment is a complex, spatially sensitive decision-making environment and as such an ideal case study for the application of these techniques and tools. Building knowledge into a system, particularly through linguistic modelling, is a challenge. This paper briefly discusses the development of such an SDSS based on fuzzy inference and describes techniques enabling the incorporation of both expert judgement and field evidence, where available, in an effort to address one of the main criticisms of linguistic (fuzzy) modelling: that of subjectivity.
31 citations
TL;DR: In this article, the authors reviewed the water quality problems that typically occur in distribution systems, the causes of these problems, and the modeling tools that are becoming available to help solve these problems.
Abstract: Drinking water quality can undergo dramatic changes in distribution systems. Because of this, many new regulations focus on monitoring water quality within the distribution system, causing utilities to face new challenges in maintaining high quality delivered to the consumer's tap. To help meet these challenges, several groups worldwide have developed computer-modeling tools so that utilities can evaluate and manage water quality in their distribution systems. This paper reviews the water-quality problems that typically occur in distribution systems, the causes of these problems, and the modeling tools that are becoming available to help solve these problems.
27 citations
TL;DR: In this article, stormwater pond sediments were collected from four stormwater ponds in Sweden and analyzed for heavy metal, water and organic material content, and sediment characteristics were evaluated, and differences between and within the ponds are presented and discussed.
Abstract: Stormwater pond sediments were collected from four stormwater ponds in Sweden and analysed for heavy metal, water and organic material content. The sediment characteristics were evaluated, and differences between and within the ponds are presented and discussed. An assessment of the water and sediment quality was also carried out. The results show that the metal content does not vary much between or within the ponds. The copper content is significantly higher than reported in earlier studies and copper is the critical metal for the ecological status of the ponds. The quality of pond sediment is comparable with sewage sludge or urban stream sediments.
25 citations
TL;DR: In this paper, the authors investigated the reproducibility of random daytime sampling of lead in water supply zones and concluded that such sampling is not suitable for differentiating the effects of water treatment, particularly in the optimisation stages.
Abstract: The random daytime sampling of lead in water supply zones has been proposed as the basis for optimising plumbosolvency control. This is because of its low cost, simplicity, efficiency and low customer burden. Extensive computer simulation, comprising a zonal lead emission model coupled to a sampling model, has been used to investigate this method of sampling, enabling far more comprehensive study than practical experimentation allows. The computer simulations have confirmed that random daytime sampling is not suitable for differentiating the effects of water treatment, particularly in the optimisation stages. It has also demonstrated the lack of reproducibility in such sampling.
20 citations
TL;DR: In this article, the applicability of using three-dimensional simulations as an engineering tool in stormwater pond design was investigated, and the agreement between measurements and simulations concerning both flow pattern and residence time distribution curves was found to be good for high flow rates.
Abstract: There are two main ways to obtain better knowledge of the hydraulics of ponds, namely measurements and simulations. In this study, the applicability of using three-dimensional simulations as an engineering tool in stormwater pond design was investigated. To do this, three-dimensional simulations were compared with measurements of flow pattern and residence time in a large physical model of a detention tank (13 × 9 × 1 m). The agreement between measurements and simulations concerning both flow pattern and residence time distribution curves was found to be good for high flow rates.
19 citations
TL;DR: In this article, the authors proposed a methodology based on the concept that the mitigation effects of distributed stormwater management practices can be expressed as a function of the changes of the hydrological parameters of a catchment.
Abstract: The urbanization process and the hydraulic insufficiency of drainage systems are two of the most common causes of urban flooding. In some technical regulations, distributed stormwater management practices (DSMPs) are regarded as a solution for urban flooding problems. They can prevent the formation of runoff, dispose of it locally, or dampen its peak before it reaches the drainage system. Due to their diffuse localization and the wide number of available solutions, the evaluation of their efficiency in terms of flood reduction is very difficult. The methodology proposed in the present paper relies on the concept that the mitigation effects of DSMPs can be expressed as a function of the changes of the hydrological parameters of a catchment. Once the relation between a DSMP and the equivalent hydrological parameter is established, the efficiency of DSMPs can be evaluated using mathematical models simulating the runoff formation and propagation in urban areas and applying methodologies similar to parameter s...
18 citations
TL;DR: On-site detention is a structural element of a property drainage system that limits the site discharge of stormwater using outlet restriction devices as mentioned in this paper, where excess stormwater runoff is temporarily stored on site in underground tanks or above-ground storage areas until the storm event recedes.
Abstract: Many countries are either currently using or considering the use of on-site detention (OSD) as a structural flood mitigation method. On-site detention is a structural element of a property drainage system that limits the site discharge of stormwater using outlet restriction devices. The excess stormwater runoff is temporarily stored on site in underground tanks or above-ground storage areas until the storm event recedes. Sydney, Australia, has a stormwater system that is completely separate from the sewerage system. The stormwater systems are mainly managed by the 43 local councils and most of these use OSD as a means of reducing site discharge of stormwater, thereby relieving catchment flooding. Sheas Creek is an urbanized catchment that lies within the South Sydney City Council Local Government Area. Since 1984 an OSD policy has been implemented in the Sheas Creek catchment. The associated design code, like most others in Sydney, is based on discharge from individual properties without consideration of ...
TL;DR: In this article, the authors analyzed user acceptance and satisfaction with dry toilets in five Mexican cities and found that when toilets functioned well, users were highly satisfied with them and that satisfaction was positively associated with motivation, choice and adequate support services.
Abstract: Dry sanitation (DS) may be part of the solution to water scarcity, water quality deterioration and lack of resources to provide or maintain waterborne sewage systems. However, the worldwide paucity of large-scale, urban case studies makes assessment of DS as a potential urban water management strategy difficult. Urban DS viability depends in part on urban users' satisfaction with dry toilets (DTs) and whether they would accept them as long-term sanitation options. We analyze user acceptance and satisfaction with DS in five Mexican cities. When toilets functioned well (four out of five sites), users were highly satisfied. Similar levels of satisfaction were found under conditions of different DT models, types of DS program and income-level of the population. User motivation, choice and adequate support services were positively associated with satisfaction. Incentives such as indoor, aesthetic DTs, maintenance and end-product collection services, as well as higher water supply pricing, would encourage peopl...
TL;DR: In this paper, a review of the state-of-the-art knowledge in modeling water quality in distribution systems is presented, focusing on simulation, optimization, chlorine control, monitoring, and water security modeling in multiquality water distribution systems.
Abstract: The objective of this paper is to review the state of the art knowledge in modeling water quality in distribution systems and to suggest future research needs in this area. Multiquality water distribution systems (MWDS) are systems in which waters from different qualities are taken from sources, possibly treated, conveyed and supplied to the consumers. In addition to the hydraulic laws which describe the system behavior, equations that describe the water quality in the system are added. The consumers' demands are for quantity, pressure, and quality. The review is focusing on simulation, optimization, chlorine control, monitoring, and water security modeling in MWDS.
TL;DR: In this article, the results of a monitoring program carried out to study the washoff of various pollutants from impermeable road surfaces by the runoff produced under artificial and real rainfall conditions were presented.
Abstract: This paper presents the results of a monitoring programme carried out to study the washoff of various pollutants from impermeable road surfaces by the runoff produced under artificial and real rainfall conditions. Among the pollution parameters analysed are solids (total, suspended and total volatile), COD (chemical oxygen demand), ammonium and heavy metals (lead, copper, zinc and iron). Analysis of the results indicates a linear relationship between the mass loading rate of total solids, volatile solids and COD. The effect of runoff rate on the magnitude of pollution washed off has also been investigated. Particle size analysis, of the washoff solids shows that the predominant size fraction is < 50 μm. The average diameter of solids has been found to increase with an increase in the runoff rate.
TL;DR: In this paper, a stormwater treatment plant, consisting of a detention pond, a constructed filter system and a constructed wetland, has been investigated according to stormwater quality improvement, sediment and heavy metals accumulation and potential toxicity of the stormwater and sediment.
Abstract: A stormwater treatment plant, consisting of a detention pond, a constructed filter system and a constructed wetland, has been investigated according to stormwater quality improvement, sediment and heavy metals accumulation and potential toxicity of the stormwater and sediment. The reduction of metal content in the detention pond was on average 26 – 84%. No acute toxicity in the stormwater was detected although heavy metal levels often exceeded guideline values during storm events. Pore water samples of the collected sediments were not toxic but the whole sediment was toxic when assessed with the Microtox® Solid-phase test. The constructed filter system became clogged due to cementation of the filter substrate.
TL;DR: In this article, a GIS-based simulation and management system, which refers to a conventional combined sewerage (wastewater and stormwater) flow model, has been developed for use in the Sindang drainage district of Seoul.
Abstract: A GIS-based sewerage flow simulation and management system, which refers to a conventional combined sewerage (wastewater and stormwater) flow model, has been developed for use in the Sindang drainage district of Seoul. The system is designed for times when wastewater and stormwater are discharged via the same drainage pipe network and sewerage treatment works, the latter being bypassed during rain storm events and after high discharge events (e.g. a thaw after heavy winter snow). A chain topology generator was developed and deployed in collaboration with relational database spatial search and retrieval functions integrated by expert knowledge. Sewerage flow volume simulations for all pipelines allowed the calculation of preferable pipe sizes for calculated volumes under assumed conditions and thus the identification of pipes most prone to cause flooding if sewerage flow volumes increase due to redevelopment/population increase. The potential to produce information that can be used in decision-making suppo...
TL;DR: In this article, an integrated approach, along with an interactive database analyser, is proposed to better explain water quality problems occurring in distribution systems (DS) by considering various types of data, on multi-criterion database queries and on data visualisation, which facilitates the analysis and identification of the probable cause (or causes) of the problem.
Abstract: The identification of causes of water quality problems in distribution systems (DS) is often a difficult task because of the wide variety of factors that may be involved in describing their origin and propagation (treatment breakthrough, intrusion, transport, microbial regrowth, etc.). An integrated approach, along with an “interactive database analyser”, is proposed to better explain water quality problems occurring in DS. The approach is based on the consideration of various types of data, on multi-criterion database queries (investigation of DS events within specific spatial, hydraulic and temporal frames) and on data visualisation, which facilitates the analysis and identification of the probable cause (or causes) of the problem.
TL;DR: In this article, the authors investigated one type of manmade substrate, stormwater conduit, commonly used to transport stormwater away from buildings, and found that pipe made of PVC and cast iron did not significantly remove copper from a synthetic stormwater spiked with copper averaging 2391μg Cu/L.
Abstract: Architectural applications of copper on roofs, gutters and facades exposes it to weathering forces, such as wind and all forms of precipitation. This leads to the dissolution of copper from these surfaces and its introduction into local watersheds. The potential for exposure in local watersheds is a function of the amount of copper entering the watershed and the assimilation capacity of a wide variety of natural and manmade substrates that transform and sequester copper, thus reducing exposure of sensitive organisms to bioavailable copper. This study investigates one type of manmade substrate, stormwater conduit, commonly used to transport stormwater away from buildings. Conduits made of PVC and cast iron did not significantly remove copper from a synthetic stormwater spiked with copper averaging 2391 μg Cu/L. Concrete conduit significantly removed copper from the synthetic water and at high rates (12 – 18%) over a short distance (610 cm). A high percentage (81 – 100%) of the copper removed from the water...
TL;DR: The main issue raised in this article is how authorities can support an everincreasing poor population with water and at the same time keep demand among households with private water connections at a reasonable level.
Abstract: Urban water management in the southern cities of Namibia is composed through both a formal and an informal system. In the formal system, controlling demand is the key issue, and in the informal system, an improved accessibility to water is fundamental. The main issue raised in this paper is how authorities can support an ever-increasing poor population with water and at the same time keep demand among households with private water connections at a reasonable level. To decrease the demand for water in Windhoek, a thorough water demand management strategy (WDM) was launched in 1994. Water managers showed a high level of adaptability to the alarming water situation. One of the lessons learned from the implementation in Windhoek is that dedicated people with active involvement and vision are important for successful WDM. The budget must be allocated on a continuous basis for the implementation of certain WDM measures and a degree of flexibility among water users is important for the strategy to be successful....
TL;DR: The first flush phenomenon was typically observed for sampled CSO events and first flush control may be effective in reducing receiving water impacts as mentioned in this paper, and the Weibull and lognormal distributions best fit the event mean concentration data and could be used to assess contaminant loading variability.
Abstract: Levels of total metals (Pb, Cu, Zn, Cr, Ni) from samples in Buffalo, NY, were generally higher in combined sewage than sanitary flow. Sewer separation should therefore be considered carefully when choosing combined sewer overflow (CSO) abatement options. The first flush phenomenon was typically observed for sampled CSO events and first flush control may be effective in reducing receiving water impacts. Event mean concentration is often used for runoff quality evaluation, without consideration of concentration variability. The Weibull and lognormal distributions best fit the event mean concentration data and could be used to assess contaminant loading variability.
TL;DR: In this paper, the removal of heavy metals from storm and surface waters by slow sand filtration is described and the importance of speciation as a technique for exploring and improving the mechanisms of removal is identified.
Abstract: The removal of heavy metals from storm and surface waters by slow sand filtration is described. The importance of speciation as a technique for exploring and improving the mechanisms of removal is identified. Laboratory-scale slow sand filters operating at conventional flow rate and depth were shown to be able to reduce concentrations of selected heavy metals (Cu, Cr, Pb and Cd) found in road runoff, surface water and sewage effluents to drinking water standard. Nitrogen, volatile solids and modified Stover speciation were used to differentiate between the potential mechanisms of removal, i.e. active biomass, organic adsorption and simple adsorption or precipitation on the surface of the sand. The data presented show that adsorption via organic ligands was the predominant mechanism for metal removal at the surface of the filter but chemical adsorption was the more important deeper in the filter. In the lower layers the adsorbed metals were more easily exchanged than the organically bound metals. The preci...
TL;DR: In this article, the authors investigated the impacts of water quality changes in urban rivers caused by storm water sewer overflows (SWO) and combined sewer overflow (CSO) in order to define hydrological assessment criteria to guide sustainable water management strategies as required by the European Community (EC) Water Framework Directive.
Abstract: In addition to assessing the impacts of water quality changes in urban rivers caused by storm water sewer overflows (SWO) and combined sewer overflows (CSO), the extent to which flow dynamics are changed by these structures must be understood in order to define hydrological assessment criteria to guide sustainable water management strategies as required by the European Community (EC) Water Framework Directive In this study, the quantitative impacts of SWOs and CSOs on the flow dynamics of an urban river and their variability are investigated For four single runoff events, hydrological measurements were accomplished in the River Dreisam, upstream and downstream of the city of Freiburg, in southwest Germany As the catchment is widely free of urban areas upstream of the city, comparison with downstream locations allowed quantification of Freiburg's effects on the changes in the hydrograph on an event scale The proposed hydrological parameter—flow acceleration, peak discharge, and discharge dosage—were sh
TL;DR: In this article, an approach to predicting regrowth potential with the objective of helping utilities in the preliminary selection of alternative treatment scenarios is presented. But the proposed approach comprises four phases: (i) applying, at bench scale, different types of treatment to a raw water to obtain treated waters to be tested for their regrowth, (ii) applying an experimental procedure to the various treated waters which consists of the study of bacterial growth during a Biodegradable Dissolved Organic Carbon (BDOC) test; (iii) partitioning BDOC into three classes of various biodegradability
Abstract: The treated water Biodegradable Organic Matter (BOM) content is one of the main factors controlling bacterial regrowth in Distribution Systems (DS). This paper presents an approach to predicting regrowth potential with the objective of helping utilities in the preliminary selection of alternative treatment scenarios. The proposed approach comprises four phases: (i) applying, at bench scale, different types of treatment to a raw water to obtain treated waters to be tested for their regrowth potential; (ii) applying an experimental procedure to the various treated waters which consists of the study of bacterial growth during a Biodegradable Dissolved Organic Carbon (BDOC) test; (iii) partitioning BDOC into three classes of various biodegradability compounds by fitting the bacterial growth curve with a biodegradation model; (iv) using the BDOC and partitioning data to simulate bacterial growth in a DS with a model describing bacterial dynamics in the DS. The various phases of the approach are detailed using ...
TL;DR: In this paper, the authors present a water resources management plan for the city of Volos' watershed, where the main objective is the choice of the best set, among others, of hydraulic projects, which will be able to re-establish the balance in the basin's deficient water budget, satisfying at the same time future urban water demand.
Abstract: The implementation of sustainable development principles in water resources management refers to an integrated management and coordination of the entirety of the actions and interventions that concern the water ecosystem, or parts of it, within a watershed. This procedure is accomplished through the development and application of an overall management plan at a hydrological basin level. This concept was followed by the water resources management plan of the city of Volos' watershed, which is presented in this paper. The main objective is the choice of the best set, among others, of hydraulic projects, which will be able to re-establish the balance in the basin's deficient water budget, satisfying at the same time future urban water demand. Decision making was carried out using a GIS tool and involved traditional water capture hydraulic projects on the one hand and sustainable water saving measures on the other. The whole procedure is being developed in an area with serious environmental problems, concerni...
TL;DR: Yeasts growing in river waters contaminated with tannery wastes and to determine if one or several yeast species are possible candidates to remove chromium and polyphenols present in such wastes and Debaryomyces hansenii was the major species were identified.
Abstract: Field and laboratory investigations were carried out in Fes, Morocco to identify yeasts growing in river waters contaminated with tannery wastes and to determine if one or several yeast species are possible candidates to remove chromium and polyphenols present in such wastes. Samples of river water were collected from 22 sites contaminated with tannery wastes and four sites not polluted with tannery wastes. Fifteen yeast species were identified in the sites polluted with tannery wastes and Debaryomyces hansenii was the major species. High values of electrical conductivity, inorganic and organic matter in suspension, salinity, ammonium ions, chlorides, chromium, nitrates, sulphates and polyphenols were found in waters collected from these sites. By contrast, in the four sites not polluted with tannery wastes, 14 yeast species were identified and five belonged to the Candida genus. D. hansenii was not recovered in these last sites. Because of its high frequency in waters polluted with tannery wastes, the ab...