Uncertainty in Design and Management of Sewer Systems

Copyright: © 2013 Liserra T, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Loads acting on urban drainage systems are intrinsically uncertain and often known with limited details given their physical complexity. External loads include climate variables (rain, snow, temperature ...), which have a naturally mutable behaviour, exacerbated by climate change. Other system variables, such as roughness of surfaces and soil permeability, are normally unknown and only partially measurable. Additional sources of uncertainty derive from the transposition of the physical system into numerical models, routinely used to make predictions about real systems and their design and management

Direct Simulation of Micro-Component Water Consumption for the Evaluation of Potential Water Reuse in Households

A study on water/energy balances at the household scale is performed using Life Cycle Assessment (LCA) to estimate Greenhouse Gas (GHG) emissions and impacts resulting from multiple scenarios incorporating various options for: (i) component sizing, (ii) energy usage, and (iii) water reuse. Sustainability indicators are evaluated to select feasible options, while reducing whole life cycle GHG emissions. Water reuse schemes using rainwater are strongly dependent on rainfall availability and require significant tank volumes. Schemes using only gray water are more compact but more energy for treatment is needed before usage. Schemes obtained by combining both options perform better in terms of reliability and sustainability

Risk Based Analysis For Assessment Of Integrated Urban Water System Watermet2 Model: A Case Study Of Oslo

Integrated urban water systems (IUWSs) generally comprise the components related to both water supply and waste water systems. These components are subject to uncertainty in terms of operation, management and information. Hence, assessment of strategies in the IUWSs over the planning horizon should include such a risk analysis of these uncertainties. Owning to the complexity of these risks, a comprehensive risk assessment tool needs to be developed. In this paper, a risk assessment tool is presented to support the evaluation of intervention strategies in an IUWS over a planning horizon. The IUWS is modelled by “WaterMet2” which is a simulation, deterministic and quantitative IUWS model and is able to quantify the principal water flows and other main fluxes in the IUWS. Risk assessment tool is connected to WaterMet2 model to analyse risk based criteria in the IUWS model. The developed approach is demonstrated through its application to the assessment of the intervention strategies for the IUWS of Oslo city in Norway over a 30-year planning horizon. The intervention strategies analysed here include \u27business as usual\u27, addition of new water resources, increased rehabilitation rates and a number of water demand schemes to improve the performance of the Oslo UWS. The assessment criteria are split into two categories of risk based and non-risk based criteria. The former is quantified by the WaterMet2 model whilst the latter is quantified by risk assessment tool. This tool recognises the relevant likelihood of occurrence for a risk in a component. The severity of impact of the risk is quantified by multiple WaterMet2 runs. The results, when compared to those without risk assessment criteria, show how much preferences the analysis can envisage once risk is involved in the assessment. This would help planners to make more robust decisions for the future of IUWSs

Advice to water management practitioners on competition, efficiency and new business opportunities

The water sector faces several challenges, which may demand a rethink of several important aspects within historically grown, traditional business models. The need for cost-effectiveness and the lack of public funding goes along with the emergence of new business opportunities. Under consideration of customer preferences, the competitive environment and the disassembling of the value chain, new business and organisational models to exploit service and technology niches are reviewed and recommended (e.g. based on price or product differentiation). This advice for water management practitioners shall help to ensure an adequate handling since competitive environment is establishing in the water sector. Therefore, the identification of the current level of efficiency within a utility as well as concrete measures for efficiency improvement are becoming increasingly important. Within this report special focus is placed on the role of business niches as well as on the possibilities of implementing business innovations. In this context, the design of enterprise-specific business models and its chances will be discussed.Hoffjan, A.; Müller, NA.; Di Federico, V.; Liserra, T. (2014). Advice to water management practitioners on competition, efficiency and new business opportunities. http://hdl.handle.net/10251/4662

Financial sustainability rating tool for urban water systems

Solid financial position of water and wastewater utilities builds the basis for their sustainable services in the future, because it allows adequate investments into infrastructure renewal, technical innovations and ecological measures. The Financial Sustainability Rating Tool (FSRT) offers water supply and/or wastewater removal companies an opportunity to rate the utility's financial sustainability. It gives the user an indication, which area from financial situation over asset management to business operation needs optimization. The Tool also evaluates different forecasts (e.g. population development) and country specific characteristics (e.g. inflation rate) to assess future trends. Barometers with green to red indicators for each area as well as overall scores visualize the results of the web based rating. The Tool aims not to denounce a utility against others or to test its creditworthiness, but to encourage utilities to identify critical areas with respect to a solid financial position and to be open-minded for improvement actions. Accordingly, it has set itself the goal to uncover economic deficits and/or best practises to show the user where potentials for development are and which financial strategies are already viable for the future. To achieve meaningful results the Tool is directed at utilities, which provide either only one of the two services or are able to split up the information and costs related to each service.Hoffjan, A.; Di Federico, V.; Liserra, T.; Müller, N. (2014). Financial sustainability rating tool for urban water systems. http://hdl.handle.net/10251/3573

Performance indicators in water distribution systems aggregated by means of bayesian networks

The current arrangement of the water distribution systems, both at a national and at an international level, makes it necessary an evaluation of the different distribution networks. This has encouraged the development of different comparison techniques. Among them, an undoubtfully fundamental instrument is represented by the Performance Indicators (PI). The PIs can be defined as a quantitative measurement of a particular aspect of a company performance or service qualitative standard. Relatively to the issue of water supply system losses, the industry's literature offers various groups of consolidated and widely-applied indicators, though none of them may be considered to be completely exhaustive in both methodology and completeness. The analysis of the different groups of indicators suggests the need for an integration and homogenization of these groups, in order to identify a common methodology capable of finding and monitoring the different aspects of the problem. This process has underlined the necessity of identifying a procedure to organize the evaluation of the performance at different scales, and thus at different levels, according to the Observatories' strategies involved into the evaluation. In this paper, a bayesian model of evaluation is described and is applied to a district of the water distribution network of the Modena city

Direct Simulation of Micro-Component Water Consumption for the Evaluation of Potential Water Reuse in Households

A study on water/energy balances at the household scale is performed using Life Cycle Assessment (LCA) to estimate Greenhouse Gas (GHG) emissions and impacts resulting from multiple scenarios incorporating various options for: (i) component sizing, (ii) energy usage, and (iii) water reuse. Sustainability indicators are evaluated to select feasible options, while reducing whole life cycle GHG emissions. Water reuse schemes using rainwater are strongly dependent on rainfall availability and require significant tank volumes. Schemes using only gray water are more compact but more energy for treatment is needed before usage. Schemes obtained by combining both options perform better in terms of reliability and sustainability

Water loss dynamic control by Automatic Meter Readings in water distribution network

Nowadays the right evaluation of water losses is one of the more interesting aspects in water networks management. Water saving is necessary in order to reduce both water and energy waste for environmental and economic purposes. Remote monitoring systems are able to read users’ water meters and it is possible to use this feature for a dynamic water balance, and also it is an excellent starting point for a water losses dynamic control approach that links the benefits of active leakage control and the ones of passive leakage control. The proposed approach is based on the data collection on all the meters at the same time. Moreover, using uncertainty analysis, useful information about water loss type (apparent or real) could be carried out. An application over a sector of the water distributions network of Fano (Italy) has shown that the “real time” monitoring allows major improvements about water losses reduction

Evaluation of Reliability Indicators for WDNs with Demand-Driven and Pressure-Driven Models

Reliability of water distribution networks (WDNs) has received much attention in recent years due to progressive aging of infrastructures and climate change. Several reliability indicators, focusing on hydraulic aspects rather than water quality, have been proposed in literature. Reliability is generally assessed resorting to well established methods coupling hydraulic simulations and stochastic techniques that describe the WDNs hydraulic performance and component availability respectively. Two main algorithms are employed to simulate WDNs: the demand driven approach (DDA) that disregards the physical relationship between actual water demand and nodal pressure, and the pressure driven approach (PDA) that explicitly incorporates it. In this paper, we show how the choice of hydraulic solver may affect reliability indicators. We modify existing quantitative indicators at nodal and network level, and define novel indicators to consider water quality aspects. These indicators are evaluated for three example WDNs; discrepancies between results obtained with the two approaches depend on network size, feeding scheme and skeletonization. Results suggest to use with caution the DDA for reliability assessment at both local and global level

I modelli quali-quantitativi a supporto della progettazione e gestione delle reti fognarie

Oggetto del lavoro è la valutazione della robustezza di due codici di calcolo commerciali (InfoWorks, sviluppato da Wallingford Ltd e MOUSE, sviluppato dal Danish Hydraulic Institute) nella simulazione del sistema drenante di un piccolo bacino di 1,15 ettari sito in prossimità della città di Bologna, sul quale sono stati, in precedenza, raccolti sia dati di portata, sia dati di concentrazione dei principali costituenti di qualità. La superficie del bacino, completamente asfaltata, è adibita ad area di transito e di sosta di mezzi pesanti e le acque drenate sono raccolte in una vasca di prima pioggia prima di essere immesse in una vasca di laminazione e successivamente inviate al ricettore finale. Per circa 8 mesi sono stati campionati con continuità sia dati di pioggia sia dati di qualità nella vasca. Tali dati sono stati utilizzati per calibrare i modelli attraverso una procedura di prova e correggi per entrambi gli aspetti di quantità e di qualità dell’acqua. È stata condotta infine un’analisi di sensitività per i principali parametri dei modelli implementati nei due software