This paper aims at comparing the cost-effectiveness of the two main types of urban drainage systems, that is, the combined sewer system and the separate sewer system, based on the analysis of ...simulations. The problem of which of the two systems is better was heavily discussed over the years and the answer given to the question was usually: 'it depends'. In this work, specific impacts are investigated in terms of a cause-effect analysis. The results are subsequently summarized and can help in the choice of the system to be implemented. Despite earlier reasoning, studies on river water quality strongly indicate that the separate system is not always the preferable solution because the polluted runoff from the street, containing e.g. different heavy metals, is discharged directly into the river. This analysis aims to compare the two different sewer systems on the basis of literature data and simulation of specific cases. The results are evaluated, as suggested in the EU-Water Framework Directive, on the basis of different assessment criteria: river water quality and morphology impacts, emissions and costs.
The fact that climate change is affecting the intensity and frequency of rainfall is well accepted in the scientific community. This is backed by a multitude of reports on the basis of daily rainfall ...series analysis; however, little research is available for short duration intensities. Due to its significant influence on the behaviour of urban drainage, it is critical to investigate the changes in short duration rainfall intensities. In this study different intensities relevant for the urban drainage and the total rainfall per rain event are analysed. The trend is investigated using the Mann-Kendall test. The rainfall series analysed are from the alpine region Tyrol. The results present differences depending on the duration of the intensity and the series considered, however an increase in the number of extreme events is detectable for short durations for the most series.
A new methodology for online estimation of excess flow from combined sewer overflow (CSO) structures based on simulation models is presented. If sufficient flow and water level data from the sewer ...system is available, no rainfall data are needed to run the model. An inverse rainfall-runoff model was developed to simulate net rainfall based on flow and water level data. Excess flow at all CSO structures in a catchment can then be simulated with a rainfall-runoff model. The method is applied to a case study and results show that the inverse rainfall-runoff model can be used instead of missing rain gauges. Online operation is ensured by software providing an interface to the SCADA-system of the operator and controlling the model. A water quality model could be included to simulate also pollutant concentrations in the excess flow.
Despite the development of urban drainage systems over the past 5000 years, there are still many challenges to their effective use. There are growing demands with respect to runoff quantity and ...quality, visual amenity (landscape aesthetics), protection of ecology and beneficial water uses and interaction with the operation of existing municipal wastewater systems. Current solutions that rely mainly on pipe networks may not be sustainable, especially in developing countries. By considering the driving forces in action during the first years of the 21st century, different scenarios for the future use and development of urban drainage systems can be proposed; all of them rather pessimistic. The implementation of the sustainable management of urban water will require an integrated approach to all the related problems, including the better delivery of urban drainage services.
It is state of the art to evaluate and optimise sewer systems with urban drainage models. Since spill flow data is essential in the calibration process of conceptual models it is important to enhance ...the quality of such data. A wide spread approach is to calculate the spill flow volume by using standard weir equations together with measured water levels. However, these equations are only applicable to combined sewer overflow (CSO) structures, whose weir constructions correspond with the standard weir layout. The objective of this work is to outline an alternative approach to obtain spill flow discharge data based on measurements with a sonic depth finder. The idea is to determine the relation between water level and rate of spill flow by running a detailed 3D computational fluid dynamics (CFD) model. Two real world CSO structures have been chosen due to their complex structure, especially with respect to the weir construction. In a first step the simulation results were analysed to identify flow conditions for discrete steady states. It will be shown that the flow conditions in the CSO structure change after the spill flow pipe acts as a controlled outflow and therefore the spill flow discharge cannot be described with a standard weir equation. In a second step the CFD results will be used to derive rating curves which can be easily applied in everyday practice. Therefore the rating curves are developed on basis of the standard weir equation and the equation for orifice-type outlets. Because the intersection of both equations is not known, the coefficients of discharge are regressed from CFD simulation results. Furthermore, the regression of the CFD simulation results are compared with the one of the standard weir equation by using historic water levels and hydrographs generated with a hydrodynamic model. The uncertainties resulting of the wide spread use of the standard weir equation are demonstrated.
Approximately 300 kg/day of food-grade CO
2
was injected through a perforated pipe placed horizontally 2–2.3 m deep during July 9–August 7, 2008 at the MSU-ZERT field test to evaluate atmospheric and ...near-surface monitoring and detection techniques applicable to the subsurface storage and potential leakage of CO
2
. As part of this multidisciplinary research project, 80 samples of water were collected from 10 shallow monitoring wells (1.5 or 3.0 m deep) installed 1–6 m from the injection pipe, at the southwestern end of the slotted section (zone VI), and from two distant monitoring wells. The samples were collected before, during, and following CO
2
injection. The main objective of study was to investigate changes in the concentrations of major, minor, and trace inorganic and organic compounds during and following CO
2
injection. The ultimate goals were (1) to better understand the potential of groundwater quality impacts related to CO
2
leakage from deep storage operations, (2) to develop geochemical tools that could provide early detection of CO
2
intrusion into underground sources of drinking water (USDW), and (3) to test the predictive capabilities of geochemical codes against field data. Field determinations showed rapid and systematic changes in pH (7.0–5.6), alkalinity (400–1,330 mg/l as HCO
3
), and electrical conductance (600–1,800 μS/cm) following CO
2
injection in samples collected from the 1.5 m-deep wells. Laboratory results show major increases in the concentrations of Ca (90–240 mg/l), Mg (25–70 mg/l), Fe (5–1,200 ppb), and Mn (5–1,400 ppb) following CO
2
injection. These chemical changes could provide early detection of CO
2
leakage into shallow groundwater from deep storage operations. Dissolution of observed carbonate minerals and desorption-ion exchange resulting from lowered pH values following CO
2
injection are the likely geochemical processes responsible for the observed increases in the concentrations of solutes; concentrations generally decreased temporarily following four significant precipitation events. The DOC values obtained are 5 ± 2 mg/l, and the variations do not correlate with CO
2
injection. CO
2
injection, however, is responsible for detection of BTEX (e.g. benzene, 0–0.8 ppb), mobilization of metals, the lowered pH values, and increases in the concentrations of other solutes in groundwater. The trace metal and BTEX concentrations are all significantly below the maximum contaminant levels (MCLs). Sequential leaching of core samples is being carried out to investigate the source of metals and other solutes.
Measurements of inclusive spectra and mean multiplicities of $\pi ^\pm $ , K$^\pm $ , p and ${\bar{\text {p}}}$ produced in inelastic p + p interactions at incident projectile momenta of 20, 31, 40, ...80 and 158 $\text{ GeV }/c$ ( $\sqrt{s} = $ 6.3, 7.7, 8.8, 12.3 and 17.3 $\text{ GeV }$ , respectively) were performed at the CERN Super Proton Synchrotron using the large acceptance NA61/SHINE hadron spectrometer. Spectra are presented as function of rapidity and transverse momentum and are compared to predictions of current models. The measurements serve as the baseline in the NA61/SHINE study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To simulate hydrological models of combined sewer systems an accurate calibration is indispensable. In addition to all sources of uncertainties in data collection due to the measurement methods ...itself, it is a key question which data has to be collected to calibrate a hydrological model, how long measurement campaigns should last and where that data has to be collected in a spatial distributed system as it is neither possible nor sensible to measure the complete system characteristics. In this paper we address this question by means of stochastic modelling. Using Monte Carlo Simulation different calibration strategies (selection of measurement sites, selection of rainfall-events) and different calibration parameters (overflow volume, number of overflows) are tested, in order to evaluate the influence on predicting the total overflow volume of the entire system. This methodology is applied in a case study with the aim to calculate the combined sewer overflow (CSO) efficiency. It can be shown that a distributed hydrological model can be calibrated sufficiently when calibration is done on 30% of all existing CSOs based on long-term observation. Event based calibration is limited possible to a limited extend when calibration events are selected carefully as wrong selection of calibration events can result in a complete failure of the calibration exercise.
Even though urban drainage has been practised for more than 5000 years, many challenges arising from growing demands on drainage still remain with respect to runoff quantity and quality; landscape ...aesthetics, ecology and beneficial uses; and operation of existing urban wastewater systems. Further advances can be achieved by adopting an integrated approach, optimal operation of the existing infrastructure, advanced pollution and runoff source controls, improved resilience of receiving waters, and adaptive water management. The specific research needs include new technologies and strategies for stormwater management, advanced treatment of urban wet-weather effluents, and tools for analysis and operation of drainage systems. High diversity of demands on, and region/site specific conditions of, urban drainage shapes the role of urban drainage experts--as mediators among the many stakeholders and fields involved.
In this work it is quantified to what extent existing water networks can cope with urban and population change developments before they fail. For that, the VIBe (Virtual Infrastructure Benchmarking) ...approach is used in order to create numerous city scale test cases (including urban form, water supply and drainage system) with different characteristics. Based on 81 test cases, probabilities of failure for different system characteristics are determined. For such an integrated assessment, a key issue is the weighting of the different technical performances when identifying stable ranges for the overall performance. Therefore, different weighting strategies are tested and compared.
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