| 51. |
- Pettersson, Thomas, 1966
(författare)
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Characteristics of suspended particles in a small stormwater pond
- 2002
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Ingår i: In: Proc. 9th International Conference on Urban Storm Drainage, Portland, Oregon, USA, 8-13 September 2002.
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Konferensbidrag (refereegranskat)abstract
- Polluted urban stormwater contains a number of hazardous constituents, such as heavy metals and polycyclic aromatic hydrocarbons (PAH). These pollutants are to a considerable extent associated with solids and can therefore be removed from the stormwater through sedimentation and particle encounter on aquatic vegetation. Due to this fact, stormwater ponds have frequently been used as a method for the treatment of stormwater. Information regarding particlecharacteristics and associated pollutants in stormwater is therefore of great importance to engineers involved in the design of ponds. This study investigates the inflow particle characteristics (such as particle size distribution, total and volatile suspended solids content and heavy metal content) of a small stormwater pond that predominantly receives stormwater drainage from a highway. Flow measuring devices and two automatic samplers were installed at the inlet and outlet of the pond. Measurements of particle characteristics and pollutant loads at the pond inflow and outflow for several storm events are carried out. The results show the particle volume in the stormwater (particle volume per stormwater volume) predominately consists of very fine particles and that the smallest particles comprise most of the surface area. Densities of particles in the inflow stormwater are presented. The stormwater pollutants exhibit strong correlation with particle characteristics, which is of great importance for pond design.
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| 52. |
- Pettersson, Thomas, 1966
(författare)
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FEM-Modelling of Open Stormwater Detention Ponds
- 1997
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Ingår i: Nordic Hydrology. ; 28:4/5, s. 339-350
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Tidskriftsartikel (refereegranskat)abstract
- Stormwater in urban areas is polluted with suspended materials which transport heavy metals and degrade the quality of the receiving waters. Since open detention ponds improve water quality, an investigation of a constructed pilot-scale detention pond was carried out.Measurements of inflow and outflow were performed and two flow-weighted samplers were used to collect representative samples of suspended solids and heavy metals. The particlesize distribution was analysed to allow an estimation of the settling of suspended solids. Particle removal from a rain event was defined as two different phases where the first phase occurs during the rain event and the second phase after the event. In this paper only the firstphase is considered. A FEM-software package (FIDAP) was used to calculate the three dimensional velocity flow field for one rain event. A sedimentation approach was applied to the flow field where paths were calculated through the detention pond for different particle sizes. The results from four different particle sizes show satisfactory agreement between FEM-calculated and observed particle removal. The results show that FIDAP is a useful tool to predict pollutant removal for open detention ponds with arbitrary geometry.
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| 53. |
- Pettersson, Thomas, 1966, et al.
(författare)
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Modelling of flow pattern and particle removal in an open stormwater detention pond
- 1998
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Ingår i: In: Proc. HydraStorm’98, Adelaide, Australia, 27-30 September 1998. ; , s. 63-68
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Konferensbidrag (refereegranskat)abstract
- In Sweden open stormwater detention ponds are more often used to reduce stormwater pollution through sedimentation. The pollution reduction occurs both during storm events and in between events. Design methods are often simplified and based on detention time only. However, not only the pond volume but also the geometry and thus the flow pattern are of concern when designing open detention ponds. In the city of Göteborg a 6200 m2 open stormwater detention pond was investigated with respect to massflows of pollutants and flow pattern. The observed data has been used to verify a FEM model established for the pond. Both 3-D and 2-D flow simulations have been performed at inflows starting at 20 l/s up to a maximum of 800 l/s. The simulations show that both 2-D and 3-D calculations give reasonable agreement with observed data. The 3-D calculations are however more accurate taking the bottom shape into account. Conclusions drawn from this study is that simulations of pond flow pattern are essential in designing pond geometry, and inlet and outlet locations.
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| 54. |
- Pettersson, Thomas, 1966, et al.
(författare)
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Modelling of open stormwater detention ponds
- 1996
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Ingår i: In: Proc. 7th International Conference on Urban Storm Drainage, Hanover, Germany, 9-13 September 1996. ; 1, s. 539-544
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Konferensbidrag (refereegranskat)
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| 55. |
- Pettersson, Thomas, 1966, et al.
(författare)
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Particle removal in detention ponds modelled for a year of successive rain events
- 1998
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Ingår i: In: Proc. Novatech 1998, 3rd international conference on innovative technologies in urban storm drainage, Lyon, France, 4-6 May 1998. ; 1, s. 567-574
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Konferensbidrag (refereegranskat)abstract
- The aim of this study was to model the removal of pollution in small open stormwater detention ponds by a simple method of particle settling. Simulations were made with a rain series for a normal hydrological year selected from a 19-year long rainfall series. TSS removal calculations were based on the US EPA-method. Measured TSS concentrations from the Järnbrott detention pond were used for comparison with the modelled concentrations. The model work showed that the removal efficiency is strongly dominated by inter-event settling. Removal efficiency may be improved by increasing the specific pond area up to 150 m2/ha. A consideration of the particle density has to be made since the removal efficiency is affected by low densities, often seen for urban runoff sediments.
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| 56. |
- Pettersson, Thomas, 1966, et al.
(författare)
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Pollutant removal efficiency in two stormwater ponds in Sweden
- 1999
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Ingår i: In: Proc. 8th International Conference on Urban Storm Drainage, Sydney, Australia, 30 August-3 September 1999. ; 2, s. 866-873
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Konferensbidrag (refereegranskat)abstract
- Open stormwater ponds have been frequently addressed as a method for treatment of stormwater since measurements show a considerable pollutant removal effect. Pollutant removal efficiency in two stormwater ponds in Sweden is studied where field measurements of inflow and outflow pollutant loads for several successive storm events are described. Cumulative effects of inflow and outflow pollutant discharges are studied and for the outflow a strong correlation to constant outflow pollutant discharges appears that indicate an independence of inflow pollutant load for the two ponds. Hereby, it becomes possible to extrapolate the annual loads from the ponds to the receiving waters of studied pollutants. The specific pond area (m2/ha) is 20 times larger in one of the ponds, which affect the pollutant removal efficiencies. A comparison between specific pond area and pollutant removal efficiency gave that the removal efficiency increases up to a certain level of surface/impervious area, 250 m2/ha, and above this level the increase is not as significant as below. Another factor that has an impact on the removal efficiency is the pond geometry.
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| 57. |
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| 58. |
- Rosen, Lars, 1962, et al.
(författare)
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Comparing risk-reduction measures to reach water safety targets using an integrated fault tree model
- 2010
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Ingår i: Water Science and Technology: Water Supply. - : IWA Publishing. - 1606-9749. ; 10:3, s. 428-436
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Tidskriftsartikel (refereegranskat)abstract
- In the third edition of the Guidelines for Drinking-water Quality, the World Health Organization concludes that an integrated management of risks in source waters, treatment systems and distribution networks is the most effective way to guarantee safe drinking water to consumers. The integrated approach is fundamental to avoid sub-optimisation of risk-reduction measures. This paper presents an application of an integrated and quantitative risk model for comparing risk-reduction measures to support decisions for reaching specified water safety targets. A fault tree approach is used for structuring the risk analysis and for estimating the risk, expressed as Customer Minutes Lost (CML). Input information is a combination of hard data and expert judgements. Uncertainties in input information are considerable and modelled by a Bayesianstatistical approach. A drinking water system in Sweden is used to exemplify model application. Quantitative safety targets have been confirmed at the political level as a basis for long-term planning of investments and reinvestments. One target defines an acceptable risk level of 144 annual CML for the average consumer. For the current system structure an estimated risk of 612CML was obtained. Four risk-reduction alternatives were compared and they reduce the risk to between 50 and 81 CML, i.e. below the acceptable level. The paper describes how a structuredand thorough analysis of risk-reduction measures can facilitate transparency and long-term planning of drinking water systems.
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| 59. |
- Schooneveldt, Gerben, et al.
(författare)
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Hyperthermia treatment planning including convective flow in cerebrospinal fluid for brain tumour hyperthermia treatment using a novel dedicated paediatric brain applicator
- 2019
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Ingår i: Cancers. - : MDPI AG. - 2072-6694. ; 11:8
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Tidskriftsartikel (refereegranskat)abstract
- Hyperthermia therapy (40–44 °C) is a promising option to increase efficacy of radiotherapy/chemotherapy for brain tumours, in particular paediatric brain tumours. The Chalmers Hyperthermia Helmet is developed for this purpose. Hyperthermia treatment planning is required for treatment optimisation, but current planning systems do not involve a physically correct model of cerebrospinal fluid (CSF). This study investigates the necessity of fluid modelling for treatment planning. We made treatments plans using the Helmet for both pre-operative and post-operative cases, comparing temperature distributions predicted with three CSF models: A convective “fluid” model, a non-convective “solid” CSF model, and CSF models with increased effective thermal conductivity (“high-k”). Treatment plans were evaluated by T90, T50 and T10 target temperatures and treatment-limiting hot spots. Adequate heating is possible with the helmet. In the pre-operative case, treatment plan quality was comparable for all three models. In the post-operative case, the high-k models were more accurate than the solid model. Predictions to within ±1 °C were obtained by a 10–20-fold increased effective thermal conductivity. Accurate modelling of the temperature in CSF requires fluid dynamics, but modelling CSF as a solid with enhanced effective thermal conductivity might be a practical alternative for a convective fluid model for many applications.
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| 60. |
- Sjöstrand, Karin, 1975, et al.
(författare)
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Water supply delivery failures-a scenario-based approach to assess economic losses and risk reduction options
- 2020
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Ingår i: Water (Switzerland). - : MDPI AG. - 2073-4441 .- 2073-4441. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Access to a reliable water supply is central for a well-functioning society. However, water supply systems are subject to a wide range of threats which may affect their ability to provide water to society. This paper presents a novel risk assessment approach that enables thorough analyses of economic losses and associated uncertainties under a range of water supply disruption scenarios. The purpose is to avoid sub-optimization when prioritizing between risk reduction measures, by integrating the full range of possible outcomes from low to high probability events. By combining risk analysis with cost-benefit analysis, additional information is provided on measures for leveraging investments in managing and reducing the risks. This enables the identification of the most economically profitable risk reduction alternatives and enables decision makers to build strategic capacity for operating in difficult and uncertain futures. The presented approach is exemplified on the island of Gotland, one of the most water scarce areas of Sweden.
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