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  • 151.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Percolation of meltwater through a snowpack1982Inngår i: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 6, nr 1, s. 73-81Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hydraulics of meltwater percolation through a snowpack is analyzed in some detail. An implicit numerical model is used for determining the meltwater movement. The effect of freezing fronts of the free liquid water in the snowpack is evaluated. It is shown that even after a moderately cold night, it takes several hours of snowmelt before the snowpack again reaches its irreducible liquid content. The meltwater flux front moves very slowly down through the depth, where the liquid water has been refrozen during a preceding night. The time delay between the initiation of snowmelt at the surface and the start of run-off at the base of the snowpack is shown to be determined from a simple continuity reasoning. Finally, a comparison between theory and field measurements is made.

  • 152.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Precolation of meltwater through a snowpack1982Rapport (Annet vitenskapelig)
  • 153.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Simulerad utveckling av Luleås inre fjärdsystem1983Rapport (Annet vitenskapelig)
  • 154.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Snowmelt estimated from energy budget studies1976Inngår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 7, nr 1, s. 3-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The snowmelt at a point is estimated through a simplified energy budget. From the energy equation a degree-day method is derived. The rate of snowmelt is found as a constant multiplied by the temperature excess over an equilibrium temperature which depends on solar radiation.The snowmelt events in Kiruna (3 years) and Luleå (4 years) are analysed utilizing energy balance computations and the degree-day method. First observed and calculated day when the ground was free of snow is for all seven years in good agreement. The rate of snowmelt calculated by the proposed degree-day method is almost identical to the rate found from energy balance computations. Snowmelt rates estimated by a simple degree-day method using a constant equilibrium temperature are too fast in the beginning and too slow at the end of the melting season.

  • 155.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Snowmelt generated run-off from small areas as a daily transicent process1981Rapport (Annet vitenskapelig)
  • 156.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Snowmelt generated run-off from small areas as a daily transient process1981Inngår i: Geophysica, ISSN 0367-4231, E-ISSN 2324-0741, Vol. 17, nr 1-2, s. 109-122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The daily variation of snowmelt generated run-off is discussed. The heat conduction in the snowcover and refreezing during cold nights are discussed. The refreezing phenomena significantly influences the saturation conditions in the top layer of the snowcover

  • 157.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Snöhydrologisk forskning1982Inngår i: Väg- och Vattenbyggaren, ISSN 0042-2177, nr 3, s. 61-64Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 158.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Snöhydrologisk forskning1983Rapport (Annet vitenskapelig)
  • 159.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Snösmältning i tätort1979Inngår i: Väg- och Vattenbyggaren, ISSN 0042-2177, nr 11/12, s. 38-42Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 160.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Snösmältning i urbana och rurala områden i Luleå 19801981Rapport (Annet vitenskapelig)
  • 161.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Snösmältning uppskattad från värmebudgetstudier1975Rapport (Annet vitenskapelig)
  • 162.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Statisk istillväxt1976Rapport (Annet vitenskapelig)
  • 163.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Stochastic Modelling of Dispersion in the Lule River1977Inngår i: Stochastic processes in water resources engineering: proceedings, second International IAHR Symposium on Stochastic Hydraulics, Lund Institute of Technology/University of Lund, Lund, Sweden, August 2-4, 1976 / [ed] Lars Gottschalk, Fort Collins, Colo.: Water resources publ. , 1977, s. 153-166Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Since turbulent diffusion is a stochastic phenomenon, it is hard to describe dispersion in a river deterministic formula, and no exact theory can be formulated. Simulation techniques are more promising in this respect. This paper described simulations of horizontal dispersion of tracer material from a finite and continuous source. A stochastic model by which the horizontal dispersion of a number of particles can be simulated was developed. The model accounts for the increased dispersion caused by horizontal shear. The input data required for the model were determined from field measurements carried out at four positions in the Lule River, after which the stochastic model was applied to an 8 km long reach of the river. It was found that Fickian Law of dispersion was not applicable since the dispersion coefficients grew still faster but were linear

  • 164.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Temperaturmätningar och värmebalans för forsar i Råne älv vintern 1975-761976Rapport (Annet vitenskapelig)
  • 165.
    Bengtsson, Lars
    Luleå University of Technology.
    The importance of refreezing on the diurnal snowmelt cycle with application to a Northern Swedish catchment1982Inngår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 13, nr 1, s. 1-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method for including night-time refreezing of the top layer of a snowpack in the degree-day method for computing daily snowmelt rates is presented. It is found that during days of large diurnal temperature variations the daily melt is more determined by the day-time conditions than by the daily mean conditions. Applications are made to an open area and a forested area. The refreezing-degree-day method is found to describe the snowmelt process very well, whereas the simple degree-day method shows a too fast snowmelt rate.

  • 166.
    Bengtsson, Lars
    Luleå tekniska universitet.
    The influence of a proposed sumped storage hydro-power plant on the thermal stratification of lake Ivö, Sweden1979Rapport (Annet vitenskapelig)
  • 167.
    Bengtsson, Lars
    Luleå tekniska universitet.
    The influence of water velocity on the formation of ice cover1978Rapport (Annet vitenskapelig)
  • 168.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Tätortsteknik och byggande i kallt klimat: långtidsprogram för forskning och forskningssamverkan vid Institutionen för berg- och anläggningsteknik : en förstudie1979Rapport (Annet vitenskapelig)
  • 169.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Vattenutbytet mellan Luleås innerfjärdar: stationära förhållanden1980Rapport (Annet vitenskapelig)
  • 170.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Vertikalprocesser vid en snöyta1975Rapport (Annet vitenskapelig)
  • 171.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Vinterförhållanden i Råne älv 1976/771977Rapport (Annet vitenskapelig)
  • 172.
    Bengtsson, Lars
    Luleå tekniska universitet.
    Wind Induced Circulation in Lakes1978Inngår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 9, nr 2, s. 75-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In most lakes the wind is the most important flow generating mechanism. In this paper, the problem of wind generated circulation - directly wind induced currents and seiches - in small lakes was reviewed. Many field observations were presented and discussed. In the thermocline and the hypolimnion, forced seiche currents were shown to dominate the directly induced wind currents. Different kinds of non-convective mathematical lake models were discussed and applied to different small lakes. Comparisons of observed and calculated current showed that lake models can be used to reproduce the currents of the upper 3-4 metres in a lake. The interaction between large-scale flow and turbulent flow is yet unknown; and therefore, it is not possible to explain the physical current pattern and density anomalies at greater depth. In respect to the limited knowledge on turbulent processes in lakes, it is acceptable to apply a quadric relationship between wind stress and wind speed with a drag coefficient of about 0.001

  • 173.
    Bengtsson, Lars
    et al.
    Luleå tekniska universitet.
    Eneris, Elna
    Luleå tekniska universitet.
    Istillväxt i sjöar analyserad med graddagarsmetoden1977Rapport (Annet vitenskapelig)
  • 174.
    Bengtsson, Lars
    et al.
    Luleå tekniska universitet.
    Lundberg, Angela
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Starius, Göran
    Luleå tekniska universitet.
    Beskrivning av vattenrörelser i den omättade markzonen: litteraturgenomgång, numerisk modell, simuleringar1982Rapport (Annet vitenskapelig)
  • 175.
    Bengtsson, Lars
    et al.
    Luleå tekniska universitet.
    Nilsson, Lisbeth
    Luleå tekniska universitet.
    Snösmältningsintensitetskurvor: delrapport1981Rapport (Annet vitenskapelig)
  • 176.
    Bengtsson, Lars
    et al.
    Luleå tekniska universitet.
    Sandkvist, Jim
    Luleå tekniska universitet.
    Ice conditions in the Luleå harbour1978Rapport (Annet vitenskapelig)
  • 177.
    Bengtsson, Lars
    et al.
    Luleå tekniska universitet.
    Westerström, Göran
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Runoff from a surface study plot1979Rapport (Annet vitenskapelig)
  • 178.
    Bengtsson, Lars
    et al.
    Lund University, Department of Water Resources Engineering.
    Westerström, Göran
    Urban snowmelt and runoff in northern Sweden1992Inngår i: Hydrological Sciences Journal, ISSN 0262-6667, E-ISSN 2150-3435, Vol. 37, nr 3, s. 263-275Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Snowmelt and runoff in urban areas in Lulea, north Sweden, are discussed and compared with rural conditions. The uneven snow distribution in cities is quantified. Energy fluxes at the snow surface in different environments are estimated. It is shown that, mainly because of increased absorbed radiative energy in the snow, the daily melt is about 10 mm higher in the city than in rural environments. In the course of prolonged snowmelt, the infiltration capacity of most soils in urban areas becomes so reduced that melt-induced peak flows from grassed and gravelled surfaces are similar to those from asphalted surfaces. When rain falls on snow, overland flow may take place from the entire area of a basin

  • 179.
    Berggren, Christian
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Dig or no dig?: En jämförelse mellan schaktfria tekniker och konventionell schakt vid VA-produktion.2015Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Sveriges offentliga vatten- och avloppsnät består av 191 000 km vatten- och avloppsledningar. Det renoveras årligen ca 380 km för lite för att hålla förnyelsetakten i takt med åldrandet av ledningarna. Renoveringarna kostar stora summor pengar vilket lär vara en av de största anledningarna till att det renoveras i för liten utsträckning. För att hålla igång produktionen i Sveriges VA-sektor behöver både ekonomi och tidsåtgång ses över.

    Detta arbete jämför ekonomin i olika förläggningsmetoder för vatten och avloppsledningar. Arbetet tar även upp utsläpp av koldioxidekvivalenter under produktion av VA-ledningar. Metoderna som har tagits upp är konventionell schakt, styrd borrning och relining. Inom styrd borrning har det tittats på JT- och AT-borrning. För relining är de granskade metoderna slip-lining och closed-fit.

    Arbetet har gjorts för Skanska Väg och Anläggning Väst som är en del av Skanska Sverige AB. Jämförelsen har utförts med en litteraturstudie som bakgrund. Kalkyler från utförda och pågående projekt samt intervjuer med olika entreprenadföretag har varit underlag för den jämförande studien kring ekonomi och miljö.

    Resultaten visar på att schaktfria tekniker släpper ut mindre koldioxid än konventionell schakt vilket inte är konstigt då det vid schaktning hanteras mycket större jordmassor. I avseende på ekonomi kan sägas att underlaget för resultatet är undermåligt men vad som är mest kostnadseffektivt varierar beroende på projekt. En generalisering kan dock göras för schaktfria metoder. Dessa tenderar att bli mer lönsamma ju djupare och längre entreprenaden är samt desto färre serviser och förgreningar det är på ledningen. Styrd borrning begränsas av det borrslam som blir en restprodukt vid produktion med metoden. För grövre ledningsdimensioner blir omhändertagandet av slammet en stor kostnad som i vissa fall kan göra det olönsamt att borra. Generellt kan sägas att styrd borrning i grövre dimensioner kräver skyddsvärda objekt ovan mark för att nå ekonomisk lönsamhet.

  • 180.
    Berggren, Karolina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Indicators for urban drainage system: assessment of climate change impacts2008Inngår i: Conference Proceedings : 11th International Conference on Urban Drainage: Edinburgh International Conference Centre, Scotland : 11 ICUD: 31st August - 5th September 2008, Munich: Oldenbourg Industrieverlag , 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Changes of the climatic conditions will affect urban drainage systems, as they are closely related to the weather phenomenon and are built as to cope with the weather occurring. The aim of this paper is to investigate indicators that can be used to describe and compare impacts and adaptation measures in existing urban drainage systems. Problems in the system due to climate change can be summarised as problems with flooding of surfaces and basements, increased amount of combined sewer overflows (CSO), increase of the inflow to waste water treatment plants (WWTP) and increase in pollutants spreading from urban areas to the environment. The impacts needs to be described with indicators taking into account the system behaviour both before, during and after an event (e.g. urban flooding) has occurred, and can be divided into (A) description of the system performance, (B) capacity exceeding in the system, and (C) description of consequences as a result of capacity exceeding. The consequences can be divided into sustainable aspects as: technical, economical, socio-cultural, environmental, and health. The research is performed within a project which will also include model simulations of urban drainage systems in four Swedish municipalities as to assess impacts and evaluate the use of indicators.

  • 181.
    Berggren, Karolina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Urban drainage and climate change: impact assessment2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    According to the Intergovernmental Panel on Climate Change (IPCC, 2007), the global mean temperature has increased by 0,7 °C during the last 100 years and, as a consequence, the hydrological cycle has intensified with, for example, more intense rainfall events. As urban drainage systems have been developed over a long period of time and design criteria are based upon climatic characteristics, these changes will affect the systems and the city accordingly.The overall objective of this thesis is to increase the knowledge about urban drainage in a changing climate. In more detail, the objective is to investigate how climate change may affect urban drainage systems, and also to suggest methods for these investigations.The thesis consists of four papers. The first paper concentrates on the Delta change method for adaptation of rainfall data from climate models for urban hydrology use. The second paper is an impact assessment with urban drainage model simulation of a study area in the south of Sweden. The third paper is also an impact study, from a cause and effect approach, where the whole urban water is included. Finally, the fourth paper contains a strategy and suggestions about tools to use for assessing impacts on urban drainage systems due to climate change. The suggested tools are urban drainage model simulations, Geographical Information Systems (GIS), and risk analysis methods.The Delta change approach is feasible for handling the differences in spatial and temporal resolution between climate model data and the needs for urban drainage model simulations, as the method is relatively simple and the temporal resolution of observed rainfall series is preserved. In the study area with separated storm water system, the model simulations show that the number of surface floods as well as the geographical distribution of the floods increases in the future time periods (2011-2040, 2041-2070, and 2071-2100). Future precipitation will also increase both the flooding frequency and the duration of floods; therefore, the need to handle future situations in urban drainage systems and to have a well-planned strategy to cope with future conditions is evident. The overall impacts on urban drainage systems due to increased precipitation may, for example, be an increased number of basement floods, surface floods, problems with property and road drainage, and also increased amount of infiltration into pipes and combined sewer overflows (CSOs). The knowledge gained from this thesis, and the strategy suggested, can be used as a starting point for impact studies on urban drainage systems. Since most impacts concern several different disciplines and a multifunctional understanding, the studies should also be performed in cooperation with parties concerned.

  • 182.
    Berggren, Karolina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Urban stormwater systems in future climates: assessment and management of hydraulic overloading2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Increasing global temperatures and tendencies of more frequent extreme weather events have been observed over the recent decades, and the continuation of this trend is predicted by future climate models. Such climatic changes impact on many human activities and hence the interest in, and focus on, climate change has increased rapidly in recent years. One of the fields strongly affected by ongoing climate change is urban water management and, in particular, the provision of urban drainage services. Modern urban drainage systems (UDSs) are designed to manage stormwater and convey residual runoff from urban areas to receiving waters, in order to fulfill such UDS primary functions as e.g., preserving local water balance; mitigating increases in runoff and the associated flood risks; and protecting water quality. There are also other drivers that influence the future urban runoff regime and the UDS performance, including urban planning, land-use changes (progressing urbanization), and implementation of sustainable stormwater management systems by such approaches as e.g., Best management practices (BMPs), Low impact development (LID), Water sensitive urban design (WSUD), and Green Infrastructure (GI). This doctoral thesis focuses on urban rainfall and runoff processes, and runoff conveyance by separate storm sewer systems, and the changes in these processes caused by climate change, with the overall objective of investigating urban stormwater systems response and performance related to future climate changes, and particularly the future rainfall regime, by means of urban rainfall/runoff modelling. Furthermore, future influences on the runoff regime of urban green/pervious areas have also been studied. Specifically, the thesis has focused on future rainfall changes and hydraulic performance of the stormwater system, and the influential response parameters needed for evaluating the simulated impacts, with the overall aim of contributing new knowledge to this field. The results included in the thesis are based on three published journal papers, one manuscript, and three conference papers. The research project started by addressing the needs for relevant UDS hydraulic response parameters (or indicators), which reflect both the capacity exceedance (when the UDS design fails) and indicate the safety margins in the system (e.g., locations with low or high capacities). The pipe flow rate and maximum water levels in the system exceeding a critical level, are examples of such parameters. Another issue addressed in this thesis is the difference in resolution (temporal and spatial) of the original climate model data (even if downscaled) compared to the requirements on rainfall input data in urban drainage modelling. Therefore, an existing statistical downscaling method (the delta change method, DCM) was refined by focusing on changes in rainfall intensities and seasonal rainfalls, and the refined DCM was recommended for use in UDS modelling. The UDS performance in future climates, studied by modelling these systems, showed that a future change in rainfall poses significant impacts on the existing UDSs. Important aspects in addressing such impacts are, for example, the input rainfall data types (e.g. design storms, or observed rainfall), as well as the climate factors, and the methods used to produce such factors. Green/permeable areas within the urban catchments may, however, provide opportunities for adaptation of urban catchments and UDS, by potentially increasing the infiltration of rainwater, instead of converting it into rapid runoff contributing high flows and flow volumes to the urban drainage systems. Influential factors in these processes include soil types, soil moisture content, groundwater levels and the rainfall input. While climate change with uplifted rainfalls tends to increase runoff contributions from all urban surfaces (impervious and green/pervious), strategic application of runoff controls in the form green infrastructure may counterbalance such increases, and even lead to reduced runoff inflows into the UDS.

  • 183.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Lans, Axel
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Ashley, Richard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Future changes affecting hydraulic capacity of urban storm water systems2012Inngår i: Urban Drainage Modelling: Proceedings of the Ninth International Conference on Urban Drainage Modeling, Belgrade, Serbia, 4-6 September 2012, Belgrade: Faculty of Civil Engineering, University of Belgrade , 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Urban areas may develop and change its character over time, but the urban drainage system is often 12 more constant in character – as the technical design life can be up to 100 years. The hydraulic capacity 13 of an existing urban storm water system is affected by future changes, e.g. rate of imperviousness 14 (urbanization), changes in the rainfall characteristics (e.g. by climate change) and system deterioration 15 (pipes and other facilities). Recently the urban planning process in Sweden and elsewhere has become 16 more appreciative of urban drainage issues, and the need to include these earlier in development 17 processes. In this paper a small urban catchment is used to study how future factors affect the 18 hydraulic capacity and the potential development of the area. Factors tested are scenarios of: (1) 19 Urbanization; (2) Climate change and (3) Pipe system deterioration. The results show that each of 20 these factors impact on the hydraulic capacity and that any sensitivity analysis should include all of 21 them to understand future development potential for the area. This type of investigation can increase 22 the understanding of the needs of the infrastructure provision in the area in a planning process context, 23 and provide information about appropriate areas of development within the catchment.

  • 184.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Moghadas, Shahab
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Gustafsson, Anna-Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Ashley, Richard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Sensitivity of urban stormwater systems to runoff from green/pervious areas in a changing climate2013Konferansepaper (Fagfellevurdert)
  • 185.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Olofsson, Mats
    Viklander, Maria
    Svensson, Gilbert
    Tools for measuring climate change impacts on urban drainage systems2007Inngår i: Techniques et stratégies durables pour la gestion des eaux urbaines par temps de pluie: NOVATECH 2007 ; 6e conférence internationale, juin 2007, Lyon, France, Villeurbanne: Graie , 2007, Vol. 1, s. 239-246Konferansepaper (Fagfellevurdert)
  • 186.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Olofsson, Mats
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Svensson, Gilbert
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Gustafsson, Anna-Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Hydraulic impacts on urban drainage systems due to changes in rainfall, caused by climatic change2012Inngår i: Journal of hydrologic engineering, ISSN 1084-0699, E-ISSN 1943-5584, Vol. 17, nr 1, s. 92-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The changes in climate were of a growing concern in the last decade, and will be even more so in the coming years. When investigating impacts on urban drainage systems due to changes in the climate, two challenges are (1) what type of input rainfall data to use, and (2) what parameters to measure the impacts. The overall objective of this study is to investigate the hydraulic performances ofurban drainage systems related to changes in rainfall, and through these hydraulic parameters describe impacts of climate change. Input rainfall data represents today's climate, as well as three future time periods (2011-2040, 2041-2070, and 2071-2100). The hydraulic parameters used were water levels in nodes (e.g. as the number of floods, frequency and duration of floods), and pipe flow ratio. For the study area, the number of flooded nodes and the geographical distribution of floods will increase in the future, as will both the flooding frequency and the duration of floods.

  • 187.
    Berggren, Karolina
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Packman, John
    Centre for Ecology and Hydrology, Wallingford, Oxon.
    Ashley, Richard
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Climate changed rainfalls for urban drainage capacity assessment2014Inngår i: Urban Water Journal, ISSN 1573-062X, Vol. 11, nr 7, s. 543-556Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Guidance on what type of rainfall to use when assessing hydraulic capacity of urban drainage systems under climate change is unclear; focus is mainly on what climate factors to use. Based on a case study in Kalmar, Sweden, this paper compares system performance using two design rainfalls, Block rainfalls and Chicago Design Storm (CDS), and selected observed rainfalls, with two methods of addressing future climate: a constant factor and Delta Change (DC) factors that depend on rainfall intensity. The use of CDS rainfalls presents the maximum hydraulic response, whereas Block rainfalls give lower responses but identify critical durations in the system, which may be useful addressing adaptation actions. Observed rainfalls of target return periods gave similar responses to CDS rainfalls, and can be applied with DC factors to address future changes in both intensity and volume. Differences between the two methods indicate a high dependence related to the maximum factors applied on the rainfalls

  • 188. Berggren, Karolina
    et al.
    Viklander, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Will the existing urban drainage systems cope with future climate?: a Swedish study2006Konferansepaper (Annet vitenskapelig)
  • 189.
    Berglund, Petter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten och landskapslära.
    Cost-benefit analysis for sustainable stormwater management: A case study for Masthuggskajen, Gothenburg2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Densication and intensied precipitation patterns due to climate change, has increased

    the need for sustainable stormwater management. Sustainable stormwater management

    can be implemented as blue-green infrastructure (BGI), which integrates green features

    for natural inltration and detention such as green roofs and rain gardens. Through the

    use of BGI, added values can be provided as ecosystem services. Authorities and organizations

    in Sweden imply the need for valuation of ecosystem services for future integration

    in decision-making. This thesis include monetary estimations of ecosystem services within

    the use of a cost-benet analysis (CBA), for two alternatives of stormwater management

    in Masthuggskajen, Gothenburg. The applied valuation methods are methods commonly

    used in economic analysis. The ecosystem services identied and monetarily estimated as

    benets within this project were 

    ood protection, water treatment, air quality regulation,

    noise regulation and added recreational value. The result of the CBA indicated that the

    most protable alternative was considered to be the implementation of BGI rather than

    underground solutions.

    The ecosystem services contributing the most to the result was added recreational value,

    noise regulation and 

    ood protection. A sensitivity analysis was concluded by altering

    the value of costs and benets. Further analysis of the uncertainty in monetary estimates

    is of importance in order to integrate ecosystem services in decision-making.

    The diculty in covering the full extent of benets generated by BGI indicates the need of

    complementary tools in decision-making. However, this study highlights the importance

    of inclusion of ecosystem services in decision-making.

  • 190. Bergman, Gunnar
    et al.
    Nordell, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Sandberg, Karl W.
    IT for the citizens as a means of development of Lillpite village, Sweden1999Inngår i: Circumpolar change: building a future on experiences from the past : proceeding / [ed] Håkan Myrlund; Lars Carlsson, Luleå tekniska universitet, 1999, s. 289-303Konferansepaper (Annet vitenskapelig)
  • 191.
    Bergman, Karin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Berkelund, Linn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Nylander, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Olsson, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Renström, Terese
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    HYDROGEOLOGISKA FÖRHÅLLANDEN I GÄVLEÅSEN: Analys av stabila syreisotoper och kemiska parametrar samt beräkning av flöden i Gävleåsen2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Detta projekt behandlar hur vatten rör sig i Gävleåsen, det vill säga åsens hydrogeologiska förhållanden. Gävle kommun tar sitt dricksvatten från Gävleåsens grundvattenmagasin. För att öka grundvattenbildningen i åsen används konstgjord infiltration av åvatten och grundvatten genom infiltrationsbassänger, infiltrationsbrunnar och en sprinkleranläggning. Projektet initierades med bakgrund att grundvattennivåerna i Gävle kommuns grundvattentäkt sjunker på grund av vattenuttaget. Syftet med projektet var att bestämma om variationer i halt löst syre, organiskt material, an- och katjoner samt stabila syre- och väteisotoper kunde användas för att förklara de hydrogeologiska förhållandena i Gävleåsen. Även storleken på flödet uppströms och nedströms om infiltrationsanläggningen samt blandningsförhållandet nedströms skulle fastställas.

    Tre modeller över hur flödet varierade i åsen utformades på grund av den stora osäkerhet som fanns vid uppskattning av åsens mättade hydrauliska konduktivitet som användes vid flödesberäkningarna. I den första modellen antogs att flödesmassbalansen i åsen stämde, det vill säga att flödet nedströms var en summa av flödet uppströms om och flödet från infiltrationsanläggningen. Den andra modellen byggde på att det skedde ett okänt nettoutflöde från åsen mellan flödet uppströms och flödet nedströms om infiltrationsanläggningen. Att vatten istället skulle ha tillkommit till akviferen från exempelvis Gavleån eller genom inträngning av äldre grundvatten undersöktes med den tredje modellen. Uppställning av en isotopmassbalans för de olika modellerna tydde på att alla modeller kunde vara en möjlig bild av hur flödena i Gävleåsens akvifer förhöll sig till varandra och infiltrationsflödet genom infiltrationsanläggningen.

    Vid beräkning av blandningsförhållandet mellan grund- och åvatten nedströms om infiltrationsanläggningen visade både syreisotopsberäkningar och beräkningar med kloridjoner att cirka 25 procent åvatten tillkommit i akviferen. De kemiska parametrarna löst syre och organiskt material visade sig inte vara lämpliga som spårämnen för att bestämma källor till ett flöde. Dock kan dessa parametrar användas för att bedöma om det skett en förändring i vattenkvaliteten.

  • 192.
    Bertino, Andrea
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630), VA-teknik, Vatten, Avlopp och Avfall.
    Study on one-stage Partial Nitritation-Anammox process in Moving Bed Biofilm Reactors: a sustainable nitrogen removal.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In the last decade, several novel and cost-effective biological nitrogen removal technologies have been developed. The discovery of anaerobic ammonium oxidation (Anammox), about 15 years ago, has resulted in new opportunities for research and development of sustainable nitrogen removal systems. Compared to conventional nitrification/denitrification, Anammox eliminates necessity of external organic carbon source, has a smaller production of excess sludge, reduces energy demand for aeration (up to 60-90%) and CO2 emissions (up to 90%). Systems based on Anammox can be of great help to comply with stricter wastewater discharge regulations and reduce environmental problems caused by nutrients discharges (e.g. eutrophication).

    This thesis investigates the partial nitritation/Anammox in one stage system under oxygen limited condi-tions (also called CANON or Deammonification) and with the Moving Bed Biofilm Reactor (MBBR™) technology. Anammox process coupled with partial nitritation can be particularly suitable to treat ammo-nium-rich wastewater with low content of biodegradable organic matter, such as the reject water from dewatering of digested sludge, which is usually recirculated back to the main stream of wastewater treat-ment plants, accounting for the 15-20% of the total nitrogen load.

    Partial nitritation/Anammox process was successfully tested on a pilot plant scale for four months at 25°C, in a 200 L Continuous Stirred Tank Reactor (CSTR), filled with 40% of Kaldnes media (model K1). At an Ammonium Surface Load (ASL) of 3.45 gN m-2d-1, the removal rate was about 2.85 gN m-2d-1. Removal efficiencies of 95%, 85% and 83% were respectively achieved for NH4+-N, inorganic nitrogen, and Total Nitrogen (TN). Bacteria activity was followed by batch tests such as Specific Anammox Activity (SAA), Oxygen Uptake Rate (OUR) and Nitrate Uptake Rate (NUR), which revealed an increase in activi-ty for Nitrosomonas and Anammox bacteria within the biofilm. Dissolved oxygen concentration in the bulk liquid was a crucial parameter, whereas pH and conductivity turned out to be two useful monitoring tools.

    Two laboratory-scale reactors were previously run for two months each, in order to evaluate the one-stage partial nitritation/Anammox process with a lower ASL. One reactor was fed with diluted reject water, whereas the other one treated the effluent from UASB (Up-flow Anaerobic Sludge Blanket) reactor after sand filtration. Fairly good efficiency (>75%) were reached but, however, in the last case the low ammo-nium nitrogen load could represent a problem for a stable full-scale installation and long-term growth of Anammox bacteria.

    Some suggestions for full-scale implementation and further research are proposed in the last chapter of this master thesis.

  • 193. Bhowmick, S.
    et al.
    Nath, B.
    Halder, Dipti
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Biswas, Ashis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Majumder, S.
    Mondal, P.
    Chakraborty, S.
    Nriagu, J.
    Bhattacharya, Prosun
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Iglesias, M.
    Roman-Ross, G.
    Guha Mazumder, D.
    Bundschuh, J.
    Chatterjee, D.
    Arsenic mobilization in the aquifers of three physiographic settings of West Bengal, India: Understanding geogenic and anthropogenic influences2013Inngår i: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 262, s. 915-923Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A comparative hydrogeochemical study was carried out in West Bengal, India covering three physiographic regions, Debagram and Chakdaha located in the Bhagirathi-Hooghly alluvial plain and Baruipur in the delta front, to demonstrate the control of geogenic and anthropogenic influences on groundwater arsenic (As) mobilization. Groundwater samples (n=90) from tube wells were analyzed for different physico-chemical parameters. The low redox potential (Eh=-185 to -86mV) and dominant As(III) and Fe(II) concentrations are indicative of anoxic nature of the aquifer. The shallow (<100m) and deeper (>100m) aquifers of Bhagirathi-Hooghly alluvial plains as well as shallow aquifers of delta front are characterized by Ca2+HCO3 - type water, whereas Na+ and Cl- enrichment is found in the deeper aquifer of delta front. The equilibrium of groundwater with respect to carbonate minerals and their precipitation/dissolution seems to be controlling the overall groundwater chemistry. The low SO4 2- and high DOC, PO4 3- and HCO3 - concentrations in groundwater signify ongoing microbial mediated redox processes favoring As mobilization in the aquifer. The As release is influenced by both geogenic (i.e. geomorphology) and anthropogenic (i.e. unsewered sanitation) processes. Multiple geochemical processes, e.g., Fe-oxyhydroxides reduction and carbonate dissolution, are responsible for high As occurrence in groundwaters.

  • 194. Bhowmick, Subhamoy
    et al.
    Halder, Dipti
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik (flyttat 20130630).
    Kundu, Amit Kumar
    Saha, Debasree
    Iglesias, Monica
    Nriagu, Jerome
    Mazumder, Debendra Nath Guha
    Roman-Ross, Gabriela
    Chatterjee, Debashis
    Is Saliva a Potential Biomarker of Arsenic Exposure?: A Case-Control Study in West Bengal, India2013Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, nr 7, s. 3326-3332Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Saliva is a biological fluid that has not been used extensively as a biomonitoring tool in epidemiological studies. This study presents the arsenic (As) concentrations in saliva and urine samples collected from populations of West Bengal, India who had been previously exposed to high As levels in their drinking water. We found a significant (p < 0.05) association between the Log transformed Daily Ingestion of As (mu g day(-1)) and the As concentration in saliva (r = 0.68). Additionally, As concentration of saliva and urine also had a significant positive correlation (r = 0.60, p < 0.05). Male participants, smokers, and cases of skin lesion were independently and significantly associated with an increase in salivary As. Thus our findings show that saliva is a useful biomarker of As exposure in the study population. The study also advocates that measurement of the forms of As in saliva may additionally provide insight into the internal dose and any individual differences in susceptibility to As exposure.

  • 195.
    Billstein, Mats
    Luleå tekniska universitet.
    Development of a numerical model of flow through embankment dams1998Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 196.
    Billstein, Mats
    Luleå tekniska universitet.
    Influence of fractures and air bubbles on the pressure distribution embankment dams2000Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In some large embankment dams unexpected pore pressure distributions within the core have been observed. As an example, the piezometer pressures in WAC Bennett Dam, Canada, which rose for about four years after the reservoir was filled, were steady for two years and subsequently declined. One peak pressure head was as much as 60 m higher than the expected steady state pressure head of 40 m. However, the pressure head had dropped 55 m from the peak value 25 years later. Four hypotheses have already been proposed to explain the anomalous pore pressures within embankment dams. The objective of this study is to examine two of them, inhomogenities (e.g. fractures) in the core and trapped air bubbles, which can both be examined from a fluid mechanical point of view. The other two mechanisms, settlements and bleeding of fine material, must also be examined from a geotechnical aspect. This examination, based on results from two numerical models, is mainly theoretical. Results from numerical simulations of simplified homogeneous and inhomogeneous embankment dams are compared with analytical solutions and basic experiments. Results from numerical simulations, including the influence of air bubbles, are evaluated using a plug flow analysis and field measurements. A Hele-Shaw cell and a bed of packed glass beads, both a homogeneous and an inhomogeneous experimental set up, were used in the examination of how inhomogenities influence the pressure distribution. In the inhomogeneous case, a horizontal fracture extended from the upstream boundary to a point within the embankment. The fracture was shown to have a significant influence on the pressure distribution, discharge, seepage level, and free surface profile. The numerical model is based on a direct solution of the conservation equations (mass and momentum). In the numerical simulations, the flow resistance is determined from a laminar velocity profile in a slot with smooth walls (Hele-Shaw cell) and from the Forchheimer equation (bed of packed glass beads). The problem is considered to be two-dimensional. Since air bubbles are always initially present in the voids, that air is compressible, and that the amount of air that can go into solution increases with pressure, a mechanism that generates hydraulic blockage in the downstream part of the core can be anticipated. The blockage decreases the hydraulic conductivity in the flow direction resulting in a pressure increase. The numerical model for this case is based on a direct solution of the conservation equations (mass and momentum) and Darcy's, Boyle's, and Henry's law. It is a two-phase problem treated as one-dimensional. The main result of the study is the development of numerical models to simulate how inhomogenities and trapped air bubbles influence the pressure distribution. These models have a solid foundation, i.e. are based on conservation principles, physical laws, and the best available empirical relationships. The models have been validated through comparisons with analytical solutions, basic experiments, and field measurements and thus provide a good starting point in the development of tools that can be used in dam engineering.

  • 197.
    Billstein, Mats
    et al.
    Luleå tekniska universitet.
    Svensson, Urban
    Computer-Aided Fluid Engineering AB.
    A numerical evaluation of air bubbles as a potential explanation to the higher than expected pore pressures in the core of WAC Bennett Dam2002Inngår i: Journal of Hydraulic Research, ISSN 0022-1686, E-ISSN 1814-2079, Vol. 40, nr 5, s. 623-630Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this study is to numerically evaluate if the Air Hypothesis is a potential explanation of the unusual pressure behaviour of the core at WAC Bennett Dam. Up to now, the pore pressures have exceeded the expected normal steady state distribution for about 25 years. The Air Hypothesis describes the influence of air bubbles on the pressure distribution in the core. An increased water pressure will compress the air bubbles and increases the amount of air that can go into solution at the upstream side of the core. At the downstream side, the situation is reversed, i.e. the air volume will increase and cause a hydraulic blockage. A one-dimensional numerical model, that is based on relevant conservation laws, physical laws (Darcy's, Boyle's, and Henry's laws) and the relationships between the relative hydraulic conductivity and water saturation level, is able to predict the pressure evolution in both a qualitative and quantitative way. The model is applied to both a hypothetical core and the core of WAC Bennett Dam. Results from a plug flow analysis on the dissolution of the air in the hypothetical core are in fair agreement with the numerical results. Comparisons with pressure measurements from WAC Bennett Dam show that the Air Hypothesis is a potential explanation to the unusual pressure distribution in the core

  • 198.
    Biswas, Ashis
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Majumder, Santanu
    Neidhardt, Harald
    Halder, Dipti
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Bhowmick, Subhamoy
    Mukherjee-Goswami, Aishwarya
    Kundu, Amit
    Saha, Debasree
    Berner, Zsolt
    Chatterjee, Debashis
    Groundwater chemistry and redox processes: Depth dependent arsenic release mechanism2011Inngår i: APPLIED GEOCHEMISTRY, 2011, Vol. 26, nr 4, s. 516-525Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Patchy occurrences of elevated As are often encountered in groundwater from the shallow aquifers (<50 m) of the Bengal Delta Plain (BDP). A clear understanding of various biogeochemical processes, responsible for As mobilization, is very important to explain this patchy occurrence and thus to mitigate the problem. The present study deals with the periodical monitoring of groundwater quality of five nested piezometeric wells between December 2008 and July 2009 to investigate the temporal changes in groundwater chemistry vis-a-vis the prevalent redox processes in the aquifer. Geochemical modeling has been carried out to identify key phases present in groundwater. A correlation study among different aqueous redox parameters has also been performed to evaluate prevailing redox processes in the aquifer. The long term monitoring of hydrochemical parameters in the multilevel wells together with hydrogeochemical equilibrium modeling has shown more subtle differences in the geochemical environment of the aquifer, which control the occurrence of high dissolved As in BDP groundwater. The groundwater is generally of Ca-HCO3 type. The dissolved As concentration in groundwater exceeded both WHO and National drinking water standard (Bureau of Indian Standards; BIS, 10 mu g L-1) throughout the sampling period. The speciation of As and Fe indicate persistent reducing conditions within the aquifer [As(III): 87-97% of As-T and Fe(II): 76-96% of Fe-T]. The concentration of major aqueous solutes is relatively high in the shallow aquifer (wells A and B) and gradually decreases with increasing depth in most cases. The calculation of SI indicates that groundwater in the shallow aquifer is also relatively more saturated with carbonate minerals. This suggests that carbonate mineral dissolution is possibly influencing the groundwater chemistry and thereby controlling the mobilization of As in the monitored shallow aquifer. Hydrogeochemical investigation further suggests that Fe and/or Mn oxyhydroxide reduction is the principal process of As release in groundwater from deeper screened piezometric wells. The positive correlations of U and V with As. Fe and Mn indicate redox processes responsible for mobilization of As in the deeper screened piezometric wells are possibly microbially mediated. Thus, the study advocates that mobilization of As is depth dependent and concentrations of As in groundwater depends on single/combined release mechanisms.

  • 199.
    Björkman, Helena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Stabilitetsberäkningar och åtgärdsförslag vid islast på Skålandammen2005Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Hydropower is an important source of energy in Sweden and accounts for about 46 % of the total energy production. Sweden has about 1 200 hydropower plants and with the intention of raising the pressure head of the water and to store water, dams are built by the power plants. The storage reservoirs make it possible to adjust the energy production by demand and season. Dams in connection to the reservoirs are subjected to additional loading during periods of high floods or when an icecap in the winter is formed on the reservoirs. In order to maintain the dam safety, the power companies in Sweden are working with guidelines for dam safety from RIDAS. An important part of the work of dam safety is FDU that is carried out with purposes of improving the work of dam safety. A FDU made for the Skålan dam in the River of Ljungan showed that the levels of the safety factors for sliding and overturning of the dam was not fulfilled when subjected to loads from an icecap. The object of this thesis was to follow up the FDU and by carrying out extensive stability calculations on all parts of the Skålan dam, investigate what safety factors the different parts will get and also investigate some proposal measures in order to increase the dam stability.

    The stability calculations for the dam have been performed according to directions in RIDAS at four loading cases. Loading case I and II means a water level to the retained water level and an ice load of 200 and 100 kN/m respectively. Loading case III and IV means a situation without ice load but with a water level to the retained water level respectively a water level to a meter above the retained water level. The stability of the dam was studied with regards to sliding and overturning. The results from the stability calculations showed for both loading case I and II that the majority of the parts of the Skålan dam did not fulfill the levels of the safety factors. The calculations also showed that some parts of the dam did not fulfill the stability criteria of sliding at loading case III, which implies that these parts of the dam actually have not enough weight.

    The measure proposals studied were the ice preventive measures IR-elements and circulation of the deep warm water and the stability increasing measure with pre strained rock anchorages. The net present value (NVP) for the different measures were calculated with a life length of the dam estimated to 60 years. The results from the calculations of the NVP showed that the most economically feasible measure is circulation of the water but when considering the results from the stability calculations, the most suitable measure is the rock anchorages. Therefore, a combination of rock anchorages on parts which not fulfills the stability criteria in combination with circulation of the water is suggested to be the best measure.

  • 200.
    Blecken, Godecke-Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Biofiltration technologies for stormwater quality treatment2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Due to high runoff volumes and peak flows, and significant contamination with (inter alia) sediment, metals, nutrients, polycyclic aromatic hydrocarbons and salt, urban stormwater is a major cause of degradation of urban water ways. Since current urban drainage systems, which heavily rely on piped sewer networks, may not be sustainable, attempts are being made to develop and refine sustainable urban drainage solutions, notably in Water Sensitive Urban Design (WSUD) and Low Impact Development (LID) concepts. Promising systems recommended for application in both WSUD and LID are stormwater biofilters (also known as bioretention systems or rain gardens) using vegetated filter media. Besides their capacity to attenuate flows and minimise runoff volumes, stormwater biofilters have proven efficacy for enhancing effluent water quality. Furthermore, they can be aesthetically pleasingly integrated even in dense urban environments. However, there are still gaps in our knowledge of the variability of biofilters' pollutant removal performance, and the factors that affect their performance.In the studies this thesis is based upon, the effects of various ambient factors, stormwater characteristics and modifications of filter design on the removal of metals, nutrients and total suspended solids (TSS) in biofilters, and pollutant pathways through them, have been investigated. For these purposes, standard biofilters and variants equipped with a submerged zone, a carbon source and different filter materials were exposed to varying temperatures and dry periods, dosed with stormwater and snowmelt, and the inflow and outflow concentrations of the pollutants were measured.Although removal percentages were consistently high (>70%), demonstrating that biofilters can reliably treat stormwater, the results show that metal outflow concentrations may vary widely depending on the biofilter design and the ambient conditions. Prolonged drying especially impaired their removal efficiency, but variations in temperature and filter media variations had little effect on metal removal rates. The adverse effects of drying could be mitigated by using a submerged zone, and thus providing a more constant moisture regime in the filters between storm events. Combined with embedded organic matter, the submerged zone especially significantly enhances Cu removal, helping to meet outflow target concentrations. Similarly, installing a mulch layer on top of the filter provides additional sorption capacity, hence metals do not ingress far into the filter and are mainly trapped on/in the top layer by sorption processes and/or mechanical trapping associated with TSS. This leads to significant metal accumulation, which facilitates biofilter maintenance since scraping off the top layer removes high proportions of previously accumulated metals, thus delaying the need to replace the whole filter media. However, removal of accumulated pollutants from the filter media is crucial for successful long-term performance of the filters to ensure that no pollutant breakthrough occurs.Nitrogen removal was found to be more variable than metal removal, and to be adversely affected by temperature increases, leading to high nitrogen leaching in warm temperatures. Phosphorus removal rates were consistently high, since most phosphorus was particle-bound and thus trapped together with TSS. However, in initial stages phosphorus was washed out from the filter media, indicating that filter media that do not have high levels of labile phosphorus should be used to avoid high effluent concentrations. Given that most outflow concentrations were far lower than those in the stormwater, biofilters are appropriate stormwater treatment systems. Dependent on the ambient conditions, the target pollutants and the sensitivity of the recipient, adaptation of the filter design is recommended. Further work is required to investigate the winter performance and improve the reliability of nitrogen removal, which is highly variable.

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