| 1. |
- Berndtsson, Ronny, et al.
(författare)
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Drivers of changing urban flood risk : A framework for action
- 2019
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Ingår i: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 240, s. 47-56
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on drivers for changing urban flood risk. We suggest a framework for guiding climate change adaptation action concerning flood risk and manageability in cities. The identified key drivers of changing flood hazard and vulnerability are used to provide an overview of each driver's impact on flood risk and manageability at the city level. We find that identified drivers for urban flood risk can be grouped in three different priority areas with different time horizon. The first group has high impact but is manageable at city level. Typical drivers in this group are related to the physical environment such as decreasing permeability and unresponsive engineering. The second group of drivers is represented by public awareness and individual willingness to participate and urbanization and urban sprawl. These drivers may be important and are manageable for the cities and they involve both short-term and long-term measures. The third group of drivers is related to policy and long-term changes. This group is represented by economic growth and increasing values at risk, climate change, and increasing complexity of society. They have all high impact but low manageability. Managing these drivers needs to be done in a longer time perspective, e.g., by developing long-term policies and exchange of ideas.
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| 2. |
- Betsholtz, Alexander, et al.
(författare)
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Sewage sludge-based activated carbon – Production and potential in wastewater and stormwater treatment
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- SummarySustainable sewage sludge management has been a heavily debated topic in Europe for more than a decade. Due to its content of pollutants such as heavy metals, pharmaceuticals and other organic micropollutants, the use of sewage sludge for farmland application is currently banned or restricted in most European countries. Therefore, alternative methods for sludge management are discussed. The production of sludge-based activated carbon (SBAC) from digested sewage sludge is an alternative that would make use of problematic waste—sewage sludge—to produce a potentially valuable adsorbent. In this study, SBAC has been reviewed based on its potential use as an adsorbent for pollutants in wastewater and stormwater. The study consists of a literature review targeting (i) different methods for SBAC production, (ii) the influence of the production methods on the physical and chemical properties of the activated carbons and (iii) the importance of physical and chemical carbon properties on the adsorption of various types of pollutants in aquatic solutions. In connection to the literature study, SBAC was produced in the laboratory using a one-step steam activation method in order to study how various production parameters, such as pyrolysis temperature and steam oxidation, affect the porosity development of SBAC. The porosity of the carbon was assessed using N2adsorption and desorption isotherms at 77 K. Several combinations of the decisive parameters at various levels were tested and consequently the steam activated SBAC with highest volume of micropores (and highest specific surface area) was selected and tested for the adsorption of chemical oxygen demand (COD) and inorganic nutrients (NH4+, NO3-and PO43-) in wastewater from Källby WWTP in Lund, Sweden. As a reference, the SBAC was compared with a commercial activated carbon (CAC), Norit Sae Super (from Cabot), with a BET surface area of 975 m2/g. The results from existing literature show that SBAC, due to their high inorganic content, in general exhibit low micropore volumes compared to CAC, and therefore also tend to have a lower adsorption potential for small organic substances. However, the larger pores of the SBAC might be advantageous for adsorption of large organic pollutants such as dyes. In addition, the inorganic content of SBAC may contribute to the adsorption of charged and/or hydrophilic substances that are adsorbed through chemical interactions with surface functional groups of the carbon, rather than by physical adsorption to the core carbon structure. With respect to SBAC production, both feedstock type (e.g. biological sludge vs. chemical sludge) and production method (chemical vs. physical activation) have large influence on the properties of the carbon. In general, chemical activation using strong acids or based tend to generate SBAC with higher micropore volumes and abundance of surface functional groups compared to physical activation methods (such as steam activation), although its applicability can be questioned due to the large required input of chemicals. The result from the laboratory studies show that steam activated SBAC with BET surface areas of up to 162 m2/g could be generated using one-step steam activation at 800 °C for 30 minutes, although activation parameters were not optimized with respect to maximum surface area generation. The adsorption experiments showed that CAC was much better at adsorbing COD in effluent wastewater compared to the steam activated SBAC produced in lab, especially at low carbon concentrations. The experiments further showed that neither CAC nor SBAC was successful in adsorbing large quantities of inorganic nutrients (NH4+, NO3-and PO43-), probably due to lack of charged surface functional groups. Much work remains in order to demonstrate large scale production of SBAC in order to evaluate the economic feasibility of the process. In connection, more work is needed to understand how to maximize the potential of SBAC for the uptake of specific substances such as heavy metals or hydrophilic micropollutants.
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| 3. |
- Davidsson, Åsa, et al.
(författare)
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Effect of anaerobic digestion at 35, 55 and 60 °C on pharmaceuticals and organic contaminants
- 2014
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 69:6, s. 1282-1288
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Tidskriftsartikel (refereegranskat)abstract
- The application of treated sewage sludge on farmland is a suggested method for recycling nutrients and reducing demand for commercial fertilizer. However, sludge needs to be safe from possible contaminants which can cause acute and long-term health and environmental problems. Residual pharmaceuticals and organic contaminants are mentioned as emerging threats since wastewater treatment plants are not designed to degrade these substances. The aim of this study was to screen and evaluate the presence, and reduction, of pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) during anaerobic digestion of mixed primary and waste-activated sludge at 35, 55 and 60°C and during pasteurization at 70°C. The study showed the difficulty of analysing pharmaceutical compounds in low concentrations in the sludge matrix. No general reduction of these compounds was seen during treatment, but for individual substances some reduction occured. The PAHs were generally not reduced during digestion or pasteurization, but for three substances (indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene (analysed together) and benzo[g,h,i]perylene) reduction (up to 60%) during digestion was seen. Digestion at 35 and 55°C resulted in about the same order of reduction of the three individual PAHs, which was higher than for digestion at 60°C.
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| 4. |
- Davidsson, Åsa, et al.
(författare)
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Effect of anaerobic digestion at 35, 55 and 60 °C ON pharmaceuticals and organic pollutants
- 2013
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Ingår i: Presented at the 1st International IWA Conference on Holistic Sludge Management, Västerås, Sweden, May 6-8, 2013. ; , s. 1-8
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Konferensbidrag (refereegranskat)abstract
- The application of treated sewage sludge on farmland is a suggested method for recycling nutrients and reducing demand for commercial fertilizer. However sludge needs to be rendered safe from possible contaminants which can cause acute and long-term health and environmental problems. Residual pharmaceuticals and organic contaminants in sludge are mentioned as emerging threats since wastewater treatment plants are not designed to degrade these substances thus yielding an accumulation in sludge. The aim of this study was to evaluate the presence, and reduction, of pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) during anaerobic digestion at 35, 55 and 60ºC and during pasteurization at 70°C. The substrate used was mixed primary and secondary sludge from a 300 000 person-equivalents municipal wastewater treatment plant in southern Sweden. In general no reduction of pharmaceuticals could be observed at any temperature or minimum exposure time, except for the beta-blocker Irbesartan and the antibiotic Trimethoprim. The results from pharmaceuticals in mesophilic sludge agreed with results in recent Swedish studies. Also, no reduction of PAHs during digestion or pasteurization (70°C – 1 hour) was seen, but for single PAHs digestion could lead to reduction.
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| 5. |
- Haghighatafshar, Salar, et al.
(författare)
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A physically based model for mesoscale SuDS–an alternative to large-scale urban drainage simulations
- 2019
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797. ; 240:15 June 2019, s. 527-536
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a deterministic, lumped model to simulate mesoscale sustainable drainage systems (SuDS) based on a conceptualization of the stormwater control measures (SCMs) making up the system and their influence on the runoff process. The conceptualization mainly relies on parameters that are easily quantifiable based on the physical characteristics of the SCMs. Introducing a nonlinear reservoir model at the downstream end of the SuDS results in a fast model that can realistically describe the runoff process at low computational cost. Modelled hydrographs for the study area in Malmö, Sweden, matched data with regard to the overall shape of the hydrograph as well as the peak discharge and lag time. These output parameters are critical factors to be considered in the design of large systems consisting of mesoscale SuDS. The algebraic foundation of the developed model makes it suitable for large-scale applications (e.g., macroscale), where the simulation time is a decisive factor. In this respect, city-wide optimization studies for the most efficient location and implementation of SuDS are substantially accelerated due to fast and easy model setup. Moreover, the simplicity of the model facilitates more effective communication between all the actors engaged in the urban planning process, including political decision makers, urban planners, and urban water engineers.
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| 6. |
- Haghighatafshar, Salar
(författare)
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Blue-green stormwater systems for citywide flood mitigation : Monitoring, conceptualization, modeling, and evaluation
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Considering the growth in urbanization, leading to an increase in impervious surfaces, and the changing climate, enhancing the intensity and frequency of rainfall events, existing urban drainage networks—separate or combined sewer systems—are presumed to face substantially elevated hydraulic loads, causing pluvial floods in urban areas. There are several ways to address these challenges. Cities can invest in replacing existing pipes with new larger pipes to enhance the hydraulic capacity of the drainage network. This solution is considered to be extremely expensive and unsustainable. An alternative solution is to manipulate urban surfaces by constructing blue-green (open) stormwater systems. These systems are built on urban surfaces and include approaches that mimic natural processes, such as infiltration, evaporation, transpiration, pond storage, and slow transport of stormwater through ditches. The implementation of blue-green stormwater systems in dense cities would, to some extent, relieve the overload. However, the method for identifying urban areas in which the implementation of blue-green stormwater systems would have a larger effect hydraulically on the existing sewer network is unestablished.Thus, general aim of this thesis was to develop a method for studying the interactions between piped drainage networks and blue-green stormwater systems on the city-scale, performed in four steps, which shape the backbone of this thesis:•An existing blue-green stormwater system—i.e. the Eco-city of Augustenborg in Malmö—was examined to understand how such systems work, locally and regarding the surrounding neighborhoods.•A simple conceptual model for blue-green stormwater systems was proposed.•Based on the proposed concept, a fast, easy-to-use, and robust modeling tool was developed, making it possible to simulate the interaction between blue-green stormwater systems and sewer networks.•The modeling tool was supplemented with a hydroeconomic optimization algorithm and evaluated on the city-scale to identify the most effective site and size for blue-green stormwater systems throughout the catchment of the sewer network.The developed method and toolchain constitute a new platform for increasing our understanding of complex urban drainage networks. This platform is also a starting point for the development of a more reliable tool for the initial screening of urban catchments to identify urban areas in which it is hydraulically and economically efficient to construct neighborhood-scale blue-green stormwater systems.
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| 7. |
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| 8. |
- Haghighatafshar, Salar, et al.
(författare)
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Conceptualization and Schematization of Mesoscale Sustainable Drainage Systems: A Full-Scale Study
- 2018
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 10:8
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Tidskriftsartikel (refereegranskat)abstract
- Sustainable Drainage Systems (SuDS) can be considered the joint product of water engineering and urban planning and design since these systems must comply with hydraulic, hydrologic, and social-ecological functions. To enhance this joint collaboration, a conceptual model of mesoscale SuDS is introduced based on the observed rainfall-runoff responses from two catchments with SuDS and a pipe-bound catchment. The model shows that in contrast to pipe systems, SuDS disaggregates the catchment into a group of discrete mini catchments that have no instant connection to the outlet. These mini catchments start to connect to each other (and perhaps to the outlet) as the rainfall depth increases. It is shown that the sequence of stormwater control measures (SCMs as individual components of SuDS) affects the system's overall performance depending on the volumetric magnitude of the rainfall. The concept is useful in the design and implementation of mesoscale SuDS retrofits, which include several SCMs with different retention and detention capacities within a system.
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| 9. |
- Haghighatafshar, Salar, et al.
(författare)
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Deep Learning for Modelling of Urban Drainage Networks: A Physics-informed Surrogate Model Using Measured and Simulated Data
- 2022
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Ingår i: Proceedings of IWA World Water Congress & Exhibition, Copenhagen 2022.
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Konferensbidrag (refereegranskat)abstract
- City-wide climate adaptation for pluvial flood mitigation requires fast and reliable simulation tools. Considering the limitations of hydrodynamic models at city-scale simulations, data driven models have high potential in the development of surrogate tools. This study explores the Google DeepMind WaveNet™ model architecture to map hydrological response of catchments onto hydraulic parameters of the pipe network in a physically informed approach to deep learning. The WaveNet-based surrogate model successfully predicted hydraulic head and pipe flow in the network at average Normalized Nash-Sutcliffe Model Efficiency Indices of above 0.8, while boosting simulation speed by a factor of 1000. The developed AI model can be used for different assessment and optimization studies on the drainage network, thanks to its physics-informed structure.
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| 10. |
- Haghighatafshar, Salar, et al.
(författare)
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Efficiency of blue-green stormwater retrofits for flood mitigation – Conclusions drawn from a case study in Malmö, Sweden
- 2018
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797. ; 207, s. 60-69
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Tidskriftsartikel (refereegranskat)abstract
- Coupled one-dimensional (1D) sewer and two-dimensional (2D) overland flow hydrodynamic models were constructed to evaluate the flood mitigation efficiency of a renowned blue-green stormwater retrofit, i.e. Augustenborg, in Malmö, Sweden. Simulation results showed that the blue-green stormwater systems were effective in controlling local surface flooding in inner-city catchments, having reduced the total flooded surfaces by about 70%. However, basement flooding could still be a potential problem depending on the magnitude of the inflows through combined sewer from upstream areas. Moreover, interactions between blue-green retrofits and the surrounding pipe-system were studied. It was observed that the blue-green retrofits reduced the peak flows by approximately 80% and levelled out the runoff. This is a substantial advantage for downstream pipe-bound catchments, as they do not receive a cloudburst-equivalent runoff from the retrofitted catchment, but a reduced flow corresponding to a much milder rainfall. Blue-green retrofits are more effective if primarily implemented in the upstream areas of a pipe-bound catchment since the resulting reduced runoff and levelled out discharge would benefit the entire network lying downstream. Implementing blue-green retrofits from upstream towards downstream can be considered as a sustainable approach.
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