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  • 1.
    Andersson, Simon
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Callin, Veronika
    Mälardalen University, School of Business, Society and Engineering.
    SMÅSKALIG VATTENKRAFT OCH FLEXIBILITET I ELSYSTEMET: En kartläggning av förväntningarna på den småskaliga vattenkraftens potential att bidra med flexibilitet.2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 2.
    Diehl, Stefan
    et al.
    Lund University, Sweden.
    Zambrano, Jesús
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Carlsson, Bengt
    Uppsala University, Sweden.
    Steady-State Analyses of Activated Sludge Processes with Plug-Flow Reactor2017In: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437, Vol. 5, no 1, p. 795-809Article in journal (Refereed)
    Abstract [en]

    Activated sludge processes (ASPs) consisting of a plug-flow reactor (PFR) and a settler are analyzed in steady-state operation using a reduced model consisting of one soluble substrate and one particulate biomass component modelling the dominating biological process. Monod biomass growth rate is assumed. Two settler models are studied. One is the commonly used ideal settler, or point settler, which is assumed to never be overloaded and to have unlimited flux capacity. The other recently published steady-state settler model includes hindered and compressive settling, and models a realistic limiting flux capacity. Generally, the steady-state concentration profiles within the PFR and the settler are governed by nonlinear ordinary differential equations. It is shown that the steady-state behaviour of the ASP can, however, be captured by equations without derivatives. New theoretical results are given, such as conditions by means of inequalities on input variables and parameters for a steady-state solution to exist. Another novel finding is that, if the incoming substrate concentration is increased from a low or moderate stationary value and the solids residence time is kept fixed, then this results in a lower effluent concentration in the new steady state. The steady-state equations are solved numerically for different operating conditions. For common parameter values, numerical solutions reveal that an ASP having a PFR, instead of a continuously stirred tank reactor, is far more efficient in reducing the effluent substrate concentration and this can be obtained for much lower recycle ratios, which reduces the pumping energy considerably.

  • 3.
    Färm, Carina
    Mälardalen University, Department of Public Technology.
    Constructed Filters for Metal Reduction in Storm Water2002In: Vatten, ISSN 0042-2886, no 3, p. 185-191Article in journal (Refereed)
    Abstract [en]

    Increased demand for storm water treatment has created development in filtration technologies for storm water. Manufacturers are using different filtration facilities and different filter materials. Therefore there is a need - from manufacturers, universities and government organisations - to put together current knowledge and to clarify important aspects concerning constructed filter systems. The first part of this paper reviews filtration facilities for storm water, filter substrates that have been tested for heavy metal reduction, and processes for contaminant transport through filter substrates. The second part of the paper presents an investigation of pine bark, used as a substrate in gully-pot filters for metal reduction in storm water.

  • 4.
    Färm, Carina
    Mälardalen University, Department of Public Technology.
    Evaluation of the accumulation of sediment and heavy metals in a storm-water detention pond2002In: Water Science and Technology, ISSN 0273-1223, Vol. 45, no 7, p. 105-112Article in journal (Refereed)
    Abstract [en]

    Accumulation of sediments and water quality were investigated in a wet storm-water detention pond in central Sweden. The drainage area surrounding the pond was covered by a section of highway and secondary roads. Sediment samples were collected from the pond and heavy-metal concentrations analysed subsequently in the laboratory. The depth of accumulated sediments was measured at several points around the pond. The investigation showed that during the 18 months that had passed since the pond was constructed, a 5-8 cm layer of sediments had accumulated near the inlet, and a 1.5 cm layer near the outlet of the pond. Storm water passing through the detention pond showed an average reduction rate of 26-84% for total metal content, 67% for total N, 78% for total P and 92% for COD.

  • 5.
    Färm, Carina
    Mälardalen University, Department of Public Technology.
    Metal Sorption to Natural Filter Substrates for Storm Water Treatment - Column Studies2002In: The Science of the Total Environment, ISSN 0048-9697, Vol. 298, no 1-3, p. 17-24Article in journal (Refereed)
    Abstract [en]

    Storm water generated from road runoff contains pollutants such as metals that are either dissolved in storm water or bound to particulates. Using detention ponds for the treatment of storm water from road runoff, where particles can settle, can reduce the level of particulate-bound metals in the water, while small particles and dissolved matter pass through the detention pond. Some of these metals can be removed by filtrating water through specially constructed filter systems. This investigation is a laboratory study where different filter substrates were tested in order to evaluate their efficiency in reducing heavy metals from water. Metal solutions were filtered through columns filled with various substrates consisting of combinations of calcium silicate rock (opoka), zeolite and peat. The metal-removal efficiency was correlated to hydraulic load, and for the metal species the reduction efficiency decreased with increased hydraulic load. Mixtures of opoka and zeolite were found to be superior to the other filter-substrate combinations tested with regard to both hydraulic aspects and removal efficiency. Peat mixed with the calcium silicate rock was not successful due to clogging which stopped the experiment. A manufactured product made from the calcium silicate rock (burned opoka) was found to be less useful because of its calcium oxide (CaO) content. Among the tested filter substrates, mixtures of opoka and zeolite seemed to be the most useful compositions with respect to reduction-efficiency and clogging aspects. The removal capacity of metals varied from 0.6 to 1.8 kg m(-3) depending on the metal and the filter substrate. 

  • 6.
    Färm, Carina
    Mälardalen University, Department of Public Technology.
    Removal of heavy metals in water by pine bark2003In: Vatten, ISSN 0042-2886, no 1Article in journal (Refereed)
    Abstract [sv]

    Metals that are dissolved in storm water can be removed by filtrating water through specially constructed filter systems. Pine bark is an interesting material for this purpose, but it needs further investigations regarding its removal efficiency of metals. This paper presents a laboratory study where pine bark was tested to evaluate its efficiency in reducing heavy metals in water. Metal solutions were prepared and used in batch tests with pine bark. The metal removal efficiency was correlated to different metal concentrations in the solution and different contact times between the pine bark and the metal solution. The results showed that a high metal removal was achieved after a short contact time. The metal removal was low for low metal concentrations (0.1 mg/L) and higher for metal concentrations from 1 to 10 mg/L. The removal capacity was found to be 2.6 g Cu, 1.3 g Zn and 3.8 g Pb per kg pine bark. An investigation of the influence of chloride in the metal solution showed that the metal removal decreased by 15-23 %, depending on the metal, in the presence of chloride. Sorption isotherms of Zn, Cu and Pb on pine are also presented in the paper.

  • 7.
    Khokhotva, Oleksandr
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Waara, Sylvia
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Urea treated pine bark -a low cost sorbent with improved metal sorption characteristics2009In: Ogolnopolska Konferencja naukowa inzynieria ekologiczna / [ed] Hanna Obarska Pempkowiak, Gdansk: Polish Academy of Science , 2009, p. 188-198Conference paper (Other academic)
  • 8.
    Olsson, Jesper
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Forkman, T.
    Swedish University of Agricultural Sciences, Sweden.
    Gentili, F.G.
    Swedish University of Agricultural Sciences, Sweden.
    Zambrano, Jesús
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Anaerobic co-digestion of sludge and microalgae grown inmunicipal wastewater: A feasibility study2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 77, no 3, p. 682-694Article in journal (Refereed)
    Abstract [en]

    In this study a natural mix of microalgae grown in wastewater of municipal character was co-digested with sewage sludge in mesophilic conditions, in both batch and semi-continuous modes. The semicontinuous experiment was divided into two periods with OLR 1 (Organic Loading Rate) of 2.4 kg VS m3 d-1 and HRT1 (Hydraulic Retention Time) of 15 days, and OLR2 of 3.5 kg VS m3 d-1 and HRT2 of 10 days respectively. Results showed stable conditions during both periods. The methane yield was reduced when adding microalgae (from 200 ± 25 NmL CH4 g VSin-1 , to 168±22 NmL CH4 g VSin-1). VS reduction was also decreased by 51%. This low digestability was confirmed in the anaerobic batch test. However, adding microalgae improved the dewaterability of the digested sludge. The high heavy metals content in the microalgae resulted in a high heavy metals content in the digestate, making it more difficult to reuse the digestate as fertilizer on arable land. The heavy metals are thought to originate from the flue gas used as a CO2 source during the microalgae cultivation. Therefore the implementation of CO2 mitigation via algal cultivation requires careful consideration regarding thesource of the CO2-rich gas.

  • 9.
    Olsson, Jesper
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Schwede, Sebastian
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Microalgae as biological treatment for municipal wastewater - Effects on the sludge handling in a treatment plant2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, ISSN 0273-1223, Vol. 78, no 3, p. 644-654Article in journal (Refereed)
    Abstract [en]

    A mix of microalgae and bacteria was cultivated on pre-sedimented municipal wastewater in a continuous operated microalgae-activated sludge process. The excess material from the process was co-digested with primary sludge in mesophilic and thermophilic conditions in semi-continuous mode (5 L digesters). Two reference digesters (5 L digesters) fed with waste-activated sludge (WAS) and primary sludge were operated in parallel. The methane yield was slightly reduced (≈10%) when the microalgal-bacterial substrate was used in place of the WAS in thermophilic conditions, but remained approximately similar in mesophilic conditions. The uptake of heavy metals was higher with the microalgal-bacterial substrate in comparison to the WAS, which resulted in higher levels of heavy metals in the digestates. The addition of microalgal-bacterial substrate enhanced the dewaterability in thermophilic conditions. Finally, excess heat can be recovered in both mesophilic and thermophilic conditions. 

  • 10.
    Samuelsson, Oscar
    et al.
    Uppsala University, Sweden.
    Björk, Anders
    IVL Swedish Environmental Research Institute, Sweden..
    Zambrano, Jesus
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Carlsson, Bengt
    Uppsala University, Sweden.
    Fault signatures and bias progression in dissolved oxygen sensors2018In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 78, no 5, p. 1034-1044Article in journal (Refereed)
    Abstract [en]

    Biofilm fouling is known to impact the data quality of sensors, but little is known about the exact effects. We studied the effects of artificial and real biofilm fouling on dissolved oxygen (DO) sensors in full-scale water resource recovery facilities, and how this can automatically be detected. Biofilm fouling resulted in different drift direction and bias magnitudes for optical (OPT) and electrochemical (MEC) DO sensors. The OPT-sensor was more affected by biofilm fouling compared to the MEC sensor, especially during summer conditions. A bias of 1 mg/L was detected by analysing the impulse response (IR) of the automatic air cleaning system in the DO sensor. The IR is an effect of a temporal increase in DO concentration during the automatic air cleaning. The IRs received distinct pattern changes that were matched with faults including: biofilm fouling, disturbances in the air supply to the cleaning system, and damaged sensor membrane, which can be used for fault diagnosis. The results highlight the importance of a condition based sensor maintenance schedule in contrast to fixed cleaning intervals. Further, the results stress the importance of understanding and detecting bias due to biofilm fouling, in order to maintain a robust and resource efficient process control.

  • 11.
    Sylwan, Ida
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Runtti, Hanna
    Oulu University, Finland.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Zambrano, Jesus
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Westholm, Lena Johansson
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    BIOCHAR ADSORPTION FOR SEPARATION OF HEAVY METALSIN MUNICIPAL WASTEWATER TREATMENT2018Conference paper (Other academic)
  • 12.
    Waara, Sylvia
    et al.
    Mälardalen University, Department of Public Technology. Mälardalen University, School of Sustainable Development of Society and Technology.
    Waara, Karl-Otto
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Forsberg, Åke
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Fridolfsson, Magnus
    Performance of a constructed wetland system for treatment of landfill leachate.2008In: Waste 2008. Waste and Resource management-A shared responsibility, 2008, p. 655-667Conference paper (Refereed)
    Abstract [en]

    The performance of a constructed wetland for treatment of landfill leachate has been evaluated based upon data obtained during 4 years (2003-2006). It consists of a series of 10 ponds with a total capacity of 52.000 m3 covering 8 ha. Using univariate and multivariate statistics (PCA) the reduction pattern of a large number of chemical parameters including heavy metals has been investigated in 3 parts of the wetland with equal volume. Analyses show that many parameters are removed to the greatest extent in the first part of the system (e.g. many heavy metals, total suspended solids) or the second part of the system (N-NH4) while other parameters such as total nitrogen are more gradually reduced (10 ton/year removed).  Toxicity testing with 5 bioassays showed that toxicity was sometimes observed at the inlet but no toxicity was observed at the outlet for 4 of the test species. The data presented will be used for optimizing the treatment process as well as to improve the monitoring program.

  • 13.
    Zambrano, Jesús
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Carlsson, Bengt
    Uppsala University, Sweden.
    Diehl, Stefan
    Lund University, Sweden.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    A Simplified Model of an Activated Sludge Process with a Plug-Flow Reactor2016Conference paper (Refereed)
    Abstract [en]

    The analysis of a simplified activated sludge process (ASP) with one main dissolved substrate and one main particulate biomass component has been conducted with respect to its steady-state. The ASP is formed by a plug flow reactor (PFR) and a settler with the recycling going to the reactor. The biomass growth rate is described by a Monod function. For this process, it is not possible to get an explicit expression for the effluent substrate concentration when the process is subject to a fixed sludge age. However,in the normal case when the influent substrate concentration is much greater than the effluent substrate concentration, then an explicit approximation for the effluent as a function of the influent and the process parameters is obtained. This work includes numerical examples considering two models for the settler. One model is the ideal settler, which assumes a complete thickening of the activated sludge through the underflow of the settler. The other model takes into account hindered settling and sludge compression. Numerical results show the effectiveness and the limitations of the proposed solution under these scenarios.

1 - 13 of 13
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