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  • 1.
    Eskandari, Samieh
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Mohammadi, Ali
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Sandberg, Maria
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Eckstein, Rolf Lutz
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Hedberg, Kjell
    Ulf Ahlden Ingenjörsfirma, Upplands Väsby.
    Granström, Karin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Hydrochar-Amended Substrates for Production of Containerized Pine Tree Seedlings under Different Fertilization Regimes2019In: Agronomy, E-ISSN 2073-4395, Vol. 9, no 7, p. 1-17Article in journal (Refereed)
    Abstract [en]

    There is a growing body of research that recognizes the potentials of biochar application in agricultural production systems. However, little is known about the effects of biochar, especially hydrochar, on production of containerized seedlings under nursery conditions. This study aimed to test the effects of hydrochar application on growth, quality, nutrient and heavy metal contents, and mycorrhizal association of containerized pine seedlings. The hydrochar used in this study was produced through hydrothermal carbonization of paper mill biosludge at 200 °C. Two forms of hydrochar (powder and pellet) were mixed with peat at ratios of 10% and 20% (v/v) under three levels of applied commercial fertilizer (nil, half and full rates). Application of hydrochar had positive or neutral effects on shoot biomass and stem diameter compared with control seedlings (without hydrochar) under tested fertilizer levels. Analysis of the natural logarithmic response ratios (LnRR) of quality index and nutrient and heavy metal uptake revealed that application of 20% (v/v) hydrochar powder or pellet with 50% fertilizer resulted in same quality pine seedlings with similar heavy metal (Cu, Ni, Pb, Zn and Cr) and nutrient (P, K, Ca and Mg) contents as untreated seedlings supplied with 100% fertilizer. Colonization percentage by ectomycorrhizae significantly increased when either forms of hydrochar were applied at a rate of 20% under unfertilized condition. The results of this study implied that application of proper rates of hydrochar from biosludge with adjusted levels of liquid fertilizer may reduce fertilizer requirements in pine nurseries.

  • 2.
    From-Aldaron, M.
    et al.
    Karlstad University.
    Sandberg, Maria
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Granström, Karin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Low Dosage Chemical Treatment for Improved Oxygenation of Pulp Mill Effluents2018In: Journal of environmental engineering, ISSN 0733-9372, E-ISSN 1943-7870, Vol. 144, no 3, article id 06017012Article in journal (Refereed)
    Abstract [en]

    Most pulp and paper mills use aerobic biological treatment for their effluents. Aeration is the single most energy intensive process of a treatment plant. Surfactants, commonly occurring in pulping wastewaters, have been shown to decrease the oxygen transfer rate. The aim of this study was to decrease the surface activity of surfactants and thereby increase the oxygen transfer rate in pulp mill effluents by the use of chemical pretreatment in very low doses. Trials using 5 g/m(3) ferric iron showed statistically significant improvement on both k(L)a(@20) and surface tension. No sludge was precipitated owing to the very low ferric iron dosage. The novel use of chemical pretreatment, in very low doses, aiming specifically at improving oxygen transfer rate, is a promising concept for reducing the need for aeration in wastewater treatment and thus lower the electricity requirement of the wastewater treatment plant. (c) 2017 American Society of Civil Engineers.

  • 3.
    Granström, Karin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Hagelqvist, Alina
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Sandberg, Maria
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Efficiency of techniques for purification of condensate from wood dryers2013Conference paper (Refereed)
  • 4.
    Granström, Karin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden..
    Sandberg, Maria
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013). Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden..
    Characterization of Wood-Dryer Condensate with Assessment of Toxicity to Microorganisms2017In: Journal of environmental engineering, ISSN 0733-9372, E-ISSN 1943-7870, Vol. 143, no 7, article id 04017019Article in journal (Refereed)
    Abstract [en]

    Drying of wood causes airborne emissions that can be reduced by recirculating all or part of the drying medium. This favors both emission control and energy efficiency, but results in a condensate that contains significant amounts of organic compounds. Drying operations have been requested by municipal regulatory bodies to clean the condensate before release. The industry has tested biological treatment of condensate from biomass dryers, but maintaining the viability of microorganisms has been a challenge. In this study, the effect of drying gas temperature and the final wood moisture content on the chemical composition and acute toxicity of the condensate was tested. Results showed that whereas the condensate from wood drying was extremely toxic to Vibrio fischeri employed in Microtox assays, the undefined mixed culture present in biosludge from a pulp and paper mill treatment plant were considerably less affected. (C) 2017 American Society of Civil Engineers.

  • 5.
    Granström, Karin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Hur påverkar undervisning om hållbar utveckling studenterna?2009In: Kapet, ISSN 1653-4743, Vol. 1, no 1, p. 37-51Article in journal (Other academic)
    Abstract [sv]

    Hållbar utveckling har integrerats i kurserna Miljökemi och Reningsteknik i högskoleingenjörsprogrammet Energi- och miljöteknik vid Karlstads universitet. Syftet med denna undersökning var att analysera studenternas kännedom om, förståelse av och attityd till hållbar utveckling, samt att se om studenterna anser att de i sin kommande yrkesroll som ingenjörer kan bidra till en hållbar samhällsutveckling.

    Enkäter användes för att mäta studenternas kunskap om hållbar utveckling, attityd till hållbar utveckling och relaterade frågeställningar, samt deras uppfattning om framtiden och sin egen roll. Studenternas förståelse av begreppet hållbar utveckling undersöktes genom analys av argumentationen vid debatter.

    Resultatet blev att kännedomen om begreppet hållbar utveckling ökade under kursernas gång, och studenterna visade prov på att ha insikter i såväl ekologisk som ekonomisk och social hållbarhet. Studenternas attityder visade på ett stort stöd för en hållbar samhällsutveckling och en hög medvetenhet om miljöproblemen. Signifikanta skillnader mellan studenter som läste Miljökemi respektive Reningsteknik var att de som läste Miljökemi hade betydligt större förkunskaper, samt att de efter kursen var mer skeptiska till bibehållen hög ekonomisk tillväxt med negativa effekter på miljön. Studenternas uppfattning om framtiden är långt ifrån enhetlig; positivt var att mätningen inte gav höga utslag vare sig för alternativet ekologisk och ekonomisk kollaps eller för alternativet att det behövs auktoritärt ledarskap. En överväldigande majoritet av studenterna ser möjligheter att efter examen, i sitt yrke, bidra till en hållbar utveckling av samhället.

  • 6.
    Granström, Karin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Williams, Helen
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Berghel, Jonas
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Frodeson, Stefan
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Renström, Roger
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Ståhl, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    The importance of a holistic perspective when investigating agricultural products as additives in sustainable pellets development2012Conference paper (Refereed)
  • 7.
    Mohammadi, Ali
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Govindarajan, Venkatesh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Eskandari, Samieh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013). Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Granström, Karin
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Life cycle assessment of combination of anaerobic digestion andpyrolysis: focusing on different options for biogas use2019In: Advances in Geosciences, ISSN 1680-7340, Vol. 49, p. 57-66Article in journal (Refereed)
    Abstract [en]

    The combination of anaerobic digestion and pyrolysistechnologies could be a novel energy-biochar productionsystem to maximize energy and nutrient recovery frompulp and paper mill sludge. Herein, the life-cycle energy productionand emissions reduction of sludge treatment from atypical pulp and paper mill were investigated, in which alternativeuses of biogas for industrial or household application,in different regions of the world, were assessed. Thethree scenarios considered for different end-uses of biogasare: (A) biogas for vehicle fuel in the transportation sectorin Sweden, (B) biogas for heat and electricity in the powersector in Brazil, and (C) biogas for cooking in households inChina. The results of Environmental Life-Cycle Assessment(E-LCA) show that for all these three scenarios, the use ofbiogas and pyrolysis gas contributes most to emissions mitigation,while the dewatering and drying processes carriedout on the sludge, contribute the most to the environmentalemissions. Addition of biochar to the soil, contributes significantlyto a reduction in global warming by sequesteringcarbon in the soil. Compared to scenarios B and C, ScenarioA, in which biogas substitutes gasoline in transportation, andheat from combusted pyrolysis gases is used for district heatingin Sweden, demonstrates the highest environmental performancefor all the evaluated impact categories.

  • 8.
    Mohammadi, Ali
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Sandberg, Maria
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Govindarajan, Venkatesh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Eskandari, Samieh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Dalgaard, Tommy
    Aarhus University, Denmark.
    Granström, Karin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Environmental analysis of producing biochar and energyrecovery from pulp and papermill biosludge2019In: Journal of Industrial Ecology, ISSN 1088-1980, E-ISSN 1530-9290Article in journal (Refereed)
    Abstract [en]

    Sweden is one of the largest exporters of pulp and paper products in the world. It follows that huge quantities of sludge rich in carbonaceous organic material and containing heavy metals are generated. This paper carried out a comparative environmental analysis of three different technologies, which can be adopted to produce biochar and recover energy from the biosludge, using landfilling as the reference case. These three thermochemical biosludge management systems—using incineration, pyrolysis, and hydrothermal carbonization (HTC)—were modeled using life cycle assessment (LCA). Heat generated in the incineration process (System A) was considered to be for captive consumption within the kraft pulp mills. It was assumed that the biochars—pyrochar and hydrochar—produced from pyrolysis (System B) and HTC (System C), respectively, were added to the forest soils. The LCA results show that all the alternative systems considerably improve the environmental performance of biosludge management, relative to landfilling. For all systems, there are net reductions in greenhouse gas emissions (–0.89, –1.43, and –1.13 tonnes CO2‐equivalent per tonne dry matter biosludge in Systems A, B, and C, respectively). System B resulted in the lowest potential eutrophication and terrestrial ecotoxicity impacts, whereas System C had the least acidification potential. The results of this analysis show that, from an environmental point of view, biochar soil amendment as an alternative method for handling pulp and paper mill biosludge is preferable to energy recovery. However, an optimal biochar system needs to factor in the social and economic contexts as well.

  • 9.
    Mohammadi, Ali
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Sandberg, Maria
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Govindarajan, Venkatesh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Eskandari, Samieh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Dalgaard, Tommy
    Aarhus University, Denmark.
    Joseph, Stephen
    University of New South Wales, Australia.
    Granström, Karin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Environmental performance of end-of-life handling alternatives for paper-and-pulp-mill sludge: Using digestate as a source of energy or for biochar production2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 182, p. 594-605Article in journal (Refereed)
    Abstract [en]

    This paper evaluates the environmental impacts of different alternatives for handling of sludge from paper and pulp mills in Sweden, using Life Cycle Assessment (LCA). The common practice of incineration of biosludge with energy recovery followed by landfilling of ash (System A) was compared with the alternative of digesting sludge anaerobically to produce biogas using different digestate residue management options. The digestate produced from anaerobic digestion (AD) was assumed to be incinerated for heat energy recovery in System B or pyrolyzed for biochar production in System C to be mixed with forest soils. The impact categories considered in this work are climate change, non-renewable energy use, mineral extraction, aquatic ecotoxicity, carcinogens and non-carcinogens. The LCA results demonstrate that the two proposed systems significantly reduce the environmental impacts of biosludge management relative to incineration. An 85% reduction in the aquatic ecotoxicity impact is achieved in System C, due to the reduced mobility of heavy metals in biochar relative to ash. System C, on the whole, outperformed the other two, leading the authors to the recommendation that the use of pulp and paper mill biosludge in biogas-biochar production systems is preferable to merely recovering energy from it.

  • 10.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Chemical Flocculation for Energy Efficient Treatment of Pulp and Paper Mill EffluentManuscript (preprint) (Other academic)
  • 11.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science.
    Efficient treatment of forest industrial wastewaters: Energy efficiency and resilience during disturbances2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This work concerns the efficient treatment of wastewaters from pulp and paper mills by means of aerobic biological processes. For treatment processes there are many aspects of efficiency and the present study investigates both energy efficiency and purification efficiency during disturbances.

    Special focus is put on wood extractives, such as resin acids and fatty acids, since they can cause negative effects in fish and other organisms in the receiving waters. They can furthermore be toxic to microorganisms in a biological treatment plant. They also affect oxygen transfer, which is important for energy efficient aeration of aerobic biological treatment processes.

    This thesis includes five papers/studies and presents a strategy for efficient treatment of forest industrial wastewaters. The results should help creating resilient wastewater treatment strategies with efficient use of energy. One new strategy proposed here includes separation of extractives before the wastewater is treated biologically, and the use of the extra amount of sludge as an energy source, shifting the energy balance from negative to positive.

  • 12.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Energieffektiv rening av skogsindustriella avloppsvatten2007In: Nordisk Papper och massaArticle in journal (Other (popular science, discussion, etc.))
  • 13.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Energy Efficient Aeration of Wastewaters from Pulp and Paper industry2009Conference paper (Refereed)
  • 14.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Energy efficient aeration of wastewaters from the pulp and paper industry2010In: Water Science & Technology, ISSN 0273-1223, Vol. 62, no 10, p. 2364-2371Article in journal (Refereed)
    Abstract [en]

    More than 50% of the electrical power needed to treat pulp and paper industry effluents is used for aeration in biological treatment stages. A large share of the oxygen that passes through the wastewater is not consumed and will be found in the off-gas. Energy can be saved by aerating under conditions where the oxygen transfer is most efficient, for example at low concentrations of dissolved oxygen Consider the sludge as an energy source; electricity can be saved by avoiding sludge reduction through prolonged aeration. High oxygen transfer efficiency can be retained by using the oxygen consumption of biosolids. Quantified savings in the form of needed volumes of air while still achieving sufficient COD reduction are presented. The tests have been made in a bubble column with pulp mill process water and sludge from a biological treatment plant. These were supplemented with case studies at three pulp and paper mills

  • 15.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Höga Halter svartlut hämmar vattenrening- låga halter aktiverar den2006In: Nordisk Papper och massaArticle in journal (Other (popular science, discussion, etc.))
  • 16.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Mill Case, Simulation and Laboratory Plant Study of Black Liquor Spill Effects on a Multiple Stage Biological Treatment Plant2009In: Canadian journal of civil engineering (Print), ISSN 0315-1468, E-ISSN 1208-6029, Vol. 36, no 5, p. 839-849Article in journal (Refereed)
    Abstract [en]

    In this study, the impact of black liquor shocks on multiple stage biological treatment plant was studied. The tests were carried out in a lab scale plant and using a mathematical simulation model. The results showed good relation to a parallel situation at the Gruvön Mill. The MultiBio concept is persistent to short-term black liquor spills due to the design where the black liquor is diluted between every compartment. According to the lab scale trials, short-term shocks (5 and 10 h) of black liquor addition reduce bio activity in the first part of the MultiBio plant. Oxygen uptake rate and chemical oxygen demand (COD) degradation decreased during high concentrations of black liquor and increased when the black liquor concentration declined. Protozoas disappeared from compartments exposed to high concentrations of black liquor. A long-term trial encompassing 24 h of black liquor addition inhibited the COD reduction in the whole plant for several weeks.

  • 17.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Mill Case, Simulation and Laboratory Plant Study of Black Liquor Spill Effects on a Multiple Stage Biological Treatment Plant2009In: Canadian journal of civil engineering (Print), ISSN 0315-1468, E-ISSN 1208-6029, Vol. 36, no 5, p. 839-849Article in journal (Refereed)
    Abstract [en]

    In this study, the impact of black liquor shocks on multiple stage biological treatment plant was studied. The tests were carried out in a lab scale plant and using a mathematical simulation model. The results showed good relation to a parallel situation at the Gruvon Mill. The MultiBio concept is persistent to short-term black liquor spills due to the design where the black liquor is diluted between every compartment. According to the lab scale trials, short-term shocks (5 and 10 h) of black liquor addition reduce bio activity in the first part of the MultiBio plant. Oxygen uptake rate and chemical oxygen demand (COD) degradation decreased during high concentrations of black liquor and increased when the black liquor concentration declined. Protozoas disappeared from compartments exposed to high concentrations of black liquor. A long-term trial encompassing 24 h of black liquor addition inhibited the COD reduction in the whole plant for several weeks

  • 18.
    Sandberg, Maria
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Positive Energy Balance in Pulp and Paper Wastewater Treatment2013In: Hollistic Sludge Management: An IWA Specialist Conference, 2013Conference paper (Refereed)
    Abstract [en]

    The treatment of pulp and industrial paper effluents uses energy. Aeration is the single most energy demanding process in pulp and wastewater treatment, and it is therefore desirable to affect when energy efficiency is wanted. The sludge from pulp and paper treatment plants has until recently been regarded as a problem. Now, the prospect of using the sludge as feedstock in biogas production through anaerobic digestion is gaining interest.

    Two possible cases for the treatment of pulp and paper effluents have been evaluated to find the most energy efficient process. In Case 1, the process effluent is treated with a conventional activated sludge process. The sludge is anaerobically digested to produce biogas. In Case 2, the process is extended with a chemical treatment stage that is added prior to the biological activated sludge stage, the purpose of which is to reduce surface-active wood extractives to obtain a more efficient oxygen transfer. The total COD reduction is the same as in case 1. The sludge is anaerobically digested. The decreased energy need for aeration, in combination with a higher potential for energy recovery in the form of biogas, leads to a positive energy balance for case 2.

  • 19.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Studies to Avoid Decreased Efficiency in Multiple Stage Biological Wastewater Treatment Plants: Concerning Forests Industry Effluents2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The aim of this study is to prevent efficiency reduction in modern wastewater treatment plants for forest industry effluents. Biological processes are usually efficient in reducing biodegradable organic material. Since the technique depends on living microorganisms (MO) it is sensitive. Toxic substances can kill the population. It takes considerable time for the MOs to grow in number and the treatment efficiency will be affected accordingly. In a pulp and paper mill, a number of liquors are handled that can reach the treatment plant by accident. In this study the impact of black liquor spills on treatment efficiency has been studied.

    Biological treatment methods have been used for a long time. They have developed from general treatment plants to multiple stage concepts, where each stage is designed for its own purpose with specific MO cultures. In this thesis, a plant with the MultiBio concept, located at Gruvön Mill in Sweden has been studied. A laboratory scale MultiBio plant has been constructed for the trials in which efficiency during black liquor exposure has been measured. The measured laboratory results were evaluated by comparing them with simulated values and a mill case.

    When a shock of toxic black liquor passing through a MultiBio concept, the black liquor is diluted between the compartments. The first compartments that are exposed to high concentrations of black liquor are affected negatively. The MOs in the first compartment are fast growing and recover in a few days. The more sensitive activated sludge compartments are located further on in the plant. A toxic concentration is found in the activated sludge compartments only when the duration of the spill is 24 hours or more.

    Denying the MOs their needs can disturb biological treatments. Among many things, a biological process needs dissolved oxygen. Since aeration is energy consuming and expensive, there is a conflict between gaining high efficiency and, at the same time, decreasing the energy consumption. In this study, an approach to saving energy for aeration is initiated.

  • 20.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Studies to Avoid Decreased Efficiency in Multiple Stage Biological Wastewter Treatment Plants: Concerning Forests Industry Effluents2008Licentiate thesis, monograph (Other academic)
  • 21.
    Sandberg, Maria
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    The addition of electrostatic precipitator ash to forest industrial wastewater treatments increases the oxygen transfer rate and saves the energy needed for aeration2014In: Digital  Proceeding Of The  ICOEST’2014 - , SIDE, 2014Conference paper (Refereed)
    Abstract [en]

    More than 30 m3 of water is needed for each metric tonne of paper. Most of the pulp and paper mills use an aerobic biological wastewater treatment. Aeration is the single most energy demanding process in the wastewater treatment plant; therefore it is desirable to control energy consumption when energy needs to be conserved. The aeration efficiency in pulp and paper industrial effluents is often low.  80 – 90% of added oxygen passes through the water volume and leaves with the off-gases. To increase the aeration efficiency, the process needs the oxygen transfer rate from the air bubble into the water to increase. The bubble size affects the oxygen transfer rate. In small bubbles, with a larger area/volume ratio the oxygen transfer rate is often fast and more efficient. The wastewater properties affect the bubble size. A decreased surface tension ensures smaller bubbles. The aim of this study was to show that a waste material, precipitator ash, could be used to decrease wastewater surface tension and thereby increase the oxygen transfer rate. The results from laboratory aeration trials show that the oxygen transfer rate coefficient (KLa) increases by 25% when small concentrations of electrostatic precipitator ash, from a flue gas treatment, were added to the process effluent.

  • 22.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    The velocity field affect of th diffusive oxygen transfer through an air-water interface2007Conference paper (Refereed)
  • 23.
    Sandberg, Maria
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Bengtsson, Simon
    Pawar, Sudhanshu
    Werker, Alan
    Willquist, Karin
    Govindarajan, Venkatesh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Novel biotechnical cascade concept to upgrade pulp and paper residues to hydrogen gas and polyhydroxyalkanoate (PHA)2018Conference paper (Other academic)
    Abstract [en]

    Pulp and paper mills use approximately 30 m3water per ton of produced paper. The process effluent has to be treated before being discharged. Mostly, the effluent is treated with aerobic biological processes using electricity for aeration, and added nutrients. The bio-sludge has low energy value and has to be disposed of. Here, we propose that effluent instead can be used as a feedstock for valuable products.

     

    Some of the bacteria in the bio-sludge can accumulatepolyhydroxyalkanoates(PHAs). PHA is a biopolymer that has a commercial value and is an important building block for the bio-plastics industry. For an efficient PHA production, volatile fatty acids (VFAs) are needed as the feedstock substrate. Process streams rich in sugars can be fermented by the thermophilic bacteria Caldicellulosiruptor, providing acetic acid and hydrogen gas. The acetic acid can then be used as substrate for PHA accumulation. 

     

    In a case study conducted at a large integrated pulp and paper mill (>700 000 ADt/y) in Sweden, the theoretical production volume of hydrogen gas and PHA were estimated. The calculations were based on measured process effluent volumes and water quality parameters, biological process yields from laboratory and pilot scale testing, and practical experience for the unit processes. The results indicated that 0.3 kg of hydrogen gas and 1.6 kg of PHA can be produced per ADt paper or board. The additional associated benefits are significant for the mill because the demand for nutrients and energy for aeration may, at the same time, decrease by 15 to 50 percent.

     

    By combining common biological treatment with fermentation and PHA accumulation, waste by-products can be transformed and upgraded to value-added hydrogen gas and PHA.  Such a secondary side-process integration helps to shift toward the circular bioeconomy. At the same time, less energy and nutrients are needed for the wastewater treatment.

  • 24.
    Sandberg, Maria
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    From-Aldaron, Mattias
    Energieffektiv aerob rening av skogsindustriella avloppsvatten2011Report (Refereed)
    Abstract

    Luftning i aerob rening av skogsindustriella avloppsvatten förbrukar el, ofta mer än 50% av reningsverkens totala elförbrukning. Kunskap om hur syrebehov kan minskas och hur syretransport till vattnet kan förbättras möjliggör energibesparingar. Skogsindustriella avloppsvatten innehåller ämnen som hindrar denna syretransport. För att påverka och utnyttja vattnets kemi till effektiv syretransport behövs kunskap om dessa föroreningarnas egenskaper.



    Syftet med projektet är att identifiera potentialen att minska energianvändandet för aeroba skogsindustriella reningsverk. Målet är att visualisera potentialen att minska energianvändandet för luftning i aeroba biologiska processer. Resultaten är till nytta för de som arbetar för energieffektiv rening av skogsindustriella avloppsvatten. Projektets resultat kan leda till minskad energiförbrukning för vattenrening och ökat energiutnyttjande av slam, för såväl nya anläggningar som befintliga. Resultaten kan även vara till nytta vid design av nya energieffektiva luftare.



    För att studera hur det kemiska innehållet i processvatten påverkar syretransporten från luftbubblor till vatten, har försökt utförts i en luftare i lab.skala. Ett 2m högt rör har konstruerats så att luftflöde och diffusör lätt kan varieras. Ett flertal försök med tillsats av vedegna ämnen gjordes. Anläggningen är portabel och har även använts ute på bruken för att testa processvatten. En modell har tagits fram för att beräkna inverkan av COD-reduktion, uttag av överskottsslam, syrehalt i det biologiska steget och anläggningens ?-värde på syreförbrukning.



    I studien fanns att processvatten kan minska hastigheten för syretransport med upp till 5 ggr, värde på 0,2. Biologisk nedbrytning av extraktivämnen och dess effekt på syretransport påvisades. Tillsats av vedegna ämnen påverkade syretransporten negativt med undantag för låga halter av fettsyra med en diffusör som gav små bubblor. Tillsats av NaCl har förbättrat syretransporten avsevärt i flera försök.



    Processvattens innehåll påverkar starkt syretransporten och därmed och energibehovet i aeroba biologiska reningsverk. Ytaktiv extraktivämnen som fettsyror och hartssyror är troligtvis de ämnen som har störst betydelse. Genom att minska halten extraktivämnen i processvatten som ska renas med aeroba biologiska processer kan syretransporten förbättras avsevärt. Med den framtagna beräkningsmodellen går det att få en uppfattning om hur mycket processparametrar påverkar syrebehovet.



    Resultatet av denna studie bör användas i fortsatt forskning. En del av resultaten, bla tillsats av salt, bör användas för pilotförsök på ett bruk. Studien har uppfyllt sina mål om att visa på potentialen för förbättrad syretransport i skogsindustriella avloppsvatten.



    Studien har genomförts av Karlstads universitet i samarbete med en referensgrupp bestående av Christian Lyckehed, Södra (sammanhållande), Hanna Björkman, Södra Cell Mörrum, Catrin Gustavsson, Billerud Gruvön, Eva-Lena Strömberg, Billerud Skärblacka, Ann-Kristin Magnusson, Stora Enso Skoghall, Erik Mattson, Stora Enso, Hans Eriksson, Holmen Iggesund, Anders Kyösti, SCA Munksund och Bengt Westin, SCA Ortviken.

  • 25.
    Sandberg, Maria
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Govindarajan, Venkatesh
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Granström, Karin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Experimental study and analysis of the functional and life-cycle global warming effect of low-dose chemical pre-treatment of effluent from pulp and paper mills2018In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 174, p. 701-709Article in journal (Refereed)
    Abstract [en]

    Aeration, as a process in pulp and paper wastewater treatment, uses the greatest share of the energy. Therefore, if the energy efficiency of the treatment has to be improved, the focus must be on aeration. A Ivey finding from the trials conducted for this paper, with effluent from a paper and pulp mill, was that the oxygen transfer coefficient could be doubled and the chemical oxygen demand could be decreased by 25%, if the effluent was pre-treated with 30 mg/I of aluminium coagulant (equivalent to 9.4 tonnes per day of AVR to 20000 cubic metres of effluent). Decrease in oxygen requirement implies decreases in aeration energy use. Pulp and paper mill effluents are not as biodegradable as municipal sewage, and the improvement in oxygen transfer properties of the effluent will have a positive influence over a longer period of time in the biological treatment. If the sludge is digested anaerobically, pre-treatment will also result in doubling the potential for methane generation. A holistic analysis of modifications to processes entails a study of the economic and environmental consequences as well. While the economic aspect is beyond the scope of this paper, only the net global warming as an environmental impact category has been studied, by taking recourse to specific emission coefficients. Of the four dosages of ferric aluminium sulphate considered in this analysis, the net greenhouse gas emissions are the least - 426 kg carbon dioxide equivalent per day when the daily consumption is 9.4 tonnes.

  • 26.
    Sandberg, Maria
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Granström, Karin
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    A chance at biological treatment for dryer condensates?2011Conference paper (Refereed)
  • 27.
    Sandberg, Maria
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Granström, Karin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Nutrients for microalgae bio-oil production at a pulp and paper mill site, experiences from a pilot plant2015Conference paper (Refereed)
    Abstract [en]

    Microalgae are a possible source of bio-oil, for example renewable biodiesel. Micro algae gives higher production capacity per area than any other oil producing crop (Chisti 2007). To become competitive with fossil fuel, the bio-oil production must be efficient and cheap. An algae production pilot plant has been running for two years at the site of Nordic Paper Bäckhammar mill in mid Sweden. The purpose is to develop a competitive production process for bio-oil. The challenge is to achieve an economically competitive process that includes, gaining high production rate even though Sweden is a comparably dark and cold country.

     

    The solar radiation is strong enough for algae growth in at least eight months of the year. Radiation inhibition that will be found in other countries closer to the equator can be avoided at this location. However, the low temperature will slow the production rate down during four of these eight months. The possibility to use the excess heat to prolong the growth season is therefore the mayor benefit of growing algae close to a pulp and paper mill. Another benefit is the closeness to the carbon dioxide rich exhaust gas from the recovery boiler. This pilot plant consists of one 25m2 raceway pond and eight smaller pools. The microalgae Scenedesmus Dimorphus is grown in wastewater from the mill. The pools are all covered with a plastic tent to maintain a carbon dioxide rich atmosphere above the surface. However the pulp and paper mill effluent is low in nutrients. The aim with this study is to find efficient and cheap nutrients for algae production, close to the pulp and paper mill site.

     

    Tested nutrients were: the pulp and paper mill effluent, bio-sludge from the pulp and paper mill wastewater treatment plant, digester reject from a close by municipal treatment plant and digester reject from algae residue anaerobic digestion. The residues are collected after the bio-oil has been extracted. In order to see if the nutrients are available for the microalgae Scenedesmus dimorphus, have the different nutrients been tested in small-scale 100 ml growth trials. Scenedesmus Dimorphus was also used in the pilot plant. Cost and energy were used to evaluate the different nutrient sources tested. Algae residues from the pilot plant were anaerobically digested in batch tests to produce the algae digester reject. The biogas potential was determined as input for the evaluation. Costs for transportation and decreased cost for energy and chemicals in the municipal wastewater treatment plant were included to evaluate the municipal digester reject.

     

    Nutrients from all tested sources, except the one from the bio-sludge, were available for microalgae growth. The concentrations of nutrients were to low in the pulp and paper wastewater to enable growth in one batch. The both rejects contain high concentrations of nutrients. The transportation costs made the municipal reject less suitable. The algae residues will give 250 nml3 methane/gVS. The contribution of energy in form of biogas is almost as large as the energy of the bio-oil. Therefore gave the reject from anaerobically digested algae residues the best results. An efficient system can be algae grown in pulp and paper wastewater complemented with recirculate nutrients from the energy recovery of the residues from the bio-oil production. 

  • 28.
    Sandberg, Maria
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Granström, Karin
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Berghel, Jonas
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Frodeson, Stefan
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Renström, Roger
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Ståhl, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Miljöaspekter på produktion och lagring av träpellets2011Report (Other academic)
  • 29.
    Sandberg, Maria
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Holby, Ola
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Black Liquor and Alkaline Shocks in a Multiple Stage Biological Treatment Plant2008In: Journal of Environmental Engineering and Science, ISSN 1496-2551, E-ISSN 1496-256X, Vol. 7, no 4, p. 335-344Article in journal (Refereed)
    Abstract [en]

    To find the impact that alkaline and black liquor spills have on multiple stage biological treatment plants, trials were made in a MultiBio lab-scale treatment plant. It was shown that the concentration of black liquor was diluted between the multiple stages. The initial bacterial stages were inhibited by high concentration of black liquor but recovered when the concentration decreased. Low pH in the feed contaminated with black liquor gave less inhibition than high pH. In a MultiBio treatment plant the active sludge stages, which are sensitive to toxic spills, are placed after the fast growing bacterial stages and are therefore protected. During normal conditions the activated sludge stages receive low concentrations of biodegradable COD. During the trials extra COD in the form of diluted black liquor induced the COD reduction. To evaluate the results, measured concentrations were compared with a computer model.

  • 30.
    Sandberg, Maria
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Rixen, Alexandra
    Chemical flocculation as pretreatment for energy efficient biological treatment2012In: 10th IWA Symposium on Forest Industry Wastewater and 8th International Conference on the fate and effect of Pulp and Paper Mill Effluents, 2012, p. 42-Conference paper (Refereed)
    Abstract [en]

    Biological treatment of forest industry wastewaters uses large amounts of electrical energy. For many mills aeration is the single most energy intensive process in the wastewater treatment plant. The oxygen transfer from bubbles into the water volume is quite slow with low aeration efficiency as result. If the oxygen transfer can be improved, the efficiency can be improved and less compressed air will be needed for aeration with decreased energy costs as the result. It has been shown that surface-active extractives, such as fatty acids and resin acids, have a large impact on oxygen transfer in diffuser aeration systems. With chemical flocculation, extractives can be removed from the process streams. Trials have been made where pulp-mill process streams were pretreated with chemical flocculation before the oxygen transfer tests. When the chemical flocculation conditions were optimized to increase surface tension in the process stream, extractives were removed and the oxygen transfer rate increased in the following oxygen transfer tests. With the pretreatment also COD concentration decreased. The effect will be less need for oxygen for degradation in the following biological process. With decreased COD concentration and increased oxygen-transfer rate, energy can be saved in the biological treatment. Energy savings resulted in greater economic return than the cost for flocculating chemicals. If waste sludge can be used as energy source, one can even achieve a better result.

    Acknowledgements. This work was supported by ÅF-forskningsstiftelse and Stora Enso Skoghall mill.

  • 31.
    Stoica, Alina
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Sandberg, Maria
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Holby, Ola
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Energy Use and Recovery Strategies within Wastewater Treatment and Sludge Handling at Pulp and Paper Mills2009In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 100, no 14, p. 3497-3505Article in journal (Refereed)
    Abstract [en]

    This paper presents an inclusive approach with focus on energy use and recovery in wastewater management, including wastewater treatment (WWT) and sludge handling. Process data from three Swedish mills and a mathematical model were used to evaluate seven sludge handling strategies. The results indicate that excess energy use in WWT processes counters the potential energy recovery in the sludge handling systems. Energy use in WWT processes is recommended to aim for sufficient effluent treatment, not for sludge reduction. Increased secondary sludge production is favourable from an energy point of view provided it is used as a substrate for heat, biogas or electricity production.

1 - 31 of 31
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