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- Anderson, Leif G, 1951, et al.
(author)
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Shelf-Basin interaction along the East Siberian Sea
- 2017
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In: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 13:2, s. 349-363
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Journal article (peer-reviewed)abstract
- Extensive biogeochemical transformation of organic matter takes place in the shallow continental shelf seas of Siberia. This, in combination with brine production from sea-ice formation, results in cold bottom waters with relatively high salinity and nutrient concentrations, as well as low oxygen and pH levels. Data from the SWERUS-C3 expedition with icebreaker Oden, from July to September 2014, show the distribution of such nutrient-rich, cold bottom waters along the continental margin from about 140 to 180 degrees E. The water with maximum nutrient concentration, classically named the upper halocline, is absent over the Lomonosov Ridge at 140 degrees E, while it appears in the Makarov Basin at 150 degrees E and intensifies further eastwards. At the intercept between the Mendeleev Ridge and the East Siberian continental shelf slope, the nutrient maximum is still intense, but distributed across a larger depth interval. The nutrient-rich water is found here at salinities of up to similar to 34.5, i.e. in the water classically named lower halocline. East of 170 degrees E transient tracers show significantly less ventilated waters below about 150 m water depth. This likely results from a local isolation of waters over the Chukchi Abyssal Plain as the boundary current from the west is steered away from this area by the bathymetry of the Mendeleev Ridge. The water with salinities of similar to 34.5 has high nutrients and low oxygen concentrations as well as low pH, typically indicating decay of organic matter. A deficit in nitrate relative to phosphate suggests that this process partly occurs under hypoxia. We conclude that the high nutrient water with salinity similar to 34.5 are formed on the shelf slope in the Mendeleev Ridge region from interior basin water that is trapped for enough time to attain its signature through interaction with the sediment.
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- Hagelqvist, Alina, 1980-
(author)
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Forest industry sludge as a resource for energy recovery
- 2009
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Licentiate thesis (other academic/artistic)abstract
- Forest industries produce large amounts of carbon rich sludges as by-products in their processes. Presently sludge is treated as a poor quality biofuel for co-incineration, some mills treat it solely as a disposal problem. This thesis provides an introduction to production, composition and disposal issues of sludge. It also includes a presentation of strategies for sludge handling.The main concern with energy recovery from sludge is connected to high content of water (50-80%). Mechanical dewatering is an energy efficient method of decreasing the water content. However, there are limitations to how far sludge can be dewatered mechanically. Thermal dewatering is sometimes required to dewater the sludge beyond these limits, in order to obtain a high quality biofuel for incineration and/or thermal gasification. It is often inefficient, from an energy point of view, to incorporate thermal dewatering in the sludge handling strategy.An interesting alternative to thermal processes is anaerobic digestion, which is a biological process used for energy recovery. Advantages with anaerobic digestion include biogas production, efficient treatment of sludge with high content of water and potential for nutrients recovery. The process and the kinetics of anaerobic digestion are presented.The aim of this thesis is to present a method for evaluating different sludge handling strategies from an energy perspective, and to further develop anaerobic digestion as a process for energy recovery from sludge. The thesis is based on two papers. Paper I presents an inclusive approach with focus on energy use and energy recovery in wastewater management, including wastewater treatment and sludge handling. Paper II explores the possibility to enhance biogas production by anaerobic co-digestion of pulp mill sludge with municipal sewage sludge.
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- Rezk, Kamal, 1983-
(author)
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CFD as a tool for analysis of complex geometry : Perspectives on time efficient simulations of interior household appliance components
- 2011
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Licentiate thesis (other academic/artistic)abstract
- Throughout recent years, computer based programs has been applied to solve and analyze industrial problems. One of these developed programs is the Computational Fluid Dynamics (CFD) program. The purpose of implementing CFD analysis is to solve complex flow behavior which is not possible with ordinary calculus. The extensive application of CFD in the industry is a result of improved commercial CFD codes in terms of more advance partial differential equations (PDE) describing various physical phenomena, CAD and mesh-grid generating tools and improved graphical user interfaces (GUI). Today, CFD usage has extended to fields such as aerodynamic, chemical process engineering, biomedical engineering and drying technology. As there is an on-going expansion of CFD usages in the industry, certain issues need to be addressed as they are frequently encountered. The general demand for simulation of larger control volumes and more advanced flow processes result in extensive requirement of computer resources. Numerous complex flow topics today require computer cluster networks which are not accessible for every company. The second issue is the implementation of commercial CFD codes in minor industrial companies is utilized as a black box based on the knowledge on fluid mechanic theory. A vital part of the simulation process is the evaluation of data through visual analysis of flow patterns, analysis on the sensitivity of the mesh grid, investigation of quantitative parameters such as pressure loss, velocity, turbulence intensity etc. Moreover, increased partnerships between industry and the academic world involving various CFD based design processes generally yields to a verbal communication interface which is a crucial step in the process given the fact of the level of dependency between both sides. The aim of this thesis is to present methods of CFD analysis based on these issues. In paper I, a heuristically determined design process of the geometry near the front trap door of an internal duct system was achieved by implementing the CFD code COMSOL MultiPhysics as a communication tool. The design process was established by two counterparts in the project in which CFD calculations and geometry modifications were conducted separately. Two design criteria presenting the pressure drop in duct and the outflow uniformity was used to assess geometry modifications conducted by a CAD-engineer. The geometry modifications were based on visual results of the flow patterns. The geometry modifications confirmed an improvement in the geometry as the pressure drop was reduced with 23% and the uniformity was increased with 3%. In paper II, volume-averaged equations were implemented in a tube-fin heat exchanger in order to simulate airflow. Focus was on achieving a correct volume flow rate and pressure drop (V-p) correlation. The volume averaged model (VAM) is regarded as a porous medium in which the arrangement of fins and tube bundles are replaced with volume-averaged equations. Hence, the computational time was reduced significantly for the VAM model. Moreover, experimental results of the (V-p) correlation showed good agreement with the VAM model.
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- Sandberg, Maria, 1968-, et al.
(author)
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Black Liquor and Alkaline Shocks in a Multiple Stage Biological Treatment Plant
- 2008
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In: Journal of Environmental Engineering and Science. - 1496-2551 .- 1496-256X. ; 7:4, s. 335-344
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Journal article (peer-reviewed)abstract
- 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.
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- Sandberg, Maria, 1968-
(author)
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Studies to Avoid Decreased Efficiency in Multiple Stage Biological Wastewater Treatment Plants: Concerning Forests Industry Effluents
- 2008
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Licentiate thesis (other academic/artistic)abstract
- Målet med den här studien är att förhindra effektivitetssänkningar i moderna biologiska reningsanläggningar för skogsindustriella avloppsvatten. Biologiska processer är vanligtvis effektiva när det gäller att reducera lättnedbrytbart organiskt material. Eftersom den utgörs av levande mikroorganismer (MO) är tekniken känslig. Toxiska ämnen kan döda en kultur av MO. Innan de har ökat i antal igen kommer reduktionseffektiviteten att vara påverkad för en ansenlig tid framöver. I ett pappers- och massabruk finns många typer av vätskor som oavsiktligt kan hamna i reningsanläggningen. I den här studien har svartluts inverkan på reduktionsgraden studerats. Biologiska reningsverk har använts under en lång tid. De har utvecklats från att vara generella reningsverk till att bli konceptanläggningar i flera steg, där varje steg har designats för sitt eget syfte med specifika MO. I det här arbetet har ett MultiBio-koncept vid Gruvön Bruk studerats. En anläggning i laboratorieskala har byggts för svartlutsförsöken. Resultatet har jämförts mot simulerade värden och värden från bruket. När ett spill av svartlut passerar genom en MultiBio späds det ut mellan varje steg. Halten av svartlut är hög i de första stegen vilka påverkas kraftigt. I de första stegen lever snabbväxande organismer som återhämtar sig på ett par dagar. De mer känsliga aktivslamstegen finns längre bak i reningsverket och är skyddade från toxiska koncentrationer av svartlut. Endast vid försök med 24-timmarstillsatser blev koncentrationen av svartlut så hög att den påverkade MO negativt. Den biologiska processen i ett reningsverk kan störas om MO förnekas något essentiellt behov. En biologisk process har ett flertal behov, bland annat behöver aeroba MO löst syre. Eftersom syresättning av vattnet är energikrävande och kostsamt är det inte problemfritt att skapa en omgivning som ger hög effektivitet samtidigt som man strävar efter att sänka energiförbrukningen. I avhandlingen beskrivs ett tillvägagångssätt för att studera energieffektiv syresättning.
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| 25. |
- Stoica, Alina, 1980-, et al.
(author)
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Energy Use and Recovery Strategies within Wastewater Treatment and Sludge Handling at Pulp and Paper Mills
- 2009
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 100:14, s. 3497-3505
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Journal article (peer-reviewed)abstract
- 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.
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