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  • 1251.
    Zhang, Di
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Measurement of Soil Water Content Using Ground Penetrating Radar.2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Ground Penetrating Radar (GPR) is an effective tool to measure the geological properties. A lot of information can be interpreted from the GPR data, such as soil water content. One of the common approaches is to determine the apparent electrical permittivity from the transmission velocity of the impulse electromagnetic wave, and to use empirical relationships to estimate the soil water content. For example, Ferre equation & Topp equation are all expressing the relationship between soil water content and electrical permittivity. However, this method has some limitations; most notably the necessity to determine the velocity from a known depth to a reflecting surface. Therefore, another approach using the frequency dependent attenuation represented by a parameter called Q* was tested and studied in this thesis. The Q* method was evaluated using laboratory measurements, which consists of a series of experiments. A new empirical model was established using experiments where Q* was estimated from measurements on a soil sample with known water contents using two types of antennas (1.6 GHz & 2.3 GHz). Finally, the adaptability of Topp equation and Ferre equation were verified, and a new empirical equation was defined. What’s more, the other method using Q* was proved to be feasible.

  • 1252.
    Zhang, Hongyu
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Significance of Nondetects in the Mapping of Soil contaminants.2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the sample data of soil contaminants, the existence of nondetects is a common phenomenon. Due to their small values, they are always ignored. However, they form an essential part of the sample distribution and arbitrary changes of their values will affect the properties of the distribution, for example, the 95% upper confidence limit of the mean (95UCLM), which is an important index in risk assessment, is strongly related with the sample distribution. Statistical analysis methods for nondetects involve substitution by half of the detection limit (DL/2), maximum likelihood estimation (MLE), Kaplan-Meier and regression on ordered statistics (ROS). The significance of nondetects was examined in this study. Two large data sets of cadmium (Cd) and mercury (Hg) containing censored observations in Annedal’s park were used, where the censored observations were known from the laboratory. Large data sets were subsampled into small data sets with different sample sizes and censoring levels. The 95UCLM value of each data set was calculated by use of the statistical software ProUCL 4.1.00. Through comparison, it was found that in most cases the 95UCLM value calculated with lab values was lower than that of the censored observation for each data set. The difference in 95UCLM values between the data set with nondetects and the data set with lab values varied in each sample and was found to be related to sample size and to the censoring level. The higher the censoring level was, the bigger the 95UCLM value difference became. Either too small or too large a sample size would reduce the difference between the 95UCLM values. This result helps in certain cases, when the 95UCLM value of the sample data is a little lower than the threshold; using the lab values instead of nondetects to recalculate the 95UCLM value may supply a manageable and economic tool to classify the contaminated area.

  • 1253. Zhang, Shulan
    et al.
    Loevdahl, Lars
    Grip, Harald
    Jansson, Per-Erik
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Tong, Yanan
    Modelling the effects of mulching and fallow cropping on water balance in the Chinese Loess Plateau2007In: Soil & Tillage Research, ISSN 0167-1987, E-ISSN 1879-3444, Vol. 93, no 2, p. 283-298Article in journal (Refereed)
    Abstract [en]

    To improve water use efficiency on drylands it is essential to understand the mechanisms affecting water balance partitioning in arable land ecosystems. A field experiment was conducted, from October 2001 to October 2004, to evaluate the effects of field management regimes on water balance and water use efficiency in a winter wheat (Triticum aestivum L.) system in the Loess Plateau, China. The field management regimes tested were: (i) conventional agricultural management (winter wheat followed by a ploughed summer fallow); (ii) conventional management plus a fallow crop used as green manure; (iii) application of wheat straw mulch (0.8 kg m(-2)), which was retained throughout the year (no summer ploughing). A process-oriented ecosystem model (CoupModel) was calibrated with field measurements of soil water contents, leaf area indices, plant heights and crop yields, then used to generate comparative simulations of the water balance partitioning under the wheat straw mulch, fallow crop and conventional management regimes. The simulations indicated that during the experimental period mulching increased soil water storage by 5-8%, decreased soil evaporation by 11-13%, and increased wheat transpiration by 2-5% compared with the conventional management regime, thus increasing the wheat yield and water use efficiency. Furthermore, water reached deeper horizons under mulching than under conventional practice, resulting in 15% more deep percolation in a wet year. The simulation results also indicated that growing green manure during the fallow period decreased soil water storage, leading to lower wheat yields. Mulching proved to be an efficient measure for increasing yields, and possibly contributed to groundwater recharge.

  • 1254.
    Zhang, Tianzi
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    The possibility of using BOD on-line measurement.2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    BOD (Biochemical Oxygen Demand) is one of the important parameters in wastewater treatment technology,  it normally takes five days to get the result. Using MFC (Microbial Fuel Cell) to build up a small on-line system to measure BOD will reduce to operating time to 20 minutes. In this report, the MFC BOD on-line measurement was processed in order to test if this rapid way would work in practical usage.

    The experiment used secondary sedimentation sludge as the bacteria source on the MFC anode pattern with GGA (Glucose and Glutamic Acid solution) as an electron producer, and the 30 minutes voltage value changing curves was gotten by measuring the voltage. At the end the curve was analyzed and compared with the real BOD value in order to get the conclusion.

    The BOD on-line measurement is quite promising and efficient when multi-samples are needed to be tested.

  • 1255.
    Zhang, Wenxin
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Physics.
    Long-term Trend of Evapotranspiration in Sweden Affected by Climate Change or Land-use Change.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Evapotranspiration (ET) is an essential component of water cycle as it is an interlinkage between atmosphere, vegetation and soil surface in terms of energy and water balance. However, whether potential ET has the same tendency to change as actual ET and how ET trend (based on the difference between precipitation and runoff) is directly driven by dominant meteorological factors alone or combined with ecosystem‘s feedbacks to climate change (like land-use change) is still under the discussion. In this report, five ET parameterizations within two rainfall-runoff models [Coupled Heat and Mass Transfer Model (CoupModel) and Hydrologiska Byråns Vattenbalansavdelning (HBV)] have been set up based on six subcatchments of Sweden. The scenario derived from CoupModel shows that the trend of ET is affected by the change of land-use, where soil evaporation tends to shift to transpiration and interception evaporation. However, HBV model produces the other scenario: the trend of ET is merely the consequence of meteorological factors. Increased ET is contributed by increased interception evaporation due to the increased precipitation. After identifying the time split of changing ET trends, a dynamic simulation constructed both from HBV and CoupModel indicate that the increased total ET is primarily from increased ET in winter time. More and more interceptive water loss and transpiration resulted from land-use change due to more vegetation. On the other hand, land-use change is also a feed back to climate change. Transpiration controlled by the mechanism of stomata and water uptake controlled by reduction of soil moisture is highly related to variations of climatic conditions.

  • 1256. Zhang, X. -M
    et al.
    Cao, W. -H
    Yu, X. -X
    Wu, Sihong
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Effect of LUCC on runoff regulation in watershed in loess gullied-hilly region of China2009In: Shuili Xuebao/Journal of Hydraulic Engineering, ISSN 0559-9350, Vol. 40, no 6, p. 641-650Article in journal (Refereed)
    Abstract [en]

    By using the measurement technique of dynamic hydrological process and the estimation method of landscape ecology, the effect of LUCC (Land Use-Cover Change) on runoff regulation in the Luoyugou watershed, located at loess gullied-hilly region of China, in the period from 1986 to 2004 was studied. The results show that the impact of LUCC on runoff regulation is significant due to the increase of forest vegetation coverage and terracing of the land on the slopes. The capacity of runoff yield will be reduced due to the optimal adjustment of land use structures and the increase of forest vegetation in any time scales, including single precipitation event, the period of rainfall season and in the whole year. The reduction percentages of average annual runoff coefficient in rich rainfall year, normal rainfall year and poor rainfall year in the latter land use period from 1995 to 2004 are approximately 51%, 85%, 84% respectively comparing with those in the former land use period from 1986 to 1994. Besides, if neglecting the influence of precipitation amount, the predicted runoff coefficient for latter period decreases by about 63% comparing with those in former period. In addition, the impact of LUCC on runoff exhibits seasonal characteristics and the peak flood amount decreases with the optimal adjustment of land use structures. Although the impact of increasing forest vegetation coverage on the capacity of runoff amount is lager than that of changing land use type from slopping farmland to terrace, both measures must be adopted for fulfilling the requirements of land resources sustainable utilization in Loess gullied-hilly region.

  • 1257. Zhang, X.
    et al.
    Yu, X.
    Wu, Sihong
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    Cao, W.
    Effects of changes in land use and land cover on sediment discharge of runoff in a typical watershed in the hill and gully loess region of northwest China2008In: Frontiers of Forestry in China, ISSN 1673-3517, Vol. 3, no 3, p. 334-341Article in journal (Refereed)
    Abstract [en]

    Land use plays a much more important role than other factors, such as climate, soil properties, topographic features, vegetation coverage, human activities and others, in affecting soil erosion and sediment discharge. In order to understand the effects of changes in land use on sediment discharge and to provide a theoretical basis for land use planning, management and ecological restoration, we used the controlled Qiaozidong watershed and the uncontrolled Qiaozixi watershed in the third sub-region of the Loess Plateau as examples and analyzed the effects of land use and land cover on the discharge of sediments. The results show that the impact of land use and land cover on the annual amount of sediment discharge is significant. Compared with the uncontrolled watershed during similar periods, the amount of sediment discharged from the controlled watershed was reduced by 44%, 75% and 86%, respectively, in wet, normal and dry years. In the controlled watershed, compared with the period from 1986 to 1994, the amount of sediments discharged was less during the period from 1995 to 2004. The impact of land use and land cover on sediment discharge demonstrated characteristics of seasonal fluctuation. The effects of sediment reduction in the controlled watershed were greater than those in the uncontrolled watershed in May and September. In the controlled watershed, the reduction effect coincided with the distribution of rainfall. The amount of discharged flood sediments is closely correlated with rainfall, rainfall intensity in a 60 min period and the volume of flood. The rainstorm-runoff process and the rainstorm-sediment discharge process demonstrate that land cover has a strong regulatory and control function in the flood process and sediment discharge in rainstorms. For the controlled watershed, given the same precipitation frequency distribution, the average amount of sediment discharged during the land use period from 1995 to 2004 was less than that during the earlier land use period from 1986 to 1994 under every recurrent period.

  • 1258.
    Zhang, Xin
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Application of Partial Nitritation/Anammox Process for Treatment of Wastewater with High Salinity.2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The combination of partial nitritation and anaerobic ammonium oxidation (Anammox) is a composting way to remove the nitrogen in the wastewater. In this article the analysis was made to investigate how the salinity in the wastewater affects the process. Two strategies of salt concentration increase were tested in two reactors. The physical, chemical parameters and the activity of the bacteria in the reactors were monitored. The results of two strategies were compared and the reactor with less salt in each period showed higher bacteria activities and efficiency. Finally the outlook for the future research was made.

  • 1259.
    Zhao, Chengyuan
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Effect of Temperature on Biogas Production in Anaerobic Treatment of Domestic Wastewater UASB System in Hammarby Sjöstadsverk.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The upflow anaerobic sludge blanket (UASB) reactor is widely used around the world to treat variety of domestic andindustrial wastewater with three main advantages: production of biogas as renewable energy, no need of support structure for development of microorganisms and high rate treatment efficiency with low rate of biomass production.

    This study evaluates the effect of temperature on biogas production and CODtotal removal in Line 4-UASB system treating domestic wastewater in Hammarby Sjöstadsverk. Eight parameters were examined including the following: Influent and effluent temperature, pH, influent CODtotal, influent rate, effluent CODtotal, volatile fatty acids, biogas production rate and methane concentration. There are eight set temperature and each is stabilized for seven days. The biogas production analysis is focus on UASB 1. Temperature rising from 19°C to 35°C achieves a general benefit result in methane yield rate and CODtotal removal efficiency. The best methane yield rate and CODtotal removal rate are 0.167l/gCODtotal and 56.84% respectively at highest working temperature 33.4°C with OLR 3.072gCODtotal/(l*day) and HRT 4.2h.

  • 1260.
    Zhao, Zhihong
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Stress Effects on Solute Transport in Fractured rocks2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The effect of in-situ or redistributed stress on solute transport in fractured rocks is one of the major concerns for many subsurface engineering problems. However, it remains poorly understood due to the difficulties in experiments and numerical modeling. The main aim of this thesis is to systematically investigate the influences of stress on solute transport in fractured rocks, at scales of single fractures and fracture networks, respectively.

    For a single fracture embedded in a porous rock matrix, a closed-form solution was derived for modeling the coupled stress-flow-transport processes without considering damage on the fracture surfaces. Afterwards, a retardation coefficient model was developed to consider the influences of damage of the fracture surfaces during shear processes on the solute sorption. Integrated with particle mechanics models, a numerical procedure was proposed to investigate the effects of gouge generation and microcrack development in the damaged zones of fracture on the solute retardation in single fractures. The results show that fracture aperture changes have a significant influence on the solute concentration distribution and residence time. Under compression, the decreasing matrix porosity can slightly increase the solute concentration. The shear process can increase the solute retardation coefficient by offering more sorption surfaces in the fracture due to gouge generation, microcracking and gouge crushing.

    To study the stress effects on solute transport in fracture systems, a hybrid approach combing the discrete element method for stress-flow simulations and a particle tracking algorithm for solute transport was developed for two-dimensional irregular discrete fracture network models. Advection, hydrodynamic dispersion and matrix diffusion in single fractures were considered. The particle migration paths were tracked first by following the flowing fluid (advection), and then the hydrodynamic dispersion and matrix diffusion were considered using statistic methods. The numerical results show an important impact of stress on the solute transport, by changing the solute residence time, distribution and travel paths. The equivalent dispersion coefficient is scale dependent in an asymptotic or exponential form without stress applied or under isotropic compression conditions. Matrix diffusion plays a dominant role in solute transport when the hydraulic gradient is small.

    Outstanding issues and main scientific achievements are also discussed.

  • 1261.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lannu
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Stress effects on nuclide transport in fractured rocks: A numerical study2010In: ROCK MECHANICS IN CIVIL AND ENVIRONMENTAL ENGINEERING, 2010, p. 783-786Conference paper (Refereed)
    Abstract [en]

    The main objective of this study was to investigate the influence of stresses on radioactive nuclide transport in fractured rocks, based on Discrete Element Method (DEM) and a particle tracking approach. Matrix diffusion was also considered in the transport simulation. The results show that stresses not only influence the particle residence time in fracture network, but also change the particle transport paths significantly.

  • 1262.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Physics.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Evaluation of hydrodynamic dispersion parameters in fractured rocks2010In: Journal of Rock Mechanics and Geotechnical Engineering, ISSN 1674-7755, Vol. 2, p. 243-254Article in journal (Refereed)
    Abstract [en]

    A numerical procedure to determine the equivalent hydrodynamic dispersion coefficients and Péclet number (Pe) of a fractured rock is presented using random walk particle tracking method. The geometrical effects of fracture system on hydrodynamic dispersion are studied. The results obtained from the proposed method agree well with those of empirical models, which are the scale-dependent hydrodynamic dispersion coefficients in an asymptotic or exponential form. A variance case is added to investigate the influence of longitudinal hydrodynamic dispersion in individual fractures on the macro-hydrodynamic dispersion at the fracture network scale, and its influence is demonstrated with a verification example. In addition, we investigate the influences of directional flow and stress conditions on the behavior of hydrodynamic dispersion in fracture networks. The results show that the magnitudes of the hydrodynamic dispersion coefficients are relatively smaller when the flow direction is parallel to the dip directions of fracture sets. Compressive stresses significantly reduce hydrodynamic dispersion. However, the remaining questions are: (1) whether the deformed fracture network under high stress conditions may make the scale-dependent hydrodynamic dispersion coefficients have asymptotic or exponential forms, and (2) what the conditions for existence of a welldefined equivalent hydrodynamic dispersion tensor are. They need to be further investigated.

  • 1263.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Particle mechanics model for the effects of shear on solute retardation coefficient in rock fractures2012In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 52, p. 92-102Article in journal (Refereed)
    Abstract [en]

    Damage on rock fracture surfaces during shear process changes the mechanical and hydrological properties of the fractures, therefore, affects the solute migration in fractured rocks. Laboratory experiments on this issue are rarely reported in literature due to technical difficulties in measuring the asperity damage and gouge generation. To conceptually investigate the effects of rock fracture surface damage on solute sorption during shear, this paper presents, for the first time, a retardation coefficient model considering the wear impacts and a generic numerical evaluation procedure. The particle mechanics model was employed to investigate the effects of gouge generation (abrasive wear) and microcrack development in the damaged zones, on the solute retardation coefficient in rock fractures. The results from demonstration examples show that the shear process significantly increases the retardation coefficients, by offering more sorption surfaces in the factures due to gouge generation (wear), microcracking and crushing of gouge particles. Conceptually three damage zones are classified to characterize the various wear impacts on the solute transport in single fractures. Outstanding issues of the present model and suggestions for future study are also presented.

  • 1264.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Neretnieks, Ivars
    Shear effects on solute retardation coefficient in rock fractures: Insights from a particle mechanics modelManuscript (preprint) (Other academic)
  • 1265.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Analytical solution of coupled stress-flow-transport processes in a single rock fracture2011In: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 37, no 9, p. 1437-1449Article in journal (Refereed)
    Abstract [en]

    A closed-form solution is presented for modeling the coupled stress-flow-transport processes along a single fracture embedded in a porous rock matrix. Necessary assumptions were made to simplify the subject into a two-dimensional (2D) problem, considering the changes of fracture aperture and matrix porosity under various stress conditions. The cubic law was assumed to be valid for the fluid flow in the fracture, with an impermeable rock matrix. For transport mechanisms, advective transport along the fracture, longitudinal hydrodynamic dispersion in the flow direction, and the matrix diffusion were considered in three different transport models under constant concentration or constant flux (Danck- werts’) inlet boundary conditions. This analytical solution can be used as a constitutive model, or as an example for validation of similar constitutive models, for modeling the coupled hydro-mechanical- chemical (HMC) processes in fracture networks of crystalline rocks. The influences of stress/deformation processes on different transport mechanisms in a single fracture under different inlet boundary conditions were studied for the first time. The results show that changes of fracture, as controlled by a combination of normal closure and shear dilatancy, have a significant influence on the solute concentration distribution both along the fracture and in the rock matrix, as well as on the solute residence/breakthrough time, especially when shear-induced dilatancy occurs. Under compressions, the decreasing matrix porosity slightly increases the solute concentration along the fracture and in the rock matrix.

  • 1266.
    Zhao, Zhihong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Numerical modeling of stress effects on solute transport in fractured rocks2011In: Computers and geotechnics, ISSN 0266-352X, E-ISSN 1873-7633, Vol. 38, no 2, p. 113-126Article in journal (Refereed)
    Abstract [en]

    The effects of stress/deformation on fluid flow and contaminant transport in fractured rocks is one of the major concerns for performance and safety assessments of many subsurface engineering problems, especially radioactive waste disposal and oil/gas reservoir fields. However, very little progress has been made to study this issue due to difficulties in both experiments and numerical modeling. The objective of this study is to systematically investigate the influence of stress on solute transport in fractured rocks for the first time, considering different stress and hydraulic pressure conditions. A hybrid approach combining discrete element method (DEM) for stress-flow simulations and a particle tracking algorithm is developed. The impact of matrix diffusion (diffusion of molecular size solutes in and out of the rock matrix, and sorption onto the surface of micropores in rock matrix) is also included. The numerical results show that stress not only significantly changes the solute residence time through the fracture networks, but also changes the solute travel paths. Matrix diffusion plays a dominant role in solute transport when the hydraulic gradient is small, which is often encountered in practice.

  • 1267.
    Zimmerman, Robert W.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Engineering Geology and Geophysics.
    The Imperial College lectures in petroleum engineering2018Collection (editor) (Other academic)
    Abstract [en]

    This book presents, in a self-contained form, the equations of fluid flow in porous media, with a focus on topics and issues that are relevant to petroleum reservoir engineering. No prior knowledge of the field is assumed on the part of the reader, and particular care is given to careful mathematical and conceptual development of the governing equations, and solutions for important reservoir flow problems. Fluid Flow in Porous Media starts with a discussion of permeability and Darcy's law, then moves on to a careful derivation of the pressure diffusion equation. Solutions are developed and discussed for flow to a vertical well in an infinite reservoir, in reservoirs containing faults, in bounded reservoirs, and to hydraulically fractured wells. Special topics such as the dual-porosity model for fractured reservoirs, and fluid flow in gas reservoirs, are also covered. The book includes twenty problems, along with detailed solutions. As part of the Imperial College Lectures in Petroleum Engineering, and based on a lecture series on the same topic, this book provides the introductory information needed for students of the petroleum engineering and hydrology.

  • 1268.
    Zimmerman, Robert W.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Engineering Geology and Geophysics.
    Lutz, M.P
    Thermal and electrical conductivity of composites with graded interfaces2006In: International Journal of Advances in Science and Technology, ISSN 2229-5216, Vol. 45, p. 1097-1102Article in journal (Refereed)
  • 1269.
    Zubrowska-Sudol, Monika
    et al.
    Technical University in Warszaw Poland.
    Trela, Jozef
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Anammox process intensification as an alternative method to remove nitrogen from wastewater2010In: Gaz, woda i technika sanitarna, ISSN 0016-5352, no 9, p. 22-25Article in journal (Other academic)
  • 1270.
    Zubrowska-Sudol, Monika
    et al.
    Department of Environment Engineering, Warsaw University of Technology, Warsaw, Poland.
    Yang, Jingjing
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Trela, Jozef
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Plaza, Elzbieta
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Water, Sewage and Waste technology.
    Evaluation of deammonification process performance at different aeration strategies2011In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 63, no 6, p. 1168-1176Article in journal (Refereed)
    Abstract [en]

    In a deammonification process applied in the moving bed biofilm reactor (MBBR) oxygen is a crucial parameter for the process performance and efficiency. The objective of this study was to investigate different aeration strategies, characterised by the ratio between non-aerated and aerated phase times (R) and dissolved oxygen concentrations (DO). The series of batch tests were conducted with variable DO concentrations (2, 3, 4 mg L-1) and R values (0-continuous aeration; 1/3, 1, 3-intermittent aeration) but with the same initial ammonium concentration, volume of the moving bed and temperature. It was found that the impact of DO on deammonification was dependent on the R value. At R=0 and R=1/3, an increase of DO caused a significant increase in nitrogen removal rate, whereas for R=1 and R=3 similar rates of the process were observed irrespectively of the DO. The highest nitrogen removal rate of 3.33 g N m(-2) d(-1) (efficiency equal to 69.5%) was obtained at R=1/3 and DO=4 mg L-1. Significantly lower nitrogen removal rates (1.17-1.58 g N m(-2) d(-1)) were observed at R=1 and R=3 for each examined DO. It was a consequence reduced aerated phase duration times and lesser amounts of residual nitrite in non-aerated phases as compared to R 1/3.

  • 1271. Zwieg, Thomas
    et al.
    Cucarella, Victor
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Kauffeld, Michael
    Novel biomimetically based ice-nucleating coatings2007In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 98, no 7, p. 597-602Article in journal (Refereed)
    Abstract [en]

    Ice nucleation and ice repellence are properties which appear to be contradictory. Both are of great importance: The former for ice generation in the food and cooling industry and the latter for avoiding the adhesion of ice to structures. By mimicking a peculiar survival mechanism of some cold-adapted organisms a new type of coating system, able to both nucleate and repel the ice was developed. A heterogeneous surface containing locally isolated nucleation points in a low surface energy matrix were synthesised by a sol-gel process. The ice nucleating and ice releasing performance of the new ice nucleating coatings (INC) has been tested in a specially designed crystallisation chamber in comparison to commercial low surface energy coating systems. A mixture of demineralised water and a water freezing point depressant was used in the experiments. Compared to the commercial coatings, the INC surfaces showed a much higher ice nucleation rate but also a distinctly better ice releasing ability. Obviously the novel concept of local embedded nucleation points improves the ice repellent properties of surfaces.

  • 1272.
    Zywna, Michal
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Analysis of Lining Properties at Landfills Using Geophysical Methods - Case Study: Tveta (Sweden).2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Recently established EU environmental legislation obliged Sweden to close many landfills until year 2020. Such an operation requires a lot of inexpensive and water resistant coverage materials. Six prototypes of linings were constructed at Tveta landfill. Built coverage consisted mainly of residual products such as compost, sludge, fly and bottom ash. Between 2004 and 2007 water permeability through tested coverage was well below the maximum limit for non-hazardous waste. However, recent lysimeter records indicated increased permeability through the constructed linings. Readings of water infiltration were verified. Direct current (DC) resistivity, induced polarization (IP) and ground penetrating radar (GPR) were the methods applied in the research. The data was processed to present resistivity distribution in 2D pseudo-sections and 3D model. Resistivity measurements confirmed increased conductivity at the area with highest lysimeter readings. Unfortunately, GPR and IP output could not be used as reference information for DC resistivity readings. Constructed prototypes seemed to be suitable for coverage lining. Leakage was probably a result of minor mass transport along the slopes of the waste pile. It was recommended to prepare additional DC resistivity measurements to verify correctness of the processed 2D pseudo-sections and 3D model.

  • 1273.
    Åkesson, Anna
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Hydraulic- hydromorphologic analysis as an aid for improving peak flow predictions2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Conventional hydrological compartmental models have been shown to exhibit a high degree of uncertainty for predictions of peak flows, such as the design floods for design of hydropower infrastructure. One reason for these uncertainties is that conventional models are parameterised using statistical methods based on how catchments have responded in the past. Because the rare occurrence of peak flows, these are underrepresented during the periods used for calibration. This implies that the model has to be extrapolated beyond the discharge intervals where it has been calibrated.

    In this thesis, hydromechanical approaches are used to investigate the properties of stream networks, reflecting mechanisms including stage dependency, damming effects, interactions between tributaries (network effects) and the topography of the stream network. Further, it is investigated how these properties can be incorporated into the streamflow response functions of compartmental hydrological models.

    The response of the stream network was shown to vary strongly with stage in a non-linear manner, an effect that is commonly not accounted for in model formulation. The non-linearity is particularly linked to the flooding of stream channels and interactions with the flow on flood-plains.

    An evaluation of the significance of using physically based response functions on discharge predictions in a few sub-catchments in Southern Sweden show improvements (compared to a conventional model) in discharge predictions – particularly when modelling peak discharges.

    An additional benefit of replacing statistical parameterisation methods with physical parameterisation methods is the possibility of hydrological modelling during non-stationary conditions, such as the ongoing climate change.

  • 1274.
    Åkesson, Anna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Stage-dependent hydraulic and hydromorphologic properties in stream networks translated into response functions of compartmental models2012In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 420-421, p. 25-36Article in journal (Refereed)
    Abstract [en]

    A distributed non-uniform routing model was constructed and applied to two stream networks in southern Sweden to investigate the effects of stage, topology and morphology on advective travel times within the stream networks.Using particle-tracking, we found markedly non-linear relationships between travel time distributions and discharge for both catchments under a range of hydraulic conditions, represented by discharges comprising percentiles between 30 and 99.9 extracted from the discharge data set for the two catchments in this study.The travel time distributions from the particle tracking were used to numerically parameterise the response function of a lumped hydrological model, which resulted in improvements, particularly in the prediction of high flows. A sensitivity analysis was performed on the routing procedure, particularly regarding the choice of Manning's friction coefficient and the choice of generic cross-sectional areas along the two stream networks showing that the uncertainty in routing parameters did not have a major effect on the final hydrograph. The new parameterisation performed better than the conventional model in every modelled case.A theoretical demonstration shows that correct descriptions of streamflow processes becomes more important with increased watershed scale, because the travel time within the stream network relative to the travel time on hillslopes increases with the watershed scale. The topology and topography of the stream network were shown to be the major factors influencing the network averaged travel time. These results demonstrate that physically based response functions (and model parameters) can be superior to compartmental model parameters that are based on numerical calibration and that are extrapolated to account for conditions during hydrological extremes.

  • 1275.
    Åkesson, Anna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Wörman, Anders
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
    Lindström, Göran
    Runoff modeling in flooded stream networks2007In: Proceedings of the International Symposium on Modern Technology of Dams – : the 4th EADC Symposium, Chengdu, China, October 12-18 2007., 2007, p. 441-450Conference paper (Other academic)
    Abstract [en]

    This paper outlines a procedure about how to create a compartment type of runoff model that is flexible for prediction of flows of different magnitudes. This methodology is expected to be most useful when applied to high flow situations, when predictions normally are conceived as extrapolations far outside calibration intervals. Focus is put on how to introduce response functions that include more detailed information regarding the river network geometry and the morphology of the channel cross-sections. The parametrisation formula is based on Manning’s equation for open channel flow and the geometrical data is derived from geographical information handled in a GIS software. These response functions can be expected to provide better extrapolations of the hydrograph for future extreme floods, especially for peak flows. This has implications for safety aspects of dams as well as for the economy of hydropower production.

  • 1276. Åström, Mats E.
    et al.
    Nystrand, Miriam
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Österholm, Peter
    Nordmyr, Linda
    Reynolds, Jason K.
    Peltola, Pasi
    Lanthanoid behaviour in an acidic landscape2010In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 74, no 3, p. 829-845Article in journal (Refereed)
    Abstract [en]

    Lanthanoids were studied in a boreal landscape where an abundance of acid sulfate soils and Histosols provide a unique opportunity to increase the understanding of flow these metals behave in acidic soils and waters and interact with soil and aqueous organic matter. In the acid sulfate soils lanthanoids are mobile as reflected in high to very high concentrations in soil water and runoff (typically a few mg 1(-1) but Lip to 12 mg 1(-1)) and abundant release by several relatively weak extractants (ammonium acetate EDTA, sodium pyrophosphate, hydroxylamine hydrochloride) applied on bulk soil. Normalisation with the lanthanoid pool in the underlying parent materials (sulphide-bearing sediments deposited in brackish-water) and soil water showed that the extensive release/retention in the acidic soil was accompanied by large, and variable, fractionation trends across the lanthanoid series. In low-order streams draining these soils, the lanthanoid concentrations were high and, as indicated by frontal ultrafiltration and geochemical modelling, largely dissolved (<1 kDa) in the form of the species LnSO(4)(+) and Ln(3+). In other moderately acidic stream waters (pH 4.3-4.6), organic complexation was predicted to be important in the <1 kDa fraction (especially for the heavy lanthanoids) and strongly dominating in the colloidal phase (1 kDa-0.45 mu m). Along the main stem of a stream in focus (catchment area of 223 km(2)), lanthanoid concentrations increased downstream, in particular during high flows, caused by a downstream increase in the proportion of acid sulfate soils which are extensively flushed during wet periods. The geochemical models applied to the colloidal Ln-organic phase were not successful in predicting the measured fractionation patterns.

  • 1277. Åström, Mats E.
    et al.
    Österholm, Peter
    Gustafsson, Jon Petter
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Nystrand, Miriam
    Peltola, Pasi
    Nordmyr, Linda
    Boman, Anton
    Attenuation of rare earth elements in a boreal estuary2012In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 96, p. 105-119Article in journal (Refereed)
    Abstract [en]

    This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6 parts per thousand). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sediment traps moored at selected locations in the estuary. Ultrafiltration, high-resolution ICP-MS and modeling were applied on the waters, and a variety of chemical reagents were used to extract metals from the settling material. Aluminium, Fe and REE transported by the acidic creek were extensively removed in the inner/central estuary where the acidic water was neutralised, whereas Mn was relatively persistent in solution and thus redistributed to particles and deposited further down the estuary. The REE removal was caused by several contemporary mechanisms: co-precipitation with oxyhydroxides (mainly Al but also Fe), complexation with flocculating humic substances and sorption to suspended particles. Down estuary the dissolved REE pool, remaining after removal, was fractionated: the < 1 kDa pool became depleted in the middle REE and the colloidal (0.45 mu m-1 kDa) pool depleted in the middle and heavy REE. This fractionation was controlled by the removal process, such that those REE with highest affinity for the settling particles became most depleted in the remaining dissolved pool. Modeling, based on Visual MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (< 0.45 mu m) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations.

  • 1278.
    Öberg, Ola
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630).
    ABBORÖS fas 1: Odling av abborre i recirkulerande system i Östergötlands och Kalmars skärgårdar2008Report (Other academic)
    Abstract [en]

    The project ABBORÖS started in fall 2006. The aim was to study the possibility to farm perch in the archipelago in a way that meets both the requirements from the goals of environmental pro-tection for the Baltic Sea as well as the economical demands put upon a commercial business. The new questions addressed in this project are how perch can be farmed in Sweden and how to perform aquaculture in closed systems in the archipelago. New is also a systematic use of compe-tence of local fishermen to develop a sustainable aquaculture system. ABBORÖS is a joint ven-ture between the Royal Institute of Technology and eight fisherman families from the Swedish South East coast. The project is divided into two parts, the first with a budget of 1.3 million € started in October 2006 and finished in February 2008. The second part runs from June 2008 to June 2010 with a preliminary budget of 2.3 million €. During the project 10 people are having work opportunities and after the project the expectation is that 15-20 people will be engaged in this kind of aquaculture. The project will develop methods for how Perch can be cultivated in a recirculating systems in the archipelago, how much water that can be reused and how much of the nutrient loss that can be caught for alternative use compared to traditional net cage fish farm-ing. During the first year test systems with floating ponds constructed in fibre glass-armed PVC tarpaulin was built at different locations together with local fishermen, who were contracted as technicians. The fishermen joined together in the company Stannafisk AB with the ambitions to build eight ongrowing units with a yearly production capacity of 30 tons each and together con-struct a hatchery and a filleting plant. By farming perch the restaurants could be more evenly supplied during the year than by wild catch which gives mainly supply in springtime. This would create a possibility to make a living on a known product in a vanishing profession. By placing the ongrowing units in the vicinity of the families residential buildings, the energy and time used for transport can be kept to a minimum. The following years the systems will be operated at different conditions for optimization. The parameters addressed are fish density, cohort size, pond size, oxygen supply, sludge removal and ammonia removal. A final goal is to compare price and taste of cultured and wild caught Perch. Know-how of aquaculture techniques and juvenile production has been built with the help of a network of international experts during the first part of the pro-ject. The participants have increased their competence and their ability to cooperate. They have also installed a base structure for six farming units and built a capacity of fish production to 15 % of the proposed size at the end of the project. This implies that they are well prepared to make experiments in full scale during the second part of the project. After the first year approximately 200 000 perch are hold in the six units. The first fishes are expected to reach a market size of 400 grams three summers after hatching, which means in September 2008. For the Royal Institute of Technology and other interested research groups engagement in the project gives admission to a field laboratory with technicians for experiments and research on aquaculture and environmental technology.

  • 1279.
    Österling, Eskil
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Environmental Geochemistry and Ecotechnology.
    Phytoremediation of Heavy Metal Polluted Soils Using Local Plants in the Msimbazi River Catchment, Tanzania.: A Minor Field Study.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis is a study of the feasibility of in situ soil remediation techniques in Dar es Salaam, Tanzania. It first looks at the existing on site remediation techniques and assesses how feasible they appear in the conditions of Dar es Salaam. Two methods were interpreted as more feasible than others, namely reactive zone remediation and phytoremediation.

    The feasibility of phytoremediation was assessed by sampling locally occurring plants and comparing their content of Cu, Pb and Zn with the respective content of the soil they grew in. If the content in the plants were elevated as compared to the soil content, the plant was deemed interesting from a phytoremediation point of view.

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