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Retter, Matthias. "Subsurface flow formation." Bern : [s.n.], 2007. http://www.zb.unibe.ch/download/eldiss/07retter_m.pdf.
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Melton, Rebecca Hobbs. "BOD5 removal in subsurface flow constructed wetlands." Texas A&M University, 2003. http://hdl.handle.net/1969.1/2301.
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The frequency of on-site systems for treatment of domestic wastewater is
increasing with new residential development in both rural and low-density suburban
areas. Subsurface flow constructed wetlands (SFCW) have emerged as a viable option
to achieve advanced or secondary treatment of domestic wastewater. The pollutant
removal efficiency in SFCW depends on design parameters. Many of these factors have
been investigated while others such as aspect ratio, design of water inlet structure and
method of dosing the wetland have yet to be fully examined. This study examined the
effect of aspect ratio and header design on BOD5 removal efficiency as well as the
impact of flow rate on flow distribution in a SFCW. An aspect ratio of 4:1 achieved
10% greater removal of organic matter than a 1:1 ratio. Tracer studies demonstrated that
wetlands loaded at a constant rate of 3.8 L/min and 7.6 L/min experienced preferential
flow. In addition, tracer studies showed wetlands with leaching chambers as headers
failed to achieve equal flow distribution. An improvement in effluent water quality was
achieved by replacing the leaching chamber for a perforated manifold as the inlet
structure. This study demonstrated the importance of the careful selection of aspect ratio
and means by which water is introduced to the wetland in the design of SFCW.
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Knowles, Paul. "Clogging in horizontal subsurface flow constructed wetlands." Thesis, Aston University, 2012. http://publications.aston.ac.uk/18725/.
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Horizontal Subsurface Flow Treatment Wetlands (HSSF TWs) are used by Severn Trent Water as a low-cost tertiary wastewater treatment for rural locations. Experience has shown that clogging is a major operational problem that reduces HSSF TW lifetime. Clogging is caused by an accumulation of secondary wastewater solids from upstream processes and decomposing leaf litter. Clogging occurs as a sludge layer where wastewater is loaded on the surface of the bed at the inlet. Severn Trent systems receive relatively high hydraulic loading rates, which causes overland flow and reduces the ability to mineralise surface sludge accumulations. A novel apparatus and method, the Aston Permeameter, was created to measure hydraulic conductivity in situ. Accuracy is ±30 %, which was considered adequate given that conductivity in clogged systems varies by several orders of magnitude. The Aston Permeameter was used to perform 20 separate tests on 13 different HSSF TWs in the UK and the US. The minimum conductivity measured was 0.03 m/d at Fenny Compton (compared with 5,000 m/d clean conductivity), which was caused by an accumulation of construction fines in one part of the bed. Most systems displayed a 2 to 3 order of magnitude variation in conductivity in each dimension. Statistically significant transverse variations in conductivity were found in 70% of the systems. Clogging at the inlet and outlet was generally highest where flow enters the influent distribution and exits the effluent collection system, respectively. Surface conductivity was lower in systems with dense vegetation because plant canopies reduce surface evapotranspiration and decelerate sludge mineralisation. An equation was derived to describe how the water table profile is influenced by overland flow, spatial variations in conductivity and clogging. The equation is calibrated using a single parameter, the Clog Factor (CF), which represents the equivalent loss of porosity that would reproduce measured conductivity according to the Kozeny-Carman Equation. The CF varies from 0 for ideal conditions to 1 for completely clogged conditions. Minimum CF was 0.54 for a system that had recently been refurbished, which represents the deviation from ideal conditions due to characteristics of non-ideal media such as particle size distribution and morphology. Maximum CF was 0.90 for a 15 year old system that exhibited sludge accumulation and overland flow across the majority of the bed. A Finite Element Model of a 15 m long HSSF TW was used to indicate how hydraulics and hydrodynamics vary as CF increases. It was found that as CF increases from 0.55 to 0.65 the subsurface wetted area increases, which causes mean hydraulic residence time to increase from 0.16 days to 0.18 days. As CF increases from 0.65 to 0.90, the extent of overland flow increases from 1.8 m to 13.1 m, which reduces hydraulic efficiency from 37 % to 12 % and reduces mean residence time to 0.08 days.
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Yuh, Sung H. "Time-lapse seismic monitoring of subsurface fluid flow." [College Station, Tex. : Texas A&M University, 2004. http://hdl.handle.net/1969.1/430.
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Koide, Sergio. "Hillslope subsurface flow study by finite element method." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46395.
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Scudeler, Carlotta. "Numerical modeling of flow and solute transport phenomena in subsurface and coupled surface-subsurface hydrology." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3421912.
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The overall aim of the work described in this thesis is to bring a number of contributions to hydrology and hydrological modeling in the framework of a specific physically-based numerical model for integrated surface subsurface and flow-transport processes, the CATchment-HYdrology Flow-Transport (CATHY_FT) model. These contributions revolve around three main themes: the enhancement of the numerical performance of hydrological models for flow and transport phenomena, the improvement of our current understanding of complex boundary conditions in order to reduce the errors associated with their modeling, and the testing and benchmarking of distributed physically-based models for groundwater flow and transport processes. The work to achieve the general objective is elaborated into four stages. First, the Larson-Niklasson post-processing algorithm is implemented in CATHY_FT to reconstruct mass-conservative velocities from a linear, or P1, Galerkin solution of Richards' equation. This is done to improve the accuracy and mass balance properties of the companion advective transport model (finite volume-based), which rely on accurate velocity fields as input. Through a comparison between the results from the reconstructed velocities and the P1 Galerkin velocities, it is shown that a locally mass-conservative velocity field is necessary to obtain accurate transport results. Second, a detailed and novel analysis of the behavior of seepage face boundaries is performed with the flow model of CATHY_FT. The numerical simulations examine the model's performance under complex conditions such as heterogeneity and coupled surface/subsurface flow. It is shown that the overall numerical solution can be greatly affected by the way seepage face boundaries are handled in hydrological models and that careful considerations are required when using simple approximations, in the presence of heterogeneous slopes, and for seepage faces forming on a portion of the land surface. Third, CATHY_FT is implemented and run at the Landscape Evolution Observatory of the Biosphere 2 facility, Arizona. A detailed modeling analysis is performed of the experimental data collected during an isotope tracer experiment and from an intensively-measured hillslope, including quantity and quality of groundwater discharge and point-scale flow and transport data. This flow and tracer data is used to incrementally explore complex phenomena and associated hypotheses (e.g., heterogeneity, fractionation, and dispersion), progressing from flow to transport and from integrated to point-scale response analysis. This incremental approach highlights the challenges in testing and validating the new generation of integrated hydrological models when considering many types and levels of observation data. Finally, a concluding analysis is performed that relates to all three themes of the thesis, describing some of the features of the CATHY_FT model, discussing key issues associated to its further development, and testing its physical and numerical behavior for both real and synthetic scenarios. This final stage of the thesis addresses the myriad challenges faced in accurately and efficiently resolving the difficult behavior of the advection-dispersion equation for subsurface solute transport, in properly handling the complex boundary conditions for solute interactions across the land surface, and generally in capturing process interactions and feedbacks between flow and transport phenomena in surface and subsurface environments.Lo scopo di questa tesi e' fornire dei contributi all'idrologia e alla modellazione idrologica nell'ambito di un modello numerico specifico, il modello CATchment HYdrology Flow-Transport (CATHY_FT), utilizzato per simulare processi integrati di superficie e sotterranei e di flusso e trasporto. Questi contributi riguardano tre temi principali: il miglioramento del comportamento numerico di modelli idrologici che simulano fenomeni di flusso e trasporto, l'approfondimento di condizioni al contorno complesse con l'obbiettivo di ridurre gli errori relativi alla loro modellazione e il test e l'analisi comparativa di modelli a base fisica utilizzati per simulare processi di flusso e trasporto sotterranei. Il lavoro per raggiungere l'obbiettivo generale viene diviso in quattro step. Nel primo step l'algoritmo di Larson-Niklasson e' implementato in CATHY_FT per ricostruire velocita' conservatrici della massa a partire da una soluzione lineare (o P1) di Galerkin dell'equazione di Richards, in modo da permettere al modello di trasporto avvettivo (basato sui volumi finiti) di conservare la massa, cosa che dipende strettamente dall'accuratezza del campo di velocita' che questo utilizza. Confrontando i risultati ottenuti con le velocita' derivanti dalla soluzione P1 di Galerkin e quelle ricostruite, viene mostrato che un campo di velocita' localmente conservativo e' necessario per ottenere risultati accurati con il trasporto. Nella seconda fase viene effettuata un'analisi dettagliata del comportamento delle condizioni ai limiti nella zona del fronte di infiltrazione con il modello di flusso di CATHY_FT. Le simulazioni numeriche esaminano il comportamento del modello in condizioni complesse come quelle di eterogeneita' e di flusso di superficie e sotterraneo accoppiato. Viene dimostrato che la soluzione numerica puo' essere fortemente influenzata dal modo in cui la zona di infiltrazione viene trattata nei modelli idrologici e che considerazioni accurate sono sempre necessarie quando si usano approssimazioni, in presenza di versanti eterogenei e per le zone di infiltrazione che si formano nella superficie terrestre. Come terzo step, CATHY_FT viene testato al Landscape Evolution Observatory del Biosphere 2 in Arizona. Viene eseguita un'analisi dettagliata di dati sperimentati raccolti durante un esperimento di tracciante isotopico e da un versante artificiale intensivamente controllato. Le informazioni comprendono la qualita' e la quantita' della portata sotterranea e dati puntuali di flusso e trasporto. Questi dati di flusso e tracciante sono utilizati per esplorare fenomeni complessi e le ipotesi associate (e.g., eterogeneita', frazionamento e dispersione), procedendo dalla risposta di flusso a quella di trasporto e dalla risposta integrata a quella puntuale. Questo approccio incrementale evidenzia le sfide legate alla validazione della nuova generazione di modelli idrologici integrati quando si guarda a diversi tipi e livelli di dati osservati. Infine, viene eseguita un'analisi conclusiva che si lega a tutti e tre i temi della tesi, descrivendo alcune caratteristiche del modello CATHY_FT, discutendo problemi chiave legati al suo sviluppo futuro e testando il suo compertamento fisico e numerico sia per scenari sintetici che reali. Questo step finale della tesi affronta la miriade di sfide legate alla risoluzione accurata ed efficace del comportamento difficile dell'equazione di avezione-dispersione per processi di trasporto di soluto sotterraneo, alla risoluzione appropriata delle condizioni ai limiti complesse per rappresentare le interazioni di soluto attraverso la superficie terrestre e, in generale, alla rappresentazione delle interazioni tra i fenomeni di flusso e trasporto nell'ambiente superficiale e sotterraneo.
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Cai, Mingchao. "Modeling and numerical simulation for the coupling of surface flow with subsurface flow /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?MATH%202008%20CAI.
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Sun, Xiaoli. "Hydraulics analysis of subsurface flow in mature rock bed wetlands /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924932.
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Mishra, Phoolendra Kumar. "Pumping test inference of saturated/unsaturated aquifer properties." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194085.
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Analytical solutions for aquifer response to pumping are commonly used to infer the hydraulic properties of aquifers. This dissertation develops new analytical solutions for the analysis of pumping test data from confined and unconfined aquifer.An analytical solution for flow to a partially penetrating well of infinitesimally small radius in a compressible unconfined aquifer is developed that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or the unsaturated zone. The effects of unsaturated zoneconstitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time is investigated; the solution is validated against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten (1980) - Mualem (1976)constitutive model; used to analyze drawdown data from a pumping test conducted by the US Geological Survey at Cape Cod,Massachusetts; and corresponding estimates of van Genuchten - Mualem parameters are compared with laboratoryvalues obtained for similar materials in the area.Drawdowns generated by extracting water from a large diameter (e.g. water supply) well are affected by wellbore storage. An analytical solution in Laplace transformed space for drawdown in a uniformanisotropic confined aquifer caused by withdrawing water at a constant rate from a partially penetrating well with storage is developed. When the pumping well is fully penetrating the solution reduces to that of Papadopulos and Cooper (1967); to that of Hantush (1964) when the pumping well has no wellbore storage; to the solution of Theis (1935) when both conditions are fulfilled; and to that of Yang et al. (2006) when the pumping well is partially penetrating, having finite radius but lacking storage. The solutionis validated against synthetic pumping test data and used to explore graphically the effects of partial penetration, wellbore storage and anisotropy on time evolutions of drawdown in the pumping well and in observation wells.The analytical solution for unconfined aquifers is extended to the case of a finite diameter pumping well with storage. The extended analytical solution is used to investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time. The solution is validated against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten (1980) - Mualem (1976) model. It is then used to analyze a seven-day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada; and to compare our results with those ofMoench (2008).
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Horton, Nial. "Influence of a turbulent stream flow on the subsurface flow through a regular porous matrix." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25938.
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Peraki, Maria. "Application Of Electrokinetics In Subsurface Energy Extraction." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/770.
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The world’s growing population results in increased energy needs that cannot yet be fully supported by the renewable sources of energy. These modern conditions and restraints have created the need to further research methods to enhance the recovery of resources previously unavailable due to technical and/or economic reasons and to reduce the environmental impacts of using fossil fuels. In this dissertation, applications of electrokinetic phenomena for the improvement of subsurface energy resource extraction are investigated using experimental and numerical tools.
Electrodialysis is proposed as a method of pre-treatment of the flow-back water produced during fracturing stage of shale gas extraction. The method targets the reduction of Total Dissolved Solids levels in the flow-back water so that it can either be treated further or be reused directly. The treatment and reuse of the flow-back water can potentially improve the sustainability of the shale gas extraction, controlling the amounts of water used and the general environmental footprint of the process.
In addition, the electrically assisted oil recovery is investigated as a potential technique for the enhancement of oil extraction, especially for the case of heavy crude oil. The high viscosity and low mobility of heavy crude oil render it almost impossible or not economical to extract. The method uses the application of low electrical field (direct current) to the oil reservoir to facilitate and increase the oil recovery by taking advantage of the mechanisms involved in electrokinetic phenomena.
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Wang, Li. "Modeling reactive transport of strontium-90 in heterogeneous variably-saturated subsurface." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/l_wang_112707.pdf.
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Nokes, Rita Lynn. "Reduction of enteric organisms in small scale, subsurface flow constructed wetlands." Thesis, The University of Arizona, 1998. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0280_sip1_w.pdf&type=application/pdf.
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Hanson, Carter Curtis. "Temporal effect on nitrogen removal in a subsurface flow constructed wetland." Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1027117.
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A subsurface flow constructed wetland planted with the common reed (Phragmites australis) and softstem bulrush (Scirpus validus) was built in East Central Indiana. The objective of this study was to determine if temperature had an effect on nitrogen (N) removal from the wetland. The research was conducted from the first week of October 3, 1995 to the first week in December 5, 1995 why the wetland froze. Water samples were taken from 5 samplings sites in the system. Each sample was analyzed for organic-N, ammonia, nitrate, and total-N. In the system statistically significant amounts of organic-N, nitrate, and total-N were removed. Ammonia lever reductions, however, were not significant. Organic-N had a mean removal of 37% (8 mg/1) 'Nitrate had a mean removal of 96% (2.3 mg/1). Total-N removal over the sampling period averaged 30% (12 mg/1). The N results were regressed against air and wastewater temperatures. Wastewater temperature was more important because it had a direct impact can the plants and microbes in the system. Warmer temperatures sustained a higher metabolism for the biota in the system. Air temperature had an indirect impact on efficiency of N removal from the wastewater flowing through the wetland. The primary impact .: f the air temperature was on water temperature which then affected the metabolism of or a nc ns in the wetland cell. Greater removal efficiencies were seen during high temperature periods and lower removal efficiencies were noted when the temperatures were low.Department of Natural Resources and Environmental Management
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Rombang, Johan Alexander. "An investigation into subsurface macropore flow using an artificial macropose system." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336690.
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Kalejaiye, Bolarinwa Olumuyiwa. "The flow of miscible and immiscible fluids in the Earth's subsurface." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619654.
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Thoms, R. Brad. "Simulating fully coupled overland and variably saturated subsurface flow using MODFLOW /." Full text open access at:, 2003. http://content.ohsu.edu/u?/etd,16.
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An, Hyunuk. "Development and applications of computational methods for saturated-unsaturated subsurface flow." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/135391.
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Redmond, Eric. "Nitrogen removal from wastewater by an aerated subsurface flow constructed wetland." Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/2971.
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The purpose of this research was to assess the ability of subsurface flow wetlands, with aeration and vegetation, to remove nitrogen in cold weather climates. Aeration was shown to enhance the wetland cell's ability to remove not only nitrogen but also CBOD, COD, and phosphorus (retention) more effectively. There was a significant difference (p< 0.05) in both total nitrogen and ammonia effluent concentrations comparing aerated to unaerated wetland cells, while no significance was found comparing planted and unplanted wetland cells. The effluent ammonia concentrations from the aerated wetland cells ranged from 2.7 to 5.7 mg N/L, while for unaerated cells effluent concentration ranged from 22 to 23 mg N/L. The effluent total nitrogen concentrations from the aerated wetland cells ranged from 9.0 to 12 mg N/L, while those from unaerated cells ranged from 23 to 24 mg N/L. The effluent concentrations showed no significant difference (p < 0.05) when comparing results of three temperature ranges. There is a correlation when comparing ammonia mass removal rates to mass loading rates. Ammonia removal in the aerated wetland cells ranged from 82 to 95%, while unaerated cells ranged from 39 to 45%. The hydraulic retention times ranged from 3.13 to 4.33 days and the tanks-in-series ranged from 1.46 to 2.84. Using this information the wetland cells were modeled using both the TIS and the PkC* models. The k values (PkC* model) of the aerated wetlands for ammonia ranged from 131 to 221 m/d, while the unaerated wetland cells had values ranging from 20.4 to 36.7 m/d. The models appear to show a good prediction of the effluent ammonia concentration for the unaerated cells but the aerated cells show the model does not effectively capture the effects of aeration.
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Guo, Haipeng, and 郭海朋. "Groundwater movement and subsurface air flow induced by land reclamation and tidal fluctuation in coastal aquifers." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40987735.
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Guo, Haipeng. "Groundwater movement and subsurface air flow induced by land reclamation and tidal fluctuation in coastal aquifers." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40987735.
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Johnson, Benjamin Waldon. "Development of a one dimensional subsurface contaminant transport model with stochastic applications." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Johnson2009_09007dcc806b6301.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 10, 2009) Includes bibliographical references.
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Mayenna, Amena Moth. "Crank-Nicolson Galerkin model for nonlinearly coupled macrophase and microphase transport in the subsurface." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Summer2008/a_mayenna_063008.pdf.
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De, Carvalho Baptista Joana. "Microbial mechanisms of carbon removal in laboratory-scale subsurface flow constructed wetlands." Thesis, University of Newcastle Upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270173.
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Shrestha, Surendra Prakash. "An effective medium approximation and Monte Carlo simulation in subsurface flow modeling." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/38642.
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Riva, Monica, Alberto Guadagnini, and Shlomo P. Neuman. "Theoretical analysis of non-Gaussian heterogeneity effects on subsurface flow and transport." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/624363.
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Much of the stochastic groundwater literature is devoted to the analysis of flow and transport in Gaussian or multi-Gaussian log hydraulic conductivity (or transmissivity) fields, Ydx_5ln Kdx_ (x being a position vector), characterized by one or (less frequently) a multiplicity of spatial correlation scales. Yet Y and many other variables and their (spatial or temporal) increments, DY, are known to be generally non-Gaussian. One common manifestation of non-Gaussianity is that whereas frequency distributions of Y often exhibit mild peaks and light tails, those of increments DY are generally symmetric with peaks that grow sharper, and tails that become heavier, as separation scale or lag between pairs of Y values decreases. A statistical model that captures these disparate, scale-dependent distributions of Y and DY in a unified and consistent manner has been recently proposed by us. This new `` generalized sub-Gaussian (GSG)'' model has the form Ydx_5Udx_Gdx_ where Gdx_ is (generally, but not necessarily) a multiscale Gaussian random field and Udx_ is a nonnegative subordinator independent of G. The purpose of this paper is to explore analytically, in an elementary manner, lead-order effects that non-Gaussian heterogeneity described by the GSG model have on the stochastic description of flow and transport. Recognizing that perturbation expansion of hydraulic conductivity K5eY diverges when Y is sub-Gaussian, we render the expansion convergent by truncating Y's domain of definition. We then demonstrate theoretically and illustrate by way of numerical examples that, as the domain of truncation expands, (a) the variance of truncated Y (denoted by Yt) approaches that of Y and (b) the pdf (and thereby moments) of Yt increments approach those of Y increments and, as a consequence, the variogram of Yt approaches that of Y. This in turn guarantees that perturbing Kt5eYt to second order in rYt (the standard deviation of Yt) yields results which approach those we obtain upon perturbing K5eY to second order in rY even as the corresponding series diverges. Our analysis is rendered mathematically tractable by considering mean-uniform steady state flow in an unbounded, twodimensional domain of mildly heterogeneous Y with a single-scale function G having an isotropic exponential covariance. Results consist of expressions for (a) lead-order autocovariance and cross-covariance functions of hydraulic head, velocity, and advective particle displacement and (b) analogues of preasymptotic as well as asymptotic Fickian dispersion coefficients. We compare these theoretically and graphically with corresponding expressions developed in the literature for Gaussian Y. We find the former to differ from the latter by a factor k5hU2 i= hUi 2 (h i denoting ensemble expectation) and the GSG covariance of longitudinal velocity to contain an additional nugget term depending on this same factor. In the limit as Y becomes Gaussian, k reduces to one and the nugget term drops out. Plain Language Summary Much of the stochastic groundwater literature is devoted to the analysis of flow and transport in Gaussian or multi- Gaussian log hydraulic conductivity fields, Y(x), (x being a position vector). Yet Y, as well as many other variables and their increments DY, are known to be generally non- Gaussian. One common manifestation of non- Gaussianity is that whereas frequency distributions of Y often exhibit mild peaks and light tails, those of increments are generally symmetric with peaks that grow sharper, and tails that become heavier, as separation scale or lag between pairs of Y values decreases. A statistical model that captures these disparate, scale- dependent distributions of Y and DY in a unified and consistent manner has been recently proposed by us. This new generalized sub- Gaussian (GSG) model has the form Y(x) 5U(x) G(x) where G(x) is (generally, but not necessarily) a multi- scale Gaussian random field and U(x) is a non- negative subordinator independent of G. The purpose of this paper is to explore analytically lead-order effects that non-Gaussian heterogeneity described by the GSG model have on the stochastic description of flow and transport. Our analysis is rendered mathematically tractable by considering mean uniform steady state flow in an unbounded, two-dimensional domain of mildly heterogeneous Y.
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Demin, Oleg Alexandrovich. "Remediation of ammonia rich minewater in constructed wetlands." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268403.
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Silliman, Stephen Edward Joseph 1957. "Stochastic analysis of high-permeability paths in the subsurface." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/191120.
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Subsurface fluids may travel along paths having a minimum permeabilility greater than the effective permeability of the rock. This may have an important impact on contaminant migration. A stochastic approach related to percolation theory is advanced to address the question of what is the probability that a high permeability path extends across a given volume of the subsurface. The answer is sought numerically through subdividing the volume of interest into a three-dimensional grid of elements and assigning a random permeability to each element. Four permeability processes are considered: 1) Stationary with independence between grid elements; 2) Stationary and autocorrelated; 3) Nonstationary due to conditioning on measured values; and 4) Random rock volume included in grid. The results utilizing data from fractured granites suggest that in large grids, at least one path having a minimum permeability in excess of the "effective" rock permeability will cross the grid. Inclusion of autocorrelation causes an increase in the expected value of the minimum permeability of such a path. It also results in a significantly increased variance of this permeability. Conditioning on field permeabilities reduces the variance of this value over that obtained by unconditional, correlated simulation, but still produces a variance greater than that obtained when independence was assumed. When conditioning is performed, the mean of the minimum permeabilities along these paths is dependent on the principal axis of the path. Finally, including a random rock volume by allowing the length of the grid to be random increases the variance of the minimum permeability.
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Regmi, Tulsi. "Influence of solids on hydraulic and treatment properties of submerged-flow wetlands /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9974676.
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Abd, Rahman N. "Finite element analysis of multiphase flow, heat flow and pollutant transport in deforming porous media for subsurface systems." Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635825.
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The simulation of groundwater contamination by nonaqueous phase liquids (NAPLs), such as organic solvents and petroleum hydrocarbons, requires a solution of the multiphase flow, heat flow and pollutant transport through soil. Also, the contaminant can exist within the gas and water phases. A multi-phase flow model, based on the two-phase flow model of Brooks and Corey, that expresses the dependence of saturation and relative permeability on capillary pressure is presented. The nonlinear behaviour of the saturation versus relative permeability functions is incorporated into a Galerkin finite element model that is used to simulate the vertical infiltration of immiscible/miscible fluid in unsaturated and saturated porous media. The governing partial differential equations, in terms of soil displacements, fluid pressures, energy balance and concentrations are coupled and behave non-linearly but can be solved by the finite element method. In order to apply the finite element model to a specific problem a number of parameters must be evaluated. These include relative permeabilities, saturation-pressure relations, mass transfer coefficients and densities. Numerical implementation of the formulation is discussed, and example problems are presented for verification. As a demonstration of the model's applicability, the migration of a contaminant is simulated in 1D and 2D problems. Also, an approximate numerical solution to the theoretical model is presented. The weighted residual finite element approach is employed to achieve spatial discretisation of the problem while temporal discretisation is achieved by a fully implicit scheme. A verification and validation programme has been implemented to assess the integrity of the theory, discretisation approach and the code itself. Several exercises verifying the consolidation model are presented. Validation exercises for the cases of isothermal, non-isothermal, saturated and unsaturated conditions of the coupled flow of heat, water and gas in a deforming porous medium, are performed. Finally, the fully coupled model is verified by comparison with results from an alternative model.
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Zhang, Sheng Ping. "Real-Time Control of Reservoir Systems Based on the Synthesized Runoff Model of Surface Flow and Subsurface Flow." Kyoto University, 1988. http://hdl.handle.net/2433/138414.
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Pedescoll, Albacar Anna. "Clogging in horizontal subsurface flow constructed wetlands: mesures, design factors and prevention strategies." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/108721.
Full textAbstract:
Constructed wetlands are alternative systems to conventional wastewater treatment for small communities
(up to 2000 PE). This is mainly due to that operation and maintenance costs are reduced.
Despite the advantages, the clogging of the bed is the most important trouble encountered by the
managers of subsurface flow wetlands treatment systems. The solids accumulation in the interstitial
spaces of the gravel over time causes the decrease of both, hydraulic conductivity and porosity.
This leads in the development of preferential paths and short-circuiting of the water through the
wetland, which converge in overland flow and contaminant removal efficiency decrease. Therefore,
clogging is the main limiting factor of the life span of a subsurface flow constructed wetland.
The strategies to reverse clogging imply important economic investments. Generally, the most
widespread option is the replacement of gravel. Hence the need to measure realibly the degree of
clogging of a system in order to identify the factors that influence this phenomenon and to search
new configurations and strategies to delay its progress, thus operations needed to reverse it.
Therefore, the aims of this thesis must contribute to establish new design criteria and operation of
horizontal subsurface flow constructed wetlands to minimize clogging processes without reducing
the contaminant removal efficiency. Then, the objectives were to compare a method to measure
hydraulic conductivity in situ, based on falling head permeameter, in order to determine the state of
clogging of wetlands and its horizontal distribution; to determine the most suitable indicator to assess
clogging in horizontal subsurface flow wetlands; to identifie new design and operation parameters
likely to cause or encourage the clogging of the filter medium; and to analyse two new configurations
in a pilot scale system in terms of contaminant removal and clogging development.
Among the different clogging indicators analysed (drenable porosity, hydraulic conductivity, accumulated
solids and effective volume from a tracer test), hydraulic conductivity seems to be the best
one. Firstly, because hydraulic conductivity provides information about the hydraulic behaviour
inside the bed, and linked appropriately with the accumulated solids (a correlation of 74.5% was
found between both indicators). Secondly, because its application in full-scale wetlands is more
straightforward than other techniques.Los humedales construidos son una alternativa al tratamiento convencional de agua residual para pequeños municipios (hasta 2000 hab-eq) ya que son fáciles de operar y mantener y tienen un coste de explotación bajo. El mayor inconveniente a que se enfrentan los explotadores de sistemas de tratamiento con humedales subsuperficiales es la colmatación del lecho. Con el tiempo, la acumulación de sólidos de diversa naturaleza en los espacios intersticiales del medio filtrante, provoca la disminución de la conductividad hidráulica y la porosidad iniciales de la grava. Esto conduce al desarrollo de caminos preferenciales y cortocircuitos en el curso del agua que convergen en la aparición de agua en superficie. A la larga, esto puede comprometer la capacidad depurativa del sistema. Por ello, la colmatación supone el factor limitante de la vida útil de un humedal construido. Las estrategias para solventar la colmatación, una vez se ha producido, son costosas y pasan por realizar inversiones no despreciables. Generalmente la opción más extendida es el cambio del material granular. De ahí la necesidad de medir, de manera fiable, en qué grado un sistema está colmatado, identificar los factores que influyen en el fenómeno e indagar en nuevas configuraciones y estrategias que permitan retrasar el avance de la colmatación y consigo, aplazar las intervenciones necesarias para devolver al sistema un estado óptimo de funcionamiento. Los objetivos de esta tesis doctoral han de contribuir a establecer nuevos criterios de diseño y operación de humedales construidos de flujo subsuperficial horizontal para minimizar, o cuanto menos retrasar, la colmatación de estos sistemas, sin mermar la eficiencia de eliminación de contaminantes del agua residual. Por ello, los objetivos son cuantificar la precisión y exactitud de un método de medición in situ de la conductividad hidráulica, basado en el permeámetro de carga variable, para la determinación del grado de colmatación de un lecho y la distribución horizontal de la misma; estudiar la idoneidad de diferentes indicadores de la colmatación de un humedal de flujo subsuperficial horizontal; evaluar la incidencia de diferentes factores de diseño y operación de humedales de flujo subsuperficial horizontal en el proceso de la colmatación; y caracterizar (en términos de eficiencia de eliminación de contaminantes y de evolución de la colmatación) dos nuevas configuraciones de humedales construidos a escala piloto.
Els aiguamolls construïts són una alternativa al tractament convencional d’aigua residual per a petits municipis (fins 2000 hab-eq) degut, principalment, a la facilitat en llur operació i manteniment y a les reduïdes despeses d’explotació. L’inconvenient més important amb què es troben els explotadors de sistemes de tractament amb aiguamolls subsuperficials és la colmatació del llit. Al llarg del temps, l’acumulació de sòlids de diversa natura en els espais intersticials de la grava, provoca la disminució de la conductivitat hidràulica i la porositat inicials. Això condueix al desenvolupament de camins preferencials i curtcircuits en el curs de l’aigua a través de l’aiguamoll, que convergeixen en l’aparició d’aigua en superfície, i que, a llarg termini pot comprometre la capacitat depurativa del sistema. Per això, la colmatació suposa el factor limitant de la vida útil d’un aiguamoll construït. Les estratègies per a fer front a la colmatació, un cop s’ha produït, passen per realitzar inversions econòmiques gens menyspreables. Generalment, l’opció més extesa és la reposició del material granular. D’aquí neix la necessitat de mesurar, de manera fiable, el grau de colmatació d’un sistema, d’identificar aquells factors que influeixen en el fenomen y qüestionar noves configuracions y estratègies que permetin retardar l’avenç de la colmatació, i per tant ajornar les intervencions necessàries per tornar al sistema a l’estat òptim de funcionament. Per tot això els objectius d’aquesta tesi doctoral han de contribuir a establir nous criteris de disseny i operació d’aiguamolls construïts de flux subsuperficial horitzontal per tal de minimitzar la colmatació d’aquests sistemes, sense minvar l’eficiència d’eliminació de contaminants de l’aigua residual. Els objectius específics són quantificar la precisió i exactitud d’un mètode de mesura in situ de la conductivitat hidràulica, basat en el permeàmetre de càrrega variable, per a la determinació de l’estat de colmatació d’un llit així com la distribució horitzontal d’aquesta; determinar l’indicador més adecuat per avaluar la colmatació d’un aiguamoll construït de flux subsuperficial horitzontal; identificar nous paràmetres de disseny y operación susceptibles de causar o afavorir la colmatación del medi filtrant; i caracteritzar (en termes d’eliminació de contaminants i d’evolució de la colmatación) dues noves configuracions d’aiguamolls construïts a escala pilot.
33
VanderKwaak, Joel E. "Numerical simulation of flow and chemical transport in integrated surface-subsurface hydrologic systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0012/NQ38276.pdf.
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Nowak, Wolfgang. "Geostatistical methods for the identification of flow and transport parameters in the subsurface." Stuttgart Inst. für Wasserbau, 2004. http://deposit.d-nb.de/cgi-bin/dokserv?idn=97474896X.
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35
He, Zhiguo. "Numerical simulation of flow, sediment, and contaminant transport in integrated surface-subsurface systems /." Full text available from ProQuest UM Digital Dissertations, 2007. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1414125241&SrchMode=1&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1221163101&clientId=22256.
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36
Izumi, Tomoki. "Inverse Modeling of Variably Saturated Subsurface Water Flow in Isothermal/Non-isothermal Soil." Kyoto University, 2012. http://hdl.handle.net/2433/157730.
Full textAbstract:
Kyoto University (京都大学)0048
新制・論文博士
博士(農学)
乙第12659号
論農博第2766号
新制||農||1003(附属図書館)
学位論文||H24||N4700(農学部図書室)
29737
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 河地 利彦, 教授 村上 章, 教授 川島 茂人
学位規則第4条第2項該当
37
Nowak, Wolfgang. "Geostatistical methods for the identification of flow and transport parameters in the subsurface." [S.l. : s.n.], 2005. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11759377.
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Wittmeyer, Gordon William. "Robust estimation of parameters in nonlinear subsurface flow models using adjoint state methods." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185329.
Full textAbstract:
Estimating the parameters of groundwater flow models by automatic calibration methods is an extremely difficult problem, but one which must be solved in order to produce reliable model predictions. The data upon which the model is calibrated are usually corrupted by measurement and model structure errors which can unduly affect the values of the parameter estimates. In this dissertation the statistically robust M-estimator of Huber is used to reduce the influence of large, outlying errors in the measured head data on the values of the estimated model parameters. The robust estimation procedure is implemented in a computer program which models unconfined, steady-state and transient flow as described by the Boussinesq equation for Dupuit-type flow. The program allows the user to estimate hydraulic conductivity, specific yield, specific storage, recharge rates, leakances, boundary heads and boundary fluxes. The nonlinear error criterion is minimized using conjugate gradient and quasi-Newton methods coupled with both accurate and innaccurate line search algorithms. The gradient of the error criterion is efficiently computed by using the adjoint state finite element method. Monte Carlo studies of a synthetic aquifer model are used to demonstrate the superior efficiency of the Huber M-estimator to that of ordinary least squares. The method is also applied to a large scale inverse modeling study of the Tucson basin regional aquifer.
39
Olson, Patricia L. "Shallow subsurface flow systems in a montane terrace-floodplain landscape : Sauk River, North Cascades, Washington /." Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/5605.
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Sharpe, Sarah S. "Control of burial and subsurface locomotion in particulate substrates." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50345.
Full textAbstract:
A diversity of animals move on and bury within dry and wet granular media, such as dry desert sand or rainforest soils. Little is known about the biomechanics and neural control strategies used to move within these complex terrains. Burial and subsurface locomotion provides a particularly interesting behavior in which to study principles of interaction because the entire body becomes surrounded by the granular environment. In this dissertation, we used three model organisms to elucidate control principles of movement within granular substrates: the sand-specialist sandfish lizard which dives into dry sand using limb-ground interactions, and swims subsurface using body undulations; the long-slender shovel-nosed snake which undulates subsurface in dry sand with low slip; and the ocellated skink, a desert generalist which buries into both wet and dry substrates. Using muscle activation measurements we discovered that the sandfish targeted optimal kinematics which maximized forward speed and minimized the mechanical cost of transport. The simplicity of the sandfish body and kinematics coupled with a fluid-like model of the granular media revealed the fundamental mechanism responsible for neuromechanical phase lags, a general timing phenomenon between muscle activation and curvature along the body that has been observed in all undulatory animals that move in a variety of environments. Kinematic experiments revealed that the snake moved subsurface using a similar locomotion strategy as the sandfish, but its long body and low skin friction enabled higher performance (lower slip). The ocellated skink used a different locomotor pattern than observed in the sandfish and snake but that was sufficient for burial into both wet and dry media. Furthermore, the ocellated skink could only reach shallow burial depths in wet compared to dry granular media. We attribute this difference to the higher resistance forces in wet media and hypothesize that the burial efficacy is force-limited. These studies reveal basic locomotor principles of burial and subsurface movement in granular media and demonstrate the impact of environmental interaction in locomotor behavior.
41
Jang, Wonyong. "Unsteady multiphase flow modeling of IN-SITU air sparging system in a variable saturated subsurface environment." Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-11172005-140745/.
Full textAbstract:
Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.Dr. Spyros Pavlostathis, Committee Member ; Dr. Mustafa M. Aral, Committee Chair ; Dr. Turgay Uzer, Committee Member ; Dr. Ching-Hua Huang, Committee Member ; Dr. Sotira Yiacoumi, Committee Member. Vita. Includes bibliographical references.
42
Browning, Catharine, and n/a. "Nutrient Removal and Plant Growth in a Subsurface Flow Constucted Wetland in Brisbane, Australia." Griffith University. School of Environmental Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040226.092311.
Full textAbstract:
One of the major water quality issues affecting waterways is eutrophication. Controlling the input of nutrients from municipal wastewater treatment plants (WTPs) is a significant step in reducing eutrophication. Tertiary wastewater treatment for water quality improvement in particular Biological Nutrient Removal (BNR) is often expensive to construct with high maintenance costs. Constructed wetlands (CWs) offer an alternative wastewater treatment and have been used successfully worldwide to treat various types of wastewater. This study investigated the effectiveness of the Oxley Creek horizontal subsurface flow (SSF) CW for tertiary municipal wastewater treatment and the suitability of four native macrophyte species, Baumea articulata, Carex fascicularis, Philydrum lanuginosum and Schoenoplectus mucronatus. The investigation consisted of four main components: 1) Plants: monitoring plant establishment, growth, impact of cropping, gravel size, nutrient content and storage for the four macrophyte species trialed; 2) Water quality - effluent treatment: monitoring water quality and quantity entering and leaving the wetland to determine wastewater treatment; 3) Organic matter: accumulation of organic carbon within the wetland cells for the different gravel sizes (5mm and 20mm) and 4) Mass balance: combining nutrient storage by macrophytes with wastewater nutrient removal to determine proportion of nutrient removal by plant uptake. The Oxley horizontal SSF CW is situated at the Oxley Creek WTP in Brisbane (South- East), Queensland, Australia which has a sub-tropical climate. The experimental design involved four different substrate treatments: Cell A new 5mm gravel, Cells B and C old 20mm gravel and Cell D old 5mm gravel. Cells B, C and D had been operational since 1995 whereas Cell A had been in use since 2000. The wetland received secondary treated effluent direct from the Oxley Creek WTP at an average flow rate of 8L/min with a median hydraulic loading rate (HLR) of 0.12m/day and a hydraulic retention time (HRT) of 2 to 3 days. Each cell consisted of three gravel sections (Section 1 to 3) separated by 1m wide open water sections. Gravel Sections 2 and 3 were planted out with the four macrophyte species in October 2000, Section 1 remained unplanted. Plant health and leaf height was monitored to assess plant establishment and growth. Investigations into plant establishment and growth demonstrated that Carex was most suitable. Carex achieved the highest maximum leaf height and was not affected by pests and disease unlike Schoenoplectus and Philydrum. Above ground biomass was cropped in May and August 2001, with biomass of cropped material measured on both occasions. Plant health and re-growth following cropping of above ground biomass in May and August 2001 demonstrated that cropping retarded regrowth of Schoenoplectus and Philydrum. Carex and Baumea recovered quickest following cropping, with Carex achieving leaf height prior to cropping within 6 months. Proportion of biomass contained above and below ground was measured by collecting biomass samples three times over 9 months and dividing into plant components (roots, rhizomes, leaves, flowers and stems). Investigations into the proportion of above and below ground components indicated that >80% of biomass is contained above ground. Therefore cropping above ground biomass would potentially remove a significant proportion of nutrient storage from the CW. The results indicated that the ideal time for cropping was in spring/summer when plants are flowering particularly for Philydrum, whose flowering stems comprised 40% of total plant biomass. Flowering stems of Philydrum could potentially have a commercial use as a cut flower. Nutrient content of the four species in each cell was measured for individual plant components when first planted and after three (summer) and six (autumn) months growth. This was combined with biomass data to quantify nutrient bioaccumulation (nitrogen and phosphorus) by the four species in each cell. In terms of ability to bioaccumulate nitrogen and phosphorus, measurements of nutrient content and storage indicated that all four species were suitable. Nutrient storage was highest for Baumea and Carex. However high nutrient content may make the macrophytes more susceptible to pest and disease attack as found in this study for Philydrum and Schoenoplectus. Nutrient storage was highest in Cell A (new 5mm gravel) as a result of higher biomass achieved in this cell. The cropping and nutrient storage experiments indicated that Carex was the most suitable species for use in SSF CWs. Carex achieved the highest nutrient storage and had the fastest regrowth following cropping. Organic carbon accumulation between gravel particles measured as the proportion of material lost at 500oC was determined for gravel samples collected from each section for all four cells at 10cm depth increments (0-10cm, 10-20cm and 20-30cm). Investigations into organic carbon accumulation within the gravel substrate showed that organic accumulation was higher in the planted sections particularly for cells that had previously been planted with Phragmites australis. Organic accumulation was highest in the top 20cm of the gravel, which can be attributed to litter fall and root material. The effect of gravel size on plant growth, biomass, root depth and organic accumulation was assessed throughout the study. Investigations indicated that gravel size did not appear to affect biomass, maximum root penetration, re-growth following cropping and organic accumulation. Water quality from the inlet and outlet of each cell was measured fortnightly over 12 months (May 2001 to May 2002). Water quantity (HLR) was measured weekly using tipping buckets located at the inlet and outlet of each cell. Water quality and quantity were combined to investigate the nutrient removal efficiency of the wetland. The Oxley wetland was highly effective in reduction of TSS (<2mg/L) and COD (<30mg/L). Principal TSS and COD removal mechanism was physical with the first gravel section acting as a filter removing the majority of particulate material. Average loading rates to the wetland were 7.1 kg/ha/d PO4-P, 14 kg/ha/d NH4-N and 5.4 kg/ha/d NOx-N. Average daily mass removal rates ranged from 7.3 kg/ha NH4-N in Cell D to 4.6 kg/ha in Cell C (i.e. 37%-22% removal efficiency respectively); 5.2 kg/ha NOx-N in Cell C to 1.3 kg/ha in Cell A (i.e. 75%-22% removal efficiency) and 0.8 kg/ha PO4-P in Cell A to 0.1 kg/ha in Cell C (i.e. 10%-1% removal efficiency). Removal efficiency was calculated on a loads basis. Insufficient retention times (2-3 days based on tracer study) and anaerobic conditions (<1mg/L) limited further nitrogen removal. Negligible phosphorus removal for all cells was attributed to short retention time and likelihood of phosphorus adsorption being close to capacity. Investigation into the proportion of nutrient removal attributed to plant uptake demonstrated that nutrient uptake and storage in plant biomass accounted for <12% TN and <5% TP. This research project has provided several useful outcomes that can assist in future guidelines for designing effective SSF CWs in the subtropics/tropics. Outcomes include the importance of maintaining an adequate water level during the initial establishment phase. Maximising effluent treatment by pre-treatment of wastewater prior to entering SSF CWs to enable ammonia to be converted to nitrate and ensuring adequate hydraulic retention time. Carex fascicularis was the most suitable species particularly where harvesting regimes are employed. Philydrum flowering stems could be used as a cut flower in the florist trade.
43
McDonald, Douglas Joseph. "The role of macropores in subsurface flow on a forested slope, an experimental investigation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ40480.pdf.
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Wiyo, Kenneth Alfred Wiskot. "Measurements and modelling of fertilizer concentrations in subsurface drain flow from a potato field." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60542.
Full textAbstract:
A 4.87 hectare potato field at St. Leonard d'Aston, Quebec was instrumented to measure surface runoff and tile drain flow over the 2 year growing season period, 1989-1990. The soil type was a Ste. Jude sandy loam. Several soil and water parameters and NPK concentrations in runoff were measured. The CREAMS (Chemicals, Runoff and Erosion from Agricultural Management Systems) computer simulation model was validated for the study site.Observed N concentrations in tile drain flow exceeded the Canadian water quality guideline of 10 mg/L. Observed P concentrations were less than 0.01 mg/L; and K concentrations, for the most part, exceeded 10 mg/L.
CREAMS overpredicted event surface runoff depths, and underpredicted event percolation depths. However, total monthly surface runoff and percolation depths closely matched observed values.
CREAMS overpredicted event nitrate concentrations in tile drain flow. There was a poor match between predicted and observed event nitrate concentrations in tile drain flow (coefficient of predictability, CP$ sb{ rm A}$ = 104.95). However, predicted total monthly nitrate load closely matched observed values (CP$ sb{ rm A}$ = 0.84). Total monthly and seasonal nitrate loads in tile drain flow were underpredicted.
45
Womack, Michael. "Temporal effects on orhophosphate removal from municipal wastewater in a subsurface-flow constructed wetland." Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1020163.
Full textAbstract:
Orthophosphate removal from wastewater in a subsurface-flow constructed wetland (SFCW) was studied during the fall of 1995. The SFCW consisted of a cell with an impervious liner, filled with 1.27 to 3.81 cm river rock and planted with common reeds (Phragmites australis) and soft-stem bulrushes (Scirpus validus). Municipal wastewater was pumped through the wetland and comparisons were made between inlet and outlet orthophosphate concentrations. Comparisons were also made at locations within the cell. A mean orthophosphate reduction of 62% with a range of 91% to 32% was observed for the duration of the study. An ANOVA test showed a significant reduction of orthophosphate in the wetland cell during the study. A regression analysis indicated that inlet wastewater temperatures played a significant role in orthophosphate removal, while outlet wastewater and ambient air temperature were not a significant factor.Keywords: Subsurface-Flow Constructed Wetlands, Orthophosphate, Municipal Wastewater, Water Chemistry, Nutrients.Department of Natural Resources and Environmental Management
46
Ndumu, Alberto Sangbong. "Fractal-based stochastic simulation and analysis of subsurface flow and scale-dependent solute transport." Thesis, Edinburgh Napier University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311040.
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47
Browning, Catharine. "Nutrient Removal and Plant Growth in a Subsurface Flow Constucted Wetland in Brisbane, Australia." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/366348.
Full textAbstract:
One of the major water quality issues affecting waterways is eutrophication. Controlling the input of nutrients from municipal wastewater treatment plants (WTP’s) is a significant step in reducing eutrophication. Tertiary wastewater treatment for water quality improvement in particular Biological Nutrient Removal (BNR) is often expensive to construct with high maintenance costs. Constructed wetlands (CWs) offer an alternative wastewater treatment and have been used successfully worldwide to treat various types of wastewater. This study investigated the effectiveness of the Oxley Creek horizontal subsurface flow (SSF) CW for tertiary municipal wastewater treatment and the suitability of four native macrophyte species, Baumea articulata, Carex fascicularis, Philydrum lanuginosum and Schoenoplectus mucronatus. The investigation consisted of four main components: 1) Plants: monitoring plant establishment, growth, impact of cropping, gravel size, nutrient content and storage for the four macrophyte species trialed; 2) Water quality - effluent treatment: monitoring water quality and quantity entering and leaving the wetland to determine wastewater treatment; 3) Organic matter: accumulation of organic carbon within the wetland cells for the different gravel sizes (5mm and 20mm) and 4) Mass balance: combining nutrient storage by macrophytes with wastewater nutrient removal to determine proportion of nutrient removal by plant uptake. The Oxley horizontal SSF CW is situated at the Oxley Creek WTP in Brisbane (South- East), Queensland, Australia which has a sub-tropical climate. The experimental design involved four different substrate treatments: Cell A new 5mm gravel, Cells B and C old 20mm gravel and Cell D old 5mm gravel. Cells B, C and D had been operational since 1995 whereas Cell A had been in use since 2000. The wetland received secondary treated effluent direct from the Oxley Creek WTP at an average flow rate of 8L/min with a median hydraulic loading rate (HLR) of 0.12m/day and a hydraulic retention time (HRT) of 2 to 3 days. Each cell consisted of three gravel sections (Section 1 to 3) separated by 1m wide open water sections. Gravel Sections 2 and 3 were planted out with the four macrophyte species in October 2000, Section 1 remained unplanted. Plant health and leaf height was monitored to assess plant establishment and growth. Investigations into plant establishment and growth demonstrated that Carex was most suitable. Carex achieved the highest maximum leaf height and was not affected by pests and disease unlike Schoenoplectus and Philydrum. Above ground biomass was cropped in May and August 2001, with biomass of cropped material measured on both occasions. Plant health and re-growth following cropping of above ground biomass in May and August 2001 demonstrated that cropping retarded regrowth of Schoenoplectus and Philydrum. Carex and Baumea recovered quickest following cropping, with Carex achieving leaf height prior to cropping within 6 months. Proportion of biomass contained above and below ground was measured by collecting biomass samples three times over 9 months and dividing into plant components (roots, rhizomes, leaves, flowers and stems). Investigations into the proportion of above and below ground components indicated that >80% of biomass is contained above ground. Therefore cropping above ground biomass would potentially remove a significant proportion of nutrient storage from the CW. The results indicated that the ideal time for cropping was in spring/summer when plants are flowering particularly for Philydrum, whose flowering stems comprised 40% of total plant biomass. Flowering stems of Philydrum could potentially have a commercial use as a cut flower. Nutrient content of the four species in each cell was measured for individual plant components when first planted and after three (summer) and six (autumn) months growth. This was combined with biomass data to quantify nutrient bioaccumulation (nitrogen and phosphorus) by the four species in each cell. In terms of ability to bioaccumulate nitrogen and phosphorus, measurements of nutrient content and storage indicated that all four species were suitable. Nutrient storage was highest for Baumea and Carex. However high nutrient content may make the macrophytes more susceptible to pest and disease attack as found in this study for Philydrum and Schoenoplectus. Nutrient storage was highest in Cell A (new 5mm gravel) as a result of higher biomass achieved in this cell. The cropping and nutrient storage experiments indicated that Carex was the most suitable species for use in SSF CWs. Carex achieved the highest nutrient storage and had the fastest regrowth following cropping. Organic carbon accumulation between gravel particles measured as the proportion of material lost at 500oC was determined for gravel samples collected from each section for all four cells at 10cm depth increments (0-10cm, 10-20cm and 20-30cm). Investigations into organic carbon accumulation within the gravel substrate showed that organic accumulation was higher in the planted sections particularly for cells that had previously been planted with Phragmites australis. Organic accumulation was highest in the top 20cm of the gravel, which can be attributed to litter fall and root material. The effect of gravel size on plant growth, biomass, root depth and organic accumulation was assessed throughout the study. Investigations indicated that gravel size did not appear to affect biomass, maximum root penetration, re-growth following cropping and organic accumulation. Water quality from the inlet and outlet of each cell was measured fortnightly over 12 months (May 2001 to May 2002). Water quantity (HLR) was measured weekly using tipping buckets located at the inlet and outlet of each cell. Water quality and quantity were combined to investigate the nutrient removal efficiency of the wetland. The Oxley wetland was highly effective in reduction of TSS (<2mg/L) and COD (<30mg/L). Principal TSS and COD removal mechanism was physical with the first gravel section acting as a filter removing the majority of particulate material. Average loading rates to the wetland were 7.1 kg/ha/d PO4-P, 14 kg/ha/d NH4-N and 5.4 kg/ha/d NOx-N. Average daily mass removal rates ranged from 7.3 kg/ha NH4-N in Cell D to 4.6 kg/ha in Cell C (i.e. 37%-22% removal efficiency respectively); 5.2 kg/ha NOx-N in Cell C to 1.3 kg/ha in Cell A (i.e. 75%-22% removal efficiency) and 0.8 kg/ha PO4-P in Cell A to 0.1 kg/ha in Cell C (i.e. 10%-1% removal efficiency). Removal efficiency was calculated on a loads basis. Insufficient retention times (2-3 days based on tracer study) and anaerobic conditions (<1mg/L) limited further nitrogen removal. Negligible phosphorus removal for all cells was attributed to short retention time and likelihood of phosphorus adsorption being close to capacity. Investigation into the proportion of nutrient removal attributed to plant uptake demonstrated that nutrient uptake and storage in plant biomass accounted for <12% TN and <5% TP. This research project has provided several useful outcomes that can assist in future guidelines for designing effective SSF CWs in the subtropics/tropics. Outcomes include the importance of maintaining an adequate water level during the initial establishment phase. Maximising effluent treatment by pre-treatment of wastewater prior to entering SSF CWs to enable ammonia to be converted to nitrate and ensuring adequate hydraulic retention time. Carex fascicularis was the most suitable species particularly where harvesting regimes are employed. Philydrum flowering stems could be used as a cut flower in the florist trade.Thesis (Masters)
Master of Philosophy (MPhil)
School of Environmental Engineering
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Galluzzo, Benjamin Jason. "A finite-difference based approach to solving the subsurface fluid flow equation in heterogeneous media." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/966.
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In this thesis, we examine the equation describing fluid flow through saturated porous medium in order to develop a new method for approximating hydraulic head values in the subsurface. In particular, we show that under reasonable assumptions, the local explicit equation (LEE) method, an accurate, finite-difference based method that is highly sensitive to changes in the assumed location of hydraulic flow parameters, can be used to approximate hydraulic head values throughout a subsurface domain of interest. This forward solution of the fluid flow equation is solved using an altered finite difference scheme, designed to account for discontinuous jumps often encountered between subsurface material types. While the method is able to handle complicated discontinuities arising from the intermingling of various underground materials, the method determines values at nodes on an easy-to-use uniform Cartesian grid and only requires information from immediately adjacent points. The results of this research directly support the development of more accurate subsurface fluid flow models for use in a wide variety of real-world situations in areas such as water management, contaminant remediation and waste storage. Furthermore, the general development of the LEE method allows it to be used as an approximation technique for any equation where the media of interest encounters a jump.
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Salley, W. Bryan. "Subsurface transport of fertilizer-applied nitrogen on the eastern shore of Virginia." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-10062009-020258/.
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Kiracofe, Brandon Dean. "Performance Evaluation of the Town of Monterery Wastewater Treatment Plant Utilizing Subsurface Flow Constructed Wetlands." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34093.
Full textAbstract:
Field tests were conducted and historical operating data were evaluated to assess the performance of the Monterey WWTP utilizing subsurface flow (SF) constructed wetlands. Previous work with SF wetlands has demonstrated adequate, but variable removal of organic matter, suspended solids, and nitrogen. Few research studies have observed the generation of compounds in the wetlands that affect other treatment processes, specifically reduced compounds that contribute to the chlorine demand. This study attempts not only to distinguish the factors leading to the inadequate performance of the SF wetlands in removing organic matter and nitrogen, but also to identify the cause of the frequent occurrences of a nondetectable chlorine residual in the chlorine contact tank at the Monterey WWTP. Collection and analysis of historical operating data from January 1998 to May 2000 revealed a constantly decreasing removal of carbonaceous biochemical oxygen demand (CBOD5) by the SF wetlands and a poor removal of ammonia-N throughout the system. The decreasing removal of CBOD5 appeared to be caused by clogging of the wetland bed media by accumulated solids. The inability to remove the accumulated solids by pumping was shown. Analysis of field data also showed that the SF wetlands removed 88% of the influent TSS and 71% of the influent CBOD5, while experiencing a 18% increase in ammonia-N. Bisulfide produced in the anaerobic wetland beds accounted for 95% of the chlorine lost in contact tank. The variable production of sulfide is the cause of the frequent nondetectable chlorine concentrations observed. The results of this study suggest that chemical costs of chlorine and sulfur dioxide may be greatly reduced if bisulfide can be removed before chlorination. Also, the use of large rocks as media in SF wetland beds may significantly reduce the physical and biological removal of organic matter.Master of Science