scholarly journals Comparative application and optimization of different single-borehole dilution test techniques

2020 ◽  
Author(s):  
Nikolai Fahrmeier ◽  
Nadine Goeppert ◽  
Nico Goldscheider
Keyword(s):  
Groundwater Monitoring ◽  
Saturated Zone ◽  
One Dimensional ◽  
Monitoring Wells ◽  
Advantages And Disadvantages ◽  
Advection Dispersion ◽  
Fractured Aquifers ◽  
Tracer Distribution ◽  
Deep Boreholes ◽  
The One

AbstractSingle-borehole dilution tests (SBDTs) are a method for characterizing groundwater monitoring wells and boreholes, and are based on the injection of a tracer into the saturated zone and the observation of concentration over depth and time. SBDTs are applicable in all aquifer types, but especially interesting in heterogeneous karst or fractured aquifers. Uniform injections aim at a homogeneous tracer concentration throughout the entire saturated length and provide information about inflow and outflow horizons. Also, in the absence of vertical flow, horizontal filtration velocities can be calculated. The most common method for uniform injections uses a hosepipe to inject the tracer. This report introduces a simplified method that uses a permeable injection bag (PIB) to achieve a close-to-uniform tracer distribution within the saturated zone. To evaluate the new method and to identify advantages and disadvantages, several tests have been carried out, in the laboratory and in multiple groundwater monitoring wells in the field. Reproducibility of the PIB method was assessed through repeated tests, on the basis of the temporal development of salt amount and calculated apparent filtration velocities. Apparent filtration velocities were calculated using linear regression as well as by inverting the one-dimensional (1D) advection-dispersion equation using CXTFIT. The results show that uniform-injection SBDTs with the PIB method produce valuable and reproducible outcomes and contribute to the understanding of groundwater monitoring wells and the respective aquifer. Also, compared to the hosepipe method, the new injection method requires less equipment and less effort, and is especially useful for deep boreholes.

Initial-boundary value problems for the one-dimensional linear advection–dispersion equation with decay

2020 ◽  
Vol 75 (8) ◽  
pp. 713-725 ◽  
Author(s):  
Guenbo Hwang
Keyword(s):  
Boundary Conditions ◽  
Dirichlet Boundary ◽  
Boundary Value ◽  
Initial Boundary ◽  
Initial Boundary Value Problems ◽  
One Dimensional ◽  
Advection Dispersion ◽  
Asymptotically Periodic ◽  
The One ◽  
Initial Boundary Value

AbstractInitial-boundary value problems for the one-dimensional linear advection–dispersion equation with decay (LAD) are studied by utilizing a unified method, known as the Fokas method. The method takes advantage of the spectral analysis of both parts of Lax pair and the global algebraic relation coupling all initial and boundary values. We present the explicit analytical solution of the LAD equation posed on the half line and a finite interval with general initial and boundary conditions. In addition, for the case of periodic boundary conditions, we show that the solution of the LAD equation is asymptotically t-periodic for large t if the Dirichlet boundary datum is periodic in t. Furthermore, it can be shown that if the Dirichlet boundary value is asymptotically periodic for large t, then so is the unknown Neumann boundary value, which is uniquely characterized in terms of the given asymptotically periodic Dirichlet boundary datum. The analytical predictions for large t are compared with numerical results showing the excellent agreement.

Effects of different hydraulic models on predicting longitudinal profiles of reactive pollutants in activated sludge reactors

2008 ◽  
Vol 58 (3) ◽  
pp. 555-561 ◽  
Author(s):  
P. Zima ◽  
J. Makinia ◽  
M. Swinarski ◽  
K. Czerwionka
Keyword(s):  
Activated Sludge ◽  
Ammonia Concentration ◽  
Minor Role ◽  
Nitrification Rate ◽  
Concentration Profiles ◽  
One Dimensional ◽  
Advection Dispersion ◽  
In Series ◽  
The One ◽  
A Minor

This paper presents effects of dispersion on predicting longitudinal ammonia concentration profiles in activated sludge bioreactor located at “Wschod” WWTP in Gdansk. The aim of this study was to use the one-dimensional advection-dispersion Equation (ADE) to simulate the flow conditions (based on the inert tracer concentrations in selected points) and longitudinal profile of reactive pollutant (based on the ammonia concentration profiles in selected points). The simulation results were compared with the predictions obtained using a traditional “tanks-in-series” (TIS) approach, commonly used in designing biological reactors. The use of dispersion coefficient calculated from an empirical formula resulted in substantial differences in the tracer concentration distributions in two sampling points in the bioreactor. Simulations using the one-dimensional ADE and TIS model, with the nitrification rate incorporated as the source term, revealed that the hydraulic model plays a minor role compared to the biochemical transformations in predicting the longitudinal ammonia concentration profiles.

Advection-dispersion modelling tools: what about numerical dispersion?

2005 ◽  
Vol 52 (3) ◽  
pp. 19-27 ◽  
Author(s):  
R. Bouteligier ◽  
G. Vaes ◽  
J. Berlamont ◽  
C. Flamink ◽  
J.G. Langeveld ◽  
...  
Keyword(s):  
Dispersion Equation ◽  
Model Calibration ◽  
Suspended Particles ◽  
Numerical Dispersion ◽  
Model Parameters ◽  
One Dimensional ◽  
Advection Dispersion ◽  
The One ◽  
Calibration Tool ◽  
Tracer Experiments

In general the transport of dissolved substances and fine suspended particles is governed by the one-dimensional advection-dispersion equation. In order to model the transport of dissolved substances and fine suspended particles, the advection-dispersion equation is incorporated into commonly used urban drainage modelling tools such as InfoWorks CS (Wallingford Software, United Kingdom) and MOUSE (DHI Software, Denmark). Two examples show the use of InfoWorks CS and MOUSE using standard model settings. Modelling results using tracer experiments show that numerical model parameters need to be altered in order to calibrate the model. Using tracer experiments as a model calibration tool, it is shown that a non-negligible amount of dispersion is generated by InfoWorks CS and MOUSE and that it is in fact the numerical dispersion that is calibrated.

scholarly journals Estimating the degree of preferential flow to drainage in an agricultural clay till field for a 10-year period

2020 ◽  
Author(s):  
David Nagy ◽  
Annette E. Rosenbom ◽  
Bo V. Iversen ◽  
Mohamed Jabloun ◽  
Finn Plauborg
Keyword(s):  
Conceptual Understanding ◽  
Preferential Flow ◽  
Lower Boundary ◽  
Saturated Zone ◽  
Model Concept ◽  
One Dimensional ◽  
Model Study ◽  
The Matrix ◽  
The One ◽  
Preferential Water

Abstract. The conceptual understanding of the preferential water flow is crucial and hence understanding the degree of water percolating rapidly through vertical macropores, or slowly through the low-permeable matrix, is vital in order to assess the risk of contaminants like nitrate and pesticides being transported through a variably-saturated macroporous clay till to drainage. This study compared six different model concepts, using the dual-permeability module of the one-dimensional model DAISY, incorporating three different macropore settings and two different groundwater tables set as lower boundary conditions. The three macropore settings included vertical macropores supplying water directly to (a) drainage, (b) drainage and matrix and (c) drainage and matrix including fractures supplying water to the matrix in the saturated zone. The model study was based on ten years of coherent climate, drainage, and groundwater data from an agricultural clay till field. The estimated drainage obtained with the six model concepts was compared to the measured drainage. No significant discrepancies between the estimated and measured drainage were identified. The model concept with the macropore setting (b) exposed to groundwater fluctuations measured in the southern part of the field, gave the best description of the drainage. Bromide leaching tests were used to evaluate the mass balance of the model concepts. The estimated water balance of all six concepts revealed that 70 % of the precipitation input to drainage was transported via macropores. According to the results of bromide leaching simulation, 54 % of the drainage was estimated to be transported via vertical macropores being initiated in the plow layer.

scholarly journals Modeling and simulation of in situ bioremediation for TCE-contaminated groundwater through methane injection in Kimitsu city, Japan

2006 ◽  
Vol 6 (2) ◽  
pp. 253-259 ◽  
Author(s):  
S.O. Soda ◽  
M. Kitagawa ◽  
M. Fujita
Keyword(s):  
Competitive Inhibition ◽  
Model Simulation ◽  
Monod Kinetics ◽  
In Situ Bioremediation ◽  
One Dimensional ◽  
Monitoring Wells ◽  
Advection Dispersion ◽  
Degradation Ratio ◽  
Tce Degradation

A one-dimensional model was developed for simulating the in situ bioremediation process in which trichloroethylene (TCE) in groundwater was transformed cometabolically by methanotrophs. The model includes basic processes such as advection, dispersion, and equilibrium sorption of methane, dissolved oxygen, methanotrophs, and TCE. Monod kinetics with a modified competitive inhibition term between methane and TCE, cell inactivation by product toxicity from TCE transformation, and deactivation of the enzyme in the absence of methane were also incorporated into this model. Simulation results were compared with data from a pilot biostimulation test performed at the Kururi site in Japan in 1998. The calibrated model provided good matches to observed changes of the chemical and the most-probable numbers of methanotrophs at the two monitoring wells for the 180 day test. Spatial distribution of the variables and the TCE degradation ratio were also evaluated using the calibrated model.

scholarly journals A Discrete Method Based on the CE-SE Formulation for the Fractional Advection-Dispersion Equation

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Silvia Jerez ◽  
Ivan Dzib
Keyword(s):  
Numerical Simulation ◽  
Analytical Solution ◽  
Fractional Derivative ◽  
Dispersion Equation ◽  
Numerical Algorithm ◽  
Initial Condition ◽  
Discrete Method ◽  
One Dimensional ◽  
Advection Dispersion ◽  
The One

We obtain a numerical algorithm by using the space-time conservation element and solution element (CE-SE) method for the fractional advection-dispersion equation. The fractional derivative is defined by the Riemann-Liouville formula. We prove that the CE-SE approximation is conditionally stable under mild requirements. A numerical simulation is performed for the one-dimensional case by considering a benchmark with a discontinuous initial condition in order to compare the results with the analytical solution.

Exploring the Multidimensional Facets of Authoritarianism: Authoritarian Aggression and Social Dominance Orientation

2008 ◽  
Vol 67 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Stefano Passini
Keyword(s):  
Social Dominance ◽  
Factor Model ◽  
Three Dimensional ◽  
Social Dominance Orientation ◽  
Model Fit ◽  
Regression Analyses ◽  
One Dimensional ◽  
Confirmatory Factor ◽  
The One ◽  
Better Than

The relation between authoritarianism and social dominance orientation was analyzed, with authoritarianism measured using a three-dimensional scale. The implicit multidimensional structure (authoritarian submission, conventionalism, authoritarian aggression) of Altemeyer’s (1981, 1988) conceptualization of authoritarianism is inconsistent with its one-dimensional methodological operationalization. The dimensionality of authoritarianism was investigated using confirmatory factor analysis in a sample of 713 university students. As hypothesized, the three-factor model fit the data significantly better than the one-factor model. Regression analyses revealed that only authoritarian aggression was related to social dominance orientation. That is, only intolerance of deviance was related to high social dominance, whereas submissiveness was not.

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