Occurrences and removal of pharmaceuticals and personal care products (PPCPs) in drinking water and water/sewage treatment plants: A review

Advective flows rapidly transport water, solutes, and particles into and out of permeable sand beds and significantly affects the biogeochemistry of coastal environments. In this paper, we reviewed the drivers of porewater and groundwater advection in permeable shelf sediments in an attempt to bridge gaps among different disciplines studying similar problems. We identified the following driving forces: (1) terrestrial hydraulic gradients, (2) seasonal changes in the aquifer level on land moving the location of the subterranean estuary, (3) wave setup and tidal pumping, (4) water level differences across permeable barriers, (5) flow- and topography-induced pressure gradients, (6) wave pumping; (7) ripple and other bed form migration, (8) fluid shear, (9) density-driven convection, (10) bioirrigation and bioturbation, (11) gas bubble upwelling, and (12) sediment compaction. While these drivers occur over spatial scales ranging from mm to km, and temporal scales ranging from seconds to years, their ultimate biogeochemical implications are very similar (i.e., they are often a source of new or recycled nutrients to seawater and transform organic carbon into inorganic carbon). Drivers 2–12 result in no net water input into the ocean. Taking all these mechanisms into account, we conservatively estimate that a volume equivalent to that of the entire ocean is filtered by permeable sediments at time scales of about 3000 years. Quantifying the relative contribution of these drivers is essential to understand the contribution of sediments to the global cycles of matter.

The driving forces of porewater and groundwater flow in permeable coastal sediments: a review

Variable-density flow and transport in porous media: approaches and challenges

Temporal and spatial variability of groundwater–surface water fluxes: Development and application of an analytical method using temperature time series

[1] Climate change in combination with increased anthropogenic activities will affect coastal groundwater systems throughout the world. In this paper, we focus on a coastal groundwater system that is already threatened by a relatively high seawater level: the low-lying Dutch Delta. Nearly one third of the Netherlands lies below mean sea level, and the land surface is still subsiding up to 1 m per century. This densely populated delta region, where fresh groundwater resources are used intensively for domestic, agricultural, and industrial purposes, can serve as a laboratory case for other low-lying delta areas throughout the world. Our findings on hydrogeological effects can be scaled up since the problems the Dutch face now will very likely be the problems encountered in other delta areas in the future. We calculated the possible impacts of future sea level rise, land subsidence, changes in recharge, autonomous salinization, and the effects of two mitigation countermeasures with a three-dimensional numerical model for variable density groundwater flow and coupled solute transport. We considered the effects on hydraulic heads, seepage fluxes, salt loads to surface waters, and changes in fresh groundwater resources as a function of time and for seven scenarios. Our numerical modeling results show that the impact of sea level rise is limited to areas within 10 km of the coastline and main rivers because the increased head in the groundwater system at the coast can easily be produced though the highly permeable Holocene confining layer. Along the southwest coast of the Netherlands, salt loads will double in some parts of the deep and large polders by the year 2100 A.D. due to sea level rise. More inland, ongoing land subsidence will cause hydraulic heads and phreatic water levels to drop, which may result in damage to dikes, infrastructure, and urban areas. In the deep polders more inland, autonomous upconing of deeper and more saline groundwater will be responsible for increasing salt loads. The future increase of salt loads will cause salinization of surface waters and shallow groundwater and put the total volumes of fresh groundwater volumes for drinking water supply, agricultural purposes, industry, and ecosystems under pressure.

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Effects of climate change on coastal groundwater systems: A modeling study in the Netherlands

1 Introduction.- 1.1 Density-Driven Flow.- 1.2 Modeling.- 1.3 Modeling Density-driven Flow in Porous Media.- 1.4 FAST-C(2D) Modeling Software.- 2 Density and Other Water Properties.- 2.1 Dependence on Temperature.- 2.1.1 Density.- 2.1.2 Thermal Expansion Coefficient.- 2.1.3 Viscosity.- 2.1.4 Specific Heat Capacity.- 2.1.5 Thermal Conductivity.- 2.1.6 Diffusivity.- 2.2 Dependence on Salinity.- 2.2.1 Density.- 2.2.2 Viscosity.- 2.3 Dependence on Pressure.- 2.3.1 Density.- 2.3.2 Compressibility.- 3 Analytical Description.- 3.1 Basic Principles.- 3.2 Oberbeck-Boussinesq Assumption.- 3.3 Hydraulic Head Formulation.- 3.4 Streamfunction Formulation.- 3.5 Vorticity Equation.- 3.6 Extended Oberbeck-Boussinesq Assumption.- 3.7 Dimensionless Formulation.- 3.8 Boundary Layer Formulation.- 3.9 Heat and Mass Transfer.- 4 Numerical Modeling (Fast-C(2D)).- 4.1 Spatial Discretization.- 4.2 Temporal Discretization.- 4.3 Boundary Conditions.- 4.4 Initial Conditions and RESTART.- 4.5 Solution of the Nonlinear System.- 4.5.1 Newton Method and Variations.- 4.5.2 Picard Iterations.- 4.6 Solution of Linear Systems.- 4.6.1 Conjugate Gradients.- 4.7 Postprocessing.- 5 Steady Convection.- 5.1 Benard Experiments in Porous Medium.- 5.2 Linear Analysis.- 5.2.1 Isotropic Porous Medium.- 5.2.2 Anisotropic Porous Medium.- 5.3 Bifurcation Analysis.- 5.4 Numerical Experiments.- 5.4.1 Isotropic Porous Medium.- 5.4.2 Anisotropic Porous Medium.- 6 Special Topics in Convection.- 6.1 Thermal Convection in Slender Boxes.- 6.1.1 Analytical Studies.- 6.1.2 Numerical Experiments.- 6.2 Variable Viscosity Effects on Convection.- 6.2.1 Introduction.- 6.2.2 Onset of Convection.- 6.2.3 Heat Transfer.- 6.3 Convection in Cold Groundwater.- 6.3.1 Streamfunction Formulation.- 6.3.2 Onset of Convection.- 6.3.3 Flow Patterns.- 6.4 Relevance of Convection in Natural Systems.- 7 Oscillatory Convection.- 7.1 Hopf Bifurcation.- 7.2 Simulation.- 7.3 Influence of Numerical Parameters.- 8 Horizontal Heat and Mass Transfer.- 8.1 Analytical Approximations and Solutions.- 8.1.1 Convection.- 8.1.2 Conduction.- 8.2 Numerical Experiments.- 8.2.1 Conduction.- 8.2.2 Convection.- 9 Elder Experiment.- 9.1 Laboratory Experiment.- 9.2 Numerical Experiments.- 9.2.1 Elder's Model.- 9.2.2 FAST-C(2D) Model.- 9.2.3 Further Models.- 9.3 Related Problems.- 10 Geothermal Flow (Yusa's Example).- 10.1 Hypothetical Situation and Analytical Description.- 10.2 Flow Pattern Characterization.- 10.3 Sensitivity Analysis.- 10.4 Other Geothermal Systems.- 11 Saltwater Intrusion (Henry's Example).- 11.1 Problem Description.- 11.2 Sharp Interface Approach.- 11.3 Henry's Example.- 11.4 Modeling Saltwater Intrusion.- 11.4.1 Henry's Example.- 11.4.2 Parameter Variation.- 11.4.3 Layered Aquifers.- 12 Saltwater Upconing.- 12.1 Problem Description.- 12.2 Modeling Saltwater Upconing.- 12.2.1 Sharp Interface Approach.- 12.2.2 Miscible Displacement.- 12.2.3 Variable Density Effects.- 12.3 Case Study.- 13 Flow Across a Salt-Dome.- 13.1 Salt Formations and Scenarios.- 13.2 HYDROCOIN Test-Case.- 13.3 Modeling the HYDROCOIN Test-Case.- 13.4 FAST-C(2D) Model.- 14 Desert Sedimentary Basins.- 14.1 System Description.- 14.2 Numerical Modeling.- Concluding Remark.- References.- Appendix I: Fast-C(2D) Input- and Output-Files.- Input-File for FAST-C(2D).- Output-Files.

Modeling Density-Driven Flow in Porous Media

Undoubtedly watersheds and their limiting groundwater divides are not steady but change. Nevertheless the temporal and spatial scales of the changes are seldom explored and rarely can be quantified. The Lake Stechlin region offers the exceptional chance to study the transient dynamics of catchments, the movement of subsurface water divides and their disappearance and reappearance. Based on long-term data of surface water and groundwater levels a computer model delivers illustrative pictures of the dynamics of natural water bodies. A simple analytically derived criterion for the occurrence of groundwater divides shows remarkable coincidence with observations and with the output from the numerical model. Copyright © 2001 John Wiley & Sons, Ltd.

The dynamics of subsurface water divides - watersheds of Lake Stechlin and neighbouring lakes

The article gives an introduction to numerical modeling of flow and transport problems and to software tools that are currently in use for modeling such phenomena. Details are explained on numerical approximations leading to different numerical models. Extensions for reactive transport are mentioned. Basic guidelines and criteria are given that should be taken into account by the modeler in order to improve the accuracy of results. Inverse modeling is presented as an advanced feature. Some examples of pre- and postprocessing, as implemented in several codes, are given, in addition to fundamental properties of solution methods. Finally, most common codes are listed with basic features and web-sites.


Keywords:

flow;
solute and heat transport;
reactive transport;
finite differences;
finite volumes;
finite elements;
software;
pre- and postprocessing;
numerical solutions;
modeling tasks

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155: Numerical Models of Groundwater Flow and Transport

Numerical experiments on free and forced convection in porous media

We describe first measurement in a novel thin-layer channel flow cell designed for the investigation of heterogeneous electrocatalysis on porous catalysts. For the interpretation of the measurements, a macroscopic model for coupled species transport and reaction, which can be solved numerically, is feasible. In this paper, we focus on the limiting current. We compare numerical solutions of a macroscopic model to a generalization of a Leveque-type asymptotic estimate for circular electrodes, and to measurements obtained in the aforementioned flow cell. We establish that on properly aligned meshes, the numerical method reproduces the asymptotic estimate. Furthermore, we demonstrate that the measurements are partially performed in the sub-asymptotic regime, in which the boundary layer thickness exceeds the cell height. Using the inlet concentration and the diffusion coefficient from literature, we overestimate the limiting current. On the other hand, the use of fitted parameters leads to perfect agreement between model and experiment.

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Ekkehard Holzbecher

Papers

Modeling Density-Driven Flow in Porous Media

The dynamics of subsurface water divides - watersheds of Lake Stechlin and neighbouring lakes

155: Numerical Models of Groundwater Flow and Transport

Numerical experiments on free and forced convection in porous media

Experimental and numerical model study of the limiting current in a channel flow cell with a circular electrode.