scholarly journals Use of column experiments to investigate the fate of organic micropollutants – a review

2016 ◽  
Author(s):  
Stefan Banzhaf ◽  
Klaus H. Hebig
Keyword(s):  
Boundary Conditions ◽  
Field Experiments ◽  
Breakthrough Curves ◽  
Transport Processes ◽  
Column Experiments ◽  
Organic Micropollutants ◽  
Transport Parameters ◽  
Column Studies ◽  
Set Up ◽  
The Individual

Abstract. Although column experiments are frequently used to investigate the transport of organic micropollutants, little guidance is available on what they can be used for, how they should be set up, and how the experiments should be carried out. This review covers the use of column experiments to investigate the fate of organic micropollutants. Alternative setups are discussed together with their respective advantages and limitations. An overview is presented of published column experiments investigating the transport of organic micropollutants, and suggestions are offered on how to improve the comparability of future results from different experiments. The main purpose of column experiments is to investigate the transport and attenuation of a specific compound within a specific sediment or substrate. The transport of (organic) solutes in groundwater is influenced by the chemical and physical properties of the compounds, the solvent (i.e. the groundwater, including all solutes), and the substrate (the aquifer material). By adjusting these boundary conditions a multitude of different processes and related research questions can be investigated using a variety of experimental setups. Apart from the ability to effectively control the individual boundary conditions, the main advantage of column experiments compared to other experimental setups (such as those used in field experiments, or in batch microcosm experiments) is that conservative and reactive solute breakthrough curves can be derived, which represent the sum of the transport processes. There are well-established methods for analyzing these curves. The effects observed in column studies are often a result of dynamic, non-equilibrium processes. Time (or flow velocity) is an important factor, in contrast to batch experiments where all processes are observed until equilibrium is reached in the substrate-solution system. Slight variations in the boundary conditions of different experiments can have a marked influence on the transport and degradation of organic micropollutants. This is of critical importance when comparing general results from different column experiments investigating the transport behavior of a specific organic compound. Such variations unfortunately mean that the results from most column experiments are not transferable to other hydrogeochemical environments but are only valid for the specific experimental setup used. Column experiments are fast, flexible, and easy to manage; their boundary conditions can be controlled and they are cheap compared to extensive field experiments. They can provide good estimates of all relevant transport parameters. However, the obtained results will almost always be limited to the scale of the experiment and not directly transferrable to field scales as too many parameters are exclusive to the column setup. The challenge for the future is to develop standardized column experiments on organic micropollutants in order to overcome these issues.

scholarly journals Use of column experiments to investigate the fate of organic micropollutants – a review

2016 ◽  
Vol 20 (9) ◽  
pp. 3719-3737 ◽  
Author(s):  
Stefan Banzhaf ◽  
Klaus H. Hebig
Keyword(s):  
Boundary Conditions ◽  
Field Experiments ◽  
Breakthrough Curves ◽  
Transport Processes ◽  
Column Experiments ◽  
Organic Micropollutants ◽  
Transport Parameters ◽  
Column Studies ◽  
Set Up ◽  
The Individual

Abstract. Although column experiments are frequently used to investigate the transport of organic micropollutants, little guidance is available on what they can be used for, how they should be set up, and how the experiments should be carried out. This review covers the use of column experiments to investigate the fate of organic micropollutants. Alternative setups are discussed together with their respective advantages and limitations. An overview is presented of published column experiments investigating the transport of organic micropollutants, and suggestions are offered on how to improve the comparability of future results from different experiments. The main purpose of column experiments is to investigate the transport and attenuation of a specific compound within a specific sediment or substrate. The transport of (organic) solutes in groundwater is influenced by the chemical and physical properties of the compounds, the solvent (i.e., the groundwater, including all solutes), and the substrate (the aquifer material). By adjusting these boundary conditions a multitude of different processes and related research questions can be investigated using a variety of experimental setups. Apart from the ability to effectively control the individual boundary conditions, the main advantage of column experiments compared to other experimental setups (such as those used in field experiments, or in batch microcosm experiments) is that conservative and reactive solute breakthrough curves can be derived, which represent the sum of the transport processes. There are well-established methods for analyzing these curves. The effects observed in column studies are often a result of dynamic, non-equilibrium processes. Time (or flow velocity) is an important factor, in contrast to batch experiments where all processes are observed until equilibrium is reached in the substrate-solution system. Slight variations in the boundary conditions of different experiments can have a marked influence on the transport and degradation of organic micropollutants. This is of critical importance when comparing general results from different column experiments investigating the transport behavior of a specific organic compound. Such variations unfortunately mean that the results from most column experiments are not transferable to other hydrogeochemical environments but are only valid for the specific experimental setup used. Column experiments are fast, flexible, and easy to manage; their boundary conditions can be controlled and they are cheap compared to extensive field experiments. They can provide good estimates of all relevant transport parameters. However, the obtained results will almost always be limited to the scale of the experiment and are not directly transferrable to field scales as too many parameters are exclusive to the column setup. The challenge for the future is to develop standardized column experiments on organic micropollutants in order to overcome these issues.

scholarly journals Preselection of a sorption model based on a column test: the algorithm and an example of its application

2021 ◽  
Author(s):  
Marek Marciniak ◽  
Monika Okońska ◽  
Mariusz Kaczmarek
Keyword(s):  
Mathematical Model ◽  
Breakthrough Curve ◽  
Breakthrough Curves ◽  
Transport Processes ◽  
Column Experiments ◽  
Transport Parameters ◽  
Sorption Model ◽  
Advection Dispersion ◽  
Conservative Tracer ◽  
Reactive Tracer

AbstractIn order to describe the contamination of saturated porous media, it is necessary to find an appropriate mathematical model that includes processes occurring in aquifers, such as advection, dispersion, diffusion, and various kinds of sorption. The identification of parameters of those processes is possible through laboratory column experiments, which result in records of breakthrough curves for a conservative tracer and a reactive tracer. An algorithm leading to the preliminary selection of the mathematical model that best describes transport processes of the reactive tracer in the experimental column is proposed in this article. A study published previously presented a sensitivity analysis for an arbitrarily adopted variability of the transport parameters. The analysis involved examining changes in the shape of breakthrough curves caused by the alteration of each parameter value. Specially defined indicators called descriptors were proposed to quantitatively describe the breakthrough curves. Then, formulas were proposed to determine the percentage deviations of descriptors of the breakthrough curve obtained for the reactive tracer in relation to the descriptors of the breakthrough curve of the conservative tracer. In the work described in this article, the deviations are analyzed and an algorithm is proposed that allows the preselection of the most suitable sorption model out of the five discussed simple (one-site) and six hybrid (two-site) models. The algorithm can facilitate and accelerate the interpretation of column experiments of contaminant transport in a porous medium. An example is provided to illustrate the usability of the proposed algorithm.

scholarly journals Breakthrough Investigation of Advective and Diffusive Transport in a Porous Matrix with a Crack

Fluids ◽  
2021 ◽  
Vol 6 (10) ◽  
pp. 358
Author(s):  
Ekkehard Holzbecher
Keyword(s):  
Flow Direction ◽  
Porous Matrix ◽  
Systematic Investigation ◽  
Breakthrough Curves ◽  
Transport Processes ◽  
Free Fluid ◽  
Transport Parameters ◽  
Transport Patterns ◽  
Set Up ◽  
Application Fields

Fluid flow and transport processes in fractured porous media are of particular interest for geologists and in the material sciences. Here a systematic investigation is presented, dealing with a generic geometric set-up of a porous matrix with a crack. In such a combined porous medium/free fluid system flow patterns have been examined frequently, while the resulting transport patterns have attracted less attention. Using numerical modeling with finite elements the problem is approached using a dimensionless formulation. With a reduced number of dimensionless parameter combinations (Darcy-, Peclet- and Reynolds-numbers) solution dependencies are examined in parametric sweeps. Breakthrough curves are fitted in comparison to those of 1D model approaches, yielding effective diffusivities and velocities. The computations reveal highest sensitivity concerning the angle between crack axis and flow direction, followed by the Peclet number and the crack axes ratio. As a dimensionless representation is used the results are scale independent. Thus, they deliver estimations concerning effective heat and solute transport parameters that can be relevant in all application fields.

scholarly journals Column Experiments on Sorption Coefficients and Biodegradation Rates of Selected Pharmaceuticals in Three Aquifer Sediments

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 14 ◽  
Author(s):  
Aleksandra Kiecak ◽  
Friederike Breuer ◽  
Christine Stumpp
Keyword(s):  
Environmental Concern ◽  
Sandy Loam ◽  
Breakthrough Curves ◽  
Coarse Sand ◽  
Transport Processes ◽  
Column Experiments ◽  
Transport Parameters ◽  
Degradation Rates ◽  
The Impact ◽  
Flow Velocities

The presence of pharmaceuticals in the environment, and in groundwater, has been recognized as a great environmental concern. Biodegradation and sorption are the main processes leading to the removal of contamination from the water phase. The aim of this study was to determine the transport processes of selected pharmaceuticals (antipyrine, atenolol, carbamazepine, caffeine, diclofenac, ketoprofen, sulfamethoxazole) in selected sediments (coarse sand, medium sand, sandy loam) in laboratory experiments. Moreover, the impact of flow velocities on the sorption and degradation rates of the selected compounds was studied. Column experiments were performed at three flow velocities, under abiotic and biotic conditions, applying conservative (bromide) and reactive tracers (pharmaceuticals). From the breakthrough curves, retardation factors and degradation rates were determined and the influence of variable flow conditions on transport parameters was evaluated. Low observed concentrations and recoveries of atenolol indicated a strong influence of sorption on its transport. Diclofenac, caffeine, and carbamazepine were also affected by sorption but to a lesser extent. Sulfamethoxazole, ketoprofen, and antipyrine were recovered nearly completely, indicating an almost conservative transport behavior. Biodegradation was small for all the compounds, as the results from biotic and abiotic column experiments were similar. Transport of the tested pharmaceuticals was not influenced by different flow velocities, as similar modelled degradation rates and retardation factors were found for all tested flow velocities.

scholarly journals Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2530 ◽  
Author(s):  
Sascha Frank ◽  
Thomas Heinze ◽  
Stefan Wohnlich
Keyword(s):  
Surface Roughness ◽  
Tracer Tests ◽  
Breakthrough Curves ◽  
Transport Processes ◽  
Natural Fracture ◽  
Transport Parameters ◽  
Fracture Surfaces ◽  
Advection Dispersion ◽  
Hydraulic Aperture ◽  
Surface Morphologies

In single fractures, dispersion is often linked to the roughness of the fracture surfaces and the resulting local aperture distribution. To experimentally investigate the effects of diverse fracture types and surface morphologies in sandstones, three fractures were considered: those generated by sawing and splitting, and a natural sedimentary fracture. The fracture surface morphologies were digitally analyzed and the hydraulic and transport parameters of the fractures were determined from Darcy and the tracer tests using a fit of a continuous time random walk (CTRW) and a classical advection–dispersion equation (ADE). While the sawed specimen with the smoothest surface had the smallest dispersivity, the natural fracture has the largest dispersivity due to strong anisotropy and non-matching fracture surfaces, although its surface roughness is comparable to the split specimen. The parameterization of the CTRW and of the ADE agree well for β > 4 of the truncated power law. For smaller values of β, non-Fickian transport processes are dominant. Channeling effects are observable in the tracer breakthrough curves. The transport behavior in the fractures is controlled by multiple constraints such as several surface roughness parameters and the equivalent hydraulic aperture.

scholarly journals Identification of transport parameters of chlorides in different soils on the basis of column studies

Geologos ◽  
2019 ◽  
Vol 25 (3) ◽  
pp. 225-229
Author(s):  
Damian Pietrzak ◽  
Jarosław Kania ◽  
Ewa Kmiecik ◽  
Katarzyna Wątor
Keyword(s):  
Pore Water ◽  
Dispersion Coefficient ◽  
Fine Sand ◽  
Water Velocity ◽  
Silty Sand ◽  
Column Experiments ◽  
Transport Parameters ◽  
Column Studies ◽  
Pore Water Velocity ◽  
Different Soils

Abstract Knowledge of transport patterns of chemicals in groundwater is essential for environmental assessment of their potential impact. In the present study, the mobility of a chloride tracer injected into three different soils was investigated, using column experiments. The column tests were performed under steady-state conditions to determine parameters of chloride migration through soils. Based on breakthrough curves, pore-water velocity, dispersion coefficient and dispersivity constant were calculated for each soil sample using CXTFIT/STANMOD software. Pore-water velocity was in the range of 0.31 cm/min for fine sand, to 0.35 cm/min for silty sand and to 0.40 cm/min for vari-grained sand. The highest values of dispersion coefficient and dispersivity constant were observed for silty sand (0.55 cm2/min and 1.55 cm, respectively), while the lowest value was found for fine sand (0.059 cm2/min and 0.19 cm, respectively). Column experiments for chlorides (conservative tracer) are a preliminary stage for further research which will be undertaken to investigate migration parameters of selected neonicotinoids (reactive tracers) through different soils.

scholarly journals Evaluation of Zeolite as a Potential Reactive Medium in a Permeable Reactive Barrier (PRB): Batch and Column Studies

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 59
Author(s):  
Liana Carolina Carvalho Rocha ◽  
Lazaro Valentin Zuquette
Keyword(s):  
Permeable Reactive Barrier ◽  
Column Experiments ◽  
Single Element ◽  
Order Kinetic ◽  
Transport Parameters ◽  
Column Studies ◽  
Reactive Medium ◽  
Reactive Material ◽  
Reactive Barrier ◽  
Batch Tests

The purpose of this work is to evaluate the capacity of a natural zeolite to be used as a reactive material in a permeable reactive barrier (PRB) to remove inorganic contaminants from groundwater. To this aim, zeolite samples were subjected to characterization tests, column experiments, batch tests and a flushing process to evaluate the adsorption and desorption capacities of the zeolite. In the column experiments, the samples were subjected to eight successive cycles involving the percolation of a potassium aqueous solution (1500 mg/L) and a subsequent flushing process with water. Batch tests were conducted by mixing 20 g of zeolite with 100 mL of single-element aqueous solutions of K and Zn with concentrations of 200 mg/L. The results indicate that the zeolite rock is composed predominantly of clinoptilolite species and has a Si/Al ratio of 6.8, a high cationic exchange capacity (CEC) of 180 cmolc/kg and a high K+ adsorption rate with a removal efficiency of 78%. The adsorption isotherms of the zeolite follow the Langmuir model and are well fit by a pseudo-second-order kinetic model showing a high correlation coefficient (r2 > 0.999) for both K+ and Zn2+ cations. Additionally, the contaminant transport parameters for K+ ions (Rd = 24.9; Dh = 1.32 × 10–2 cm2/s and α = 1.42) reveal that the zeolite is resistant to the dispersion of ions in the barrier, indicating that the material has advantageous characteristics for use in a PRB. However, the flushing process of the material is not efficient, indicating that the appropriate use of the zeolite is in clean-up systems in which the adsorbent material can be exchanged after losing its efficiency as a reactive barrier.

Waste Fungal Biomass for Mercury Biosorption – Column Studies

2007 ◽  
Vol 20-21 ◽  
pp. 623-626
Author(s):  
Lenka Svecova ◽  
Martin Kubal ◽  
Eric Guibal
Keyword(s):  
Fungal Biomass ◽  
Fixed Bed ◽  
Breakthrough Curves ◽  
Inert Material ◽  
Column Experiments ◽  
Batch Experiments ◽  
Column Studies ◽  
Fixed Bed Column ◽  
Bed Height

Granulated Tolypocladium biomass (industrial waste) was tested as mercury biosorbent in continuous mode (fixed bed column). Supplied material contained approx. 70% of fungal biomass and 30% of inert material (diatomaceous earth). Prior to column experiments, batch sorption was also performed. The results of batch experiments were compared to our previous results obtained for powdered biomass (100% biomass material) and an important drop of sorption capacity was observed. For column experiments, the bed height and flow rate were kept constant and the influence of both initial mercury concentration and bead size was investigated. The Adams Bohart, the Thomas and the Yoon and Nelson models were used for the characterization of breakthrough curves.

scholarly journals Transect Scale Solute Transport Measured by Time Domain Reflectometry

2002 ◽  
Vol 33 (2-3) ◽  
pp. 145-164 ◽  
Author(s):  
Magnus Persson ◽  
Ronny Berndtsson
Keyword(s):  
Solute Transport ◽  
Mass Balance ◽  
Water Content ◽  
Time Domain ◽  
Field Experiments ◽  
Breakthrough Curves ◽  
Time Domain Reflectometry ◽  
Transport Parameters ◽  
Entire Experiment

Two quasi steady-state solute transport experiments were carried out in a loamy sand under field conditions. The flux was 40 mm/d in experiment 1 and 18.7 mm/d in experiment 2. Both water content (θ) and resident concentration (Cr) measurements were taken using 64 time domain reflectometry probes at depths ranging from 0.05 to 0.90 m. The Cr measurement was calibrated in situ for each probe location in the field. The convective dispersive equation (CDE) and convective lognormal transfer function (CLT) models were fitted to the breakthrough curves (BTCs). The results indicated fingered flow, which has been shown to exist in previous studies of this soil. The finger width was larger in experiment 1 leading to smaller horizontal heterogeneity and a relatively smaller solute transport velocity. The location of the fingers was consistent between the two experiments resulting in a high correlation between the velocity and mass balance fields. Mass balance calculations showed that the solute mass integrated over depth one day after the solute application was larger than the mass balance for the entire experiment (integrated over time). The probable reason being that solutes were transported out of the measurement volume by horizontal flow across the Ap/E horizon boundary. The investigation of the transport parameters revealed that both the CDE and CLT models could be successfully used to predict most individual BTCs. Horizontally averaged global CDE and CLT models were also fitted to the data. Global solute transport was better modeled with the CDE model in experiment 1, while in experiment 2, the CLT model was better. This study clearly shows the applicability of using TDR with the in situ calibration technique in field experiments with varying water content.

The effect of planting combinations and weeding on the growth and yield of component crops of maize/bean and maize/pumpkin intercrops

2002 ◽  
Vol 138 (2) ◽  
pp. 193-200 ◽  
Author(s):  
T. TEMBAKAZI SILWANA ◽  
E. O. LUCAS
Keyword(s):  
South Africa ◽  
Field Experiments ◽  
Farming System ◽  
Growth And Yield ◽  
Land Equivalent Ratio ◽  
Equivalent Ratio ◽  
Baseline Information ◽  
Set Up ◽  
The Individual

A diagnostic survey carried out in 1997 to obtain baseline information on the farming situation in Transkei area of South Africa, showed that agriculture in this area was characterized by low technological inputs which invariably led to low agricultural outputs. The main farming system of the majority of the farmers (98%) was based on intercropping involving maize, beans and pumpkin combined in an haphazard fashion.Based on the above findings, two field experiments were set up in 1998 designed to bring out the best planting combinations for maize/beans and maize/pumpkin intercrops which could be introduced to the farmers. Effect of weeding on the intercrops was also investigated.In both intercrops, intercropping adversely affected the plant heights and circumferences of the component crops. Also, the yield of the individual crop in each intercrop was depressed by intercropping compared with its sole yield. In maize/beans intercrop, the yield of maize was depressed by 15% and that of beans by 13%. However in both intercrops, productivity as measured by Land Equivalent Ratio (LER) was the highest with maize at 10000 plants/ha combined with beans at 150000 plants/ha (2·60) with weeding while the combination with the best LER (1·50) in maize/pumpkin intercrop was at 30000 plants/ha of maize combined with pumpkin at 2500 plants/ha, with weeding. However, before any final recommendation is made, the profitability of each combination has to be considered.Weeding was found to enhance intercrop yields in maize/bean combination by 35% and by 30% in maize/pumpkin combination.

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