Modeling of Pollutant Migration and its Immobilization in Porous Reactive Barrier

Anna Adach, Faculty of Chemical and Process Engineering, Warsaw University of Technology, Poland, Waryńskiego 1, 00-645 Warsaw, Poland, Tel.: 048-22-660-64-94, Fax: 048-22-825-14-40, Email: adach@ichip.pw.edu.pl
Stanisław Wroński, Faculty of Chemical and Process Engineering, Warsaw University of Technology, Poland, Waryńskiego 1, 00-645 Warsaw, Poland, Tel: 048-22-660-62-95, Fax: 048-22-825-14-40, Email: adach@ichip.pw.edu.pl
Marian Jacek Łączny, Central Mining Institute, Plac Gwarków 1, 40–166 Katowice, Poland, Tel: 048-32-259 2242 Fax: +48 32 259-27-74, Email: sei@gig.katowice.pl
Sebastian Iwaszenko, Central Mining Institute, Plac Gwarków 1, 40–166 Katowice, Poland, Tel: 048-32-259 2225, Fax: +48 32 259-27-74, Email: sei@gig.katowice.pl

The wastewater effluents may origin from different point sources, e.g. propagation of toxins from radioactive point disposals, solid wastes sites etc and they negative impact to the environment can exist for a very long time.

The implementation of reactive barriers is a well-known in situ remediation technique [1]. The reactive barriers are permeable zones (single-layer or of a composite structure), characterized by the appropriate physico-chemical and hydrological properties and when located on the groundwater “route” can effectively immobilize the toxins.  Modeling of pollutant migration and its immobilisation within the barrier (verified by the experiments) would give the obvious advantages: the overview on the undergoing processes, the decisive mass transfer resistances and could be a good tool for the evaluating barrier effectiveness, design as well as its utilization time.

The mathematical general model of the substance migration in the porous media, formed in the earlier works [2]-[3] has been modified according to the problem of pollutants propagation and immobilization in the barrier. In the proposed model it seems reasonable to divide the whole barrier (and the ground) into 2 horizontal layers: the “upper layer”, extending from the ground level to that of the groundwater with the partial saturation, infiltrated by the rainfall water (liquid flow only in the vertical direction), and the “lower layer”, extending from the groundwater level to the surface of the impermeable layer, where the groundwater flow takes place (that zone is fully saturated).

Following the presented suggestions, in the system where the groundwater flow takes place under hydraulic gradient, assuming the appropriate boundary conditions, the model equations were formulated, taking into account both convective and diffusive mechanism of mass transfer as well as possible processes of substance immobilization: sorption on the grains of the barrier and chemical reaction of pollutant decay.

The aim of the present model is to simulate the hydrological and mass transfer processes that take place within the reactive barrier under the conditions of the contaminated groundwater flow.  

Literature

Czurda K.A., Haus R., Reactive barriers with fly ash zeolithes for in situ groundwater remediation, Appl. Clay Science (Elsev.), 2002, 21, 13-20
Adach A., Bożek U., Vladimirov V., Wroński S., Pierienos massy w poristich sriedach, prabliema niertawnomiernosti raspriedielienija massowych istocznikow sorpcji, cz.1, Wisnik Kijowskowo Uniw., seria Fiziko-Matiematiczieskije Nauki, 2004, 363-373 (in russian).
Adach A., Modelling of contaminant’s migration in the granular layer and their removal using sorptive materials, PhD Thesis, 2003.

Delineation of Three-Dimensional Zones of Contribution for Production Wells 

Mary O’Reilly, CH2M HILL, 318 East Inner Road, Otis ANG Base, MA, 02542, Tel: 508-968-4670 ext 5629, Fax: 508-968-4490, Email: moreilly@ch2m.com
Scott DeHainaut, CH2M HILL, 318 East Inner Road, Otis ANG Base, MA, 02542, Tel: 508-968-4670 ext 5667, Fax: 508-968-4490, Email: sdehainaut@ch2m.com
Rose Forbes, Air Force Center for Environmental Excellence, 318 East Inner Road, Otis ANG Base, MA, 02542, Tel: 508-968-4670 ext 5613, Fax: 508-968-4490, Email: rose.forbes@brooks.af.mil

Understanding the spatial relationship between groundwater contamination and the capture zone of a production well often requires a three-dimensional perspective of the hydraulic conditions that affect both subsurface contaminant transport and the flow of groundwater to a production well.  During an investigation of a chlorinated solvent plume at the Massachusetts Military Reservation (MMR), contamination was detected near the two-dimensional wellhead protection area for a production well.  To understand better the spatial relationship between the contaminant plume and the capture zone of the production well, groundwater modeling was used to: (1) delineate the zone of contribution for the well in three dimensions, and (2) determine if the migration of the plume is either affected by pumping or if it would affect the water quality at the production well in the future.  Because of the seasonal variation in groundwater use on Cape Cod, both the long-term average pumping rate and the maximum permitted pumping rate of the production well were evaluated.  Model output was combined with GIS data to produce three-dimensional representations of the hydraulic capture zone, the contaminant plume, and the surrounding region.  Interactive models, animations, and figures produced from these results were highly effective in conveying the relationship between the contaminant plume and the portion of the aquifer affected by the pumping of the production well to regulatory agencies and the public.

Extending the Utility of the Three-Dimensional Sediment Model

Dennis P. Callaghan, Environmental Standards, Inc.  1140 Valley Forge Road, P.O. Box 810, Valley Forge, PA 19482-0810, Tel: 610-935-5577, Fax: 610-935-5583, Email: dcallaghan@envstd.com
Joseph P. Kraycik, P.G., Environmental Standards, Inc.  1140 Valley Forge Road, P.O. Box 810, Valley Forge, PA 19482-0810, Tel: 610-935-5577, Fax: 610-935-5583, Email: jkraycik@envstd.com
Kevin W. Frysinger, P.G., Environmental Standards, Inc.  1140 Valley Forge Road, P.O. Box 810, Valley Forge, PA 19482-0810, Tel: 610-935-5577, Fax: 610-935-5583, Email: kfrysinger@envstd.com

A three-dimensional contaminant distribution model has been developed for a contaminated river sediment site located in the Northeast to aid in the assessment and evaluation of collected analytical data.  The model was developed using the Mining Visualization System (MVS) software package.  The model and associated output was composed of individual grid cells modeled on a 10 ft by 10 ft horizontal grid dimension and a 2 ft vertical dimension.  The resulting model consisted of approximately one million cells. 

Modeling results for the constituents of concern were graphically displayed as three-dimensional sampling locations, three-dimensional sediment volumes, and three-dimensional Kriged geological surfaces.  Modeling algorithms included use of the Kriging geostatistical interpolation method based on a weighted moving average for chemical distribution prediction.  Sediment constituents modeled included organic compounds and metals.

Predicted contaminant volume and mass calculations from each cell were used to develop sediment volume and contaminant mass removal estimates for various remedial action scenarios.  The modeling technique allowed for minimum, nominal, and maximum sediment volume and mass removal estimates to be undertaken within a very fine grid.  A unique and innovative approach was taken in analyzing sediment volumes, contaminant mass, and locations based on this detailed three-dimensional data. 

The innovative approach taken to model the contaminated sediments at the site in an unusually precise manner and the impact this precision had on the project team decision making process during development and presentation of remedial scenarios to regulators will be discussed.  In addition, the influence various sampling, modeling, and analysis systems had when developing the model will also be examined. 

Thermodynamic Simulation of Trace Metals Behavior in River Water Subjected to the Pollution

Olecya Sokolova, Geochemistry division, Geological Department, Moscow State University, Moscow, 119992, GSP-2, Russia. Tel: (8-10-007)(495)135-07-16, Email: olecyarab@mail.ru

A thermodynamic model has been presented to predict trace metal behavior in aquatic ecosystems subjected to the pollution. The streams of National park “Elk Island”, which are located in the northeast of Moscow, were the object of our research. Previous observations pointed out that National park has been exposed to both industrial and transport pollution (from nearby highway) long since. It has been shown that transport pollution caused increased concentration of Zn and Pb in water and bottom sediments and high contents of Na and Cl in water. The latter depends on the application of NaCl as de-icing salt on the highway. NaCl as reagent has been replaced by CaCl₂ in Moscow since 2002. The ecological effect of such replacement has not known yet. Thermodynamic simulation has been carried out to forecast influence of NaCl and CaCl₂ pollution on trace metals behavior in the system ”water-bottom sediment”.

Proposed model based on the thermodynamic calculation of equilibrium distribution of trace metals between water and sediments which contain 3 sorbents: clay minerals, organic matter and Fe oxyhydroxides. Bulk system composition was given by data obtained from field surveys of National park. Calculations were performed using the computer package HCh (Shvarov, Bastrakov, 1999).

Thermodynamic speciation calculation for dissolved metals has shown that the most abundant species of Zn and Ni are the free metal ions Zn²⁺ (66%) and Ni²⁺ (75%), whereas those of Pb is carbonate complex PbCO₃ (79%). An important fraction of the dissolved Cu is complex with fulvic acids (81%). Thermodynamic simulation has suggested that CaCl₂ have an adverse effect not only on river water composition, but also on speciation of metals. There is a probability of desorption of Zn and Pb which equilibrium concentrations in interstitial water could increase in 6 and 2 times consequently.

This research was supported by the Russian Foundation for Basic Research (RFBR grant 05-05-64976)

Top