Assessing the Hydraulic Performance of a Bioremediation Curtain for Plume G at the Schoolcraft Site, MI Using an Integrated Hierarchical Groundwater Model
Soheil Afshari, Shu-Guang Li, Qun Liu, Phanikumar Mantha, and Michael Dybas
 Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI 48824
http://www.egr.msu.edu/igw/

 

1-OBJECTIVES

This paper describes a 3D multiscale flow and transport modeling effort for a contaminated aquifer at the Schoolcraft site in western Michigan. The ultimate goal is to design a broadly applicable ‘‘biocurtain’’ which be applied to remediate this site using a recirculation well gallery installed normal to groundwater flow.

2-SCALE INTERACTIONS

Characterization of flow and transport phenomena during the delivery and treatment process is crucial for designing the biocurtain. But this process is significantly complicated by the potential complex interaction of the flow dynamics across a number of relevant spatial scales present at the site –the “delivery unit-scale” O(10m), the “biocurtain scale” –O(100m), the “site scale” –O(1000m), and the “regional scale” –O(10,000m). 

  • At the unit scale, the closely-spaced injection and extraction wells create complex and rapidly varying head variation and a grid resolution on the order of 10 centimeter is required to resolve the local spatial dynamics. For the accurate modeling of transport and delivery process an even smaller grid size may be required to drive the numerical dispersion to an acceptable level. Creating such high resolution, 3D unsteady model is only feasible for a relatively small area (e.g., on a unit scale). 
  • On the other hand the presence of heterogeneity can potentially induce significant unit-to-unit interaction and evaluation of this interaction requires modeling simultaneously multiple delivery units of the entire biocurtain on a fine grid. 
  • Additionally, potential impact from seasonal irrigation further complicates the site characterization since it may equire expanding substantially the modeling domain from the site-scale to on the order 10,000 meter.

 

3-HIERARCHICAL PATCH DYNAMICS PARADIGM (HPDP)

In this paper, we apply the hierarchical patch dynamic paradigm (HPDP) (Li et al., in press) to model efficiently the complex interplay of the flow dynamics across multiple scales in the vicinity of the Schoolcraft site.
 

The HPDP takes advantage of hierarchy theory, divides and conquers complexities, and decouples scale-dependent dynamics hierarchically. The object-oriented HPDP represents a generalization of the “telescopic-mesh-refinement” (TMR) techniques, providing dynamic model coupling, visual interactive steering, and freeing the modelers from the impractical task of having to interact offline and iteratively with potentially large numbers of modeling patches. The HPDP provides a valuable tool for understanding scale-dependent processes and for practical groundwater investigations.

The resulting integrated hierarchical modeling system is used to characterize, evaluate, and optimize the performance of the biocurtain and the three dimensional delivery system with and without the presence of large-scale heterogeneity and seasonal irrigation.

4-SITE CHARACTERIZATION AND TRACER TEST

5-UNIT SCALE MODEL

  • Site characterization
  • Tracer data calibration

 

 

Input parameters for unit scale model

Predicted concentration distribution at the end of 4 hours tracer test. The plume is calibrated to the tracer data.

Calibration process animation (AVI movie) for the 4 hour tracer test (3.1 MB)

6-BIOCURTAIN SCALE MODEL

  • Assess the unit-to-unit interaction
  • Assess the impact of heterogeneity on design parameters

         

    Conceptual sketch for the biocurtain scale model

                         

 

                         

                              Predicted head and tracer concentration distribution at the end of the delive

  

The “squeeze effect” or interaction between the delivery units increases the concentration breakthrough

Delivery process animation (AVI movie) for biocurtain scale model for duration of 24 hours (4.77 MB)

 

                    

   

                    Concentration breakthrough a) at the extraction well and b) between the units. 

Note the concentration between the units is  much more uncertain and is influenced more by the presence of  heterogeneity

                   Delivery process animation (AVI movie) for biocurtain scale model for duration of 24 hours in the presence of heterogeneity (2.6 MB)

 

Concentration distribution along the biocurtain [see profile D-D in the conceptual sketch]

              

Notice that the concentration coverage along the biocurtain drops below the desire standard coverage [i.e, 40ppm],

 the gap occurs between the extraction injection sets [point W conceptual sketch]

 

Biocurtain distribution during “treatment” at different times (after shutting off the delivery wells)

               

Notice that after shutting down the recirculation system the gap between the delivery units gets smaller and the biocurtain becomes more uniform. 

7- REGIONAL HIERARCHICAL MODELING

Assess the impact of seasonal irrigation on the local delivery and biocurtain dynamics

    

The HPDP allows us to model regional scale flow dynamics and simultaneously assess the performance of delivery at the biocurtain scale.

  

8- CONCLUSIONS

We developed a hierarchical model that can be used to evaluate and optimize the bioremediation curtain at the plume G site, Schoolcraft, MI. 

  • The unit scale model is calibrated to the tracer data, and the agreement between the model and the observations at both extraction and injection wells are excellent. 

  • The biocurtain scale model shows that the interaction between the units enhance the performance of the delivery system. The biocurtain scale model also shows that the presence of larger scale heterogeneity has little impact on the tracer breakthrough at the extraction wells but can potentially create gaps between the delivery units. 

  • The regional hierarchical model shows that the impact of irrigation on delivery process is much more significant during the treatment time than during the delivery/recirculation period.

 

9- ACKNOWLEDGEMENTS

  • Michigan Department of Environmental Quality (MDEQ) 

  • National Science Foundation (NSF)

 

Download the Entire 2005 AGU Fall Meeting Poster (1.78 MB)

 

References:

Soheil, Afshari (2006). "Application of a Hierarchical Patch Dynamics Paradigm (HPDP) for Modeling Complex Groundwater Systems Across Multiple Spatial and Temporal Scales" Ph.D. Desertion, Michigan State University, East Lansing, MI.

Graulau, Santiago J. (2003). " Development and application of a methodology to evaluate natural attenuation of chlorainated solvents using conceptual and numerical models" Ph.D. Desertion, Michigan State University, East Lansing, MI.

Li, S.G. and Q. Liu, "A real-time, computational steering environment for integrated groundwater modeling". Recommended for publication, under revision, Ground Water.

Li, S.G., Q. Liu, and S. Afshari, "An Object-Oriented Hierarchical Patch Dynamics Paradigm (HPDP) for Groundwater Modeling". Accepted for publication, under revision, Environmental Modeling and Software.