Lasagna® process

An innovative technology called the "lasagna" process is based on the electrokinetic phenomenon called electro osmosis. The lasagna process was created to treat difficult wastes in low permeabiUty, sdt- and clay-laden soils (40). The lasagna process is so named because it consists of a number of layered subsurface electrodes and treatment zones. These layers can be constmcted either horizontally where contaminants are forced to more upward or in vertical position where lateral contaminant movement is desired. 

U.S. Environmental Protection Agency, "EPA and Industry Sign CRADA to Develop Iimovative Lasagna Process," in Bioremediation in the Field, Center for Environmental Research Information, Cincinnati, Ohio, 1994. 

The technology has proven effective in bench-scale tests for the treatment of trichloroethylene (TCE), dichloroethane (DCA), and p-nitrophenol (PNP) and can potentially treat a variety of organic, inorganic, and mixed wastes. Bench-scale and pilot-scale field tests have been conducted, and further testing of the Lasagna process is in progress. 

Figure 12.14 illustrates a vertical flow arrangement, but other configurations are also possible. The process as illustrated in Figure 12.14 is being developed by Monsanto Company and is known as the lasagna process because of the layered structure of the treatment zones (Ho et al. 1993). 

FIG. 12.14 The use of electroosmosis in environmental remediation (known as the lasagna process). (Redrawn with permission of Ho et al. 1993.)... 

Ho, S. V., Sheridan, P. W., Athmer, C. J., Brodsky, P. H., Heitkamp, M. A., and Brackin, J. M., Integrated In Situ Remediation Technology - The Lasagna Process, paper presented at the American Chemical Society meeting, Atlanta, GA, September 1993 (Paper 279, Session 43). 

Ho, S. V., Athmer, P.W., Sheridan, P. W. and Shapiro, A. (1997) Scale-up Aspects of the Lasagna Process for in-situ Soil Remediation, Journal of Hazardous Materials, Special Edition on Electrochemical Decontamination of Soil and Water, Edited by Yalcin B. Acar and Akram N. Alshawabkeh, pp. 39-60. 

A well-documented field application of electrochemical remediation is reported to address the problem of chlorinated solvent (TCE) in clay soil at the DOE site in Paducah, Kentucky. This process is known as Lasagna (Terran Corporation, Beavercreek, OH) and it combines the electro-osmotic transport of TCE in pore water and degrades it in vertical curtains installed along the flow path within the soil that are filled with iron filings and kaolin clay. Pore water accumulated at the cathode is recycled by gravity back to the anode as makeup water and neutralize the acid formed at the anode. Overall, the treatment is found to be effective. The implementation and performance results are presented in detail in Chapter 30. The same Lasagna process is implemented very recently at another site contaminated with TCE in Fonde du Lac, Wisconsin, and performance is being monitored (Chapter 30). 

Ho SV, Sheridan PW, Athmer CJ, Heitkamp MA, Brackin JM, Weber D, Brodsky PH. (1995). Integrated in situ soil remediation technology The Lasagna process. Environmental Science Technology 29 2528-2534. 

Note Electroosmotic flow is reversed upon switching electrical polarity. Figure 30.1. Typical configuration of the Lasagna process. 

When a DC potential is applied to a medium containing water and ions, such as soil, acid is generated at the anode and base at the cathode due to the electrolysis of water. The highly acidic environment near the anode could be detrimental to the electroosmosis process if the zeta potential in the soil falls too low or reverses. Two clever approaches are utilized in the Lasagna process to both minimize the acid effect on soil and keep the anode pH between 5 and 7. First, steel plates are used as the anode material to promote iron oxidation as the main anodic reaction instead of water oxidation, which forms acid (H+). Second, the basic pore water accumulated at the cathode (pH > 12) is recycled by gravity back to the anode as makeup water, which is required for continuing the operation of electroosmosis and at the... 

Overall, the Lasagna process has proven to be a very safe method to treat high concentrations of chlorinated solvent. No contaminated material is removed from the site. All materials are emplaced directly into the contaminated soil by the mandrel system, minimizing exposures to the workers. The contamination is degraded below grade and very httle, if any, vapor reaches the site worker or nearby residents during construction and operation. 

To date, the Lasagna process has been successfully implemented at two large sites the DOE Gaseous Diffusion Plant site in Paducah, Kentucky, and the former Quicfrez site in Fond du Lac, Wisconsin. The contaminant treated at both sites is TCE. 

Currently, the Lasagna process is a commercially viable soil remediation process that has been proven especially effective in treating chlorinated solvent contamination in low-permeabiUty soils. The use of DC electrical current to heat the soil and to mobilize pore water and contaminants directionally into degradative treatment zones makes in situ remediation possible. The process is a truly treatment in-place method since no contamination is brought aboveground. Transport and destruction take place within the soil mass. 

The cost of the Lasagna process continues to drop with increasing field experience and technology adaptation. Current installation methods and equipment allow the costs to approach 100 per ton. The materials required, iron filings, kaolin clay, and steel plates, are as natural and innocuous as they can be. The cost of materials and rectifiers is determined primarily by steel prices. Electricity costs are only about 10% of the total and may be further managed by negotiation with the electric company. 

Ho SV, Athmer CJ, Sheridan PW, Shapiro AP. (1997). Scale-up aspects of the Lasagna process for in situ soil decontamination. Journal of Hazardous Materials 55 39-60. 

Field scale studies and projects were carried out by a consortium of industrial partners (Monsanto, DuPont, and General Electric), the USEPA and the DOE [1]. The electrokinetic process designed and operated for the removal of TCE at Paducah (KY, USA) was called the Lasagna process. It utilizes a DC electric field to move pore water and contaminants uniformly through the soil mass to treatment zones emplaced within the contaminated area. The treatment materials emplaced are typically irtMi, coke, and kaolin. The process results in little or no wastes. The system was operated over a 2-year period when the cleanup target ctmcentration of TCE (5.6 mg/kg) was met. The final results show an average TCE concentration of 0.38 mg/kg. 

Figure 1. Horizontal and Vertical Configurations of the Lasagna Process, Reproduced with permission from reference 24. Copyright 1997 Elsevier...

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