HAZWASTES: "Lasagna" Process Strives To Improve Soil Remediation

Jeff Lenard

If a consortium of companies have their way, the word "lasagna" may soon be used to refer to something other than a cheesy Italian dish.

Monsanto, Du Pont and General Electric, in collaboration with the Environmental Protection Agency and the Department of Energy (DOE), have combined their expertise and resources to develop the latest technology in soil remediation - the lasagna process.

Developed for large-scale applications, the three-month field test will determine if the process can effectively remove trichloroethylene (TCE) and other contaminants from soil at the DOE's gaseous diffusion plant in Paducah, Ky.

Called "lasagna" because of the layered appearance of electrodes and treatment zones, the process will be used to treat contaminated heterogeneous soil compositions which require in-situ soil remediation efforts.

The promise of the lasagna process lies in its accessibility in low-permeability soils, which are generally found at DOE sites on the eastern coast of the United States. Soil contaminants such as clay, silts and fine sands pose a significant technical challenge to in-situ remediation efforts. Because of poor accessibility to the contaminants and difficulty in delivering treatment reagents, existing in-situ treatments such as bioremediation, vapor extraction and pump and treat have proven ineffective in these applications.

The lasagna process, however, utilizes the synergistic combination of electro-osmosis with a layered treatment zone. Since the zones are deliberately located close to one another, it requires less time to move the liquid by electro-osmosis from one zone to the adjacent one.

The process has reportedly pro-ven effective in removing contaminants from very heterogeneous soil mixtures such as clay in sand. Moreover, occasionally reversing the electrical polarity of the process can minimize operational complications such as soil drying and steep pH gradients associated with conventional applications of electro-osmosis.

Administrators of the field test hope to demonstrate that the process can remove TCE from the contaminated soil and trap it in adjacent carbon treatment zones, which is also useful for checking the TCE mass balance. Next year's field tests will involve the full configuration - removal of TCE plus in-situ degradation, either biologically or chemically.

Proponents of the technology claim that it will have minimal im-pact on the environment because the treatment takes place in subsurface soil under existing natural soil conditions, which reportedly won't generate secondary wastes.

The consortium expects the project to be cost-effective, with estimated costs at $50 per cubic yard of treated soil. However, commercialization of the technology is three to five years away - if all goes according to plan.