Theme: 01. Remediation Technology Innovations

Topic Area: 1d2. Combined Remedies and Treatment Train Technologies for Chlorinated Contamination

Formatted Title:

In Situ Soil Washing as Lead-Out for More Effective ISCO and ISCR Full-Scale Implementation for Chlorinated Solvents

Background/Objectives:

In situ remediation is typically viewed as challenging. This due to the natural sorption of hydrophobic contaminants, that at increasingly higher concentrations, they phase partition to form globules, and floating, or sinking, non-aqueous phase liquids (NAPL). NAPL can become entrained in the soil and groundwater, with limited availability for physical, biological and chemical remediation, due to inhibition of mobility caused by interfacial tension. The limited availability of contamination in soil and groundwater inhibits conventional remediation processes, such as ISCO, ISCR, which are stoichiometrically unfeasibly for site with high concentrations, resulting is repeated chemical applications failures, in what are characteristically known to be very long and very costly in situ remediation projects, due to the inherent limitations of single remediation technology applications.

With prevailing regulatory and market mandates for more environmentally sustainable remediation of contaminated sites in Europe, this has challenged remediation practitioners to be more innovative. This pressure has driven a recent trend to pursue novel ways to overcome the conventional limits of contaminant availability for physical, biological and chemical remediation. This has been characterized by site remediation employing innovative technology, and the synergistic combinations of technologies, to realize what is to become a new sustainable paradigm in soil and groundwater remediation, regardless of soil texture and contaminant concentration.

Approach/Activities:

An example of this innovative trend that breaks from conventional remediation, employs the use of non-emulsifying surfactants as lead out for NAPL and globule mass removal, resolving interfacial tension and opening blocked inter-pore-space pathways, with >99.99% of employed surfactant removal, before undertaking a separated step, more effective ISCO and/or ISCR, for resolution of the involved chlorinated impacts.

Results/Lessons Learned:

The principle objective of the surfactant injections are to enhance contaminant mass removal, via desorption and resolving interfacial tension. Once the bulk of contamination has been removed, then the remaining residual contaminant, in the soil and groundwater can be more effectively treated with ISCO and/or ISCR, with the choice of oxidant and/or reductant, which can be used in combination, depending upon the contaminants to be treated, and prevailing site conditions (pH, redox-potential, conductivity, etc.).

Depending on the degree of contamination, a minimum removal of >70% of the bulk contaminant mass is pursued with the in situ soil flushing, before moving on to the separated (non-surfactant) step in situ techniques, to realize >99.9% mass reduction in soil and groundwater regimes.

Glenn Heernaert

Affiliation

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(Group 2, Poster Board #180) In Situ Soil Washing as Lead-Out for More Effective ISCO and ISCR Full-Scale Implementation for Chlorinated Solvents