TCE Remediation

Industry: Real estate

Site history: At this site, where an office building was planned for construction, a suspicion arose of groundwater contamination due to past operations in close vicinity to the site. No industrial operations had been carried out at the site itself, but plants for refrigerators, paint and metal work, garages and fuel stations had been in operation nearby.

Before start of construction on the site, an observation well to a depth of 22 meters was drilled at the site center. A sampling conducted in late 2007 revealed high concentrations of Trichloroethylene (TCE) in groundwater – in excess of 14,300 ppb. (The Drinking Water Standard (2007) permits a maximum concentration of 50 ppb.)

In the first half of 2008, water was pumped at this site to lower the groundwater level, in order to excavate and build several floors of underground parking. In August 2008, sampling of water pumped from the 6 wells (wells 0 5) on this site found chlorinated organic contaminants in the pumped underground water, especially TCE at concentrations of 300 11,300 ppb. As part of the construction permit for this project, the site owner was required to have the groundwater below the project area treated, and to drill 2 new multi-level monitoring drillings outside and adjacent to the site.

Objective: Remediation of Trichloroethylene (TCE) contaminated underground water

Solution: Groundwater remediation at this site was achieved by a unique method, including injection of an active agent EHC-F, which promotes biological decomposition of the contaminants into harmless materials. In fact, this was the first time such work has been carried out in Israel. The operating mechanism of EHC-F combines both chemical and biological treatment. Chemical reduction is caused by the contaminant coming into contact with Zero Valent Iron (ZVI); the reduction thermodynamics are improved by reducing the redox potential to -300 mV, and increasing the reactive surfaces thanks to dissolved iron and iron salts, such as magnetite. Biological decomposition by anaerobic fermentation produces fatty acids and hydrogen – resulting in decomposition of chlorine from the contaminant molecule.

In October 2009, some 5 tons of EHC-F was injected into wells 1-4. Half the quantity was injected into well 2, and the remainder into the other wells.

In November 2009, we started frequent monitoring of groundwater in the injected wells and monitoring throughout the site. In early 2010, we installed 2 multi-level monitoring bores. Each bore consists of 3 monitoring pipes, enabling us to sample water at depths of 1, 6 and 11 meters below the groundwater level (wells 10-12 and 13-15).

In 2010-2011, we continued monitoring the groundwater in wells within and outside the site, through the multi-level wells, for existence of chlorinated organic solvents.

Two years after the injections of the EHC, we can see that in the four injected wells there was a dramatic decrease, in excess of 99%, in TCE concentrations to within drinking water standard, and in excess of 90% in concentrations of all chlorinated organic contaminants. The overall average across all wells on-site shows a significant decrease of over 95% in TCE concentrations, to within drinking water standard, for most wells, and an 80% decrease in concentrations of all chlorinated organic contaminants.

Given the findings two years after injection, we can say that the remediation project has been successful beyond the target specified (decomposition of 90% of TCE), and has reduced all chlorinated solvents by more than one order of magnitude – The project was awarded site closure by the water authority two years after its initiation.

Site: Confidential

Zoning: Office building

Location: Tel Aviv

Contaminants: Trichloroethylene (TCE)

Soil type: Heavy brown clay soil to a depth of 8.5 meters; clay sand to a depth of 11 meters; eolianite sand to groundwater level

Groundwater level -1 meter (absolute height), 14.3 meters below the surface

Final condition: TCE concentrations decreased to within drinking water standard



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