FREQUENTLY ASKED QUESTIONS

Installation of the Pilot System

How are bench-scale test results used to develop full scale-up recommendations?

A specific stoichiometry will be determined through a bench-scale lab study, with preliminary treatment quantities calculated. Application is typically tested in the field during a pilot program to determine the efficiency and radial extent of treatment, which varies depending on the site's subsurface characteristics. Based upon a successful lab study and pilot program, design and implementation of full-scale remediation is proposed (if required).

The addition of acid to water generates heat. Also, the dissociation of hydrogen peroxide is exothermic. PVC is not capable of withstanding the heat of reaction. Practical experience has shown that PVC wells will melt, collapsing and becoming unusable.

PVC does not decompose until the temperature reaches a high of 148-149oC (or 298-300oF). Under normal treatment conditions, ISOTEC modified Fenton's reaction temperatures rarely exceed a high of 10oC over background groundwater temperatures, which is significantly lower than the temperatures of concern. Furthermore, ISOTEC has used PVC injection points at numerous sites in the past and has found evidence of PVC melting only at sites with free product or high organic loading such as a peat layer, which can cause an aggressive reaction upon contact with hydrogen peroxide. Stainless steel wells are recommended in those instances. An additional point to note is that the ISOTEC process does not involve adding concentrated acid to the subsurface aquifer and therefore, will not generate such high reaction temperatures.

Injecting the H2O2 under hydrostatic pressure may only succeed in treating the area immediately around the injection point...H2O2 should be applied under moderate pressure.

It is true that hydrostatic pressure may not be adequate to attain the desired radial effect if permeability is low. ISOTEC designs its injection points for low to moderate pressure application where it is considered necessary. As mentioned before, a pilot study is performed to determine the conditions that are most suited for full-scale remediation of the site.

What information on full-scale processes have you implemented in residential areas or other areas that are populated (shopping centers, roadways, etc.)?

The ISOTEC process has and is currently being implemented within numerous residential areas. Full-scale programs have been completed from a small project within a residential dwelling basement where a former AGST spill occurred (See Lake Front Residence, New Jersey case study), to larger ongoing treatments within a warehouse (case study not completed) where total site VO’s (TCE/PCE) levels have been reduced from 151 ppm to 3 ppm after 2 treatment applications. Several ISOTEC case studies have been enclosed in the case studies section of this web site.

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