Optimization of Full‐Scale Permanganate ISCO System Operation: Laboratory and Numerical Studies

Abstract

Laboratory characterization studies, one‐dimensional flow‐through studies, and numerical model simulations were conducted to examine site conditions and system features that may have adversely affected in situ chemical oxidation (ISCO) performance at the Naval Training Center’s (NTC) Operable Unit 4 located in Orlando, Florida, and to identify potential ISCO system modifications to achieve the desired remediation performance. At the NTC site, ISCO was implemented using vertical injection wells to deliver potassium permanganate into a ground water zone for treatment of tetrachloroethylene and its breakdown products. However, oxidant distribution was much more limited than anticipated. Characterization studies revealed that the ground water zone being treated by ISCO was very fine sand with a small effective particle size and low uniformity coefficient, along with a high organic carbon content, high natural oxidant demand (NOD), and a high ground water dissolved solids concentration, all of which contributed to full‐scale ISCO application difficulties. These site conditions contributed to injection well permeability loss and an inability to achieve the design oxidant injection flow rate, limiting the actual oxidant distribution at the site. Flow‐through experiments demonstrated that more favorable oxidant delivery and distribution conditions are enabled by applying a lower oxidant concentration at a faster delivery rate for a greater number of pore volumes. Numerical simulations, run for a variety of conditions (injection/extraction well flow rates, injected oxidant concentration, amount of NOD present, and NOD oxidation rate), also revealed that low–oxidant concentration injection at a high flow rate is a more effective method to deliver the required mass of oxidant to the target treatment zone.

Permanganate oxidation of polycyclic aromatic compounds (PAHs and polar PACs): column experiments with DNAPL at residual saturation

“…Permanganate injections induced very little change in the hydraulic conductivity of the porous medium, in line with (i) the low quantity of precipitates formed due to low oxidative activity and (ii) the remobilization of those particles with the drop of ionic strength immediately after the end of oxidation. In contrast, many field studies have shown clogging of porous media during permanganate injections in soils (Heiderscheidt et al 2008). The high hydraulic conductivity and homogeneity of our medium and its simplified composition (only glass beads without a nucleus to favor precipitation) may explain the difference between our results and field observations.…”

Characterisation of hydraulic and hydrogeochemical processes in a reducing and alkalinity-producing system (RAPS) treating mine drainage, South Wales, UK

“…From these calculations, we obtain a first estimate of the effective bulk porosity of the RAPS at 32-35%, although this may be an overestimate, due to the finite volume of the partially ochre-filled supernatant water layer. hydraulic conductivity is controlled by the aperture of the throats (Doyen, 1988;Rezaee et al, 2006), connecting pore spaces, which can become clogged very easily, rather than by the aperture of the pores themselves (Heiderscheidt et al, 2008). The spread of values in Figure 3b also provides some impression of the accuracy of the hydraulic data obtained from analysis of these tracer tests, approximately 30% around the mean value.…”

Oxidation of trichloroethylene, toluene, and ethanol vapors by a partially saturated permeable reactive barrier

“…Moreover, the method is not effective for aerobic biodegradation of many chlorinated hydrocarbons (Hinchee, 1993;USEPA, 1995). In-situ chemical oxidation (ISCO) of VOCs has been well developed as a remediation technology of dissolved VOCs in groundwater (Heiderscheidt et al, 2008;Li and Schwartz, 2004;Tsitonaki et al, 2010;Yuan et al, 2013). However, only a few studies have applied ISCO to the unsaturated zone using permanganate (Hesemann and Hildebrandt, 2009) or other oxidants (Cronk et al, 2010).…”