Cost and Performance Report for a Persulfate Treatability Study at Naval Air Station North Island

From Theory to Practice: Leveraging Chemical Principles To Improve the Performance of Peroxydisulfate-Based In Situ Chemical Oxidation of Organic Contaminants

“…Nonetheless, it is well documented that biotic and abiotic attenuation mechanisms reduce the impact of these processes to levels considered safe by regulatory agencies in a period of 1 to 4 months. 18,26 The direct injection process is mostly performed with temporary push points (Figure 2A); however, permanent injection wells can also be used. The typical direct push method involves using a machine with a hydraulic hammer that pushes small-diameter metal rods with an injection tool to the targeted treatment depth.…”

“…32 Although large quantities of acid are generated as the injection fluid decomposes, the pH of groundwater after treatment typically ranges from 2 to 5 due to the neutralization of protons by minerals (e.g., CaCO 3(s) ) associated with the aquifer material. 18,26 Furthermore, the neutralization of acidity is not instantaneous; pH values typically increase over several days after treatment ends. In well-buffered systems, pH values eventually return to preinjection pH values.…”

“…However, at sites with a paucity of minerals capable of neutralizing persistent acidity, pH values below 2 have been observed. 18 The drop in pH often results in the release of toxic trace elements and/or the formation of new mineral species. Elevated concentrations of trace elements such as arsenic, chromium and vanadium have been reported in treatment zone wells where S 2 O 8 2− -ISCO was employed even after pH values returned to preinjection levels.…”

“…172−175 Field measurements made during ISCO treatment have revealed elevated concentrations of chloromethane and methylene chloride, which are precursors to trihalomethanes; however, chloroform or other trihalomethanes have not been detected at elevated concentrations after the application of S 2 O 8 2− . 18 Therefore, more research is necessary to assess the formation of halogenated byproducts under the conditions typical for S 2 O 8 2− -based ISCO. Another concern is the potential production of chlorate (ClO 3 − ); due to sequential oxidation of Cl − , concentrations that could pose a health hazard have been reported under conditions similar to those employed for ISCO.…”

“…55 To thermally activate S 2 O 8 2− in the field, various techniques have been employed, including in situ thermal treatment using steam, resistive heating and preceding S 2 O 8 2− addition by application of H 2 O 2 , which generates heat as it is converted into O 2 and •OH. 18,56,57 Although these approaches have some advantages over base addition, they face their own set of challenges. For example, it is difficult to achieve uniform steam distribution in the subsurface, and steam generation can be complicated if the water used requires the addition of softeners to prevent the buildup of calcium, lime and rust in the steam lines.…”