Initial investigation on the use of waterjets to place amendments in the subsurface

Abstract

Quasi-passive in situ remediation technologies, such as the use of permeable reactive barriers to treat contaminated groundwater or applications of granular activated carbon to treat polychlorinated biphenyl (PCB)-contaminated, near-surface sediments, are proven or promising technologies that may be limited in application due to the traditional construction techniques normally used for placement in the environment. High-pressure waterjets have traditionally been used to excavate material during mining operations or to cut rock or other durable material. Waterjets have the potential to place amendments in the subsurface at depths greater than those that can be obtained using traditional construction techniques. Likewise, waterjets may have less negative impact on near-surface utilities and/or sensitive ecological systems. Laboratory experiments were performed to characterize the placement of two solid amendments in a simulated saturated aquifer. A second set of experiments was performed to characterize the effectiveness of waterjets for placing a third amendment in simulated intertidal sediments. The laboratory work focused on characterizing the nature of the waterjet penetration of the aquifer matrix and the saturated sediments, as well as the corresponding waterjet parameters of pressure, nozzle size, and injection time. The laboratory results suggest that field trials may be appropriate for future investigations. INTRODUCTIONThe U.S. Environmental Protection Agency (US EPA; 2000) stated that the poor performance of pump-and-treat systems in the early-to-mid-1980s provided a drive for research to better understand abiotic subsurface processes. This led to the development of new remediation technologies, based on the application of subsurface in situ processes to overcome the factors limiting remediation success. One of the more successful in situ technologies was the use of zero-valent iron (ZVI) to produce an environment of abiotic reductive dechlorination in the aquifer system. The initial success of ZVI permeable reactive barriers led to the use of ZVI to treat other classes of contaminants, such as nitroaromatic compounds, as well as the development of new amendments to treat chlorinated organic compounds in the subsurface. Likewise, amendments such as granular activated carbon (GAC) have been used for the in situ remediation of contaminated, near-surface sediments. An important factor for the success of any in situ remediation of both contaminated aquifers and near-surface sediments is the method of placement. While traditional construction techniques such as trenching and soil mixing may be appropriate for many remediation sites, these techniques may not be appropriate for all sites. This article • a simulated aquifer and • simulated sediments Two amendments, ZVI and EHC™, were evaluated for placement into a saturated aquifer. Zero-valent iron has been proven to be effective in abiotically degrading several chlorinated organics (US EPA, 1998). EHC™ is a patented combination of carbon in the form of a cont...

Development of a waterjet system for direct delivery of granular iron and activated carbon to remediate contaminated aqueous sediments

“…The notion of injecting remediation amendments into contaminated sediment has been previously researched by Cantrell et al (1997) and Cable et al (2005). Both of these research groups attempted to develop a delivery method that would inject particulate amendments as a slurry into the sediment.…”

Waterjet injection of powdered activated carbon for sediment remediation

“…This direct relationship between the AC-contaminant mixing and the reduction in contaminant bioavailability has provided the major motivation for this study. Cable et al (2005) evaluated the potential use of waterjets to deliver liquid amendments to contaminated aquifers and sediments, and the purpose of this paper is to evaluate the use of waterjets to deliver powdered activated carbon (PAC) to a saturated sediment that is inundated with a prescribed height water column at the time of injection. Summers (1995) stated that high pressure waterjets ranging from 1.0×10 5 to 1.0×10 6 psi have been used for large-scale mining and excavation purposes for more than a century.…”