Groundwater subsurface treatment

For practitioners of in situ technologies, note that U.S. EPA has issued a policy statement that reinjection of contaminated groundwater is allowed under Resource Conservation and Recovery Act (RCRA)35 36 as long as certain conditions are met. This policy is intended to apply to remedies involving in situ bioremediation and other forms of in situ treatment. Under this policy, groundwater may be reinjected if it is treated aboveground prior to reinjection. Treatment may be by a pump-and-treat system or by the addition of amendments meant to facilitate subsurface treatment. Also, the treatment must be intended to substantially reduce hazardous constituents in the groundwater (either before or after reinjection) the cleanup must be protective of human health and the environment and the injection must be part of a response action intended to clean up the environment.37... 

Subsurface drains are essentially permeable barriers designed to intercept the groundwater flow. The water must be collected at a low point and pumped or drained by gravity to the treatment system (Figure 8). Subsurface drains can also be used to isolate a waste disposal area by intercepting the flow of uncontaminated groundwater before it enters into a contaminated site. 

A permeable reactive barrier (PRB) is defined as an in situ method for remediating contaminated groundwater that combines a passive chemical or biological treatment zone with subsurface fluid flow management. Treatment media may include zero-valent iron, chelators, sorbents, and microbes to address a wide variety of groundwater contaminants, such as chlorinated solvents, other organics,... 

Direct infiltration of (treated) wastewater through sand beds and infiltration of sewage water from laundry ponds or septic systems are among the major contamination sources of surfactants into subsurface and groundwaters. Most studies published on this issue were released by research groups from the USA where these treatment techniques have found some use (Table 6.7.3). 

Biosurfactants are commercially available compounds for the in sim or ex situ treatment of hydrocarbons and non-aqueous-phase hquids (NAPLs) in soil and groundwater. Surfactants are highly surface-active compounds that solubilize and/or mobilize contaminants in the subsurface. 

Environmental Remediation Consultants, Inc. (ERC) offers the BIO-INTEGRATION method for in sitn and ex situ destruction of organic compounds in soil, sediment, sludge, groundwater, snrface water, and wastewater. The BIO-INTEGRATION approach combines biotic and abiotic treatment methods to remediate subsurface contamination. On-site bioreactors are used to grow substrate- and contaminant-specific microbes. The microbes are combined with abiotic amendments and injected into the subsurface. 

EnviroWall is a barrier. It serves to isolate contaminants and must be combined with another technology to treat contaminants. According to the vendor, EnviroWaU barriers can be installed to a maximum depth of 50 ft. The presence of boulders in the subsurface will increase treatment costs. The long-term durability of the HDPE material is not known. The system is best suited to treat contaminated groundwater and leachate at depths up to 50 ft when the contaminated media is underlain by an aquitard or other impermeable layer. 

The Trench Bio-Sparge (TBS) system is an in situ technology for the treatment of groundwater contaminated with organic compounds. The system employs diversion walls to direct the contaminant plume to a subsurface trench reactor, where treatment is achieved by physical and/or biological means. The technology has been field tested at the pilot scale but is not yet commercially available. 

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