Description:

A typical injection well consists of concentric pipes, which extend several thousand feet down from the surface level into highly saline, permeable injection zones that are confined vertically by impermeable strata. The outermost pipe or surface casing, extends below the base of any underground sources of drinking water (USDW) and is cemented back to the surface to prevent contamination of the USDW. Directly inside the surface casing is a long string casing that extends to and sometimes into the injection zone. This casing is filled in with cement all the way back to the surface in order to seal off the injected waste from the formations above the injection zone back to the surface. The casing provides a seal between the wastes in the injection zone and the upper formations. The waste is injected through the injection tubing inside the long string casing either through perforations in the long string or in the open hole below the bottom of the long string. The space between the string casing and the injection tube, called the annulus, is filled with an inert, pressurized fluid, and is sealed at the bottom by a removable packer preventing injected wastewater from backing up into the annulus.

Synonyms:

Subsurface injection, Underground injection, Class I injection wells.

Applicability:

The target contaminant groups for deep well injection are VOCs, SVOCs, fuels, explosives, and pesticides. However, existing permitted deep well injection facilities are limited to a narrow range of specific wastes. Success at expanding existing permits to manage hazardous wastes seems unlikely.

Limitations:

Factors that may limit the applicability and effectiveness of these processes include:

• Injection will not be used for hazardous waste disposal in any areas where seismic activity could potentially occur.
• Injected wastes must be compatible with the mechanical components of the injection well system and the natural formation water. The waste generator may be required to perform physical, chemical, biological, or thermal treatment for removal of various contaminants or constituents from the waste to modify the physical and chemical character of the waste to assure compatibility.
• High concentrations of suspended solids (typically >2 ppm) can lead to plugging of the injection interval.
• Corrosive media may react with the injection well components, with injection zone formation, or with confining strata with very undesirable results. Wastes should be neutralized.
• High iron concentrations may result in fouling when conditions alter the valence state and convert soluble to insoluble species.
• Organic carbon may serve as an energy source for indigenous or injected bacteria resulting in rapid population growth and subsequent fouling.
• Waste streams containing organic contaminants above their solubility limits may require pretreatment before injection into a well.
• Site assessment and aquifer characterization are required to determine suitability of site for wastewater injection.
• Extensive assessments must be completed prior to receiving approval from regulatory authority.

Data Needs:

A detailed discussion of data elements is provided in Subsection 2.2.2 (Data Requirements for Ground Water, Surface Water, and Leachate).

Performance Data:

Injection wells have been used for the disposal of industrial and hazardous wastes since the 1950s, so the equipment and methodology are readily available and well known; however the use of them today is continuing under very strict regulatory control.

Cost:

NA

References:

Innovative Remediation Technologies:  Field Scale Demonstration Project in North America, 2nd Edition

Abstracts of Remediation Case Studies, Volume 4, June 2000, EPA 542-R-00-006

Guide to Documenting and Managing Cost and Performance Information for Remediation Projects - Revised Version, October, 1998, EPA 542-B-98-007

EPA, 1985. Report to Congress on Injection of Hazardous Waste, EPA, Office of Drinking Water, EPA/9-85-003.

Reeder et al., 1977. Review and Assessment of Deep Well Injection of Hazardous Waste, Volume I, EPA/600/2-77/029a.

Warner and J.H.Lehr, 1977. An Introduction to the Technology of Subsurface Wastewater Injection, EPA/600/2-77/240.

• DOI Demo Bureau of Mines Tuscaloosa Research Center, AL

General FRTR Agency Contacts

A list of vendors offering Water Containment Treatment is available from  EPA REACH IT which combines information from three established EPA databases, the Vendor Information System for Innovative Treatment Technologies (VISITT), the Vendor Field Analytical and Characterization Technologies System (Vendor FACTS), and the Innovative Treatment Technologies (ITT), to give users access to comprehensive information about treatment and characterization technologies and their applications.

Government Disclaimer

To be added