In-Situ Bioremediation

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Pump And Treat Systems

In pump and treat systems groundwater is pumped to the surface, treated, and either used directly or returned to the ground. Surface treatment often involves aeration, the addition of nutrients, and in some cases seeding with microbial cultures capable of degrading contaminants known to be in the ground.

Bio-sparging

In-situ bioremediation systems typically consist of a combination of injection wells (or galleries or trenches) and one or more recovery wells. In most instances, the recovered ground water will be treated prior to amendment with nutrients and/or an oxygen source and re-injection. Ground-water treatment has frequently consisted of an air stripper tower or activated carbon but may incorporate an oil/water separator, a biological treatment unit, an advanced oxidation unit, or combinations of treatment units.

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Case Studies - In-Situ Groundwater Treatment

ORC & HRC Injection

ORC (Oxygen Releasing Compound) and HRC (Hydrogen Releasing Compound) are products manufactured by Regenesis for in situ treatment of groundwater contamination, and have been used by Land Clean successfully in a number of projects. Land Clean Ltd recommends Regenesis products due to proven performance (including within the UK), time-release properties (up to a year of treatment from a single application), ease of handling, and cost effectiveness.

ORC – provides a time-release application of oxygen into groundwater to enhance the activity of aerobic bacteria and degrade the majority of hydrocarbons including vinyl chloride, BTEX, diesel range and mineral oils dissolved in groundwater.

HRC – provides a release of hydrogen over a specific time period and is suitable for anaerobic conditions where dechlorination of dissolved chlorinated solvents and pesticides is required.

Land Clean Ltd is able to provide the following service:

• Remediation design (if required).
• Supply and installation.
• Restricted access applications.
• Mixing equipment and injection pumps.
• Validation monitoring/testing.
• Performance monitoring.

These treatments do not require a Mobile Plant Licence if it is only groundwater that is being treated. However, the Environment Agency are understandably keen to be kept informed of these projects.

Design Considerations

Please bear in mind the following issues when considering these options for treatment:

• A sound understanding of the hydrogeological regime is required
• Source removal should be undertaken as part of the treatment scheme.
• Other oxygen requirements in the system should be allowed for (BOD/COD).
• Applications can include source area mixing in excavations (e.g. UST removal), plume treatments, and barrier applications (e.g. on a site boundary).
• Chlorinated solvents often require treatment in a two stage process as PCE, TCE and DCE isomers are usually most rapidly degraded in an anaerobic environment where HRC would be suitable. However, vinyl chloride is most readily degraded in an aerobic environment where ORC would be the suitable treatment option. Therefore, in this instance plumes can be subdivided into zones requiring different treatment methods or treatment can be undertaken in two stages.