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HBR Head Office
7 Appleton Court, Calder Park,
Wakefield, WF2 7AR

Telephone: 01924 250 132

Fax: 01924 251 394


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Coggeshall Road, Earls Colne
Essex, CO6 2JX

Telephone: 01787 222768

Fax: 01787 224391

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4 Bredon Court, Brockeridge Park,
Twyning, Gloucestershire
GL20 6FF

Telephone: 0844 482 9685

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Broken Cross,
Douglas Water,
ML11 9PB

Telephone: 01324 483713

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In-situ Biodegradation Study

  • 27-06-2012


In order to re-evaluate design parameters for an in-situ soils and groundwater project for a major petroleum company, HBR undertook a novel approach for assessing the potential of the sub-surface to biodegrade hydrocarbon contamination to below site-specific target levels agreed with the Regulator.





Widely employed ex-situ biodegradation studies, which first require expensive recovery of fresh soil and groundwater samples from the impacted area using drilling equipment, were disregarded in favour of an in-situ technique which allows culturing of the microbial community in-situ, followed by molecular DNA analysis to identify the type and numbers of microbes present.


This technique, developed by EnviroGene Ltd in combination with the University of Tulsa involves placing samplers or BioTraps (cartridges filled with activated carbon beads) within the saturated zone to collect actively growing micro-organisms that rapidly colonise the large absorptive surface area of each bead (~600m2/g).  Subsequent Polymerase Chain Reaction (PCR) analysis of the bead culture can identify specific DNA sequences or genes to confirm the presence of bacteria capable of degrading the site contaminants.

remediation DNA


Unlike ex-situ methods which monitor parameters such as oxygen consumption, CO2 production and contaminant reduction under artificial conditions in the laboratory, the BioTrap technique allows full-scale design based on real data recovered from the subsurface.


A BioTrap sampler was lowered into 3 existing wells and positioned within the saturated zone to gather data upstream of and within the contaminant source area for a period of 45 days. One of source area wells was augmented with a pulsed supply of bubbled air to determine the response to full-scale air sparging operations on the rate of biodegradation.


For the HBR study, the BioTrap beads were baited with a pre-determined concentration 13C-labelled benzene, the lead contaminant of concern on the site.  In this way, analysis of the DNA of the recovered bacteria enabled HBR to categorically demonstrate that the micro-organisms had used the 13C benzene as a food source.


Once removed from the sub-surface the BioTraps were sent for PCR analysis to EnviroGene Ltd in South Wales.


The study found that the highest rate of benzene degradation occurred within the source zone area under oxygen augmentation and confirmed a large resident, well adapted microbial population.  Degradation rates were lowest upstream of the main plume where high microbial numbers were less adapted to the contaminant source.


By combining the various data responses, the study allowed benzene half-life calculation and unequivocal demonstration of benzene mineralisation facilitating re-assessment of design parameters, such as well spacing and treatment timeframes for the system proposed.


BioTraps are being utilised during the full-scale works, in combination with process data and third party monitoring to demonstrate the performance of the treatment approach and assist in site close out.

remediation report