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Insitu bioremediation accelerates site clean up

INSITU BIOREMEDIATION has allowed rapid clean up of a site in High Wycombe, Buckinghamshire.

Response Bioremediation Contracting, a division of Response Environmental Services, came up with a risk based, site-specific insitu bioremediation scheme using its patented Response Bio-Gel to clean up the petroleum hydrocarbon contaminated site.

This non-toxic, non-corrosive, organic, food grade substance is found in most foods and used commonly in the pharmaceutical industry. It is used as a carrier, an insulator and an initial source of nourishment for the bacteria used in bioremediation of soil and water contaminated with petroleum hydrocarbons.

The 3800m 2site is being redeveloped by client Michael Shanly Homes for residential use. Site investigations by consultant AP Geotechnics revealed that the main contaminant was 1,1,1 Trichloroethane with concentrations of 212.66mg/kg to 2.9m depth.Ground conditions are typically 0.7m of fill over 9.3m of stiff silty and gravely clay, all overlying the major chalk aquifer.

After consultation with the local authority, the NHBC and the Environment Agency (including the National Groundwater and Contaminated Land Centre) both the remediation strategy and the remediation target values of 10mg/kg for total VOCs and 5mg/kg for 1,1,1 Trichloroethane, were confirmed.

Response Bio-Gel contains nonpathogenic bacteria, found naturally in soils, nutrients and dissolved oxygen to maximise the interface of bacteria and contaminant. This promotes the development and colonisation of biomass, facilitating bioremediation. As part of the colonisation process the bio-gel is consumed and converted into carbon dioxide and water. The gel is specifically engineered to respond to the site-specific ground conditions and contaminant properties, including the risk of lateral and vertical contaminant mobilisation.

Work began last November, with the gel manually injected into the target area using 19mm diameter injection lances at 0.75m spacing in a regular grid.

Remediation was monitored six and 11 weeks after injection, with window samples tested by environmental analysis. TPH contamination was also detected during works and this too was sampled and tested.

Results confirmed that in just 11 weeks, the bioremediation had achieved the target levels, with maximum concentrations recorded as 1.54mg/kg total VOCs and 0.02mg/kg of 1,1,1 Trichloroethane. TPH contamination was remediated to 5mg/kg.

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