A former triacetate production facility caused heavy xylene contamination with 27,850 mg/kg in soil and 89,000 µg/l in groundwater to 10 m below ground level resulting in 83 ton of xylene that required active treatment. Treatment of the first 10 m of the soil would allow the deeper plume until 25 m to be treated by natural attenuation. This contract proposed a 100% on-site and in-situ biological remedial approach, as it was more sustainable and economical than conventional off-site techniques.
The remediation consisted of excavation and 100% on-site biopiling for soil and biosparging for groundwater (2 areas completed, 1 area ongoing). The excavated soils are placed in biopiles, where dosing of nutrients and bioventing stimulates biodegradation of the contaminants. After soil treatment and in areas that could not be excavated due to logistical utility restrictions, an enhanced in-situ biosparging system has been installed below ground level. This in-situ system treats residual soil and groundwater contamination. During the remediation two innovative soil vapor treatment techniques were developed: Biopile Air Filtration Technique (BAT) and Regenerative Bioscrubber (RBS).
After and during soil treatment, the ‘completed’ biopiles from Area 1 were restructured using GreenSoil’s BAT to treat the soil vapors (500–7000 ppm of xylene) originating from the piles in the heavily polluted Area 2.
The RBS technique was used to treat soil vapors (contaminated air and groundwater) with a continuous regeneration system of carrier material.
The project showed the power of circular bioremediation in all its aspects and has evidenced that innovation, sustainability and cost can go hand in hand. 99% of the contamination was degraded biologically either in soil, groundwater or air. In addition, 0 m³ of soil left the site and cleaned-soil was used as air-treatment. Another remarkable outcome is that the active carbon consumption was reduced with 98% reducing waste. The main financial costs at risk being (off site) soil treatment, activated carbon consumption and waste processing were managed by the circular bioremediation model allowing to offer a guaranteed outcome by this lump sum contract.
Starting from concentration levels upto 4,000 mg/kg, individual biopiles were reduced within 60–80 days to concentrations levels below 50 mg/kg. App. 25,000 m3 of heavily contaminated soil were treated to levels far below remedial target (379 mg/kg), many verification samples showed < detection limit.
The biological water treatment system was highly efficient, given the high influent concentrations (an efficiency rate of 99–99.9%), removing the bulk of the incoming groundwater mass and leading to a noticeable reduction of activated carbon. The biological water treatment system was highly efficient, given the high influent concentrations (an efficiency rate of 99–99.9%), removing the bulk of the incoming groundwater mass and leading to a noticeable reduction of activated carbon.
The impacted groundwater, up to 89.000 µg/l of xylene, was treated by in-situ biosparging resulting in a structural 70-99% decrease of concentration levels within one-year time.
Both BAT and RBS processes helped to treat 60–90% of highly loaded soil vapors (up to 7,000 ppm of xylene) originating from other active biopiles
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