At a glance
Location: Florida
Geology: Fine (silt/clay), Silty sand
Contaminant(s): BTEX, Light petroleum, Naphthalene
ETEC Solution(s): CBN, PetroBac
Unique challenge(s): Integrated existing infrastructure
Site Summary
In a clear example of how bioremediation can enhance other techniques, ETEC was able to reduce VOC concentrations by 97% in a 5 month period at an agriculture manufacturing site with historic diesel releases. An existing AS/SVE system provided the infrastructure, and despite prior limited results, produced fantastic rapid reductions with the addition of bioremediation.
Site conditions and remedial goal
A former agriculture maintenance facility in central Florida was impacted by historical diesel releases that affected both shallow soil and groundwater. Petroleum hydrocarbons were present as dissolved-phase contamination, with elevated concentrations of BTEX and naphthalene identified in the groundwater. Subsurface conditions consisted primarily of fine sands with localized clay layers within the saturated zone.
Prior to ETEC’s involvement, the site had been equipped with an active remediation system consisting of four soil vapor extraction wells and twelve air sparge wells. The AS/SVE system operated for approximately six months but achieved limited contaminant mass removal. Based on performance data collected during this period, the original consultants concluded that the AS/SVE system alone was not effectively addressing the residual contaminant mass.
ETEC was brought on board to evaluate whether the existing remedial infrastructure could be improved through the addition of biological enhancement.
ETEC Solution
ETEC reviewed operational data, groundwater analytical results, and site geochemistry to assess the feasibility of aerobic bioremediation. Rather than replace the existing remediation system, ETEC designed an approach that used AS/SVE wells to distribute our Custom Blend Nutrients (CBN™), along with a hydrocarbon-degrading bacterial consortium and rhamnolipids (PetroBac™) throughout the target area. This strategy eliminated additional infrastructure costs while maximizing the value of the existing remedial infrastructure.
The overall goal was to enhance aerobic biodegradation of diesel-range hydrocarbons by taking advantage of the oxygenated environment that the AS/SVE system provided. Monthly applications were proposed to promote distribution of CBN™ and PetroBac™ within the treatment zone, accelerating breakdown of petroleum constituents.
Remedial outcome
Groundwater monitoring over the next year indicated that this collaborative effort resulted in rapid and sustained contaminant reductions. In the 5 months of treatment, the total naphthalene concentrations were reduced by 99%, benzene concentrations were reduced to non-detect levels and the remaining VOC concentrations onsite were reduced by more than 97%.
Continued groundwater monitoring confirmed that contaminant rebound did not occur following ETEC’s initial involvement, demonstrating that mass removal was taking place in both the dissolved- and adsorbed-phase. The results validated the effectiveness of integrating aerobic bioremediation into an existing AS/SVE system.