ORIN successfully treated petroleum contaminated groundwater with enhanced bioremediation chemistry. Saturated contaminant levels were reduced from 4,250 ug/L to less than detection over a two-month period. ORIN’s approach saved the client approximately $27K to $60K over traditional remediation approaches.

Site Characteristics:

  • Geology – silty clay with trace fine sand
  • Groundwater velocity – 10-4 to 10-5 cm/sec
  • Size of plume treated – 50,400 ft3
  • Contaminants:
    • 2,400 ug/L benzene
    • 120 ug/L toluene
    • 130 ug/L ethylbenzene
    • 1,600 ug/L xylene

Remediation Approach:

  • Treatment chemistry – PermeOx® Plus
  • Treatment application – Chemical injection through a series of direct push points

Chemistries used during injection

An initial bench level treatability study performed at ORIN’s treatability laboratory found that PermeOx® Plus, a slow, oxygen releasing compound, effectively reduced the concentrations of BTEX found at this site. Successful bioremediation of petroleum contamination via aerobic microbial respiration depends on a number of factors including the presence of appropriate microbes, nutrients, electron donors and terminal electron acceptors. In the aerobic metabolism of petroleum contaminants, oxygen acts as a terminal electron acceptor and petroleum contaminants act as electron donors, which are oxidized. Often, the limiting factor in aerobic bioremediation of petroleum contaminants is oxygen.

Summary of Ex-situ Implementation

The chemistry was designed for the enhanced bioremediation of BTEX compounds found in the groundwater at this site. The majority of the targeted injection area at the site was down gradient of the maintenance building. Twenty-eight direct push injection points received 50 gallons of PermeOx® Plus. Ten direct push points were also cored through the floor of the maintenance building each of these points received 50 gallons. Evidence of oxidant influence was observed during the injection by the increase of key groundwater parameters such as DO, ORP, pH and conductivity in monitoring wells within the plume. Chemical was visually observed in down and side gradient wells.

Effectiveness

Two months following the injection, monitoring wells were purged and sampled for BTEX constituents. Benzene concentrations were reduced from 2,400 ug/l to 19 ug/l in the highest impacted well within the plume. Down and side gradient groundwater monitoring wells were purged and sampled and also showed a significant reduction.

The Bottom Line

ORIN successfully remediated the site by injecting PermeOx® Plus through a series of direct push points over a three-day period. Compared to alternative cleanup approaches, using chemical injection not only reduced site disruption, but also was quicker and cheaper. Performing chemical injection saved the client over $27,000 compared to competitive injection chemistries and over $60,000 for a dig and haul approach.