Petrox organisms yield cost-effective in-situ soil bioremediation to remove residual petroleum contamination. Instead of ripping up the service station to excavate the soil or installing a slow vapor extraction remediation system, an environmental consultant in east Texas used Petrox microbes to remove high concentrations of benzene and xylene from soil at a gas station. Petrox bioremediation saved the property owner time and money.
Benzene and xylene contaminated shallow soil at concentrations of 230 mg/kg and 9,200 mg/kg respectively. Although benzene drove the environmental risk up, xylene, which has a high soil absorption factor, can be more difficult to remediate. Vapor extraction would have had problems extracting xylene from the sandy, clay soil.
Petroleum metabolism, including benzene and xylene, requires oxygen. A calcium peroxide compound was added to supplement the natural oxygen for Petrox metabolism.
The treatment area was 500 square feet with an assumed treatment depth to 11 feet. The consultant injected 220 gallons of hydrated Petrox solution and 25 pounds of calcium peroxide.
Post-treatment sampling showed the contaminant concentrations decreased by 97% in less than 90 days. The benzene concentration dropped from 230 to 4.0 mg/kg. The xylene concentration decreased from 9,200 to 309 mg/kg.
The Petrox and calcium peroxide materials cost was less than $6,000. On top of the cost savings, bioremediation did not interrupt business operations.