John Haselow, PhD, PE, Redox Tech, LLC, 1006A Morrisville Parkway, Morrisville, NC 27560, Tel: 919-460-0330, Email: haselow@redox-tech.com
Philip A. Block, PhD, FMC Corporation, 1735 Market St, Philadelphia, PA, 19103, Tel: 215-299-6645, Email: philip_block@fmc.com
Frank Sessa, FMC Corporation, 1735 Market St, Philadelphia, PA, 19103, Tel: 215-299-5993, Email: frank_sessa@fmc.com

Thermally activated sodium persulfate was implemented at a pilot scale as the remedial technology at a former petroleum underground storage tank area located in South Carolina.  Contamination at the site included BTEX, MTBE and naphthalene.  Initial concentrations of the BTEX components were in excess of one ppm, with the MTBE and naphthalene concentrations at 200 ppb.  Air sparging was utilized at the site previously, reducing the contaminants to less than 300 ppb for each of the BTEX constituents, and less than 100 ppb for MTBE and naphthalene respectively.  However, after two years of air-sparging, persistent concentrations remained, predominantly in the central portion of the plume.

Heat activation of the sodium persulfate was achieved by injecting steam into four points around the surrounding persulfate pilot injection well. The steam injection was not continuous, and was injected approximately eight hours per day for the first three days, followed by eight hours a day for two days one week after the first injection.  Approximately ten million BTU’s of thermal energy were injected over the total forty-hour injection period.  Thermocouple monitoring points positioned in four locations around the injection well indicated subsurface temperature increases, in some cases up to 90 º C. 

Samples were collected seventy-two hours after the steam injection period.  The thermally activated persulfate successfully reduced all contaminants to non-detectable levels, or to levels below their regulatory limits.  It was also demonstrated that steam injection was a cost effective approach to activating persulfate, with the entire pilot project costs being $15,000.

Top