GeoHydrologic Consultants, Inc. performed ozone sparging tests at two separate gas station sites in Garden Grove, California to remediate petroleum hydrocarbon impacted groundwater, with tert butyl alcohol(TBA) being the primary target compound. The first site (Site A) contained pre-ozone sparging TBA groundwater concentrations at a maximum of 5,820 µg/L. Two separate ozone sparging events were performed at this site, with the first taking place for approximately one month in late 2004, followed by a second three
month long event in the third quarter of 2005. Concentrations of TBA at the conclusion of the first test were reduced from 2,920 µg/L in well MW-3 to 234 µg/L, reduced from 5,820 µg/L in EW-1 to 1,820 µg/L, and reduced in well MW-5 from 356 µg/L to <10 µg/L. At the
conclusion of the second test TBA concentrations were further reduced to 28 µg/L in MW-3, 73 µg/L in EW-1, and remained <10 µg/L in MW-5. The second site (Site B) had pre-ozone sparging TBA concentrations in groundwater at a maximum of 4,450 µg/L. Ozone injection was
performed for approximately 47 days. TBA was reduced in well RS-5R form 337 µg/L to 180 µg/L, in MW-12 from 4,450 µg/L to 3,100 µg/L, and MW-11R from 707 µg/L to <10 µg/L. Ozone sparging for treatment of TBA in groundwater appeared to be very successful at both Sites.
Groundwater in areas where gas stations are located has shown to be contaiminated by petroleum hydrocarbon which contains tert butyl alcohol. Two locations in Garden Grove, CA underwent remediation using vapor extraction and pump and treat. Despite the remediation performed tert butyl alcohol were not at acceptable regulatory levels. Ozone has shown to be effective in destroying tert butyl alcohol and is often used in above ground remediation. It was decided to test the effectiveness of ozone in underground remediation.
Ozone sparging remediation systems were installed at two sites. At the first site the generator was programmed to inject into sparge point 1 for 30 minutes, then sparge point 2 for 30 minutes, and then stopping for 20 minutes before repeating. This was performed 18 times each day for a total of 9 hours a day. At the second site the ozone generator was programmed to inject ozone in each sparge points for 10 minutes, or 8 sparge points for 3 hours a day.
At the first site ozone sparging for almost four months resulted in large reductions in groundwater hydrocarbon concentrations, including MTBE and tert butyl alcohol (TBA). At the second site, after ozone sparging for a month, the results were similar with groundwater hydrocarbon concentrations reduced. The tests demonstrated that ozone sparging for underground water remediation is effective.
Richard A. Vogl
GeoHydrologic Consultants, Inc, 5912 Bolsa Ave, Suite 200
Hungington Beach, CA 92649, USA