In Well Air Stripping at Two Dry Cleaners, Various Locations

Site Name:

Multiple (2) Dry Cleaners - In Well Air Stripping


- Schloff Chemicals and Supply Company, Inc., St. Louis Park, MN
- Former Base Laundry & Drycleaning Facility, Orlando, FL

Period of

- Schloff: September 1994
- Former Base: December 10, 1997


Full scale

IWAS - UVB; Pump & Treat (P&T)
- Two UVB wells installed
- Water being pumped into the UVB-200-1 reactor at 4 m3/h, and back into the two UVB-200-2 stripping reactors at 2 m3/h

Former Base:
- Two UVB wells installed 300 ft downgradient of the facility, approximately 85 ft apart; wells constructed of 10-inch diameter schedule 80 PVC with two stainless steel screens (0.01-inch slots)
- Contaminated groundwater was extracted through the upper screen (3.5 -12.5 ft bgs - upper surficial aquifer)
- Water was treated in an in-well stripping unit installed on the top of the wellhead.
- Treated water was injected through the lower screen interval (39-45 ft bgs - lower surficial aquifer)
- Design flow rate for each submersible pump was 40 gpm
- VOC emissions from the system were estimated to be approximately 2.0 lbs/day; therefore no emissions treatment was installed

Cleanup Authority:

Varied by site

Tetrachloroethene (PCE); Trichloroethene (TCE); Volatiles-Halogenated
- Schloff: PCE - 7,800 µg/L; TCE - 240 µg/L
- Former Base: Groundwater - PCE - 34,000 µg/L; TCE - 15,000 µg/L; Soil - PCE - 430 µg/kg; TCE - 27 µg/kg; plume size - 245,000 ft2

Waste Source:
Waste and wastewater from drycleaning operations

Type/Quantity of Media Treated:
Groundwater, Soil

- Depth to groundwater: 8 - 12 ft bgs
- Subsurface geology: 0-27 ft fine to coarse grained sand; 27-75 ft bedrock
- Aquifer conductivity: 0.5 - 25.2 ft/day
- Groundwater gradient: 0.004 - 0.005 ft/ft
Former Base:
- Depth to groundwater: 3.3 - 10.1 ft bgs
- Subsurface geology: (Upper surficial aquifer) 0-17 ft bgs fine-grained sand; 17-20 ft bgs moderately to well indurated silty, fine-grained sand. (Lower surficial aquifer) 20-54 ft bgs fine-grained sand; 54-71 ft bgs silty, fine, fine to coarse sand with phosphate nodules and shells; 71 - depth of investigation silty, clayey sand with clay interbeds
- Aquifer conductivity: Upper surficial aquifer - 10 ft/day; Lower surficial aquifer - 40 ft/day
- Groundwater gradient: 0.008 ft/ft

Purpose/Significance of Application:
Use of IWAS to treat chlorinated solvents in groundwater at dry cleaner facilities

Regulatory Requirements/Cleanup Goals:
Not provided

Former Base: Groundwater (MCLs) PCE - 3 µg/L; TCE - 3 µg/L; cis 1,2-DCE - 70 µg/L

Not provided

Former Base:
Results not available because the system could not achieve design pumping rates and therefore, did not achieve capture of the downgradient portion of the contaminant plume.

Cost Factors:
- Schloff: $773,716 (total cost as of 1999)
- Former Base: Not available

In Well Air Stripping (IWAS) - UVB was implemented at full scale at Schloff Chemicals in Minnesota and Former Base Laundry in Florida. The contaminants at the sites were mainly halogenated volatiles, including PCE and TCE. PCE was found in groundwater at concentrations as high as 34,000 µg/L, and TCE as high as 15,000 µg/L. In the soil, concentrations of PCE and TCE were 430 µg/kg and 27 µg/kg, respectively.

The application of UVB technology at Schloff was the first application of its kind in the state of Minnesota. However, results were not provided for the project. At Former Base, results were not available because the system could not achieve design pumping rates. The system had many operational and maintenance problems including silt/sand entering the well screens, failed packers, biofouling, precipitation, and problems associated with equalizing influent and effluent pumping rates.