Weston Solutions, Inc

Demonstration of Resin Adsorption Techology for Treatment of VOCs in Groundwater

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Aberdeen Proving Ground (APG) has been a center for the development, testing, and manufacture of military-related chemicals since World War I, with industrial activities concentrated in the Canal Creek Area. Groundwater at APG has been impacted by these historical practices. The APG Installation Restoration Program (IRP) is implementing the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) process throughout APG. A Record of Decision (ROD) has been completed for the East Canal Creek Area Plume, specifying groundwater extraction, treatment, and beneficial reuse or discharge of treated water.

Volatile organic compounds (VOCs) are the primary contaminants of concern in the East Canal Creek Area plume. In addition to common commercial solvents such as trichloroethylene (TCE) and its breakdown products, the East Canal Creek Area plume is contaminated with 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA). Based upon preliminary treatability testing during the CERCLA Feasibility Study (FS), the treatment approach specified in the ROD includes precipitation and filtration to remove iron and manganese followed by synthetic resin adsorption with on-site steam regeneration to remove VOCs. The plant was intended to provide a supplemental potable water supply to the base or to discharge to surface water.
A predesign pilot study was conducted to evaluate resin adsorption performance, and support the design of the groundwater treatment plant for the East Canal Creek Area groundwater plume.

The primary pilot test objectives were to confirm the effectiveness of the medium to remove VOCs to levels suitable for potable water beneficial reuse (Safe Drinking Water Act [SDWA] Maximum Contaminant Levels [MCLs], Maximum Contaminant Level Goals [MCLGs], or riskbased standards) or surface water discharge (National Pollutant Discharge Elimination System [NPDES]-equivalent limit, including Ambient Water Quality Criteria), and to define the capacity of the media after multiple exhaustion and regeneration cycles. The pilot plant was constructed at APG, and testing was conducted on groundwater from an existing well within the Canal Creek Area plume. Eight column exhaustion and nine regeneration cycles were completed during the
testing program. The pilot treatment system included pretreatment equipment to remove iron and
manganese from the groundwater followed by two columns, in series, of Ambersorb® 563 media operating in lead-lag mode to increase the treatment run length while producing final effluent containing low to non-detectable VOCs. At or near breakthrough for each test run, the lead column was regenerated with steam to remove the VOCs as a vapor, which was condensed to produce an aqueous and an organic phase. Samples were collected for VOC analysis at the firststage influent and effluent (before and after the lead column) and the final (lag column) effluent.

The principal VOCs found in the supply well for the pilot test were cis- and trans-1,2-dichloroethene (1,2-DCE), TCE, vinyl chloride (VC), and 1,1,2,2-TeCA. The total VOC concentration of the influent ranged between approximately 2,000 µg/L and 3,100 µg/L. VC is a critical parameter in the design and operation of this treatment technology because it is the first to break through the lead column, thereby defining the adsorption capacity. It is also noncondensable during regeneration and requires capture in a vapor control system. Results of the pilot study demonstrate that with proper control of the service cycle and regeneration of the media, the selected treatment train will produce water containing no detectable VOCs for extended periods. The volumetric VOC loading capacity on the resin demonstrated by the pilot test would allow a 22-day service cycle at design contact times after each regeneration. The mass loading capacity for the limiting parameter, VC, in terms of mass VC/ft3 of resin, was proportional to the influent VC concentration, over the range of conditions observed in the pilot test, resulting in a fixed volumetric capacity over the range of expected VC levels. Because trace metals and solids may foul the resin bed, the full-scale design was revised to incorporate a barrier filter to remove micron-size solids from the influent water to the columns. Design, construction, and startup of the facility have been completed and the facility
has been in full-scale operation since April 2003. In the first 11 months of full-scale operation, approximately 71 million gallons of contaminated groundwater were treated with an average total VOC removal efficiency of 96%.

KEYWORDS: 1,1,2,2-Tetrachloroethane, Ambersorb® 563, CERCLA, groundwater treatment, pilot testing, resin adsorption, resin attrition, volatile organic compound.

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