(519b) Economic Assessment for Replacement of Granular Activated Carbon Treatment of Groundwater at Two Treatment Plants at Former Kelly Air Force Base

Extracted groundwater from hazardous waste sites undergoing remediation at the former Kelly AFB is treated for volatile organic compounds (VOCs) by ultraviolet oxidation (UV/Ox) at three different groundwater treatment plants. One of the treatment plants has utilized UV/Ox for VOC treatment for over ten years, and the current VOC levels in the extracted groundwater are relatively low (part per billion levels) at all plants. The electrical and bulb replacement costs for operation and maintenance (O&M) of the UV/Ox systems are high. As a result of a Remedial Process Optimization performed by the AF for former Kelly AFB, an evaluation to consider replacement of the UV/Ox treatment with a less costly process such as granular activated carbon (GAC) was recommended.

Pilot studies and detailed economic comparisons were performed to complete the evaluation. Adsorption isotherm data and carbon usage equations were used to predict the rate of GAC usage, and thus the primary O&M cost for comparison to the existing UV/Ox O&M costs. The costs for GAC only treatment were found to be significantly less than that for UV/Ox for the treatment of VOCs in groundwater at two plants. Therefore, designs were prepared for plant modifications to changeover to GAC only treatment. At the larger plant, a full-scale pilot test was performed to verify the GAC usage rate predicted, and to confirm the ability of GAC only treatment to consistently attain the discharge limits under which this plant operates.