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Table 1: Test Matrix Test No. Flow [H 2 O 2 ] UV Lamps (gpm) (mg/L) (on/off) 1 0.5 0 off 2 0.5 0 on 3 0.5 5 on 4 0.5 10 on 5 0.5 20 on 6 1.0 5 on 7 1.0 10 on 8 1.0 20 on 9 2.0 5 on 10 2.0 10 on 11 2.0 20 on Run number 1 was a control run intended to demonstrate that negligible contaminant reduction occurs in the absence of UV and H 2 O 2 . This test was also intended to validate the integrity of the contaminant and H 2 O 2 stock injection, sample collection, handling and analytical procedures. Run 2 was with no H 2 O 2 and will demonstrate the level of 1,4-dioxane treatment by direct UV photolysis, which was expected to be negligible. The remaining 9 test runs cover 3 H 2 O 2 concentrations and 3 flow rates. Quantitative analysis of the UV AOP system performance is typically based upon measurement of the contaminant log reduction and the system’s electrical energy per order (EEO ) parameter. These parameters require measurable levels of contaminants in both the reactor influent and effluent streams. Therefore, the influent concentration of contaminant must be sufficiently high that the effluent will be comfortably above the analytical detection limit. The influent concentration of contaminants can be adjusted based on the analytical detection limits and the expected log reduction provided by the system. Trojan predicted that up to ~3.5-log reduction of 1,4-dioxane will be provided in Test No. 5. Given an analytical method detection limit for 1,4-dioxane of 0.07 µg/L Trojan planned for a maximum influent 1,4-dioxane concentration of about 200 µg/L. Trojan recommended that a small GAC contactor be installed to both quench residual H 2 O 2 leaving the UV reactor and to adsorb the low µg/L levels of 1,4-dioxane that are expected in the UV reactor effluent. St. Anthony provided a 55 gallon Disposorb™ drum of GAC for this purpose that contained 165 pounds of GAC. The empty-bed-contact-time (EBCT) required for quenching residual H 2 O 2 is approximately 4 minutes or less which would only require about 8 gallons of GAC bed. Therefore, assuming an apparent density of 0.5 g/cc the GAC bed totals 40 gallons and the associated EBCT at 2 gpm would be 20 minutes which is more than adequate for both peroxide quenching and organic adsorption. 4.3 SAMPLE HANDLING AND ANALYSIS The above test matrix presented in Table 1 resulted in the collection of 22 water samples (11 influent & 11 effluent) for analysis of 1,4-dioxane and H 2 O 2 . All the samples to be analysed for 1,4-dioxane were sent to Pace Analytical Services, Inc. in Minneapolis at the completion of the tests on August 27th where they were analysed by EPA method 522 which has an analytical reporting limit of 0.07 µg/L. 9