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<br />reduced to 1” diameter and exits vertically before turning and continuing on to the GAC vessel. The <br />effluent sample port is located between the UV reactor and the GAC contactor. <br /> <br /> <br />Figure 2: Photo of UV/H 2 O 2 Pilot System <br /> <br />The system performance was determined by collecting pairs of water samples from the UV reactor <br />influent and effluent sample ports and analysing contaminant concentrations in these samples. In order to <br />quantitatively determine the system performance it is necessary to have effluent contaminant <br />concentrations that are above the analytical reporting limit. Therefore, many of the proposed test <br />conditions were expected to produce water with measurable contaminant concentrations. <br /> <br />Trojan recommended quenching residual hydrogen peroxide and adsorbing residual contaminants <br />leaving the UV reactor with a granular activated carbon (GAC) contactor. The size of the contactor is <br />typically defined by the empty-bed-contact-time (EBCT) and a minimum of 2 to 4 minutes is <br />recommended for quenching most of the H2 O2 . The City of St. Anthony supplied GAC contactor <br />comprising a 55 gallon drum, shown in Figure 2. The proposed test matrix described below indicates a <br />flow range between 0.5 and 2 gpm and therefore the EBCTs provided range from about 20 minutes to <br />about 80 minutes. This should be more than enough to reduce residual H 2 O 2 leaving the UV reactor to <br />non-detect. <br /> <br /> 7