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<br />E EO is a reactor, contaminant, and water-quality specific metric and the figure of merit accepted by the <br />Photochemistry Commission of the International Union of Pure and Applied Chemistry for UV- <br />photolysis/UV-oxidation technologies. It is a measure of the efficiency with which a given <br />contaminant is treated by UV-photolysis and UV-oxidation. Different contaminants will have <br />different E EO values in the same UV reactor in water with the same water quality. Different reactors <br />will have different E EO values as the term measures a UV reactor’s hydraulic, optical and electrical <br />efficiency (when comparing two reactors treating the same contaminant under the same conditions). <br />E EO is directly proportional to the required power draw: the lower the E EO , the lower the power <br />required by the system. The following formula can be used to compute the E EO of a UV treatment <br />system in units of kWh/kgal/order with flow in gallons per minute (gpm) and power draw in kilowatts <br />(kW): <br /> <br /> <br /> <br /> <br />×× <br />= <br /> <br /> <br /> <br /> <br /> <br />• <br />C <br />Cgpmflowrate <br />kWdrawpowerreactormeasured <br />orderkgal <br />kWhE <br />o <br />EO <br />log06.0)( <br />)( <br /> Where <br />• 0.06 is a conversion factor that converts minutes to hours and <br /> normalizes the flow rate on a 1000-gallon basis <br />• C o is the concentration of contaminant at the influent of the reactor <br />• C f is the concentration of contaminant at the effluent of the reactor <br /> <br />In general, the energy required to reduce the contaminant initially by 90% is the same as the energy <br />required to treat 90% of the remaining contaminant, for a total of 99% reduction (log-linear kinetics). <br />In other words, the same energy is needed to reduce 100 units of contaminant to 10 units of <br />contaminant as is needed to reduce 10 units of contaminant to 1 unit of contaminant. <br />A related term to E EO is the electrical energy dose (EED) which is determined by dividing the system <br />power draw (kW) by the flow rate. Typical units of EED are kWh/kgal or kWh/m3. <br /> <br /> <br /> <br />2.3.1 Parameters affecting EEO <br /> <br />• Reactor design. Different reactors (even those using the same type of lamp) can have <br />significantly different E EO values for a given water and contaminant. This is due to reactor <br />characteristics such as lamp spacing, lamp orientation, and location of influent/effluent ports. <br />Therefore, E EO is a reactor-specific measure. The implications of this are that project <br />specifications cannot specify design E EO values as they will differ from UV system to UV <br />system. <br />• Reactor Lamp Type. Properties of the lamp such as UVC power conversion efficiency and <br />emittance spectrum can have a significant impact on E EO . <br />• Water quality. Water quality parameters that impact E EO are: <br />– UV transmittance (UVT): E EO increases as UVT decreases. That is, as the water <br />becomes less transmissive to UV light, more power is required to achieve a desired <br />log reduction in the contaminant concentration. <br />– Hydroxyl radical scavenging demand: E EO increases as the hydroxyl radical <br />scavenging demand of the water increases. That is, with greater competition for <br /> 4