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Ultraviolet Light Process Model Evaluation Presented by: Jennifer Hartfelder, P.E. Brown and Caldwell

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Models to Evaluate UV Performance USEPA Mathematical Protocol – USEPA Design Manual Municipal Wastewater Disinfection UVDIS – Software Developed by HydroQual, Inc. based on the USEPA Mathematical Protocol NWRI/AWWARF Protocol – Ultraviolet Disinfection Guidelines for Drinking Water and Water Reuse

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UV Process Design Model Chicks Law: N = N o e -kIt N = bacterial concentration remaining after exposure to UV No = initial bacterial concentration k = rate constant I = intensity of UV t = time of exposure

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USEPA - Step 1 Calculate Reactor UV Density

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USEPA - Step 2 Calculate Intensity Biological Assay Direct Calculation Method

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Intensity Field Point Source Summation Method

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Intensity vs. UV Density

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Lamp Configuration

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Average Intensity I avg = (nominal I avg )(F p )(F t ) Fp = the ratio of the actual output of the lamps to the nominal output of the lamps Ft = the ratio of the actual transmittance of the quartz sleeve or Teflon tubes to the nominal transmittance of the enclosure

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USEPA - Step 3 Determine Inactivation Rates K = aI avg b

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USEPA - Step 4 Determine Dispersion Coefficient Establish relationship between x and u h L = c f (x)(u) 2 Plot log(u) and log(x) versus log(ux) Dispersion number, d d = E/(ux) d = 0.03 to 0.05 E = 50 to 200 cm 2 /sec

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USEPA - Step 5 Determine UV Loading Plot log(N/No) vs. Q/Wn and u vs. Q/Wn

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USEPA - Step 6 Establish Performance Goals N p = cSS m N = N - N p

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USEPA - Step 7 Calculate Reactor Sizing Number of lamps required: Q/W n – determined from the log (N/N o ) vs. maximum loading graphs developed in Step 5 for the N developed in Step 6 Lamps required = Q/(Q/W n )/W n

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UVDIS Input Arc length Centerline spacing Watts output Quartz Sleeve Diameter No. of banks in series Aging Factor Fouling Factor Flow Dispersion Coefficient Average Intensity Number of lamps Staggered Percent transmissivity

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UVDIS Output

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NWRI/AWWARF Protocol Determine UV inactivation of selected microorganisms under controlled batch conditions by conducting a bioassay Dose-Response Curves Microorganism MS-2 bacteriophage E. coli Pilot vs. full scale study

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Bioassay Results

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UV Dose German drinking water standard: 40 mW-sec/cm 2 US wastewater industry standard: 30 mW-sec/cm 2 CDPHE WWTP design criteria: 30 mW-sec/cm 2 US reuse standard: mW-sec/cm 2 NWRI/AWWARF based on upstream filtration: Media mW-sec/cm 2 Membrane - 80 mW-sec/cm 2 Reverse Osmosis - 40 mW-sec/cm 2

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Protocol Evaluation For peak hour conditions: Q = 3.5 MGD (9,200 lpm) SS = 45 mg/L N o = 1.50E+06 No./100 mL N = 6,000 No./100 mL Transmittance = 60% Allowable headloss = 1.5 inches

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System Specific Design Criteria ParameterTrojan 3000PlusWedeco TAK55 Arc length (cm) S x (cm)7.613 S y (cm)7.613 D q (cm) W uv (watts) Staggered ArrayNo FtFt 0.7 FpFp

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Number of Bulbs Required Utilizing Various Sizing Methods Sizing MethodTrojan UV3000Plus Wedeco TAK55 USEPA Mathematical Protocol 3525 UVDIS Software Program4240 Bioassay4855 Manufacturers Recommendation 4834

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USEPA Mathematical Protocol Pros Apply same calculations to all systems Can be used for uniform, staggered, concentric, and tubular lamp arrays Cons Least conservative Assumes flow perpendicular to lamp

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UVDIS Pros HydroQual is in the process of updating the program to address some of the cons More conservative than USEPA protocol Cons Less conservative than bioassay For low-pressure systems only For flow parallel to lamps only Dispersion coefficient, E, is assumed

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NWRI/AWWARF Protocol Pros Most conservative May assume a conservative required dose (50 to 100 mW-sec/cm 2 ) Cons Bioassay tests have not been conducted yet for all systems Bioassay is costly Scale-up issues Bioassays have not used the same protocol (i.e., microorganism) More research on how to select required dose is necessary

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Conclusions Bioassay is most conservative sizing method More research required: Dose selection protective of human health Scale-up issues Target organism Engineer should require a field performance test and performance bond

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