Ultraviolet Light Process Model Evaluation Presented by: Jennifer Hartfelder, P.E. Brown and...
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Transcript of Ultraviolet Light Process Model Evaluation Presented by: Jennifer Hartfelder, P.E. Brown and...
Ultraviolet Light Process Model Evaluation
Presented by:
Jennifer Hartfelder, P.E.
Brown and Caldwell
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
UV Process Design Model
Chick’s Law: N = Noe-kIt
N = bacterial concentration remaining after exposure to UV
No = initial bacterial concentration k = rate constant I = intensity of UV t = time of exposure
USEPA - Step 1Calculate Reactor UV Density
1. Liquid volume per lamp:
z
4
d - zs
lamp
V2q2v
2. Density:
lamp
Voutput UVnominalz
Dv
USEPA - Step 2Calculate Intensity
Biological Assay Direct Calculation Method
Intensity FieldPoint Source Summation Method
Intensity vs. UV Density
Lamp Configuration
Average Intensity
Iavg = (nominal Iavg)(Fp)(Ft)
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
USEPA - Step 3Determine Inactivation Rates
K = aIavgb
USEPA - Step 4Determine Dispersion Coefficient
Establish relationship between x and u hL = cf(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 cm2/sec
USEPA - Step 5Determine UV Loading
n
n
v
n
W
Q
W
V
t
2/1
2
o
'
u
KE411E2
uxexp
N
N
Plot log(N’/No) vs. Q/Wn and u vs. Q/Wn
USEPA - Step 6Establish Performance Goals
Np = cSSm
N’ = N - Np
USEPA - Step 7Calculate Reactor Sizing
Number of lamps required: Q/Wn – determined from the log (N’/No) vs.
maximum loading graphs developed in Step 5 for the N’ developed in Step 6
Lamps required = Q/(Q/Wn)/Wn
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
UVDIS Output
NWRI/AWWARF Protocol
Determine UV inactivation of selected microorganisms under controlled batch conditions by conducting a bioassay Dose-Response Curves Microorganism
MS-2 bacteriophageE. coli
Pilot vs. full scale study
Bioassay Results
UV Dose
German drinking water standard: 40 mW-sec/cm2
US wastewater industry standard: 30 mW-sec/cm2
CDPHE WWTP design criteria: 30 mW-sec/cm2
US reuse standard: 50 - 100 mW-sec/cm2
NWRI/AWWARF based on upstream filtration: Media - 100 mW-sec/cm2
Membrane - 80 mW-sec/cm2
Reverse Osmosis - 40 mW-sec/cm2
Protocol Evaluation
For peak hour conditions: Q = 3.5 MGD (9,200 lpm) SS = 45 mg/L No = 1.50E+06 No./100 mL N = 6,000 No./100 mL Transmittance = 60% Allowable headloss = 1.5 inches
System Specific Design Criteria
Parameter Trojan 3000Plus Wedeco TAK55
Arc length (cm) 147 143
Sx (cm) 7.6 13
Sy (cm) 7.6 13
Dq (cm) 1.5 4.8
Wuv (watts) 100 125
Staggered Array No No
Ft 0.7 0.7
Fp 0.7 0.7
Number of Bulbs Required Utilizing Various Sizing Methods
Sizing Method Trojan UV3000Plus
Wedeco TAK55
USEPA Mathematical Protocol
35 25
UVDIS Software Program 42 40
Bioassay 48 55
Manufacturer’s Recommendation
48 34
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
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
NWRI/AWWARF Protocol
Pros Most conservative May assume a
conservative required dose (50 to 100 mW-sec/cm2)
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
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