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ABSTRACT
A multiphase inactivation model of an advanced oxidation process that uses O3/UV was developed and successfully validated with pilot-scale experiments. Using the inactivation rate constants and dispersion number estimated from the pilot-scale experiments, the inactivation efficacy of O3/UV under full-scale conditions was predicted. Uncertainty analysis in quantitative microbial risk assessment was performed to examine the impact of the hydraulic conditions of the O3/UV contactor. It was demonstrated that the estimation of the dispersion number in the full-scale contactor is necessary to improve the accuracy of the risk estimates.
Nomenclature
The following symbols are used in this article:
| d = | = | dispersion number (dimensionless); |
| kdw = | = | water-quality-dependent ozone decomposition rate constant (1/s); |
| kdUV = | = | ozone decomposition rate constant by UV irradiation (1/s); |
| kD = | = | overall first-order ozone decomposition rate constant (1/s); |
| = | inactivation rate constant by ozonation (L/(mg·s)); | |
| = | inactivation rate constant by UV (cm2/mJ); | |
| H = | = | depth of water column in contactor (m); |
| L = | = | length of lamp (m); |
| R = | = | inner radius of contactor (cm); |
| r = | = | optical path length (cm); |
| r0 = | = | outer radius of the quartz tube (cm); |
| = | ozone molecule molar absorption coefficient at 254 nm; | |
| I = | = | mean volume UV fluence rate (mW/cm2); |
| = | water absorption coefficient at 254 nm using logarithms to the base e (1/cm); | |
| P = | = | UV254 light output (W); |
| = | mean hydraulic residence time (min); | |
| J = | = | UV fluence (mJ/cm2); |
| I = | = | UV fluence rate (mW/cm2); |
| QL = | = | water flow rate (m3/h); |
| UL = | = | water approach velocity (m/h); |
| QG = | = | gas flow rate (m3/h); |
| UG = | = | gas approach velocity (m/h); |
| CL,0 = | = | dissolved ozone concentration in influent water (mg/L); |
| CL = | = | dissolved ozone concentration (mg/L); |
| CG,0 = | = | gas phase ozone concentration entering the contactor (mg/L); |
| CG = | = | gas phase ozone concentration (mg/L); |
| N0 = | = | initial E. coli concentration in influent water (CFU/mL); |
| N = | = | viable E. coli concentration (CFU/mL); |
| T = | = | temperature; |
| m = | = | Henry’s law constant (dimensionless); |
| kLa = | = | volumetric mass transfer coefficient (1/s); |
| dB,0 = | = | average bubble diameter with UG = 0 (cm); |
| dB = | = | average bubble diameter (cm); |
| VB = | = | bubble rise velocity (cm/s); |
| μL = | = | absolute viscosity of liquid phase (cP); |
| Sh = | = | Sherwood number (dimensionless); |
| RG = | = | gas phase Reynolds number (dimensionless); |
| ScL = | = | liquid phase Schmidt number (dimensionless); |
| νL = | = | kinematic viscosity of liquid phase (cm2/s); |
| g = | = | gravitational constant (m/s2); |
| DL = | = | molecular diffusivity of ozone in water (m2/s); |