Full Description

Existing water disinfection processes, such as chlorination, have frequentlyfailed to comply with the Safe Drinking Water Standards because of the formation ofdisinfectant byproducts (DBP). The formation of undesirable DBPs can be prevented byusing ultraviolet light (UV), which can inactivate microorganisms by damaging theirDNA. The major disadvantages of UV disinfection are: UV intensity decreasessharply with its passage in water and its decrease is even more significant with high waterturbidity; microorganisms attached (hidden) to suspended particles may escape UVirradiation reducing the UV treatment efficiency; and, microbial DNA, once damagedby UV, can be repaired via enzyme repair systems (e.g., photlyase and excision repair)resulting in survival of the microorganisms. In this study, a water disinfection processusing UV in conjunction with ultrasound (US) was investigated. A series of experimentswere carried out to test the following hypotheses: Hypothesis 1 - UV and US interactsynergistically to enhance the disinfection efficiency; Hypothesis 2 - the rates ofdisinfection by UV, US, and their combination (UVUS) follow the first order or pseudo-first-order kinetics. Experiments were performed in a 4-liter batch reactor equipped withUV and US sources. Water containing Escherichia coli (K-12 strains), as surrogatebacteria, was run through the reactor. Using the total viable count data and mathematicalmodel, the inactivation rate constants, kuv, kus, and kuvus for the UV, US, and UVUStreatments, respectively, were determined. The results suggest that the combined effect ofUV and US are likely synergistic, and that the rate of inactivation by UV, US, and UVUScan be explained by the first-order kinetics. Includes 12 references, table, figures.

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Edition: Vol. - No. Published: 06/01/2007 Number of Pages: 43File Size: 1 file , 1.3 MB