Enhanced photo-sono process for disinfection of surface and subsurface water

Existing water disinfection processes, such as chlorination, have frequently failed to comply with the Safe Drinking Water Standards because of the formation of disinfectant byproducts (DBPs). The DBP problem underscores the need to develop a safe and reliable disinfection process to overcome the drawbacks inherent in the use of chemical disinfectants.; The formation of undesirable DBPs can be prevented by using ultraviolet light (UV), which can inactivate microorganisms by damaging their DNA. The major disadvantages of UV disinfection are: (1) UV intensity decreases sharply with its passage in water and its decrease is even more significant with high water turbidity; (2) microorganisms attached (hidden) to the suspended particles may escape UV irradiation, reducing the UV treatment efficiency; and (3) microbial DNA, once damaged by UV, can be repaired via enzyme repair systems (e.g., photolyase and excision repair), resulting in survival of the microorganisms.; In this study, the efficacy of the water disinfection process using UV in conjunction with ultrasound (US) was investigated. A series of experiments were carried out in a reactor equipped with UV and US sources to test the following hypotheses: Hypothesis 1 - The disinfection kinetics of UV, US, and the combination of UV and US (UVUS) is first-order or pseudo first-order; Hypothesis 2 - UV and US interact synergistically to enhance the disinfection efficiency.; The bench-scale reactor was run in batch and flow-through modes. Water containing Escherichia coli (K12 strains) was exposed to UV, US, and UVUS in the reactor. Water samples exposed to UV, US, or UVUS in the reactor were withdrawn periodically from the effluent sampling ports for microbial analysis. Culturable bacterial counts were performed to evaluate the germicidal efficiency of UV, US, and UVUS for batch and flow through reactor. The inactivation rate constant of the disinfection kinetics were evaluated from the experimental data by employing the reactor modeling approach. The results obtained suggest that the inactivation rates by UV, US, and UVUS follow the pseudo first-order kinetics, and that UVUS produces the synergistic effect on inactivation of E. coli.