Qualls, R.G., M.H. Dorfman and J.D. Johnson. 1989. Evaluation of the efficiency of ultraviolet disinfection systems. Water Research 23:317-325.

Abstract. One problem in using ultraviolet light (u.v.) for full-scale wastewater disinfection is the difficulty in measuring the dose of u.v. and in monitoring the immediate results of disinfection. A bioassay method for measuring the average u.v. intensity and the residence time distribution (RTD) was tested on two small and two large multiple-lamp u.v. systems. Spore suspensions of u.v. resistant Bacillus subtilis were injected into the u.v. units as a spike and collected at a known time from injection in the effluent so that the exposure time was known. The survival could be related to a standard curve of survival vs u.v. dose. In one unit the bioassay measurements of intensity corresponded so well with the predictions of a method of calculating intensity across a wide range of fluid u.v. absorbance values. The problems with interpreting the results of a continuous flow of the bioassay spores were demonstrated. The measurement of average intensity, RTD, volume of the chamber and the lamp u.v. output enabled us to assign measures of capacity and efficiency to the systems. The analysis illustrated a means of quantitatively isolating the factors involved in the overall efficiency of the disinfection system and a means of comparing different systems.

Key words–ultraviolet light (u.v.), disinfection, modeling, bioassay, flow dispersion, coliform, bacteria, intensity

Reproduced from Water Research, Vol. 23, No.3. Qualls, R.G., M.H. Dorfman and J.D. Johnson. 1989, "Evaluation of the efficiency of ultraviolet disinfection systems", pp. 317-325, 1989, with permission from Elsevier Science.

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