Quantitative Characterization and Prediction Modeling of Photoreactivation of Coliforms After Ultraviolet Disinfection of Reclaimed Municipal Wastewater
2013
Guo, Mei-Ting | Huang, Jing-Jing | Hu, Hong-Ying | Liu, Wen-Jun | Yang, Jian
Photoreactivation is considered to be one of the principal disadvantages of the application of ultraviolet disinfection, but knowledge about the photoreactivation potential is limited since few studies to model photoreactivation have been carried out. In order to develop a model for the prediction of the photoreactivation potential, the photoreactivation of Escherichia coli, fecal coliforms, and total coliforms in the tertiary effluent of a wastewater treatment plant was investigated using traditional plate count methods in this study. The tested bacteria were exposed to various UV doses (5-80 mJ/cm2) with a low-pressure UV-collimated beam apparatus and then put under sunlight lamp to experience photoreactivation for up to 72 h. All tested bacteria underwent photoreactivation with a similar trend. When the UV dose increased from 5 to 20 mJ/cm2, the maximum reactivation value of E. coli decreased from 105 to 10 CFU/mL over 8 h, and the reactivation rate decreased from 3.6 to 3.0 × 10-4/h. Based on the photoreactivation results, an exponential model was developed to predict the possible maximum photoreactivation level (N m = αD - β N 0). This simple photoreactivation potential prediction model contains only two variables (UV dose and initial bacterial count), with two constants related to the microorganism species. This model can be easily generalized and is helpful for the optimum design of UV disinfection systems. © 2013 Springer Science+Business Media Dordrecht.
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