Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/2425
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Title: Disinfection of municipal wastewater by sensitized photooxidation
Authors: Li, XZ
Zhang, M
Chua, H
Issue Date: 1996
Source: Water science and technology, 1996, v. 33, no. 3, p. 111-118
Abstract: To optimize the disinfection of treated municipal wastewater by sensitized photo-oxidation as a new alternative disinfection method, secondary unchlorinated activated-sludge-treated effluents from a sewage treatment plant were treated by semiconductor-sensitized photo-oxidation. Experiments of disinfection were performed in a photo-reactor system, which is a cylindrical borosilicon glass reactor with an effective volume of 1.1 litre. A NEC black light lamp (T10 20W) is placed at the centre of the reactor as an artificial light source to provide near UV irradiation with a maximum intensity at 350 nm. Hydraulic retention time (HRT) was used up to 60 minutes in this study. The effluents, after adding titanium dioxide as sensitizer, were exposed to the illumination of near UV light for various irradiation time and incident light intensities. Number of bacteria and coliforms were significantly declined from 35,000/100 ml to 59/100 ml after 60 minutes treatment, with existing of titanium dioxide, light irradiation and aeration. After the photo-oxidation process, the titanium dioxide in the treated effluent was separated by precipitation. The influence of light energy from 5.2 to 45 W/mᒾ, absorbed by the sensitizer in the visible range, on micro-organisms in secondary effluents was determined by testing for Escherichia. coli (E. coli) and total coliforms. An optimum titanium dioxide concentration found in the test is about 1 g/L. While the destruction rate of E. coli was affected by pH, dissolved oxygen (DO) and temperature (T), it was found that number of bacteria destroyed during disinfection mainly depends on incident light intensity (I₀) and irradiation time (t), which follows an exponential relationship. A kinetic model has been developed using the product of I₀ and t defined as a Dose Number (D) for this disinfection reaction.
Keywords: Disinfection
Photo-oxidation
Sensitized
Sensitizer
Semi-conductor
Titanium dioxide
Wastewater
Sewage
Treatment
Kinetics
Publisher: Elsevier Science Ltd on behalf of the IAWQ
Journal: Water science and technology 
ISSN: 0273-1223
DOI: 10.1016/0273-1223(96)00305-8
Rights: © IAWQ 1996. The definitive peer-reviewed and edited version of this article is published in Water Science and Technology, v. 33, no. 3, p. 111-118, 1996 and is available at www.iwapublishing.com.
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