1049 Research Article Received: 31 October 2009 Revised: 29 November 2009 Accepted: 11 December 2009 Published online in Wiley Interscience: 12 April 2010 (www.interscience.wiley.com) DOI 10.1002/jctb.2396 Peracetic acid-enhanced photocatalytic and sonophotocatalytic inactivation of E. coli in aqueous suspensions Catherine Drosou, a Alberto Coz, a,b Nikolaos P. Xekoukoulotakis, a Armando Moya, c Yolanda Vergara c and Dionissios Mantzavinos a* Abstract BACKGROUND: Although chlorination is an effective and widely employed method of water disinfection, it suffers serious drawbacks such as the formation of toxic chlorinated by-products. Therefore, other disinfection technologies have been researched and developed, including advanced oxidation. RESULTS: The efficacy of heterogeneous photocatalysis and sonophotocatalysis induced by UV-A irradiation and low frequency (24–80 kHz) ultrasound irradiation in the presence of TiO 2 as the photocatalyst and peracetic acid (PAA) as an additional disinfectant to inactivate E. coli in sterile water was evaluated. PAA-assisted UV-A/TiO 2 photocatalysis generally leads to nearly complete E. coli inactivation in 10 – 20 min of contact time with the extent of inactivation depending on the photocatalyst type and loading (in the range 100 – 500 mg L -1 ) and PAA concentration (in the range 0.5 – 2 mg L -1 ). The simultaneous application of ultrasound and UV-A irradiation in the presence of TiO 2 and PAA prompted further E. coli inactivation. CONCLUSIONS: The proposed advanced disinfection technology offers complete E. coli inactivation at short treatment times and low PAA doses. c  2010 Society of Chemical Industry Keywords: peracetic acid; E. coli; TiO 2 ; photocatalysis; sonolysis; disinfection INTRODUCTION The most important issue in water disinfection is, of course, safe drinking water. According to the WHO and UNICEF, polluted drinking water and lack of sanitation are responsible for the death of approximately 4500–5000 children every day, and one billion people still lack access to safe drinking water. 1 The disinfection agents commonly used at drinking water and wastewater treatment plants are chlorine and its related compounds. However, in the early 1970s, it was found that chlorine reacts with the natural organic matter present in water and wastewater to produce various undesirable chlorinated disinfection by-products (DBPs). 2 Additionally, they cannot inactivate totally all the pathogenic microorganisms (like protozoa) that may be present in wastewaters or drinking water owing to their low oxidative action. 3 Another drawback of water chlorination is associated with taste and odour problems caused not only by chlorine itself but also from odorous DBPs. 4 Other common disinfection methods such as UV-C irradiation, ozonation and membrane filtration suffer other problems; for instance, the performance of UV-C irradiation is affected adversely by water turbidity, ozone disinfection has high capital, operating and maintenance costs, while membrane fouling can necessitate frequent backwashing and chemical cleaning procedures. In addition, membrane technologies require monitoring and continuous maintenance to assure integrity. 5 As a result of these problems, ongoing research is focused on the development of alternative disinfection methods. Granular activated carbon doped with silver has been proven an effective means for E. coli inactivation in water due to the biocide action of silver. 6 Nonetheless, the long-term stability of the adsorbent has been an issue of concern. In recent years, advanced oxidation processes (AOPs) have received considerable attention for the degradation of organic contaminants, as well as the inactivation of pathogens in waters and wastewaters. 7 AOPs find useful applica- tions for the simultaneous (i) removal of emerging contaminants, like endocrine disrupting compounds 8,9 and pharmaceutical and personal care products, 10 and (ii) disinfection in surface waters and groundwaters destined for potable water production, as well as in secondary treated municipal effluents destined for reuse. Het- erogeneous photocatalysis based on TiO 2 semiconductors and homogeneous photo-Fenton systems induced by artificial or solar ∗ Correspondence to: Dionissios Mantzavinos, Department of Environmental Engineering, Technical University of Crete, Polytechneioupolis, GR-73100 Chania, Greece. E-mail: mantzavi@mred.tuc.gr a Department of Environmental Engineering, Technical University of Crete, Polytechneioupolis, GR-73100 Chania, Greece b Department of Chemical Engineering and Inorganic Chemistry, University of Cantabria, ETSII y T. Avda Los Castros s/n, 39005 Santander, Spain c OX-CTA S.L., Parque Tecnol´ ogico de Walqa, Edificio CEEI ARAG ´ ON, Ctra. Zaragoza, km 67 en Cuarte (Huesca) D.P. 22197, C.I.F. 60870433, Spain J Chem Technol Biotechnol 2010; 85: 1049–1053 www.soci.org c  2010 Society of Chemical Industry