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Dehghani et al. / J Zhejiang Univ Sci B 2007 8(7):493-497493Investigation and evaluation of ultrasound reactor for reduction of fungi from sewage*DEHGHANI Mohammad Hadi, MAHVI Amir Hossein, JAHED Gholam Reza, SHEIKHI Razieh(Department of Environmental Health Engineering, School of Public Health, Medical Sciences/University of Tehran, P.O. Box 14155-6145, Tehran, I.R. Iran)E-mail: [email protected] Received Oct. 19, 2006; revision accepted Mar. 5, 2007Abstract:The objective of the investigation was to study the application of ultrasound reactor technology (USRT) as a disin-fectant for reduction of fungi from sewage effluent. Fungi are carbon heterotrophs that require preformed organic compounds as carbon sources. USRT is an attractive means to improve water quality because of the system simplicity and no production of toxic by-products. An ultrasound reactor produces strong cavitation in aqueous solution causing shock waves and reactive free radicals by the violent collapse of the cavitation bubble. These effects should contribute to the physical disruption of microbial structures and inactivation of organisms. There was significant reduction in fungal growth, with decreased fungal growth with increasing USRT. In this study, ultrasound irradiation at a frequency of 42 kHz was used to expose suspensions of fungi to evaluate the disinfection efficacy of the ultrasound reactor. Also, this study showed that in this system more than 99% reduction of sewage fungi was achieved after 60 min. Key words: Ultrasound reactor, Sewage, Fungi, Cavitation, Frequencydoi:10.1631/jzus.2007.B0493 Document code: A CLC number:X52INTRODUCTION Fungi importance It has been estimated that there are approxi-mately 1.5 million species of fungi and among these approximately 400 species have so far been found to cause disease in humans and animals. Fungi including yeasts and filamentous species or molds are ubiqui-tously distributed, achlorophyllous, heterotrophic organisms with organized nuclei and usually with rigid walls. Fortunately normal healthy individuals rarely suffer from serious fungal diseases; it is im-munocompromised individuals that are at risk of fatal fungal infections. Water used in hospitals to wash burns, flush eyes, mix solutions and other uses where it will come in contact with injured or damaged tis-sues should be sterile. Any water used for people with compromised immune systems must also be sterile since pathogenic fungi are a serious risk for such people (Anon, 2000; Deinega, 1986). Fungi and their spores are ubiquitous. Fungi are present in, and have been recovered from, diverse, remote, and extreme aquatic habitats including lakes, ponds, rivers, streams, estuaries, marine environ-ments, wastewaters, sludge, rural and urban storm water runoff, well waters, acid mine drainage and aquatic sediments (APHA, 1989).

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