Wastewater pretreatment with ultrasonic irradiation to reduce toxicity

In order to industrialize an ultrasonic process for wastewater treatment, s everal works were undertaken. The first one was the study of pentachlorophe nol degradation [E. Gonze, Y. Gonthier, P. Boldo and A. Bernis, Can. J. Che m. Eng. 75 (1997) 245]. Association of high-frequency ultrasound transducer s was investigated [E. Gonze, Y. Gonthier, P. Boldo and A. Bernis, Entropie 204 (1997) 21] and the mapping of ultrasonic fields in various reactors wa s studied [E. Gonze, Y. Gonthier, P. Boldo and A. Bernis, Chem. Eng. Sci. 5 3 (1998) 523; V. Renaudin, N. Gondrexon, P. Boldo, C. Petrier, A. Bernis an d Y. Gonthier, Ultrasonics Sonochem. 1 (1994) S81]. The third step presente d here consists of considering the ultrasonic process as a preoxidation tre atment before a classical biological purification. During the ultrasonic ir radiation of a sodium pentachlorophenate solution (NaPCP), the concentratio n of NaPCP, the acute toxicity effects on bacteria (Vibrio fischeri) and on daphnids (Daphnia magna) as well as the biodegradability of the pollutant solution were simultaneously monitored. Experimental results provide eviden ce that an ultrasonic treatment is an efficient preoxidation step. (C) 1999 Elsevier Science S.A. All rights reserved.