Abstract

Use of Ultrasound in Waste Water Treatment

O.V.Abramov, V.M.Kuznetsov (Institute of General and Inorganic Chemistry of RAS, Moscow, Russia); C.Stoll (KACU, Germany)

e-mail: LUTT@IGIC.RAS.RU

The possibilities of the use of ultrasound for purification of waste water contaminated with organic substances (nitroaromatic compounds, o-chlorophenol), heavy metals (Сd, Zn, Cu, Pb) and petroleum products (toluene, С6 . С14) are analyzed. For effect on waste water, ultrasonic vibrations of frequency 24 . 1.5 kHz at the density of acoustic energy introduced into a liquid phase up to 2 W/l were used. In a number of cases, ultrasonic irradiation was combined with electrocoagulation, low-current electrolysis, and introduction of coagulants, flocculants and oxidants (hydrogen peroxide, oxygen, ozone) into the liquid under treatment. Experiments have shown that in an ultrasonic field the rate of the process of purification from heavy metals (Сd, Zn, Cu, Pb) by electrocoagulation is increased by a factor of 2.3 in comparison with that in a reference series. The efficiency of the effect of ultrasound on the process of the purification of waste water from dyes depends on current density: in an optimum case (J = 2.4 mА/cm2) the rate of the decolorization of waste water in the ultrasonic field is raised by a factor of up to 5.8 as compared with that in the absence of ultrasound. In the purification of waste water from petroleum products by reagent method (using an alumosilicon flocculant-coagulant . ASFC), the rate and degree of purification in the ultrasonic field is increased by a factor of 3 in comparison with those in a reference series. This allows one to decrease the consumption of coagulant and the time of waste water purification from petroleum products by reagent method. To remove the dyes and organic substances that are most resistant to oxidation (dinitroaromatic compounds, chlorophenol), such oxidative systems as H2O2/catalyst, O3, etc. are used. In the ultrasonic field the rate of the oxidation destruction of chlorophenol with H2O2/Fe(II) is raised by only 10 . 20 %. A significant increase in the rate of the oxidation destruction of dinitrobenzene and dinitrotoluene is observed only during joint use of low-current electrolysis and ozone treatment in the ultrasonic field.

Section : 11