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abstract 870

PRETREATMENT OF ACTIVATED SLUDGE BY ULTRASONIC IRRADIATION

Author(s): Rana Kidak, Berthe Ratsimba, Anne-Marie Wilhelm, Henri Delmas
Laboratoire de Genie Chimique, INP-ENSIACET, Site Basso-Cambo, 31106 Toulouse, France

Keyword(s): waste activated sludge, pre-treatment, sonochemistry, power intensity

Article:

Poster:

Session: Poster session 2

AbstractThe waste activated sludge (WAS) is an environmental problem

as it is produced in very large amounts in the wastewater treatment plants. The ultimate solution to this problem is

considered to be the complete stabilization of the organic content, complete disinfection of the pathogenic bacteria

and the reduction of the sludge volume by removing the water portion (initially up to 90%). Catalytic

oxidation is one of the innovative techniques used for sludge treatment. The aim of this study is to provide better

conditions for the catalytic oxidation of sludge treatment by applying ultrasound as a pre-treatment. These

improvements cover the disrupting of the flocs and/or lysing the bacterial cells, leading to a reduction in particle size

in the solution and providing availability of the organic materials for further oxidation. In this study, by using the 20

kHz ultrasonic probe system, we have treated the waste domestic sludge. A gross amount of sludge sample with

25% humidity was obtained from a municipal wastewater treatment plant. An ultrasonic homogenizer Autotune

(Bioblock Scientific), was used as the ultrasonic apparatus. This apparatus was equipped with an ultrasonic probe

and a generator which work with an operating frequency of 20 kHz and the maximum applied power of about

240W. Batch experiments were carried out in a reactor without and without temperature regulation. During the 1

hour treatment process, samples were taken to investigate the chemical kinetics. Several analytical parameters were

investigated through the samples which were obtained from the treated solution before, during and after the treatment

process. These parameters include: solubilized COD, solubilized TOC, dp50 (average particle size diameter) and the

total protein content. In order to observe the changes in the bacterial population of the sludge, we have measured the

protein content in the liquid phase which is an indirect method. The release of the bacterial protein materials into the

liquid phase increases by the application of ultrasound. This difference indicates the disintegration rate of the bacterial

cells. We have observed that under increasing applied power values, the solubilized COD, solubilized TOC and the

protein content in the liquid phase increase up to an applied power intensity of around 50 W/cm2, while the mean

particle diameter is decreased. Further increments in the power intensity provide little improvements in some very

cases but in most of cases it is in vain.

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PRETREATMENT OF ACTIVATED SLUDGE BY ULTRASONIC IRRADIATION