Physico-Chemical Effluent Treatment

The effectivity of oxidation processes initiated by radicals, created by heterogeneous catalysis and by high pressure process

Wet oxidation offers a possibility to reduce the pollutant content in the water. Alternative wet oxidation processes with heterogeneous catalysis and cavitation initiation are developed. The catalytic process is able to lower the pollutant content of highly contaminated sewages up to 70 %. The process is convinient for industrial use. Cavitation reduces the pollution level only up to 30 %. So the use of cavitation in industrial scale sewage cleaning plants under the parameter conditions tested in the project has no chance to be realized in the industrial practice as by technical as by economical reasons. 

Summary

Persistent and highly toxic sewages with an extremely high content of substances are still a problem in the waste water management. Wet oxidation offers a possibility to reduce the pollutant content in the water. Comparative experiments of the efficiency of oxidation initiated by radicals were carried out, using as heterogeneous catalysis on strap catalyst base as cavitation.

Results:

Heterogeneous catalysis

By means of the wet oxidation on strap catalyst base with H2O2 as oxidation reagent it was possible to decontaminate effectively as single pollutants in model sewages as complex mixtures in real sewages.

The tested catalytic systems worked especially effectively for high pollutant concentrations. At lower concentrations of sewage pollutants the amount of H2O2 must be increased in regard to the actual CSB. In real sewages the pollutant decrease was, related on the TOC, in the cut, at 50%, a raise of the average concentration of the oxidation agent didn’t produce any further decrease of the pollutant concentration. Aromatic hydrocarbons could be reduced more effectively than aliphatic ones.

The conception for a technical plant was developed including cost estimate.

Cavitation

The reduction of pollutants by cavitation was fundamentally lower than by using the heterogeneous catalysis way. Without addition of an oxidation agent (i.e. H2O2) only a TOC decrease of approx. 15% was registered in real sewages. The pollutant reduction increased a higher pollutant concentration. A complete elimination of all pollutants could not be obtained in none of the examined cases neither at model nor at real sewages.

Especially the long reaction times (6 to 24 h) of the cavitation process in comparison with those, necessary for the catalytic reaction (2 to 6 h) are hindering a technical realization of the cavitation process, which seems to be doubtful for this and other reasons. So the use of cavitation in industrial scale sewage cleaning plants under the parameter conditions tested in the project has no chance to be realized as by technically as by economical reasons.

Project Participants

Implementing Institution

Institut für Neuwirtschaft GmbH

More Project Informations

Project title:  Development and comparison of the effectivity of oxidation processes initiated by radicals, created by heterogeneous catalysis and by high pressure process for the reduction of persistent organic sewage pollutants

Project number:  02WA9924/1

Project period:  1999 - 2002

Project region:  Germany (Baden-Württemberg)

Project contact:

Frau Prof. Bach

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Source: German National Library of Science and Technology Hannover (TIB)