Optimization of the degradation of sewage sludge by wet air oxidation. Study of the reaction mechanism on a cellulose model compound

Abstract

Abstract. The aim of this work is to optimize the degradation yield of an activated sludge and to study the reaction mechanism on a cellulose model compound. This optimization is performed with a Simplex design with four parameters: reaction temperature (280-350°C), injected air pressure (40-60 MPa), reaction time (10-45 minutes) and COD concentration (0.5-5 g L -1 ). The better yield obtained on TOC concentration is 82 5% at 330°C. Over this temperature, the yield substantially decreases. The use of cellulose as a model compound for activated sludge confirms optimization results and leads to the identification of by-products and free radical species participating in the reaction. Two major organic compounds have been detected: 4-oxo pentanoïc acid and 3-oxo butanoïc acid, and three types of radicals: HO°, CO 2°-and °CH(OH)CH 3 .

Catalytic Wet Oxidation of Pharmaceutical Sludge by Molecular Sieve Loaded with Cu/Ce

“…It has been widely acknowledged that OH is the most active species in wet oxidation system. In Ricq's study, the reaction mechanism of the degradation of sewage sludge by wet air oxidation was studied [17]. The study of the use of cellulose as a model compound for activated sludge confirms optimization results and leads to the identification of by-products and free radical species participating in the reaction.…”

Effects of operational conditions on sludge degradation and organic acids formation in low-critical wet air oxidation

“…Subsequently, a technology to replace the current sludge treating process is a prerequisite, and the thermal oxidation (TO) was applied in this study to develop an alternative sludge reduction technology. Wet air oxidation (WAO) among TO methods is considered suitable for highly concentrated organic matters including difficult-to-decompose ones, excretions, or sludge containing small amount of organic matters when incinerated and biologically processed [1][2][3][4][5][6]. The WAO accomplishes oxidation at elevated temperatures (150-325 • C) and oxygen pressures (10-200 atm).…”

Enhanced Wet Oxidation of Excess Sludge from Pharmaceutical Wastewater Treatment by NaOH

“…OH-has been widely considered the most active species in wet oxidation systems. In Ricq's study, the reaction mechanism of sewage sludge degradation by wet air oxidation was studied [29]. Cellulose was selected as a model compound for activated sludge, and the results induced the identification of by-products and free radical species participating in the reaction.…”