Environ. Sci. Technol. 2005, 39, 355-362
Generalized First-Order Kinetic Model for Biosolids Decomposition and Oxidation during Hydrothermal Treatment A. SHANABLEH* Department of Civil Engineering and Research and Studies Center, University of Sharjah, P.O. Box 27272, Sharjah, United Arab Emirates
The main objective of this study was to develop generalized first-order kinetic models to represent hydrothermal decomposition and oxidation of biosolids within a wide range of temperatures (200-450 °C). A lumping approach was used in which oxidation of the various organic ingredients was characterized by the chemical oxygen demand (COD), and decomposition was characterized by the particulate (i.e., nonfilterable) chemical oxygen demand (PCOD). Using the Arrhenius equation (k ) koe-Ea/RT), activation energy (Ea) levels were derived from 42 continuousflow hydrothermal treatment experiments conducted at temperatures in the range of 200-450 °C. Using predetermined values for ko in the Arrhenius equation, the activation energies of the various organic ingredients were separated into 42 values for oxidation and a similar number for decomposition. The activation energy values were then classified into levels representing the relative ease at which the organic ingredients of the biosolids were oxidized or decomposed. The resulting simple first-order kinetic models adequately represented, within the experimental data range, hydrothermal decomposition of the organic particles as measured by PCOD and oxidation of the organic content as measured by COD. The modeling approach presented in the paper provide a simple and general framework suitable for assessing the relative reaction rates of the various organic ingredients of biosolids.
Introduction The commercialization of supercritical water (i.e., temperatures >374 °C) oxidation of wastewater treatment sludge (1), including biological sludge or biosolids, is a major leap following over 10 years of research and development, which started with basic studies (2-4) and extension of the traditional subcritical (
