DEVELOPMENT OF A MATHEMATICAL-MODEL FOR THE SIMULATION OF THE BIODEGRADATION OF ORGANIC SUBSTRATES IN A HIGH-SOLIDS ANAEROBIC-DIGESTION PROCESS

A kinetic model is developed to simulate the biodegradation of the org anic fraction of municipal solid waste in a high-solids complete-mix c ontinuous-flow anaerobic digestion process. A mass balance correction factor (f) is used to account for (i) the water that is incorporated i nto the production of biogas, and (ii) the water vapor present in the biogas. With the inclusion of the factor f, expressions are developed to determine the substrate removal efficiency based on first-order and Monod kinetic models. Simulations using first-order and Monod kinetic models are carried out to illustrate the importance of the f factor o n the substrate mass removal and microorganism concentration in the hi gh-solids anaerobic digestion process. The effect of the value off on kinetic constants, and the error involved in considering the high-soli ds process as a low-solids process are discussed. Finally, experimenta l results from a pilot-scale high-solids complete-mix batch-fed anaero bic digestion process are used to estimate the first-order rate consta nt for the biodegradable fraction of municipal solid waste.