ABSTRACT
In the simplest approach, an anaerobic digester can be modelled as a continuous stirred tank reactor (CSTR). The influent is continuously fed to the reactor and the effluent is continuously withdrawn. A continuous flow rate of gas is also generated in the reactor. In a system like this the only design parameter, that is the only parameter that can be used to design the process, is the residence time (for a given composition and properties of the influent wastewater, and for given values of the temperature, pH and pres sure of the reactor). In this case the residence time of the liquid and of the solids coincides, since there is no liquid-solid separation. The performance of the process as a function of the residence time can be simulated by writ ing and solving the appropriate mass balances.
