Study of the Anaerobic Digestion Model Number 1 as a modeling platform for different configurations of reactors used in anaerobic treatment of sugarcane vinasse with sensitivity analysis and statistical validation of the model

Abstract

Over the years, the search for measures capable of mitigating and even eliminating thenegative effects of waste from the productive processes of the industries is growing, in order thatthese environmental wastes do not affect the environment and human health. Sugarcane vinasse,a residue resulting from the ethanol production process, presents a high polluting potentialdue to its physicochemical characteristics, such as high concentrations of organic matter, highconcentration of suspended solids, high biochemical oxygen demand (BOD), low pH values,high corrosivity and high concentrations of potassium, nitrogen, phosphorus and sulfate. Thiswastewater can be treated biologically using anaerobic reactors, which have the advantage oflower energy expenditure and lower sludge production in the treatment process when compared toaerobic systems, and the energy produced in this kind of treatment can be recovered in the form ofbiogas: mainly composed by hydrogen (acidogenic reactor) and methane (methanogenic reactor).For example, in a system composed of an acidogenic reactor followed by a methanogenic reactor(two-phase system), two streams of biogas will be generated, one consisting predominantly ofhydrogen and another of methane. In the system composed only of a methanogenic reactor (singlephase system), as the name says, the gas stream will be formed primarily by methane. Fromthe experimental data collected for different conditions, it is important to model the anaerobicprocess in order to allow predictions and simulations of the treatment in different scenarios andto evaluate which initial conditions are more relevant to the treatment process. For this purpose,ADM1 modeling platform, which covers many biochemical and physicochemical processes ofanaerobic digestion, will be used [1]. The modeling of anaerobic treatment of vinasse using theADM1 platform will be done in Matlab software, in which the production of hydrogen will firstbe verified (acidogenic reactor), in the sequence will be made the modeling for the productionof methane (methanogenic reactor). After that, a local and global sensitivity analysis will beperformed aiming to select the input parameters that have or not influence in the final resultfor each of the models. Then, with the model concluded for acidogenic and for methanogenicreactors, the Markov Chain Monte Carlo will be used to optimize the free parameters of theADM1 and do the statistical validation of the model, to verify if the ADM1 accurately representsthe experimental data. Finally, the predictions of the model for different conditions will beevaluated and, with this, it will be possible to predict which scenarios lead to a higher productionof methane and hydrogen.