Experimental and Numerical Analysis of the Co-Digestion Process of Municipal Sludge with Fruit and Vegetable Waste

Anaerobic digestion is the most commonly applied process for waste sludge treatment, which enables obtaining energy from the produced biogas. Biogas produced by anaerobic co-digestion of sludge with various additives can be used as an alternative fuel. Mathematical modeling of the Anaerobic Digestion (AD) process can greatly explain and facilitate the full-scale implementation of this process. In this work, a simulation of the process of co-digestion of waste sludge with fruit and vegetable waste was carried out numerically, with Anaerobic digestion model no. 1 model (ADM1) and experimentally. The data used to run the ADM1 model and its verification were obtained in a batch pilot reactor (25 L) and refer to Total Solids (TS), Volatile Solids (VS), Total Chemical Oxygen Demand (TCOD), Total Kjeldahl Nitrogen (TKN), total ammonia nitrogen, volatile fatty acids (VFA), pH value, conductivity, biogas volume produced and its composition. The verification of the model was performed with experimental data about the biogas production, methane production, and pH value. Also, a sensitivity analysis was performed by variation of 53 parameters, to identify the most sensitive parameters of the ADM1 model for the co-digestion process. The best agreement between experimental and simulated data was obtained for methane production, while the most sensitive parameters are the biochemical hydrogen inhibition constant and the half-saturation constant.