Implementation of IWA anaerobic digestion model No. 1 (ADM1) for simulating the thermophilic anaerobic co-digestion of olive mill wastewater with olive mill solid waste in a semi-continuous tubular digester

The anaerobic digestion model No. 1 (ADM1) developed by the international water association (IWA) task group for mathematical modelling of anaerobic digestion processes is the most sophisticated model established for full-scale industrial plants design, systems operational analysis and control, assisting technology transfer from research to industry and a common basis for further model development and validation studies. In this work the original ADM1, implemented in the simulation software package MATLAB/Simulink, was adapted and applied to replicate with reasonable degree of accuracy the thermophilic anaerobic co-digestion of olive mill wastewater (OMW) with olive mill solid waste (OMSW) in a semi-continuous tubular digester. The data set from lab-scale experiments described in our previous work was used to calibrate and validate the model. The simulations results indicated that the modified ADM1 was able to predict reasonably well the steady-state results of gas flows, methane and carbon dioxide contents, pH and total volatile fatty acids (TVFA) observed with all influents concentrations (43, 67 and 130 g COD/l) digested at the hydraulic retention times (HRTs) of 24 and 36 days. Also the reactor failure observed at a HRT of 12 days for an influent concentration of 67 g COD/l was predicted and well justified by the modified ADM1.