Although, anaerobic digestion (AD) modeling can provide significant benefits in the design, operation and optimization of the digestion performance, AD model inputs are relatively complex and may require a wide array of components which are most of time not measured in wastewater treatment facilities. Therefore, the selection of an appropriate digestion model is crucial in integrating AD modeling in liquid stream simulations. A comparison between the structure and benefits of the Anaerobic Digester Model (ADM-1) and the General Activated Sludge – Digestion Model (ASDM) is assessed in the content of this study. The influent wastewater characteristics have shown to have a significant impact in AD modeling. Model calibration and validation studies have also shown that the hydrolysis rate has tremendous effect on the mode predictions and this may have to be modified to predict plant performance. The gas production and volatile solids reduction (VSR) proved to be highly affected by the quality of the input data while the alkalinity was less influenced. The effects of design and operational parameters on the performance of AD were also assessed by using a calibrated and a validated model. An integrated AD model can be utilized to simulate numerous different scenarios to design a new digestion system and/or upgrade an existing one.