Proper treatment system for palm oil mill effluent (POME) is crucial to protect waterways systems and enhance sustainability. Conversion of POME into electricity can utilize POME and generate economic return to the palm oil mill. Optimization modelling can demonstrate optimal operation processes and estimate potential economic return. The objective of this study is to analyze the potential treatment system of POME using a mixed-integer programming (MILP) model. The developed model considered multiple factors such as capital cost, maintenance cost, technology capacity, conversion ratio, and electricity price. General Algebraic Modelling System (GAMS) software version 26.1.0 major release was selected to optimize the developed MILP model. Based on case study, the developed model selects the anaerobic lagoon system (ALS) with biogas and the anaerobic digester (AD) as the most profitable treatment system for POME. The profit gained from the selected system was RM 2,153 900.00. The payback period for the investment was about 9.69 years with a return of investment (ROI) value of 97.71%.