Industrial Symbiosis (InSym) capitalises on the proximity of entities to gain a competitive advantage through collective strategies. Within the Circular Economy, this involves the circular exchange and reuse of water, energy, and resources among participating businesses, enhancing resource valorisation in manufacturing. However, as a distinct business model, InSym requires collaboration among multiple stakeholders working toward a shared goal, posing challenges in achieving mutually beneficial outcomes. Operations Research (OR) - particularly computer modelling and simulation techniques - can help mitigate risks in InSym implementation by enabling an experimental approach to decision-making. This paper presents a hybrid modelling framework to support InSym decision-making. The framework integrates four OR techniques: Agent-Based Simulation (ABS), Discrete-Event Simulation (DES), System Dynamics (SD), and Multiple Criteria Decision Analysis (MCDA) to develop a hybrid InSym model. ABS captures stakeholder behaviour, DES simulates operational processes, SD represents dynamic interactions, and MCDA incorporates stakeholder perspectives. The model evaluates collective treatment strategies for olive mill wastewater, addressing key challenges such as scattered small-scale olive mills, seasonal wastewater discharge, and high organic loading. This innovative framework addresses InSym decision-making at operational, tactical, and strategic levels, transforming the economy-environment dilemma into a win-win scenario for olive oil businesses and local authorities.