A re-equilibrium model was developed which ensures that the rights of the Public Private Partnership (PPP) project stakeholders are preserved during renegotiation and minimizes the chances of disputes. The model develops the typical renegotiation scenarios which include: increasing the service charges, increasing the concession period, or paying a lump sum amount to the party of concern in order to maintain a fixed rate of return and keep the return on equity constant. Moreover, a decision support system was developed with the aid of Microsoft Excel 2013, Visual Basic for Applications (VBA) programming language, and the Precision Tree 5.5 for Excel addin, in order to facilitate the process of selecting the optimum scenario which maximizes the satisfaction of both parties (the private sector and the public sector). In this paper, data is obtained from a case study of a wastewater treatment plant in Egypt, and applied to the proposed model. The results obtained from the model are close to the ones obtained from the Independent Financial Expert (IFE) of the wastewater treatment plant project. This verifies and validates the objectives of the model.