The pulp and paper mill process requires large amounts of water. Therefore, the need to reuse water through the application of coagulation-flocculation processes, which is effective in the removal of solids and colloidal particles, has risen. In such processes, zeta potential (ZP) provides important information about the efficiency of the reagents used. The purpose of this study was to develop individual and combined tests of reagents to study turbidity and COD reduction based on ZP in the process of wastewater internal treatment for recirculation in the pulp and paper process. Factorial models were developed to explain the behavior of ZP depending on the different coagulants/flocculants. The statistical analyses showed that ZP had a positive correlation with parameters related to removal (COD and turbidity). It was demonstrated that innovate use of lentil extract (Lens esculenta) applied with aluminum sulfate favored the treatment, consistent with a coagulation-flocculation mechanism. The optimum doses of lentil extract were able to reduce the requirements of aluminum sulfate by almost 29%, providing an alternative strategy for water reuse processes in the pulp and paper industry.