Wastewater treatment plants (WWTPs) are intended to be transformed from energy consumers into sources of energy. This experimental study assessed the performance, sludge and methane production, and energy content of a chemically enhanced precipitation treatment (CEPT) reactor compared with a conventional primary sedimentation treatment (CPST) reactor. The optimization of operational factors such as coagulant (alum (AlSO4)), coagulant aid (polyelectrolyte), sedimentation time, and pH were analyzed by the response surface method (RSM). The results of the CPST reactor indicated that the TS, VS, TSS, VSS, and COD removal rates were 60%, 43%, 69%, 8.96%, and 45%, respectively. Meanwhile, the CEPT reactor was able to remove a high percentage of all pollution (94.99% TS, 50.79% VS, 98.92% TSS, 95.40% VSS, and 95.70% COD) in optimum operation conditions, including sedimentation time 150 min, pH 7.9, coagulant aid 2.5 mg/L, and coagulant 106.2 mg/L.