The present study has been undertaken to evaluate performance efficiency of wastewater treatment plants (WWTPs) in El-Fayoum Markaz, El-Fayoum governorate in Egypt. The wastewater treatment plants using different treatment techniques were Active sludge, Oxidation ponds, Secondary - active sludge and Chemical (nanotechnology) which wastewater samples were collected from both influent and effluent of each plant. The key performance of each plant is estimated based on the treated wastewater quality data. Based on the results, they showed that Old Quhafa (Secondary - active sludge technology) operates with removal efficiencies higher than 80% for biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) were established. While Ezbet Ashour accomplished lowest performance efficiency that operates with chemical-nanotechnology. This analysis applied to define a performance measuring plan based on the most important parameters that can be reliable and applicable for any WWTP. The study suggested formula for performance WWTPs that described by the expressing removal efficiencies as relative values or percentages and the remaining fraction. The study recommended that sedimentation units must be cleaned, monitoring frequently of sludge analysis and calculation of building capacity for all WWTPs.