Reclaimed wastewater has become an important component of Egypt's water resources as a result of acute water scarcity and growing demand for various applications. The current study aimed to assess the performance efficiency of wastewater treatment plants in Egypt's El-Sharkia Governorate. The monthly reports of twenty Sharkia wastewater treatment plants (January 2023 to December 2023) included total suspended solids (TSS), ammonia (NH₃), nitrite (NO₂^–), nitrate (NO₃^–), phosphate (PO₄^3–), total nitrogen (TN), chemical oxygen demand (COD) and biological oxygen demand (BOD) values. The first goal of this study was to determine the per capita pollution generation per day (PCPL) from primary wastewater. The 90^th percentile PCPL values for TSS, COD, BOD, TN, and PO₄ were 47.56, 120.30, 76.60, 10.97, and 0.693g/capita/day, respectively. The other goal was to determine the wastewater quality index “WWQI" to evaluate the governorate's WWTP efficiency. WWQI calculations showed that only 4 plants provide good performance (20%), 11 plants provide medium performance (55%), 4 WWTPs provide marginal performance (20%), and one WWTP is in poor condition (5%), indicating that overall performance in the governorate is rated marginal. It was demonstrated that a straightforward multiple linear regression model could accurately predict WWQI for WWTPs. The presented techniques and procedures in this paper provide an assessment framework for the wastewater treatment monitoring programs.