Monthly reports from June 2017 to May 2018 of Twenty-one wastewater treatment plants in Sharkia were evaluated for the following parameters: temperature, pH, total dissolved solids (TDS), total suspended solids (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrate (NO3), oil and grease (O&G) and Dissolved Oxygen (DO) values. The first aim of this study was to estimate the main wastewater per capita pollution generation per day (PCPL) and found that the 90th percentile PCPL for TSS, COD, BOD, NO3 and O&G were equal to 57.42, 91.59, 59.13, 1.64 and 12.39 (g/capita/day) respectively. The second aim was to assess the performance of the WWTPs in the governorate, by calculating of the wastewater quality index (WWQI) of each plant and for the entire governorate which shows that; 2 WWTPs gives a good performance, 9 WWTPs gives a fair performance, 9 WWTPs gives a marginal performance and 1 WWTP is in bad conditions, the average performance all over the governorate is considered marginal. A simple empirical formula had been established to be used for calculation of the WWQI based on the tested parameters using the multiple linear regression and found to be very effective in predicting the WWQI for the WWTPs.