This study evaluated the seasonal performance of a Conventional Activated Sludge (CAS), a Sequencing Batch Reactor (SBR), and a combined treatment configuration (S2 + S3) for domestic wastewater treatment using physicochemical analyses. Monthly monitoring was conducted over a 12 - month period to determine pH, temperature, dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), and turbidity. The influent wastewater showed considerable seasonal variability, with COD ranging from 293 to 1050 mg/L and a mean BOD₅/COD ratio of 0.41, indicating generally good biodegradability. All treatment systems achieved high removal efficiencies for organic pollutants, exceeding 98% for BOD₅, 94% for COD, and 96% for TSS, while complying with the discharge limits of Council Directive 91/271/EEC for these parameters. The SBR system showed lower average effluent concentrations of TN (27.68 mg/L) and TP (0.78 mg/L), corresponding to removal efficiencies of 79.75% and 94.05%, respectively, whereas CAS exhibited lower nutrient removal performance. The findings demonstrate that all investigated biological systems effectively removed organic pollutants, while SBR showed improved observed performance for nutrient removal under the investigated operating conditions.