Optimizing conventional activated sludge and sequencing batch reactors through chemical analyses in domestic wastewater treatment

Abstract

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 physi - cochemical 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 con - siderable 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 concen - trations 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 showed lower nutrient removal performance. The findings demonstrate that all inves - tigated biological systems effectively removed organic pollutants, while SBR showed improved performance for nutrient removal under the investigated operating conditions.