A hybrid biofilm reactor with intermittent cycle extended aeration system (ICEAS) operation for surface water treatment

ABSTRACT This study evaluates the performance of a hybrid Sequencing Batch Moving Bed Biofilm Reactor (SBMBBR), operated under a continuous-inflow ICEAS configuration, for the treatment of polluted surface water from the Qarasu River in western Iran. The system was tested under 27 operational scenarios with influent COD concentrations of 100, 150, and 200 mg/L; cycle times of 4, 6, and 8 hours; and anoxic mixing durations of 30, 60, and 90 minutes. Under optimal conditions (COD: 200 mg/L, cycle time: 8 h, mixing time: 90 min), the system achieved removal efficiencies of 93% for COD, 94% for BOD₅, >99% for TKN (effluent below the detection limit of 0.2 mg/L), and over 97% for total phosphorus (TP), reducing effluent TP to below the method detection limit (0.05 mg/L). Total nitrogen removal reached up to 73%. The pH remained within a neutral to slightly alkaline range (7.2–7.8), and alkalinity was adequate to maintain stable biological activity throughout the tested conditions. Turbidity was reduced to below 1 NTU under optimal conditions, while electrical conductivity remained stable. These findings indicate the potential of SBMBBR as a compact biological treatment option for decentralized surface water treatment, particularly in regions with variable pollutant loads and limited infrastructure; however, these results are based on laboratory-scale experiments and long-term and pilot-scale validation is required.