Influence of Operational Cycle Time on the Performance of a Sequencing Batch Reactor Treating Dairy Effluents

Abstract

Abstract– Dairy effluents generated during ice cream production are characterized by high organic loads, suspended solids, and operational variability, as well as low alkalinity and acidic pH, which hinder stable biological treatment. The objective of this study was to evaluate the influence of operational cycle time (OCT) on the performance of a sequencing batch reactor (SBR) for treating effluents from an ice cream production plant. The wastewater was characterized through physicochemical parameters following standard methods. A laboratory-scale SBR (2 L working volume; 30% biomass) was operated using acclimated biomass under three treatments (OCT = 6, 8, and 10 h), maintaining a sludge retention time of 25 days. The removal of COD, BOD, nitrogen species, phosphorus, pH, and alkalinity was evaluated. Increasing the OCT improved organic matter removal, achieving 70.2–89.7% COD and 86.2–97.5% BOD removal, with significant differences between 6 h and OCT ≥ 8 h. Nitrification–denitrification was observed, with nitrification efficiencies of 80.3–95.0% and denitrification efficiencies of 83.3–90.3% without the addition of an external carbon source. Phosphorus removal was moderate (30.4–45.4%). The SBR proved to be an effective alternative for treating ice cream effluents. An OCT of 8 h significantly improved system performance and enabled simultaneous removal of organic matter and nitrogen under stable operational conditions.