Optimization of moving bed biofilm reactor (MBBR) operation for biodegradation of Diuron herbicide and organic load removal from synthetic wastewater

Abstract

This study evaluates the performance of a laboratory-scale Moving Bed Biofilm Reactor (MBBR) for the biological removal of the herbicide Diuron and simultaneous reduction of chemical oxygen demand (COD) from synthetic wastewater. The reactor was operated under varying hydraulic retention times (HRT = 24, 48, and 72 h), carrier fill fractions (30%, 50%, and 70%), influent COD levels (500–1500 mg L⁻¹), and Diuron concentrations (10–25 mg L⁻¹). Results show that increasing HRT and carrier fill fraction significantly enhanced treatment efficiency. The highest Diuron removal (98.68%) and COD removal (93.4%) were achieved at HRT = 71.7 h, carrier fill fraction = 52.6%, organic load = 502.4 mg L⁻¹, and Diuron concentration = 10.13 mg L⁻¹. Statistical analysis (ANOVA, p < 0.05) confirmed that HRT, fill fraction, Diuron concentration, and organic load all significantly influenced removal performance. Although the MBBR demonstrated high efficiency for Diuron degradation, residual concentrations under even optimal conditions (e.g., ∼212 µg L⁻¹ from 10 mg per L influent) remain well above regulatory thresholds (e.g., EU limit: 0.1 µg L⁻¹), indicating that MBBR is best suited as a pre-treatment step prior to advanced polishing technologies. The system proved robust under elevated Diuron loads (up to 25 mg L⁻¹) and variable organic loading, highlighting its potential for treating pesticide-laden industrial and agricultural effluents when integrated into a multi-barrier treatment train.