Response Surface Methodology for Optimization of Rotating Biological Contactor Combined With An External Membrane Filtration

Abstract A large amount of wastewater is directly discharged into water bodies without treatment causing surface water contamination. Conventional treatment techniques produce lower effluent quality and are energy extensive. Rotating biological contactor (RBC) is an attractive biological wastewater treatment that offers a low energy footprint. However, its unstable removal efficiency makes it less popular. This study optimizes operating parameters in RBC combined with external membrane filtration (RBC-ME) in which the latter acts as a post-treatment step to stabilize the biological performance. Response Surface Methodology (RSM) was employed to optimize the biological and filtration performance by exploiting three parameters of disk rotational speed, hydraulic retention time (HRT), and sludge retention time (SRT). Results show that RBC-ME exhibits excellent biological treatment capacity and higher effluent quality. It attained 87.9 ± 3.2% of chemical oxygen demand, 45.2 ± 0.7% total nitrogen, 97.9 ± 0.1% turbidity, and 98.9 ± 1.1% ammonium removals. The RSM data demonstrated that the experimental data and model predictions agreed well. Under the most optimum parameters, the permeability of 144.6 L/m2 h bar could be achieved at 36.1 rpm disk rotational speed, 18 h HRT, and 14.9 d SRT. This work demonstrates the effective use of statistical modeling to enhance RBC-ME system performance to obtain a sustainable and energy-efficient treatment process to prevent human health and the environment.