Enhanced nitrogen removal in single-stage sequencing batch rotating biological contactors

The Rotating Biological Contactor (RBC), recognized for its energy efficiency, eliminates the need for aeration and sludge return in wastewater treatment. This study evaluates a Biocage-modified RBC, aimed at enhancing biomass retention and optimizing treatment efficacy. We compare continuous (C-DRBC) and sequential batch influent modes (SB-DRBC) concerning denitrification effectiveness. The continuous mode shows limited total nitrogen (TN) removal at 32.8 %, constrained by higher dissolved oxygen levels in the biofilm, which impede stable denitrification. Conversely, the SB-DRBC, operating at a hydraulic retention time of 6 h and a rotation speed of 3 rpm, substantially increases TN removal to 64.1 %. This enhancement is attributed to the development of an anoxic zone within the biofilm, conducive to denitrification. The biofilm's uptake of polyhydroxyalkanoates and glycogen metabolism by glycogen-accumulating organisms further augments nitrogen removal. Microbial analyses indicate a predominance of denitrifying bacteria such as Paracoccus, Thauera, and Azoarcus in the SB-DRBC mode. Reducing rotational speed fosters larger anoxic zones, thus elevating denitrification efficiency. These findings advocate the SB-DRBC approach as a formidable strategy for achieving efficient nitrogen removal and energy conservation in wastewater treatment.