Nitrogen Removal in Moving Bed Sequencing Batch Reactors with Polyurethane Foam Cube and Luffa Sponge Carrier Materials

Abstract

Nitrogen removal performance was investigated in a sequencing batch reactor (SBR) and two moving bed sequencing batch reactors (MBSBRs) containing a given proportion (20% v/v) of various carrier materials. The maximum total nitrogen (TN) removal efficiency (78%) was achieved using an MBSBR packed with luffa sponge (LS) substrate; polyurethane (PU) foam cube-packed MBSBR and SBR systems followed at 71% and 62%, respectively. Suspended-growth biomass played a role in the conversion of ammonium-N to nitrite-N and nitrate-N. Simultaneous nitrification and denitrification (SND) processes enhanced TN removal in the MBSBRs. In addition, LS facilitated denitrification by serving as a carbon source. Pyrosequencing analysis showed that the enhanced nitrate removal rates in Reactor B (RB; MBSBR-PU) and Reactor C (RC; MBSBR-LS) systems may be attributed to Clostridia enrichment; the higher relative abundance of Clostridia in RC may have caused the superior nitrate removal rate therein. Pseudomonas was the dominant genus in denitrification processes in RB and RC. This work demonstrates that MBSBRs are capable of outperforming traditional SBRs and that the choice of carrier material is essential to MBSBR wastewater treatment performance.