Regular articleOxygen transfer dynamics and nitrification in a novel rotational sponge reactor

•For the first time, oxygen transfer dynamics and nitrification in a pilot scale novel rotating sponge (RS) reactor was studied.•The RS reactor achieved similar oxygen transfer capability at one-eighth of the rotational speed of conventional RBCs.•Nitrification efficiency of the RS reactor was 97% with effluent NH4+-N concentration of 1 mgL−1.•The RS reactor is practically applicable for nitrification without external aeration.

The nitrification process demands higher oxygen supply, which is fulfilled through external aeration in wastewater treatment. To perform nitrification without external aeration, this study developed a novel rotating sponge (RS) reactor and estimated its oxygen transfer capability. The reactor obtained an oxygen transfer coefficient (KLa) value of over 100 d−1 at 40 rounds per hour (rph), which is one-eighth of the rotational speed of conventional rotational biological contactors. Within 53 days of operation, reactor achieved 97% nitrification efficiency with an effluent NH4+-N concentration of 1 mgL−1. On the other hand, the volumetric oxygen transfer rate in the reactor was 245 mg-O2L−1d−1 at 10 rph during the experimental period. However, the average volumetric oxygen consumption rate during nitrification was 187 mg-O2L−1d−1, which was below the oxygen transfer rate. Microbial community analysis revealed high relative abundance of bacteria such as Nitrosomonas, Nitrospira, and Nitrobacter in the RS reactor, which contributed to nitrification.

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