Intermittent rotation as an innovative strategy for achieving nitritation in rotating biological contactors

The nitritation step is essential when the anammox process is focused, and alternative technologies to achieve partial nitritation-anammox are required. Rotating Biological Contactors (RBCs) are a promising and cost-effective technology, allowing the development of aerobic and anoxic zones in the biofilm, coupled to low energy consumption. This study evaluated nitritation in a RBC with two discs rotation strategies: continuous and intermittent. Continuous rotation resulted in high dissolved oxygen (DO) concentrations and was not favorable for achieving stable nitritation. However, intermittent rotation, coupled with a nitrogen load of 1000 g N·m^-3·d^-1 and a HRT of 12 h, decreased DO by 77.8% and resulted in nitritation efficiencies of 45.3%. FISH analyses suggested that simultaneous partial nitritation/anammox (PN/A) could also be favored. These results indicated that intermittent rotation may be a core strategy for producing an anammox-suitable effluent or even to promote PN/A in RBCs, upgrading their applicability for wastewater treatment.