Post carbon removal nitrifying MBBR operation at high loading and exposure to starvation conditions

This study investigates the performance of MBBR nitrifying biofilm post carbon removal at high loading and starvation conditions. The nitrifying MBBR, treating carbon removal lagoon effluent, achieved a maximum SARR of 2.13gN/m²d with complete conversion of ammonia to nitrate. The results also show the MBBR technology is capable of maintaining a stable biofilm under starvation conditions in systems that nitrify intermittently. The biomass exhibited a higher live fraction of total cells in the high loaded reactors (73-100%) as compared to the reactors operated in starvation condition (26-82%). For both the high loaded and starvation condition, the microbial communities significantly changed with time of operation. The nitrifying community, however, remained steady with the family Nitrosomonadacea as the primary AOBs and Nitrospira as the primary NOB. During starvation conditions, the relative abundance of AOBs decreased and Nitrospira increased corresponding to an NOB/AOB ratio of 5.2-12.1.