Anaerobic Ammonia Oxidation (ANAMMOX) processes for Ammonium-rich Lagoon Supernatant Treatment

Abstract

Ammonium-N and phosphate-P-rich anaerobic digester sludge liquor recovered during sewage sludge dewatering contributes more than 30% of the total nitrogen loading when returned to the municipal wastewater plant. Hence, side stream treatment could offer an economic alternative given its relatively low flow and high concentration of nutrients. However, traditional biological nitrification/denitrification requires considerable energy for nitrification and organic carbon for denitrification. During the past decade, considerable work has described the mechanism of the partial nitrification (nitritation) and anaerobic ammonia oxidation (anammox). The nitritation-anammox processes have been demonstrated to be efficient for nitrogen reduction from high ammonia content waste streams. However, no comprehensive study has compared different reactor configurations, operational conditions and their application for sludge liquor treatment. Hence, the objectives of this PhD dissertation were to assess different reactor design and operational strategies, investigate microbial population diversity, density and functional stability to optimize ammonium reduction processes. In order to assess reactor design, one and two-stage nitritation-anammox reactor configurations, MBBR (moving bed biofilm reactor) and IFAS (integrated fixed film activated sludge) were compared under varying operation conditions (e.g., various aeration, seeding, feeding and control strategies), along with the need of pre-treatment to reduce P-inhibition. Under best operation conditions, average NH4+-N removal efficiency was 89-91% with an NH4+-N loading rate of 0.62-0.68 kg N/(m3·d). Intermittent aeration, maintaining a low DO concentration (0.18-0.28 mg/L), sludge recycling for keeping AOB active and specific anammox activity (SAA) monitoring were important strategies for successfully operation of the nitritation-anammox reactor. Microbial analysis showed that nitritation-anammox biomass harbored a high microbial diversity when feed raw lagoon supernatant. High throughput sequencing indicated that the dominant nitrifiers in the IFAS-SBR, Nitrosomonas, facilitated nitritation; and that Candidatus Brocadia was the dominate bacteria responsible for the anaerobic ammonia oxidation observed. Overall the present study showed that application for lagoon supernatant treatment is achievable by applying nitritation-anammox processes, either by two-stage or one-stage operation, but that the one-stage configuration provided considerable simplification and reduced nitrite inhibition with sequential aeration strategy provided.