Start-up of Anaerobic Ammonium Oxidation (Anammox) from Conventional Return Activated Sludge in Up-flow Anaerobic Sludge Blanket (UASB) Reactor for Autotrophic Nitrogen Removal from Wastewater

A bench-scale up-flow anaerobic sludge blanket (UASB) reactor was applied to start-up the anaerobic ammonium oxidation (Anammox) process from conventional return activated sludge. The reactor was operated for approximately 170 days and was fed synthetic wastewater containing mainly nitrite (NO2^− ) and ammonium (NH4^+ ) as main substrates. After 106 days of operation, the first evidence of Anammox activity was detected in the reactor by simultaneous consumption of 2 NO^− and NH4^+ coupled to the production of nitrate (NO3^− ) . The start-up period of the Anammox UASB reactor was within 4.5 months. During the course of the start-up period, three distinct stages were distinguished: cell lysis, Anammox cultivation and finally the appearance and enrichment of Anammox bacteria. On the basis of the results, it seems that the successful cultivation of Anammox bacteria in this study was probably due to the capacity of UASB reactor in retaining Anammox biomass and the inherent properties of the activated sludge.