One-Stage Nitritation/Anammox Process Using a Biofilm Reactor with Two-Inflow

Abstract

A new one-stage nitritation/anaerobic ammonium oxidation (anammox) process with two-inflow was proposed to provide suitable coexistence conditions for ammonium oxidation bacteria (AOB) and anammox bacteria. Reactor performances were examined using a two-inflow biofilm reactor fed with artificial ammonia-containing wastewater. For start-up, an anammox biofilm was cultivated in a wound filter set in the center of the reactor until the anammox process occurred stoichiometrically. Then, sponge media containing abundant AOB were added to the reactor, and aeration of the reactor began, also nitrite concentrations in the substrate decreased and the ammonium concentration increased gradually. Both anammox and nitritation occurred in the reactor. The maximum nitrogen removal efficiency achieved was 49%, the maximum ammonium conversion efficiency was 60%, and the maximum nitrogen removal rate was 0.228 kg-N/(m³·d) at the nitrogen loading rate of 0.5 kg-N/(m³·d). It was estimated that ammonium oxidation (nitritation) occurred in the sponge; hence, the anammox reaction occurred in the biofilm attached to the filter.