Tolerance of anammox reactor packed with zeolite to partial supply of nitrite or ammonium using purified livestock wastewater

Abstract

ABSTRACTAnammox reaction requires nitrite and ammonium in the ratio of 1.1–1.3. However, controlling a partial nitrification process prior to the anammox process to maintain this ratio in an influent to the anammox reactor is not easy. In this study, the effect of zeolite on anammox reaction was investigated to determine a method of ammonium preservation in case of partial supply of nitrite or ammonium. Up-flow column type anammox reactors, filled with either zeolite or non-woven fabric, were operated in two-week intervals with purified livestock wastewater containing either ammonium or nitrite. The zeolite reactor showed significantly higher nitrogen removal rates than the non-woven fabric reactor for both influents. When the influent contained ammonium, it was adsorbed onto zeolite, while anammox tolerated starvation for two weeks. In a subsequent reaction cycle, when the influent contained nitrite, anammox used the nitrite and the ammonium desorbed from zeolite. The highest nitrogen removal rates were 0.71 and 0.29 gN/L/day, observed in the zeolite reactor, with the ammonium and nitrite influents, respectively. The limiting factor for reactor performance was zeolite saturation level when the influent contained ammonium and anammox reaction rate when the influent contained nitrite. This study demonstrated that zeolite can buffer the unbalance of the nitrite to ammonium ratio in an anammox reaction, and showed the scopes for improvement under each influent.