Startup and Performance Stability of a Nitritation-Anammox Reactor Using Granular Sludge

Abstract

The nitritation-anammox single-stage autotrophic nitrogen-removal process has the potential for broad application in the treatment of wastewater with a low carbon/nitrogen ratio [1][2]. In existing technologies, nitritation and its coupling with anammox are rate-limiting steps in the whole process and are critical breakthrough points for increasing the processing capacity [3][4][5].The key to achieving an effective nitritation process is to enrich ammonia-oxidizing bacteria (AOB) while inhibiting nitrite oxidizing bacteria (NOB). This enables AOB to have a competitive advantage and to achieve nitrite accumulation. Researchers have conducted numerous studies on ways to achieve nitritation, and have achieved nitrite accumulation by controlling one or more parameters, e.g., pH, dissolved oxygen (DO), free ammonia (FA), or free nitrous acid (FNA) [6][7][8]. However, NOB are highly adaptive and gradually resume their activity after the system has operated for a certain period. This makes it difficult to maintain long-term stability of the nitritation process.DO is a critical factor used to achieve efficient and stable operation of the single-stage reactor. Low DO has a reversible inhibitory effect on anammox, whereas the inhibitory effect of high DO is irreversible [9-10]. Liu Pol. J. Environ. Stud. Vol. 26, No. 1 (2017), 173-180 AbstractA nitritation-anammox single-stage autotrophic nitrogen-removal system was started and achieved stable, efficient operation. The startup process occurred in three stages: aerobic granulation, nitritation regulation, and autotrophic nitrogen removal. Granular sludge was successfully incubated after 57 d of acclimation. Through an operating strategy of gradual reduction in organic loading and an increase in ammonia nitrogen loading, stable nitritation was successfully achieved (average NH 4 + -N/NO 2 ratio maintained at 1.32). Nitritation was coupled with anammox to achieve autotrophic nitrogen removal. The nitrogen loading rate was increased to 0. Test results showed that during the autotrophic nitrogen removal stage, anaerobic ammonia-oxidizing bacteria were considerably enriched, and that there was an organic balance between these and ammonia-oxidizing bacteria in the system.