Successful establishment of Anammox by cultivating residual sludge and its response to elevated nitrogen loading

Abstract

Anaerobic ammonia oxidation (Anammox) process was one of the most economical nitrogen removal technology, however, the slow growth rate and the shortage of sufficient seed sludge limit its application. In this study, Anammox was successfully established using residual sludge as seed sludge, and the variation in its nitrogen removal, stability, and microbial characteristics in response to the elevated ammonia and nitrite were explored. The sludge exhibited Anammox activity on day 34, and the system was successfully established on day 67, while the hzo gene expression increased from 1.1 * 104 to 9.4 * 105 copies/mL. The established Anammox system showed good resistance to the high nitrogen shock (200–1000 mg/L), and the relative abundance of Candidatus_Kuenenia notably increased. However, when the total nitrogen in influent reached 1200 mg/L, the nitrogen removal of the Anammox system was suppressed. And Candidatus_Kuenenia abundance significantly decreased while Arenimonas increased. Residual sludge could be adopted for establishing Anammox system, and the system could be used for efficiently treating wastewater with nitrogen lower than 1000 mg/L. The result in the present study has significance to the application of Anammox process and deeply save the economic cost of seed sludge since residual sludge was widely available.