Enrichment of Anammox bacteria in seed sludges from different wastewater treating processes and start-up of Anammox process

Abstract Three seed sludges (sludge A, B and C) were collected from various wastewater treatment processes. Then they were inoculated in Reactor A, B and C in parallel. After 67 days of operation, only Reactor A successfully started up the Anaerobic ammonia oxidation (Anammox) process, while the other two reactors failed. The Anammox activity was observed within 49 days and a final nitrogen removal rate of 0.19 g NH 4 + –N L − 1  d − 1 and 0.21 g NO 2 − –N L − 1  d − 1 was achieved after 95 days. In Reactor A, Fluorescence in situ hybridization (FISH) analysis confirmed that Anammox bacteria became the dominant population on day 90, and Scanning electron microscope (SEM) observation also showed that short rod and spherical bacteria predominated in the cultivated sludge. FISH analysis also disclosed that sludge A had aboriginal Anammox bacteria but the other two have no signal of Anammox bacteria. From a new micro-ecological viewpoint, the wastewater treating process, which sludge A was taken from, could provide Anammox ecological niche, but the other two processes could not. The results indicated that selection of the seed sludge from the special wastewater treating process providing Anammox ecological niches made the Anammox start-up more effectively and quickly.