Response of Anammox bacteria to elevated nitrogen and organic matter in pre-digested chicken waste at a long-term operated UASB reactor initially seeded by methanogenic granules

Up-flow anaerobic sludge bed (UASB)reactor originally inoculated by methanogenic granules was operated for nine months for total ammonia nitrogen (TAN)removal through anaerobic ammonium oxidation (Anammox)route with external nitrite source (NH₄:NO₂ = 0.99 ± 0.19). However, bioreactor was operated at elevated TAN (330 ± 48 mg/L)and total chemical oxygen demand (tCOD)(2868 ± 378 mg/L)in diluted chicken waste digestate between 120 and 274 d with respective removals up to 57 ± 7% and 80 ± 4%. The response of microbial cultures, especially Planctomycetes (Anammox bacteria)to such influent TAN and tCOD was also investigated by high-throughput sequencing analyses. Results indicated the co-existence of denitrifying bacteria playing significant role in nitrogen removal with Anammox bacteria. Firmicutes and Bacteroidetes phyla doubled their relative abundances; however, a sharp decrease in Planctomycetes was observed. Moreover, predominant phylum changed from Proteobacteria to Firmicutes while dominance of Euryarchaeota remained constant indicating nitrogenous and organic matter contents were the most important factors dominating the bacterial community structure.