OCCURRENCE OF KSU-1 TYPE ANAMMOX BACTERIA AND PERDOMINANCE OF BETA-PROTEOBACTERIA IN THE ANAMMOX GRANULAR SLUDGE

The enrichment of anammox bacteria using upflow anaerobic sludge bioreactor was successfully conducted for 400 days of continuous operation. This process exhibited high removal efficiency of NH4+-N and NO2−-N of 90±11% and 96±11%, respectively. The NH4+-N to NO2−-N ratio in the feed was maintained at 1:1, while the ratio of 1:1.32 was reported as the optimum ratio. As the process was stabilized, the granular sludge turned brownish red due to the attachment of anammox bacteria on the surface of the seeding anaerobic granules. The overall microbial community structure included Proteobacteria (47%), Planctomycetes (25%), Chloroflexi (18%), Chlorobi (8%), and Acidobacteria (2%). The most predominant subphylum was β-Proteobacteria (45%) and Rhodocyclales in β-Proteobacteria subclass was identified. The second predominant phylum was Planctomycetes (anammox bacteria) and the most similar clone was KSU-1 Planctomycetes (AB057453) searched by BLAST. The third predominant phylum was Chloroflexi which is responsible for maintaining the granule structure as well as for triggering bulking. In addition, the presence of AOB (Ammonia Oxidizing Bacteria) and their diversity were identified by clone library and T-RFLP based on amoAgene sequences. The AOB clones were affiliated with Nitrosomonas europaea/nitrosococcus mobiliscluster and Nitrosomonas communiscluster. The diversity of AOB estimated by applying T-RFLP was more diverse than the result of clone library. Anammox bacteria coupled with AOB clones might play a key role to remove high efficiency of nitrogen.