Physico-chemical and microbial characterization of compartment-wise profiles in an anammox baffled reactor.

In this study, compartment-wise investigation of an anammox baffled reactor (AnBR) was performed. The AnBR achieved steady-state conditions after a start-up period of ∼50 days and achieved NH and NO conversion percentages of 88.5 and 99.3%, respectively. Examination of the nitrogen mass balance revealed that an AnBR with a two-compartment configuration was sufficient for nitrogen loading rates (NLRs) ranging from 0.125 to 1.975 kg N/m/d and resulted in a nitrogen removal efficiency (NRE) of 86.7-93.7%. Higher NLRs (4.04-5.05 kg N/m/d) required four compartments to achieve an NRE of 82.2-87.1%. Further, an overall NLR increase of up to 5.93 ± 0.23 kg N/m/d resulted in complete AnBR failure. The maximum nitrogen removal rate was consistently recorded in the 1 compartment for all NLRs examined; as a result, this compartment exhibited the highest bacterial activity. Biomass concentration, specific anammox activity, extracellular polymeric substances, and average granule diameter in the 1 compartment with an overall NLR of 0.05 kg N/m/d were estimated to be 11.2 g/L, 0.03 mg N/g/h, 84.3 mg/g and 0.65 mm, respectively. These values increased to 26.1 g/L, 11.80 mg N/g/h, 242.1 mg/g and 2.31 mm, respectively, when the overall NLR was incremented to 4.04 kg N/m/d. However, a gradual reduction in bacterial activity was observed from the 1 to the 5 compartment. The microbial community analysis indicated that the dominant phyla in the 1 compartment (NLR of 0.252 kg N/m/d) with the highest nitrogen removal were Chloroflexi (38.13%), Planctomycetes (22.62%), and Proteobacteria (14.75%).