A fast start-up of the organotrophic anammox process inoculated with constructed wetland sediment

Organotrophic anaerobic ammonium oxidation (anammox) bacteria can utilize small volatile fatty acids with nitrate as electron acceptors with less energy consumption and no biomass production. To achieve a faster and stable start-up of organotrophic anammox process, in this study, the growth of organotrophic anammox bacteria seeded from hybrid constructed wetland (CW) sediment under different TOC/TN ratios and different chloramphenicol concentrations were investigated. The incubation study was conducted at the TOC/TN ratio = 0.0375-0.1 or 0.1-0.2 for the period of over five months by using serum bottles. The anammox bacteria revealed a higher activity when the TOC/TN ratio was 0.1, with the removal efficiency of NH4+-N (60-80%) and NO2--N (similar to 100%). The relative abundances of anammox in the incubated CW sediment were about 30% higher in comparison with the municipal waste water treatment plant sludge, suggesting the CW sediment could be a viable source for the enrichment of organotrophic anammox bacteria. On the contrary, the continuous addition of 50 mg/L chloramphenicol completely inhibited the anammox activity in our study. Following the results of the batch tests, Candidatus Brocadia caroliniensis was successfully enriched with the CW sediment in an auto-controlled SBR for the period of 40 days.