Start-up And N-removal Characteristics And Microbial Community At Different N/S Ratios Of The Denitrifying Ammonium Oxidation (DEAMOX) Process

Denitrifying ammonium oxidation?DEAMOX?,which was based on sulfide-dependent autotrophic denitrification?SDAD?and anammox,can achieve the simultaneous removal of nitrogen and sulfide.Previous studied have paid less attention to the inoculation sludge and start-up characteristics of DEAMOX reactor.And the influent N/S?NO₃^--N/S?ratio is the key parameter of DEAMOX process.In this study,two anammox reactors inoculated with two kinds of mixture sludges successfully started up.Then,replaced the influent ingredients of NO₂^--N and NH₄⁺-N by S^2-,NO₃^--N and NH₄⁺-N to start up the DEAMOX process.The influences of the N/S ratio on the removal of nitrogen and sulfide in the DEAMOX reactor were investigated.Illumine High-throughput sequencing results revealed the microbial community structure and the functional microbes with excess or limited NO₃^--N.Two different mixed sludges?aerobic nitrifying sludge and anammox-denitrification sludge:R1,and anaerobic digestion flocculent sludge and anammox-denitrification sludge:R2?,were used as inoculum in two UBF reactors to enrich anammox bacteria.Both kinds of mixed sludge set up the anammox process successfully.It took 36 days for R1 to succeed in setting up the anammox process with volumetric loading rate increasing from 0.13 kg·?m³·d?^-1to 0.65 kg·?m³·d?^-1,while it took 53 days for R2.It showed that the aerobic nitrifying sludge could promote the enrichment of anammox bacteria.The simulation results of the Modified Stover-Kincannon model implied that the N-removal potential of R1 was superior to that of R2.Furthermore,the relative abundance of anammox bacteria of 3.2%in R1 was higher than that in R2 of 2.4%.The DEAMOX reactor inoculated with anammox sludge successfully started up on the39th day by adjusting the concentration of S^2-and NO₃^--N in the influent.The removal efficiency of NO₃^--N,NH₄⁺-N and TN was 81.0%,93.0%and 86.5%,respectively.In the DEAMOX reactor,efficient N-removal was achieved with the cooperation of SDAD and anammox.Anammox bacteria won in the competition for NO₂^--N produced by partial denitrification.The removal efficiency of NH₄⁺-N and NO₃^--N was obviously affected by the N/S ratio in the DEAMOX system.Maximum NH₄⁺-N removal efficiency?82.8%?was accomplished at the N/S ratio of 2.38 in this research.NO₃^--N removal efficiency was higher than 94.8%when the N/S ratio was below 0.73.Sulfide was nearly completely removed and the removal efficiency was higher than 98.6%.S⁰ accumulation was observed when the N/S ratio was below 1.The N removal contribution of SDAD and anammox were accounted for 3.7%⁴7.8%and52.2%⁹6.3%,respectively.Limited NO₃^--N was beneficial to Betaproteobacteria and Epsilonproteobacteria.When NO₃^--N was excess,Thiobacillus and Candidatus Kuenenia were dominated in the DEAMOX reactor.When NO₃^--N was limited,Sulfurimonas became dominated besides Thiobacillus and Candidatus Kuenenia.