Comparison of Performance and Microbial Communities in Single Stage Suspended and Attached Growth Partial Nitritation/Anammox Reactors Under Different Temperatures

Two laboratory-scale partial nitritation/anammox (PN/A) bioreactors-suspended growth (SR) and attached growth (AR)-were initiated to investigate microbial population differences under an elevated temperature (35 degrees C) and room temperature (21 degrees C). During more than 300 days of operation, SR was able to remove 0.54 +/- 0.093 kg-N/(m(3).d) at 35 degrees C and 0.57 +/- 0.061 kg-N/(m(3).d) at 21 degrees C. Similarly, AR could remove 0.60 +/- 0.111 and 0.56 +/- 0.103 kg-N/(m(3).d(1)) at 35 degrees C and 21 degrees C, respectively. Similarity in nitrogen removal rates was probably due to presence of similar microbial communities predominated by three phyla: Chloroflexi, Planctomycetes, and Proteobacteria, nearly same numbers of key functional genes and similar nitrogen loadings. Although seeded from different biomass sources, both the SR and AR operated as sequential batch reactors harbored the same anammox bacteria of Brocadia fulgida and ammonium oxidizing bacteria of Nitrosomonas sp., which suggested the existence of competitive advantages over other species. Moreover, this study indicated that increasing temperature during startup could accelerate the startup process for PN/A systems. Ammonia monooxygenase (amoA) functional gene copy numbers were 1.25 +/- 0.08 x 10(9) and 1.85 +/- 0.16 x 10(9) in SR and AR, respectively, at 35 degrees C. The amoA gene copy numbers were 0.78 +/- 0.11 x 10(9) and 1.9 +/- 0.09 x 10(9) in SR and AR, respectively, at 21 degrees C indicating a negligible change in amoA gene copy numbers with temperature decrease. Similar results were obtained with hydrazine synthase (hzsA). Although, this article presents results in the context of sidestream application of PN/A systems, results are equally important for mainstream PN/A applications.