Impacts of diel temperature variations on nitrogen removal and metacommunity of anammox biofilm reactors

摘要

The influence of diel temperature variations (DTVs) on nitrogen removal and bacterial communities was investigated in two parallel anammox reactors (i.e., control and DTV reactors). The control reactor was ope rated at a constant temperature of 30 degrees C, whereas the DTV reactor was operated in a temperature fluctuation mode with a cycle of 12/12 h of high/low temperatures. Nine water temperature variations for t he dayight periods were set from 30/30 degrees C (i.e., Delta 0 degrees C) to 38/22 degrees C (i.e., Delta 16 degrees C). An increase in DTVs from Delta 8 degrees C (34/26 degrees C) to Delta 16 degrees C (38/22 degrees C) caused a significant decline in reactor performance and a shift in bacterial diversity. Compared to the control reactor, for instance, nitrogen removal efficiency decreased (P 0.05) when temperature fluctuations exceeded Delta 8 degrees C in the DTV reactor with a decreasing Delta NO3-/Delta NH4+ ratio (from 0.21 +/- 0.15 to 0.16 +/- 0.04). The results of 16S rRNA gene sequencing showed that the initial disturbance of temperature variations led to increased levels of bacterial diversity (i.e., alpha diversity) and decreased community levels of anammox consortia whereas they slightly recovered at the and of each DTV phase. Notably, Candidatus Jettenia was more sensitive to strong water temperature fluctuations, with the lower relative abundance at Delta 14 degrees C (17.11 +/- 5.01%) and Delta 16 degrees C (17.83 +/- 7.22%) than at Delta 4 degrees C (39.82 +/- 0.01%). In contrast, Ca. Brocadia and Ca. Kuenenia had higher relative abundance at Delta 14 degrees C (i.e., 0.24 +/- 0.07% and 0.09 +/- 0.02%, respectively) and Delta 16 degrees C (i.e., 0.28 +/- 0.05% and 0.12 +/- 0.03%, respectively) compared to that at Delta 4 degrees C (i.e., 0.15 +/- 0.04% and 0.04 +/- 0.01%, respectively). Nitrifiers (i. e., unidentified_Nitrospiraceae and Nitrosomonas) and denitrifiers (i.e., Denitratisoma) were also capable of tolerating high temperature perturbations. Overall this study furthers our knowledge of responses of the microbial ecology of anammox bacteria to DTVs in anammox processes, which could aid us in optimizing anammox-related wastewater treatment systems and in understanding the nitrogen cycles of natural ecosystems. (C) 2019 Elsevier Ltd. All rights reserved.