Impacts of salt shocking and the selection of a suitable reversal agent on anammox.

Abstract

In this study, an anaerobic ammonium oxidation (anammox) reactor, which was inhibited by a salinity of 50 g NaCl L-1 during a long-term experiment, was rapidly restarted by decreasing the salinity to 20 g NaCl L-1 and adding biomass. The effects of exposure time and shock concentrations on the anammox reactor indicate that anammox granular sludge has a high tolerance to salinity and strong ability for self-recovery. The nitrogen removal efficiency was higher than 50% after exposure to 50 g NaCl L-1 for 66 h. To shorten the time taken for effluent nitrogen concentrations to attain national standards (GB18918-2002) after the anammox reactor was shocked with NaCl, reactor performance (i.e., recovery) after the addition of K+, glycine betaine, Fe2+, and hydroxylamine were compared after the reactor was inhibited by 80 g NaCl L-1. The results indicate that hydroxylamine was the best reversal agent. The recovery time of the anammox reactor could be shortened by 50% following the addition of hydroxylamine. The most favorable NH2OH-N/NO2--N concentration ratio for improving nitrogen removal of anammox was 1:11. The abundances of Planctomycetes and its genera Candidatus Kuenenia and Brocadiaceae_g_unclassified increased after repeated salinity shock-recovery phases, indicating that Candidatus Kuenenia and Brocadiaceae_g_unclassified are able to adapt to NaCl shocking and recovery.