Insight into the Microbial Interactions of Anammox and Heterotrophic Bacteria in Different Granular Sludge Systems: Effect of Size Distribution and Available Organic Carbon Source

Microbial interactions between Anammox and heterotrophic bacteria in different granule distributions in an Anammox system (AMX) and partial denitrification coupled with Anammox system (PDA) were analyzed in this paper. Candidatus Brocadia was the main Anammox microorganism in granules of 1.0 > d > 0.5 mm with the highest abundance of 21.5 % in AMX, significantly higher than the maximum proportion of 2.3 % in PDA sludge > 2.0 mm. However, the total nitrogen (TN) removal of 77.9 % in AMX was lower than PDA (94.0 %) because of the excessive NO3-N generated by nitrite-oxidizing bacteria (NOB). Anammox activity could be stimulated by heterotrophs via simple organic carbon, which decreased with the increasing size of sludge in AMX but increased in PDA. This highlighted that regulation of the distribution of sludge size and organic carbon source had an essential effect on efficient nitrogen removal of Anammox technology.