Bioprotection of the structure and function of activated sludge microbial communities against chloroaniline shock loads

Bioaugmentation of bioreactors generally focuses on the removal of specific xenobiotics. Often, less attention is hereby paid to the recovery of other reactor functions such as ammonium-nitrogen removal. This work evaluated the effects on activated sludge reactor functions of a 3–chloroaniline (3–CA) pulse and the protective bioaugmentation by inoculation with the 3–CA degrading strain Comamonas testosteroni https://www.w3.org/1998/Math/MathML" display="inline"> I 2 g f p . Changes in functions such as nitrification, removal and sludge compaction were monitored with the sludge community structure, in particular the nitrifying populations. Molecular techniques characterized and enumerated the ammonia oxidizing microbial community immediately after a 3–CA shock load. Two days after the 3–CA shock, ammonium accumulated and the nitrification activity did not recover over a 12 -day period in the non-bioaugmented reactors. In contrast, nitrification in the bioaugmented reactor started to recover from day 4 on. The molecular analysis showed that the ammonia oxidizing microbial community of the bioaugmented reactor recovered both in structure, activity and abundance, while in the non-bioaugmented reactor the number of ribosomes of the ammonia oxidizers decreased drastically and the community composition changed and did not recover. This study demonstrates that bioaugmentation of wastewater reactors to accelerate the degradation of toxic chlorinated organics such as 3–chloroaniline protected the nitrifying bacterial community, thereby allowing faster recovery from toxic shocks.