The enzymes-based intermediary model explains the influence mechanism of different aeration strategies on nitrogen removal in a sequencing batch biofilm reactor treating simulated aquaculture wastewater

Aquaculture wastewater can be efficiently treated by sequencing batch biofilm reactor (SBBR) via simultaneous nitrification and denitrification (SND), which is heavily influenced by different aeration strategies. The triangular associations among functional microbial abundance, key enzymes, and purification performance can be helpful to explain their influence mechanism on nitrogen removal from SBBR. For the present study, ten such systems for aquaculture wastewater polishing were operated under the pre-aeration (Pre-A) or post-aeration (Post-B) mode with different ratios of aeration to non-aeration or non-aeration to aeration. It was found that the average percent removals of ammonium (NH4+-N) and total inorganic nitrogen (TIN) were 84.72% and 61.98% in Pre-A, and were 93.84% and 55.29% in Post-B, with no obvious nitrite accumulation (0.13 +/- 0.07 mg/L in Pre-A and 0.6 +/- 0.2 mg/L in Post-B). The proteomic analysis illustrated that the aeration sequence affected the intermediary effect of ammonia monooxygenase (EC1.14.99.39) and hydroxylamine dehydrogenase (EC1.7.2.6). Post-aeration was beneficial to the consistency of the nitrifier abundance, the key nitrifying enzyme abundance, and NH4+-N removal. Meanwhile, the aeration sequence influenced the triangular associations among the heterotrophic denitrifier abundance, the denitrifying enzyme abundance, and TIN removal. In addition, nitrous-oxide reductase (EC1.7.2.4) was inhibited in the Post-B treatment. The different aeration strategies had no obvious impact on the taxonomic composition of autotrophic nitrifiers in these SBBR systems, but greatly influenced the taxonomic composition of heterotrophic denitrifiers at the genus level, especially affecting the proportion of denitrifying polyphosphate accumulating organisms (PAOs).

Automated summary

Aquaculture wastewater can be effectively treated by using sequencing batch biofilm reactor (SBBR) with simultaneous nitrification and denitrification (SND), and the choice of aeration strategy plays a significant role in the treatment process. The study found that changing the aeration sequence can affect the abundance of functional microbes, key enzymes, and the removal efficiency of nitrogen from the wastewater. Post-aeration was found to be more beneficial in maintaining the abundance of nitrifying bacteria and key enzymes, as well as improving the removal efficiency of ammonium nitrogen.