Innovative method for stable operation of low ammonia nitrogen nitrification systems: integrated enhancement strategy

Abstract

This study proposes an integrated strategy combining intermittent aeration, methyl p-hydroxy-phenylpropionate (MHPP) with syringic acid (SA), and hydrazine (N₂H₄) to address the instability of nitritation in autotrophic nitrogen removal systems treating low-ammonia wastewater. Achieving stable nitritation is critical for efficient autotrophic nitrogen removal in such systems. Yet, it remains challenging due to the difficulty in selectively suppressing nitrite-oxidizing bacteria (NOB) under low ammonia-conditions. Nitrogen transformation patterns and microbial community succession were analyzed by comparing the effects of the two inhibitors with N₂H₄. The R1 reactor employing the MHPP + N₂H₄ + intermittent aeration strategy achieved a nitrite accumulation rate (NAR) of 83.75% in the third phase, with a nitrate accumulation efficiency of only 9.64%. In contrast, the R2 reactor (using SA + N₂H₄ + intermittent aeration) reached an NAR of only 55.61%, while its nitrate accumulation efficiency exceeded 38.63%. Functional gene prediction revealed a 98% increase in the abundance of the AMO gene in R1 compared to the initial phase, confirming that MHPP selectively inhibits nitrite-oxidizing bacteria (NOB) while promoting the metabolism of ammonia-oxidizing bacteria (AOB). High-throughput sequencing further verified a significant reduction in NOB abundance in the R1 system (0.017%, p < 0.01). Microbial community reconstruction revealed that stable system performance was achieved through the synergistic inhibition of NOB and the optimization of the AOB ecological niche. This study offers an innovative approach to stabilize nitrogen removal in low-ammonia wastewater treatment, addressing an urgent need for effective and sustainable solutions under challenging operational conditions.