Targeted construction of artificial multicellular SND microbial communities and high ammonia-nitrogen wastewater treatment efficiency analysis

Simultaneous nitrification-denitrification (SND) offers a cost-effective approach to nitrogen removal, yet its efficiency is often limited by the instability of natural microbial consortia under fluctuating conditions. This study constructed three artificial multicellular SND microbial communities (consortium A, consortium B, consortium C) by continuously enriching and acclimating using samples from different process sections as the carrier. It elucidated their nitrogen removal mechanisms and engineering application potential. Results demonstrated that consortium B achieved NH₄⁺-N and total nitrogen (TN) removal efficiencies of 95.46 % and 75.84 % within 48 h in a mixed nitrogen source (NH₄⁺-N 350 mg/L, NO₃⁻-N 120 mg/L), with its TN removal rate being 1.10 and 1.16 times higher than those of consortium A and consortium C, respectively. Nitrogen balance and enzyme activity analyses revealed that consortium B exhibited specific activities of 0.6874 U/mg for the key enzyme ammonia monooxygenase (AMO) and 0.4530 U/mg for membrane-bound nitrate reductase (NAR), which were significantly higher than other bacterial flora. The metagenomic analysis revealed that the stable consortium centered on Acinetobacter (62.97 %) was systematically recombined. Among the up-regulated nitrogen metabolism genes, ammonia assimilation, nitrification, and denitrification accounted for 36.85 %, 22.27 %, and 25.03 %, respectively. The nitrogen removal efficiency of consortium B on high-nitrogen wastewater (TN 924.77 mg/L) was 74 % higher than that of the control group in a laboratory-scale bioreactor. This study provides theoretical support and a technological paradigm for optimizing wastewater nitrogen removal using engineered microbial communities.