Simultaneous biodegradation of nitrogen-containing aromatic compounds in a sequencing batch bioreactor

Area of Science:

• Environmental microbiology
• Environmental chemistry
• Wastewater treatment engineering

Background:

• Nitrogen-containing aromatic compounds (NACs) pose significant environmental risks and are challenging to remove from wastewater.
• Effective treatment methods are crucial for mitigating the impact of NACs on water bodies.

Purpose of the Study:

• To evaluate the efficacy of a sequencing batch reactor (SBR) for simultaneous removal of multiple hazardous NACs.
• To identify the microbial communities responsible for NAC degradation and elucidate their metabolic pathways.

Main Methods:

• A sequencing batch reactor (SBR) was operated with synthetic wastewater containing nitrobenzene (NB), 4-nitrophenol (4-NP), aniline (AN), and 2,4-dinitrophenol (2,4-DNP).
• 16S rRNA gene clone libraries were used to analyze the microbial community structure.
• "Cycle tests" were performed to assess the system's response to altered feeding and aeration parameters.
• Aromatic ring-cleaving dioxygenase activities were measured to infer degradation pathways.

Main Results:

• The SBR system achieved over 99% removal of NB, 4-NP, AN, and 2,4-DNP at high loading rates.
• Dominant bacterial groups identified included Bacteriodetes, Candidate division TM7, alpha-Proteobacteria, and beta-Proteobacteria.
• The microbial community demonstrated rapid adaptation to changing operational conditions, with O2 consumption correlating with NAC mineralization.

Conclusions:

• SBR technology is highly effective for the simultaneous removal of diverse hazardous NACs from contaminated water.
• Specific enzymatic pathways, including catechol 2,3-dioxygenase and 1,2,4-benzentriol 1,2-dioxygenase, are involved in the degradation of AN, NB, and 4-NP.
• The microbial biome in the SBR system is robust and adaptable, offering a promising solution for industrial wastewater treatment.