Evaluation of characteristics and microbial community of anaerobic granular sludge under microplastics and aromatic carboxylic acids exposure

The influences of polyether sulfone (PES) microplastics and different structures aromatic carboxylic acids such as benzoic acid (BA), phthalic acid (PA), hemimellitic acid (HA), and 1-naphthoic acid (1-NA) on the performances and characteristics of anaerobic granular sludge as well as the microbial community were investigated. The chemical oxygen demand (COD) removal efficiency was the highest in the experimental group with 40 mg/L BA, reaching 90.1%. The inhibitory effect of aromatic carboxylic acids addition on the 2,3,5-triphenyltetrazolium chloride (TTC) activity was more obvious than that on 2-para (iodo-phenyl)-3(nitrophenyl)-5(phenyl) tetrazolium chloride (INT) activity. Compared with the control group (only 0.5 g/L PES microplastics, 60.6 mg TF.g TSS.h(-1)), the inhibition effect of TTC activity was 32.5 mg TF.g TSS.h(-1) and 44.3 mg TF.g TSS.h(-1) in the 40 mg/L HA and 40 mg/L 1-NA experimental groups, respectively. When aromatic carboxylic acids were added, the activities of acetate kinase and coenzyme F420 in the anaerobic granular sludge decreased. The excitation-emission matrix (EEM) fluorescence spectra indicated that loosely bound extracellular polymeric substances (LB-EPS) began to decay. After the addition of different aromatic carboxylic acids, the C-C and C-H functional groups of the anaerobic granular sludge increased, suggesting that aromatic carboxylic acids migrated to the surface of anaerobic granular sludge, such a transfer would lead to changes in anaerobic granular sludge performance. High-throughput sequencing technology showed that the dominant microbial communities in the anaerobic granular sludge were Proteobacteria, Methanothrix, and Methanomicrobia. After the addition of aromatic carboxylic acids, the relative abundances of Proteobacteria, Methanobacterium, and Methanospirillum increased. In the presence of PES, 1-NA had the most serious toxicity to the anaerobic granular sludge. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study revealed that different aromatic carboxylic acids have impacts on the performance and microbial communities of anaerobic granular sludge, with benzoic acid showing the highest efficiency in COD removal. The addition of aromatic carboxylic acids led to an increase in functional groups in the anaerobic granular sludge and affected the decay of LB-EPS.