Study on acute exposure of polyethylene terephthalate microplastics on the performance of anammox granular sludge

Anaerobic ammonia oxidation is a new and efficient biological denitrification process, which has been used in practice. Research on the effect of microplastics (MPs) on anaerobic ammonia oxidation (anammox) process is limited.

In this study, the effects of short-term exposure of polyethylene terephthalate (PET) with different particle sizes for 12 h on anammox granular sludge (AnGS) and the metabolic mechanism of anaerobic ammonia oxidizing bacteria (AnAOB) were studied.

The results showed that the acute exposure of anammox reactor to PET-MPs could promote the denitrification rate of the reactor. The enzyme activity of hydrazine dehydrogenase (HDH), the key enzyme of anammox reaction, was increased under acute exposure of different particle sizes of PET-MPs. PET-MPs with larger particle size had a stronger promoting effect on the treatment efficiency and HDH activity of the reactor. PET-MPs could stimulate AnAOB to secrete a large amount of extracellular polymeric substances (EPS). Metabonomic analysis showed that after the addition of PET-MPs, the abundance of 3-methoxytyramine was down-regulated, and the abundance of L-serine decreased. In the 13 μm PET-MPs group, the abundance of L-asparagine was up-regulated, changes in these metabolites affected various amino acid metabolism, proteolytic enzymes, and AnAOB biosynthesis.

This study provides valuable insights into the response characteristics and mechanism of the anammox process exposed to MPs, which may be helpful for the application of MPs in wastewater treatment.