Work

Smaller sizes of polyethylene terephthalate microplastics mainly stimulate heterotrophic N2O production in aerobic granular sludge systems

Year: 2024

Type: article

Abstract: • Effects of PET MPs with different particle sizes on N 2 O turnovers are firstly uncovered. • PET MPs (especially 0.1 mm) stimulate total N 2 O production by denitrification in the AGS system. • 0.1 mm PET MPs induce N 2 O accumulation by decreasing electron transport during denitification. • 0.1 mm PET MPs further restrain N 2 O-sink capability by reducing key genes related to N 2 O reduction. Widespread polyethylene terephthalate microplastics (PET MPs) have played unintended role in nitrous oxide (N 2 O) turnovers (i.e., production and consumption) at wastewater treatment plants (WWTPs). Mainstream aerobic granular sludge (AGS) systems possess potentially strong N 2 O-sink capability, which may be reduced by PET MPs stress through altering N 2 O-contributing pathways, electron transfer, and microbial community structures. In this study, the effects of PET MPs with two common particle sizes of effluent from WWTPs (0.1 and 0.5 mm) on N 2 O turnovers, production pathways and N 2 O-sink capability were systematically disclosed in AGS systems by a series of biochemical tests and molecular biological means to achieve the goal of carbon neutrality. The results indicated that 0.1 mm PET MPs could more significantly stimulate N 2 O production in AGS systems by inhibiting denitrifying metabolism, compared with control and 0.5 mm PET MPs systems. Specifically, 0.1 mm PET MPs slightly increased the relative abundance of Nitrosomonas , reducing N 2 O yields via promoting the hydroxylamine (NH 2 OH) oxidation pathway during nitrification. Also, 0.1 mm PET MPs inhibited the electron transport system activities and the relative abundance of N 2 O reductase, hindering N 2 O reduction during denitrification. Most importantly, 0.1 mm PET MPs more apparently reduced the N 2 O-sink capability based on the ratio of N 2 O reductase gene and nitrite reductase gene.

Source: Water Research X

DOI: 10.1016/j.wroa.2024.100299