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Concentration-dependent effects of polystyrene microplastics on methanogenic activity and microbial community shifts in sewer sediment
Summary
This study tested how polystyrene microplastics affect methane-producing microbes in sewer sediments and found that low concentrations boosted methane production by over 200%, while higher concentrations had a smaller stimulating effect. The findings matter for wastewater management because microplastics entering sewer systems could alter greenhouse gas emissions and disrupt the microbial processes that treatment plants rely on.
Microplastics (MPs) are emerging environmental contaminants that interfere with microbial processes, yet their effects on methanogenesis in anaerobic systems remain insufficiently understood. This study investigates the impact of polystyrene microplastics (PS-MPs) on methanogenesis, microbial community structure, and metabolic pathways in simulated sewer sediment systems, with exposure concentrations of 5, 50, and 250 mg·L. The results revealed a concentration-dependent effect of PS-MPs on methanogenesis: a 222.2 % increase at 5 mg·L, and 72.2 % and 88.9 % increases at 50 mg·L and 250 mg·L, respectively, indicating a non-linear response. PS-MPs exposure enhanced coenzyme F420 (F420) activity, a key indicator of methanogenic activity, but also inhibited methyl coenzyme M reductase (Mcr), disrupting critical methanogenic pathways. At lower concentrations, PS-MPs promoted the abundance of hydrogenotrophic methanogens, whereas higher concentrations suppressed overall methanogenic activity. Furthermore, PS-MPs had a dose-dependent effect on CH oxidation, influencing the structure of methanotrophic communities. These findings establish a clear dose-response relationship between PS-MPs concentration and CH dynamics in anaerobic systems, highlighting the complex role of microplastics in methanogenesis and microbial interactions. This research provides valuable insights into the environmental implications of microplastics in wastewater systems and their potential impacts on biogas production and CH mitigation, aligning with the objectives of environmental bioengineering and sustainable waste management.