Lingwei Kong

The accumulation of biodegradable plastics (BPs) in wastewater treatment plants (WWTPs) presents a novel environmental concern, while carbon deficiency concurrently limits advanced biological denitrification. Herein, this research explored the fate of BPs and their viability as solid-phase carbon donors for denitrification. Six prevalent BPs were selected; results showed that microbially synthesized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was identified as the optimal solid-phase carbon source with superior DOC bioavailability, achieving a denitrification rate of 0.72 mg/(g·h). Light irradiation and pH variations accelerated DOC release via surface micro-cleavage, predominantly yielding highly active aliphatic oligomers without disrupting the primary polymeric backbone. Furthermore, macromolecular depolymerization genes (cellulase, hexosaminidase) and nitrous oxide reductase genes (nosZ, nosD) were strongly temperature-dependent, which induced the directional enrichment of the core denitrifying genus Thauera and upregulated expression at 25 °C, which promoted NO₃⁻ reduction. This research provides the theoretical basis for the in situ resource utilization of BPs for advanced wastewater denitrification.

The accumulation of biodegradable plastics (BPs) in wastewater treatment plants (WWTPs) presents a novel environmental concern, while carbon deficiency concurrently limits advanced biological denitrification. Herein, this research explored the fate of BPs and their viability as solid-phase carbon donors for denitrification. Six prevalent BPs were selected, results showed that dissolved organic carbon (DOC) release from BPs varies considerably with the synthesis type, microbially synthesized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as the optimal solid-phase carbon source with superior DOC bioavailability, achieving the denitrification rate of 0.72 mg/(g·h). Light irradiation and pH variations accelerated DOC release via surface micro-cleavage, predominantly yielding highly active aliphatic oligomers without disrupting the primary polymeric backbone. Furthermore, macromolecular depolymerization genes (acsABCDE, cdhCDE) and nitrous oxide reductase genes (nosZ, nosD) were strongly temperature-dependent, which induced the directional enrichment of the core denitrifying genus Thauera, and upregulated expression at 25 °C that promoted NO₃⁻ reduction. This research provided the theoretical basis for the in-situ resource utilization of BPs for advanced wastewater denitrification.

Constructed wetlands (CWs) are widely used for advanced treatment of wastewater treatment plant effluents and their nitrogen (N) removal performance is often inhibited by antibiotics. Biofilms on CW substrates play a fundamental role in pollutant biodegradation, microbial community stability and antibiotic resistance gene (ARG) dissemination. This study investigated the effects of substrate filling ratios (90% and 60%) in modular moving bed constructed wetlands (MMB-CWs) on operational performance, biofilm properties and antibiotic resistance risks. The MMB-CW with higher substrate filling ratio exhibited a better N removal efficiency of 83.7% and a significant reduction of N2O emissions by 72.6%. The higher substrate filling ratio increased the protein/polysaccharide ratio of extracellular polymeric substances (EPS) in biofilm, forming a hydrophobic barrier that enhanced antibiotic surface adsorption and structured a highly modular microbial network with pronounced niche differentiation. Genome-centric analysis revealed that core taxa carrying denitrification and anammox genes (narG, narH, nirS, nosZ, hzs, hdh) enriched by 1.5- to 12.6-fold in abundance. Notably, Desulfobacillus increased by 1.7-fold in abundance and served as a keystone species driving denitrification, EPS construction, oxidative stress adaptation and energy production. The elevated abundances of enzymes catalyzing key electron- and energy-generating steps in the tricarboxylic acid (TCA) cycle and denitrification enzymes drove a more complete denitrification process. The highly modular network restricted horizontal gene transfer of ARGs, mitigated the enrichment of pathogenic antibiotic-resistant bacteria (PARBs) and occurrence of high-health-risk ARGs in MMB-CW. The findings provide an optimization strategy for MMB-CW applications in view of treatment performance and ecological risk.