Improved emerging contaminant removal in SBR with mycelial pellets (MPs): Insights into performances, microbial communities and mechanisms

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Abstract
The increasing prevalence of emerging contaminant (EC) in aquatic environments has raised significant public concern, owing to their environmental persistence and potential ecological risks even at trace concentrations. This study evaluated a novel and environmentally sustainable strategy for enhancing EC removal in sequencing batch reactors (SBRs) through the addition of Aspergillus niger mycelial pellets (MPs). An optimal MPs-to-sludge inoculum ratio of 3:1 (w/w) was identified as for promoting aerobic granular sludge (AGS) formation and improving contaminant elimination. Two lab-scale SBRs, R1 (Test, with MPs) and R0 (Control, without MPs), were operated over 90 days to assess systems performances. Results showed that MPs supplementation in R1 considerably accelerated aerobic granulation and increased biomass retention. Notably, diclofenac sodium (DCF) removal efficiency in R1 reached an average of 68.8%, representing a 14% improvement over R0. Simultaneously, R1 demonstrated even higher removal efficiencies for COD (94.2% vs. 93.7%), total nitrogen (69.5% vs. 66.3%), and total phosphorus (94.4% vs. 90.1%) compared to the control R0. Mechanistic investigations through morphological analysis, extracellular polymeric substance (EPS) quantification, enzyme activity assays, and 16S rRNA gene sequencing revealed that the superior performance in R1 was attributed to the synergistic effects of larger granular structures (411 μm vs. 165 μm), enhanced biomass retention, elevated EPS and enzyme production, and increased microbial diversity. In conclusion, the integration of fungal mycelial pellets into SBRs provides an effective and green strategy for enhancing the removal of emerging contaminant from wastewater.

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