Substrate filling ratio affects nitrogen removal and antibiotic resistance risk in modular moving bed constructed wetland: Biofilm-mediated microbial community succession and resistome profiles reshaping.

Metagenomic insights into suppressing antibiotic-resistant bacteria in mesocosm-scale constructed wetlands: calamus-biochar alleviates selective pressure and disrupts genetic co-occurrence network.

As a mainstream technology for the advanced treatment of wastewater treatment plant effluents, constructed wetlands (CWs) exhibit limited efficiency in antibiotic removal and may instead serve as reservoirs for antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB). To address this, a mesocosm-scale CW amended with 4.0% calamus-biochar (PBC) filler was developed, achieving average antibiotic removal efficiencies above 92.7%. Compared with the blank system, the average ARGs removal efficiency increased by 54.2% and the proliferation of ARB was suppressed by an average of 65.1%. Furthermore, we found that the PBC filler adsorbed 41.8% of antibiotics while associating with only 1.4% of total culturable microorganisms, which may alleviate antibiotic selection pressure. Metagenomic analysis revealed that PBC filler reduced the normalized abundance (copies per cell) of mobile genetic elements (MGEs) by 0.68-5.98 cpc, accounting for 24.7-56.1%, weakened ARG-MGE co-occurrence and decreased the abundance of ARG-MGE co-localized contigs. Metagenome-assembled genome (MAG) analysis identified that Pseudomonadota was the dominant ARB phylum, predominantly harboring multidrug resistance genes and transposases, with a 56.7% reduction in relative abundance compared to the blank system. Batch experiments further confirmed that the PBC filler inhibited the potential for horizontal gene transfer (HGT) by sequestering ARGs. This study developed a CW system supplied with PBC filler for efficient removal of antibiotics, ARGs and ARB. It further elucidated the underlying mechanisms, with the PBC filler potentially decreasing antibiotic bioavailability and the potential for HGT of ARGs, thereby suppressing ARB proliferation.

Circular Resource Recovery in Constructed Wetlands: Microbial Community Succession and Plant Microbe Synergy in the Treatment of Petroleum Refinery Wastewater

Micro-electric field-associated restructuring of bacterial communities enhances wastewater purification in constructed wetlands

Summary To improve microbial activity and shock resistance in constructed wetlands (CWs), we established micro-electric field (MEF) enhanced CW systems to investigate their regulatory effects on domestic sewage treatment performance and bacterial communities. The results showed that MEF significantly improved the removal efficiencies of TP (16.97%–17.13%), NH4+-N (16.32%–28.93%), and COD (28.55%–53.81%). MEF also enhanced bacterial α diversity (Chao1, Shannon, Simpson) and altered community structure, with significant enrichment of Pseudomonadota and Bacteroidota that positively correlated with pollutant removal. Network analysis indicated that the MEF increased microbial network complexity and connectivity, and promoted competitive interactions within the community. Functional prediction revealed that MEF upregulated key pathways involved in carbon metabolism and nitrogen metabolism. We hypothesize that the MEF improves pollutant removal performance and stability in CWs by optimizing micro-environmental conditions and promoting a more diverse and functional microbial community. This work provides a microbiological foundation for developing energy-efficient, low-carbon wetland technologies.

A Potential Difference-Driven Cascade Effect of Cathode Biofilm–Plant Physiology Governs the Efficiency-Energy-Risk Trade-Off in Constructed Wetland–Microbial Electrolysis Cells

Conventional potential difference optimization in microbial electrolysis cell-integrated constructed wetlands (ECWs) treating antibiotic-laden wastewater frequently prioritizes single-dimensional removal efficiency, critically overlooking trade-offs with energy consumption and ecological risks. By evaluating four ECWs operated under varying potential differences treating chloramphenicol (CAP) wastewater via physicochemical metrics, multiomics, structural equation modeling, and comprehensive risk assessment, we identified a potential difference-driven “cathode biofilm–plant physiology” cascade effect governing this “efficiency-energy-risk” trade-off. Specifically, moderate potential differences (0.5 and 0.8 V) achieved superior total nitrogen (79.5–80.1%) and substantial CAP (90.9–92.5%) removal, driven by the selectively enriched electroactive, dissimilatory nitrate reduction to ammonium and CAP-degrading bacteria (e.g., Geobacter sp., Ectobacillus sp., Defluviilinea sp016789025). These microbiomes provided continuous ammonium supply, activating diverse plant nitrogen pathways and stimulating robust root radial oxygen loss to engineer a microoxic-anoxic microenvironment for comprehensive risk mitigation. Concurrently, relative to the 0.2 V control group, the 0.5 V condition minimized greenhouse gas emissions (a 49.2% reduction), lowered effluent ecotoxicity by 47.4%, and suppressed AMR risk by 56.0%, without incurring excess energy input. Ultimately, the optimal 0.5 V potential difference establishes a sustainable efficiency-energy-risk equilibrium, empowering ECWs as robust biogeochemical barriers under a unified “One Health” perspective.

Suspended sludge-Biofilm Niche Cooperation Enables Stable Mainstream Nitrogen Removal via Mixotrophic Partial Denitrification coupled with Anammox.

The sustainable application of partial denitrification/anammox (PD/A) under mainstream wastewater conditions depends critically on relieving the strong competition between heterotrophic and autotrophic microorganisms for substrates and ecological space. In this study, ferrous sulfide (FeS) was employed as a biofilm carrier to establish a mixotrophic PD/A (MPD/A), which maintained a total nitrogen removal efficiency of 90.25% under fluctuating organic carbon conditions in mainstream wastewater. To elucidate how niche differentiation between suspended sludge and biofilms supports synergistic nitrogen removal, community composition and predicted functional genes were analyzed to resolve the coexistence and division of labor of key microorganisms. The results showed that FeS, protein-like EPS, and multiple functional microbial populations jointly supported biofilm establishment and stability, enabling the preferential retention and enrichment of anammox bacteria (AnAOB) (14.09%), autotrophic denitrifiers, and other microorganisms involved in synergistic nitrogen removal. Together with suspended sludge, biofilms formed a cooperative nitrogen removal network integrating autotrophic and heterotrophic partial denitrification, complete denitrification, and anammox. Functional gene responses further revealed that autotrophic and heterotrophic partial denitrification within the biofilm sustained NO2--N supply, while FeS strengthened electron transfer and growth metabolism in AnAOB, thereby enhancing nitrogen removal kinetics and process stability. These findings provide a new strategy for expanding the ecological niche of anammox in mainstream denitrification tanks and a practical basis for the stable retention, enrichment, and sustained functional expression of AnAOB.

Plant–Substrate Interplay Regulates Nutrient Attenuation and Microbial Communities in Vertical-Flow Constructed Wetlands Treating Municipal Wastewater Treatment Plant Effluent

Advanced treatment of plant effluent (tailwater) is critical for mitigating agricultural non-point source pollution; however, plant–substrate synergy in vertical-flow constructed wetlands (VFCWs) remains poorly understood under subtropical conditions. This one-year pilot study evaluated the effects of substrate type (zeolite vs. gravel) and P. australis presence on nutrient removal, seasonal performance stability, and microbial community assembly in tailwater treatment. Methodologically, twelve VFCWs were operated across seasons, and their performance was assessed via water quality monitoring and high-throughput sequencing. The results indicate that all configurations consistently met stringent discharge standards. Planted treatments significantly outperformed unplanted controls in removing TN, COD, and TP (p < 0.05), while no significant difference emerged between zeolite- and gravel-planted systems, confirming vegetation’s dominance over substrate selection under low-concentration loads. Seasonal analysis revealed temperature-dependent TN removal (p < 0.01), whereas TP, COD, and NH4+-N removal remained stable. Microbial analysis showed P. australis selectively enriched functional taxa driving N and organic matter mineralization despite a shared core microbiome at the genus level. Gravel-planted VFCWs exhibited superior long-term resilience compared to the transient sorption of zeolites. We considered that vegetation-driven biological pathways offer a resilient design for polishing nutrients in tailwater, showing potential for agricultural irrigation and nutrient interception.