Microbial electrolysis cells (MECs) offer a promising approach for nitrate-contaminated sewage wastewater treatment oxidative stress-induced damage to electroactive biofilms, and inadequate hydrogen availability for complete denitrification. This study presents a novel redox-mediated Zn electrode designed to Zn²⁺/Zn⁰ redox couple selectively scavenges highly reactive oxidative species, including hydroxyl radicals (•OH) and peroxynitrite (ONOO⁻), thereby mitigating oxidative stress and protecting electroactive microorganisms and redox-active enzymes. The Zn-redox electrode demonstrated remarkable antioxidative capacity, reducing •OH and ONOO⁻ levels by 88.3 ± 2.8% and 89.1 ± 3.2%, respectively. This radical scavenging activity translated into significant improvements in cellular health and metabolic function. Geobacter sulfurreducens and mixed denitrifying consortia exhibited 12.51 ± 0.53 higher survival rates after 48-hour exposure, accompanied by a 78% increase in succinate levels (72.4 mM/mg protein), an elevated NADH/NAD⁺ ratio (4.98 ± 0.43), and a tripling of ATP content (72.3 ± 2.23 nmol/mg protein). Nitrate removal efficiency reached Hydrogen96% within 12 h using the Zn-redox cathode, compared to only 58% for conventional carbon felt controls. Current density peaked at 15.1 A/m² (control 3.7 A/m²), while maximum power density reached 3.9 W/m² (control 0.6 W/m²). Biomass density on the electrode surface increased threefold, from 0.18 to 0.78 mg protein/cm². Notably, nitrate removal was 98 ± 1, nitrite accumulation was reduced to <2 mg/L (control: 28 mg/L), and N₂O emissions decreased by 90%, addressing two major concerns in biological denitrification. The Zn-redox electrode selectively enriched Proteobacteria and Actinobacteriota, while promoting dominant electroactive and denitrifying genera including Geobacter, Pseudomonas, and Trichococcus. Concurrently, the system promoted efficient denitrification through enhanced extracellular electron transfer and hydrogen-assisted nitrate reduction, enabling rapid nitrate-to-N₂ conversion with minimal nitrite accumulation and markedly reduced N₂O emissions. The Zn-redox electrode maintained stable performance over 10 operational cycles with only 20% mass loss, demonstrating practical applicability.
To address harmful algal blooms (HABs) and mitigate their threats to ecological security and human health, developing advanced treatment technologies is imperative. In this study, a novel metal-carbon composite (CuCe/NCS), which couples CuCe-layered double oxides with modified porous carbons, was synthesized and applied for the catalytic ozonation of Microcystis aeruginosa. The synthesized CuCe/NCS featured a well-developed porous structure and abundant active sites, thereby enabling excellent catalytic performance. The CuCe/NCS-catalyzed ozonation process achieved nearly 100% algae removal within 40 min, with a reaction rate constant of 0.096 min-1, which is approximately 6.4-fold higher than that of the sole O3 process. The practical efficacy of CuCe/NCS-catalyzed ozonation was further validated through the treatment of real algae-laden waters. Mechanistically, the algae inactivation and removal were attributed to irreversible oxidative damage to cell membranes, intracellular/extracellular components as well as photosynthetic and antioxidant systems, induced by the substantial attack of reactive oxygen species (ROS) formed during the catalytic ozonation process. A series of experimental measurements and theoretical calculations clarified the catalytic ozonation mechanisms over CuCe/NCS, specifically involving the synergistic interaction between metal sites and the carbon matrix in promoting O3 adsorption-activation and ROS formation. Additionally, the ecotoxicity assessment using zebrafish as the indicator species confirmed the improved safety profile of the treated effluent. Overall, this study presents a promising ozonation catalyst and offers a highly efficient strategy for HABs remediation.
The effective removal of persistent and trace-level emerging contaminants (ECs) from aquatic systems presents a critical challenge to ensuring ecological security and achieving sustainable water resource management. Conventional advanced oxidation processes (AOPs) are hindered by a high dependence on external oxidants, leading to significant chemical consumption and secondary pollution risks for trace-level ECs elimination. This "Making Waves" article focuses on the innovative paradigm of endogenous-driven Fenton-like systems as a transformative solution. By leveraging catalyst design strategies via built-in electric field, these systems utilize the chemical potential energies of endogenous components in water (such as dissolved oxygen (DO) and ECs), thereby establishing an advanced treatment system using the endogenous-driven forces for the removal of trace-level ECs. We provide a systematic overview of the conceptual clarity, fundamental mechanistic paradigm of endogenous-driven Fenton-like catalysis, and critically examine its application scenarios as well as the merits/demerits compared to conventional exogenous AOPs. We further assess the challenges and future research directions toward endogenous-driven systems, extending beyond substrate-dependent catalysis mechanisms, operation stability, and reactor engineering, etc. Ultimately, this work outlines the pathway for endogenous-driven Fenton-like catalysis to evolve into a greener, and more intelligent technology for the advanced treatment of water matrixes with trace-level ECs.
With the phase-out of legacy brominated flame retardants (BFRs), particularly polybrominated diphenyl ethers (PBDEs), the use of novel brominated flame retardants (NBFRs) has increased steadily. This study investigated 42 PBDEs and 13 NBFRs in seawater, sediments, and atmospheric aerosols from the East China Sea (ECS). Regional investigations were integrated with a coupled dynamic material flow analysis-Level IV fugacity model and ecological risk assessment to characterize present contamination patterns and project long‑term trends over the coming decades. Legacy and novel BFRs co-occurred across all media, with lower-brominated congeners relatively enriched in seawater and highly brominated compounds dominating sediments and aerosols. Model results identified sediments as the major sink for BFRs, accounting for most of the ECS system inventory. PBDE concentrations peaked around 2007 and subsequently declined, whereas NBFRs increased rapidly after 2006 and are projected to gradually surpass PBDEs in aquatic and sedimentary environments under current emission trends. Most BFRs posed low average risks in seawater, but elevated risks occurred at nearshore sites, and sediment-associated risks were substantially higher. Our results reveal an ongoing shift from legacy PBDE contamination to NBFR-dominated pollution and highlight sediments as a long-term reservoir of BFR risk in the ECS.
Medium-chain fatty acid (MCFA) production from waste activated sludge (WAS) is considered to rely on the syntrophic interactions among distinct functional microorganisms. Whether phages represent an overlooked ecological component involved in MCFA biosynthesis remains unclear. MCFA production is often inhibited by high total ammonia nitrogen (TAN). Conductive materials have been proposed as effective strategies to enhance or recover MCFA production under TAN stress. Therefore, the inhibition-recovery system could provide a useful framework for investigating whether viral ecological responses are associated with MCFA-related metabolic processes. In this study, magnetite (Fe3O4) was selected as the recovery strategy of MCFA production under TAN stress. Results showed that a total of 3915 vOTUs and 118 metagenome-assembled genomes were recovered from the anaerobic bioreactors subjected to three conditions: Control (without TAN stress), TAN stress, and TAN stress with Fe3O4 presence. Under high TAN environment (∼5 g/L), MCFA production reduced by 49% (1.3 g COD/L) in comparison to that without high TAN stress. The ecological coupling between temperate phages and MCFA-related bacterial hosts was weakened, accompanied by substantial decreases in the abundance and transcriptional abundance of phage-associated auxiliary metabolic genes (AMGs) related to MCFA synthesis (e.g., fatty acid biosynthesis, acyl-chain metabolism). In the presence of Fe3O4 (i.e., 10 g/L), MCFA production was four and two times higher than those with and without high TAN stress. In addition to enhanced phage-bacteria ecological coupling and increased the abundance and transcription of AMGs related to MCFA formation, Fe3O4 increased the abundance and expressions of electron-transfer-related AMGs (e.g., cbb3-type cytochrome c oxidase, type IV pilus assembly genes) and QS-related LuxR-family and HTH-type regulators, indicating that such indirect pathway could be largely overlooked during MCFA synthesis. This is also the first-time reporting that phages could represent an ecological layer responsive to iron oxide. Analyses of publicly available metagenomes collected from MCFA-oriented anaerobic systems further confirmed that phages could be broadly associated with the metabolic processes involved in MCFA biosynthesis. Taken together, this study reveals that phages could serve as an overlooked ecological layer associated with MCFA metabolism and provide a viral-ecology perspective for understanding TAN inhibition and iron oxide-mediated recovery during WAS-to-MCFA bioconversion.
The performance of conventional heterogeneous catalytic ozonation (HCO) is severely impaired in hypersaline wastewater due to the scavenging of hydroxyl radicals (HO•) by chloride ions (Cl⁻). Herein, we fabricate a mechanochemically tailored Cu(I)-rich CuxO/MnOx catalyst to steer ozone activation toward a Cu(III)-mediated non-radical pathway. Ball milling promotes the formation of interfacial Cu-O-Mn linkages, enabling electron transfer from MnOx to Cu sites and stabilizing surface Cu(I). Using oxalate as a model recalcitrant contaminant, the CuxO/MnOx/O3 system achieves 93.2 %-100 % oxalate removal over a pH range of 4.0-9.0 and retains 81.7 % removal at 300 mM Cl-. Multiple lines of evidence confirm that Cu(III), rather than HO•, acts as the dominant oxidant. Notably, this system exhibits oxidative stability owing to continuous Cu(I)/Cu(III) redox cycling, which could be attributed to the electron replenishment to Cu sites from MnOx and O2•⁻ mediated by Cu-O-Mn bonds. Furthermore, when applied to real hypersaline wastewaters with total dissolved solids of 8.1-24.1 g L-1, the CuxO/MnOx membrane catalytic system attains 56.7 %-76.8 % TOC removal, representing a 1.6- to 2.7-fold enhancement over ozonation. This work provides a robust strategy for developing salt-resistant non-radical HCO systems for hypersaline wastewater treatment.
Foam fractionation has emerged as a promising technology for remediating per- and polyfluoroalkyl substances (PFAS) from aquatic environments. However, its sustainable application is critically hindered by the reliance on toxic synthetic co-surfactants and the intrinsic hydrodynamic trade-off between pollutant removal and enrichment. Here, we investigate how the molecular structure and charge characteristics of zwitterionic and anionic biosurfactants regulate PFAS capture and foam-fractionation performance. The study compares zwitterionic lauramidopropyl betaine (LAB) and lauryldimethylbetaine (BS-12) with anionic rhamnolipids (RLs) and sophorolipids (SLs). Interfacial thermodynamics and mechanistic characterization using FTIR, zeta-potential measurements, and molecular docking indicate that zwitterionic biosurfactants form cohesive interfacial assemblies with PFAS, whereas bulky anionic biosurfactants experience severe steric and electrostatic constraints. The stronger hydrogen-bonding capacity and polarizability of the sulfonate group also contribute to the more favorable interfacial association of perfluorooctane sulfonate (PFOS) than perfluorooctanoic acid (PFOA). Systematic variation of biosurfactant dosage, pH, ionic strength, and gas velocity reveals how interfacial adsorption and foam drainage jointly determine the balance between PFAS removal and enrichment. Under the optimized conditions, the LAB-assisted system achieved a maximum PFOS removal efficiency of 97.4% and an enrichment ratio of 10.4-13.2. The performance of the LAB system was further evaluated in deionized water, tap water, river water, and simulated wastewater, and supplementary experiments were conducted for the representative short-chain PFAS. Overall, this study links biosurfactant structure, interfacial interaction, foam hydrodynamics, and PFAS separation performance, providing a mechanistic basis for designing biosurfactant-assisted foam-fractionation processes for PFAS-contaminated wastewater and concentrated process streams.
Wastewater-based epidemiology (WBE) data are commonly normalized to a human fecal indicator to account for the variability in sample composition and analytical efficiency, which can be introduced by environmental or sewer system differences (e.g., infiltration and inflow, wastewater travel time) as well as sample processing. Normalizing pathogen concentrations by a surrogate can theoretically improve cross-site and longitudinal comparability by providing some measures of how some difficult-to-measure factors affect nucleic acid dilution, decay, and recovery. Members of Crassvirales (‘crAssphage’), bacteriophages with high human specificity and abundance in the human gut, have been used as a human fecal strength indicator with moderate success in improving data credibility. In this study, we leveraged the wastewater crAssphage quantification data accumulated over four years in New York State. We evaluated the spatiotemporal variability of crAssphage load, and whether crAssphage fulfills dual roles as a normalization factor and quality control for COVID-19 wastewater surveillance. The results suggest that crAssphage load has significant spatiotemporal variability, decreasing its potential as a normalizing factor for WBE. Normalizing SARS-CoV-2 wastewater concentrations to crAssphage had very limited effect on the correlation between SARS-CoV-2 concentration and COVID-19 clinical measures. However, we found that the threshold-exceeding values and non-detection of crAssphage may serve as a quality control step for SARS-CoV-2 surveillance. Our findings refine how the co-quantification of crAssphage can assist WBE.
Precise ion separation is fundamentally constrained by the disordered nanochannel and heterogeneous charge. Here, we report a dendrimer-directed strategy for engineering confined nanochannels and regulated charge environments within polyamide nanofilms. Self-assembled quaternary ammonium imidazole dendrimers (QASIDs) are covalently integrated into the polymer network during interfacial polymerization, enabling the formation of narrowed transport pathways for divalent ions with reduced electrostatic attraction. The resulting membranes exhibit substantially enhanced ion sieving performance, including a 48.94% expansion of the effective Li⁺/Mg²⁺ separation regime. Under high-salinity conditions (Mg²⁺/Li⁺ = 31.2), the membrane achieves an exceptional Li⁺/Mg²⁺ selectivity of 124, nearly one order of magnitude higher than that of conventional polyamide membranes, while maintaining a high water permeance of 283.13 ± 8.89 L·m⁻²·h⁻¹·MPa⁻¹. In addition, a high Cl⁻/SO₄²⁻ separation factor of 236.81 is achieved. Molecular simulations reveal that the incorporation of QASIDs generates more uniform confined nanochannels and optimizes the coupling between size exclusion and electrostatic interactions, thereby suppressing Mg²⁺ transport while preserving rapid Li⁺ permeation. The introduced positive charges effectively reduce the net negative charge density of the membrane, thereby weakening the electrostatic attraction toward Mg²⁺ rather than relying on Donnan repulsion. This work establishes a generalizable framework for programmable nanochannel engineering in polymer membranes toward high-performance ion separations.
