Composting is an effective strategy for organic waste recycling, however, the frequent coexistence of heavy metals and antibiotics in mixed feedstocks introduces substantial challenges. These co-contaminants can impair microbial activity and raise ecological risks in end products. This study investigated the effects of biochar amendment on composting under combined heavy metal and antibiotic contamination. Biochar significantly improved composting performance by extending the thermophilic phase and enhancing system stability. It promoted nitrogen stabilization, as indicated by increased organic-to-inorganic nitrogen ratios from 24:76 in the control to 33:67, 43:57, and 51:49 under 5%, 10%, and 15% biochar treatments, respectively. Humification was also enhanced, with the CHA/CFA ratio increasing from 1.0 to 1.5 at the highest biochar dosage. In addition, biochar facilitated stabilization of heavy metal, achieving high removal efficiencies of sulfamethazine (98.2%) and ofloxacin (99.3%). Microbial community analysis revealed sustained dominance of Firmicutes and enrichment of Actinobacteria up to 23.2% with higher biochar doses. These results indicate that biochar improved compost maturity and contaminant stabilization under co-contaminated conditions, providing a feasible strategy for safe and efficient recycling of organic wastes.

Sudden shock loads in wastewater influent can severely disrupt biological treatment processes and cause effluent quality exceedances in wastewater treatment plants, particularly in domestic-industrial integrated facilities. Timely and reliable early warning of such disturbances is critical for enabling proactive intervention and minimizing environmental and operational risks. This study develops a COD-centric closed-loop early warning framework that integrates a machine-learning-based soft-sensing module with a multi-step effluent prediction module, in which anomaly tagging is automatically triggered by effluent discharge limit thresholds. Two coupling architectures were evaluated: a serially coupled architecture (SCA) that sequentially connects influent sensing and effluent prediction, and a jointly coupled architecture (JCA) that enables end-to-end learning within a unified model. Feature importance was interpreted using SHAP analysis and validated through ablation studies to identify the key process variables that govern predictive performance and early-warning responsiveness. In a full-scale integrated wastewater treatment plant (IWTP) case study, the proposed framework achieved 95.0% accuracy and 87.2% anomaly detection precision for 12 h ahead warnings, with JCA outperforming SCA. These results demonstrate that backward inference from predicted effluent compliance risk enables timely identification of upstream disturbances before limit violations occur. This integrated and interpretable framework provides a novel, real-time, and cost-effective solution for linking effluent-risk forecasting with influent-anomaly diagnosis, substantially enhancing the operational resilience and proactive management of IWTPs.

Interfacial electron transfer (IET) between aqueous Fe(II) (Fe(II)(aq)) and iron (oxyhydr)oxides is a widespread process that generates highly reactive Fe(III) species (Fe(III)(labile)), facilitating rapid mineral recrystallization into stable crystalline phases. These systems are known to be more reducing towards a wide variety of electron accepting species. However, these same systems show anomalous redox reactivity toward arsenic, in that they favor oxidation of As(III) rather than reduction of As(V). We hypothesized this reactivity arises from a direct quantitative connection between Fe(III)(labile) production and As(III) oxidation. Here we tested this hypothesis by employing magnetite nanoparticles with varying stoichiometries (Fe(II)/Fe(III) ratios), denoted Mt(0.48), Mt(0.37), and Mt(0.24), as representative minerals that, along with varying Fe(II)(aq) amendment, were used to manipulate Fe(III)(labile) generation and establish its role in reactions with As(III) and As(V). Magnetite could generate Fe(III)(labile) through dual pathways of Fe(II)(aq) release and adsorption, driven by reversible electron redistribution across the magnetite-solution interface. At pH 7.0 and 20-100 & micro;M arsenic, the adsorption rates and capacities for both As(III) and As(V), as well as As(III) oxidation extents, followed the order Mt(0.48) > Mt(0.37) > Mt(0.24), despite the lower apparent redox potentials of more stoichiometric particles. These reactions were accompanied by extensive depletion of Fe(III)(labile), showing a strong global linear correlation between Fe(III)(labile) consumption and As(III) oxidation across all systems. DFT calculations further revealed the strong electronic interactions and substantial Bader charge transfer (1.943-2.212 e) from As(III) to Fe(III)(labile). Our results identify Fe(III)(labile) as the critical redox-active species controlling arsenic adsorption and As(III) oxidation on magnetite nanoparticles, providing new mechanistic insights into the role of this important species and coupled arsenic-iron cycling in subsurface environments.

The stringent effluent standards rise strong demand for efficient wastewater treatment, particularly for the superior removal of nitrogen and phosphorus. To address the issues of membrane fouling and insufficient phosphorus removal in the internal circulation aerated membrane bioreactor (ICAMBR) treating municipal wastewater, this study achieved significantly improved system performance and effective membrane fouling control through the addition of polyaluminum chloride (PAC). The findings showed that the addition of PAC resulted in average removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) of 98.87%, 98.46%, and 94.83%, respectively, while the effluent TP level was reduced to 0.26 mg/L. Additionally, PAC effectively reduced the extracellular polymeric substances (EPS) content and enhanced sludge settleability, which led to a decrease in membrane fouling from 1.42 × 1012 m−1d−1 to 0.54 × 1012 m−1d−1. The irreversible membrane resistance decreased from 1.98 × 108 m−1 to 0.35 × 108 m−1, thereby effectively alleviating membrane fouling in the system. Microbial analysis revealed that PAC fostered the enrichment of denitrifying and ammonia-oxidizing bacteria, which in turn enhanced the abundance of key nitrogen metabolism genes, thereby reinforcing the nitrogen removal pathways in the system. This study provides both theoretical insights and technical support for the enhanced operation of ICAMBR through PAC addition in municipal wastewater treatment.

Background The removal of heavy metal ions from aqueous solutions has received increasing attention due to their non-biodegradability and potential for bioaccumulation in the food chain. Methods In this study, epichlorohydrin-crosslinked alginate fibers (EAFs) were synthesized via an organic covalent crosslinking strategy as an alternative to the traditional Ca(II) ionic crosslinking method, aiming to enhance the adsorption performance of alginate-based adsorbents toward heavy metals. Significant Findings Compared with Ca(II) crosslinked alginate fibers (Ca(II)-AFs), the Pb(II), Cd(II), Zn(II), Ni(II), Cu(II), and Co(II) uptakes on EAFs increased by 8.5%, 8.9%, 63.6%, 19.7%, 24.5%, and 46.1%, respectively, with adsorption capacities reaching 401.9 mg/g, 149.0 mg/g, 85.1 mg/g, 92.6 mg/g, 124.8 mg/g, and 82.6 mg/g. Adsorption equilibrium was achieved within 20 mins, indicating rapid kinetics. Furthermore, EAFs could be readily regenerated using a HNO3 solution, retaining >85% of the initial adsorption capacity after four adsorption-desorption cycles, demonstrating excellent reusability. Finally, the adsorption mechanism was elucidated through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses, which suggested that heavy metals were primarily captured through electrostatic attraction and coordination between the carboxyl groups of alginate and the heavy metal ions.

Ammonia-laden wastewater containing residual tetracycline (TC) and insufficient readily biodegradable carbon poses a challenge for stable biological nitrogen removal. In this study, a microaerophilic anoxic/oxic process based on the Biological Low Oxygen and High Activated Sludge concentration (Bio-LOHAS) strategy was applied to treat synthetic high-ammonia, low-C/N wastewater under stepwise TC loading (0-5.0 mg/L). Compared with conventional AO operation, Bio-LOHAS combines low dissolved oxygen and high sludge concentration to promote simultaneous nitrification and denitrification (SND) and improve tolerance to antibiotic stress. At TC <= 1.0 mg/L, the system maintained stable COD and total nitrogen (TN) removal above 90% and 85%, respectively. At 5.0 mg/L TC, nitrite accumulated because nitrite-oxidizing bacteria were more strongly inhibited than ammoniaoxidizing bacteria, shifting nitrogen conversion toward partial nitrification and denitrification. However, relatively high TN removal was still retained because denitrification was less affected than nitrification. Recovery was achieved after influent TC reduction or withdrawal, indicating improved tolerance of acclimated sludge during re-exposure rather than unrestricted stable operation under continuously high TC loading. Overall, BioLOHAS is a promising strategy for improving nitrogen-removal resilience in antibiotic-impacted, carbon-limited ammonia-rich wastewater.

Pentachlorophenol (PCP) is a persistent chlorinated organic pollutant with high toxicity, strong environmental stability, and resistance to biodegradation. Although persulfate-based oxidation is promising for PCP remediation, its performance in contaminated soil is often limited by complex soil matrices and unclear activation mechanisms. In this study, CaO-activated persulfate was applied to PCP degradation in actual contaminated soil, with emphasis on synergistic alkaline–thermal activation and calcium-associated PCP transformation. CaO significantly enhanced PCP degradation, achieving 86.0% removal after 7 d, whereas persulfate alone showed limited oxidation capability. Mechanistic analysis showed that CaO promoted PCP degradation through Ca(OH)2-induced alkaline activation, hydration-induced transient thermal activation, and Ca2+-mediated formation of calcium-associated pentachlorophenolate species (PCP-Ca). PCP-Ca formation reduced the apparent degradation activation energy from 112.8 to 92.3 kJ mol−1 and increased the apparent pseudo-first-order rate constant by 62.7% at 30 °C, indicating enhanced oxidative susceptibility. SO4•- and •OH were identified as the main reactive species. LC-MS analysis suggested that PCP degradation proceeded through hydroxylation, dechlorination, and ring-cleavage pathways, generating intermediates with lower predicted toxicity. This study reveals the multifunctional role of CaO in persulfate activation and provides mechanistic insight into PCP degradation in contaminated soil.

High-concentration glyphosate (Gly) wastewater presents a formidable remediation challenge due to its recalcitrance and the inherent risk of generating toxic intermediates like aminomethylphosphonic acid (AMPA). Herein, we report a facile "waste-treats-waste" strategy utilizing a self-accelerated Fe(II)/O2 system that operates efficiently under neutral pH, effectively circumventing the acidic constraints of traditional Fenton processes. This system achieved a 57% Gly removal efficiency (initial concentration 0.5 g/L) within 60 min, with a kinetic rate constant (kobs = 0.029 min-1) significantly outperforming conventional oxidation technologies. Mechanistic investigations reveal that Gly acts as a suicide ligand, forming an inner-sphere Fe(II)-Gly complex that lowers the Gibbs free energy barrier, thereby rendering O2 activation thermodynamically favorable. The degradation proceeds via a dual-pathway mechanism, synergizing hydroxyl radical (•OH) attack (∼40%) with a dominant intramolecular ligand-to-metal charge transfer (LMCT) process (∼60%). Crucially, density functional theory (DFT) calculations elucidate that Fe(III) coordination induces a regioselective weakening of the C-N bond adjacent to the phosphonate group. This steric and electronic modulation steers the reaction pathway toward the preferential formation of benign glycine, successfully suppressing the generation of highly toxic AMPA. Bioassays using Tetrahymena thermophila confirmed that this glycine-selective pathway optimization significantly mitigates the acute toxicity of the effluent, validating the system as a sustainable and eco-safe solution for herbicide wastewater treatment.

Iron oxides can facilitate anaerobic digestion but are faced with electron competition between methanogens and iron-reducing bacteria. In this study, we developed a highly crystalline iron oxide material via the pyrolytic synthesis of metal-organic framework (MOF) precursors and systematically investigated its mechanistic role in improving anaerobic digestion. The results showed that 10 g/L of the MOF-derived iron oxide (MDF) enhanced the methane yield to 547.91 mL/g volatile solids. Characterisation of the MDF material revealed that it had a highly ordered crystalline structure (95.56 % crystallinity) and superior electrochemical activity, with a positively charged surface facilitating microbial adhesion. Microbial analysis revealed that MDF selectively enriched Methanosarcina (methanogens) and Clostridium_sensu_stricto_1 (syntrophic bacteria), while up-regulating genes associated with conductive pili (PilA) and quorum-sensing signalling molecules. This shift established a direct interspecies electron transfer-driven metabolic network. Furthermore, the high crystallinity of MDF suppressed the enrichment of iron-reducing bacteria (Trichococcus abundance, < 2.5 %), thereby mitigating iron reduction competition for acetate/hydrogen and overcoming the limitations of conventional Fe2O3. This superior stability was further confirmed in a long-term experiment, where MDF exhibited both higher methane yield and greater resistance to reduction than Fe2O3. This study provides fundamental insights into crystallinity-dependent electron transfer pathways for methanogenesis and a strategic framework for engineering stable conductive materials to enhance the efficiency and stability of anaerobic digestion.

Commercial adsorption resins are widely used for heavy metals removal from industrial wastewater, yet their selection still depends on labor-intensive and time-consuming experiments. Machine learning (ML) offers a promising alternative, but its predictive power is often constrained by insufficient mechanistic understanding. In this study, a hybrid grid search-extreme gradient boosting (GS-XGBoost) model was developed by integrating adsorption mechanisms into a data-driven framework. Key physicochemical descriptors, including chemical structure, atomic number, valence, electronegativity, atomic radius, as well as environmental conditions including temperature and pH, are incorporated, achieving high predictive accuracy (R2 = 0.915). SHAP analysis identified chemical structure as the most critical factor, where nitrogen-containing functional groups (excluding symmetrical N-containing motifs) enhanced heavy metal adsorption, whereas long-chain structures suppressed it. To further improve generalization, Density Functional Theory (DFT) were employed to identify actual adsorption sites, thereby refining the model's prediction of intramolecular adsorption configurations. This approach reduced the average relative error from 57.13 % to 24.27 %. This study establishes a robust framework for rapid adsorbent screening and provides a novel strategy for integrating mechanistic insights into data-driven models, advancing the intelligence design of adsorbents for environmental remediation.

Propionate is a key intermediate in anaerobic digestion (AD), and its accumulation may lead to over-acidification and process failure. This study assessed methanogenic tolerance to increased propionate concentrations. The specific methane yield ranged from 238.0 to 277.3 mL/g COD at the initial propionate concentration of 2 to 10 g COD/L, and slightly decreased to 260.6 and 233.3 mL/g COD at 13 and 16 g COD/L, respectively. Kinetic analysis indicates lower inoculum-to-substrate ratio primarily negatively affected digestion time rather than accumulated methane yield. No clear inhibition occurred, even at 16 g COD/L, indicating a substantial propionate tolerance in AD. 16S rRNA gene analysis revealed that Desulfobacterota, particularly the family Syntrophobacteraceae was positively associated with propionate degradation, showing a linear correlation (p < 0.01) with both initial propionate concentration and digestion duration. Genome-centric metagenomic analysis further identified Bin.002 (Syntrophobacteraceae JABUEY01) and Bin.012 (Syntrophobacteraceae sp.) as dominant syntrophic populations, exhibiting high RPKM abundance and encoding the complete methylmalonyl-CoA (mmc) pathway. A metabolically diverse methanogenic community was also enriched, including aceticlastic Methanosarcina mazei (Bin.006), Methanothrix spp. (Bin.009 and Bin.014), and hydrogenotrophic Methanobacterium spp. (Bin.011 and Bin.026), which rapidly consumed metabolic intermediates, thereby avoiding inhibition at high propionate concentrations. Overall, the batch experiments demonstrated strong propionate tolerance under stable anaerobic conditions, supporting the conclusion that propionate accumulation is more likely a consequence rather than a primary cause of anaerobic reactor imbalance.

Polymerization transfer (PT) technology is highly advantageous for treating high-salinity wastewater due to its high tolerance to coexisting anions and superior electron utilization efficiency. Here, we report the unusual simultaneous achievement of rapid pollutant removal (pseudo-first-order rate constant of 0.15 min(-1), 56.0-fold higher than unmodified counterparts) and high PT ratio (>65 %) in a peroxymonosulfate (PMS) activation system. This was achieved by simply tuning the Fe content within a rationally designed Fe/N engineered pine sawdust biochar catalyst. Performance enhancement stems from Fe-induced graphitization improving electron transfer, coupled with N-induced moderate orbital hybridization between Fe 3d (Fe/N biochar) and O 2p (PMS) atomic states, optimizing PMS adsorption-desorption and yielding the lowest energy barrier for Fe(IV)=O formation. Remarkably, the system maintains robust performance under high salinity conditions (500 mM Cl-, HCO3-, NO3-, and SO42-) and achieves 67.5-77.3 % chemical oxygen demand (COD) removal during 17-day continuous-flow treatment of real coking wastewater, where polymerization-mediated organic removal through CC/CO coupling. Furthermore, residual oligomers are efficiently removed by subsequent activated carbon (AC) adsorption or poly-ferric sulfate (PFS) coagulation, establishing an integrated "catalytic polymerization-AC/PFS polishing" paradigm for sustainable treatment of refractory organics in high salinity coking wastewater.

Poor sludge properties and weak hydrodynamics severely limit mass transfer and solid-liquid separation in anaerobic membrane bioreactors (AnMBRs) treating food waste. This study developed a synergistic foulingmitigation strategy that couples moderate biogas sparging with a self-antifouling reciprocating membrane module. Compared with reciprocation alone, the integrated operation extended the stable filtration period from 19 to 60 days, and enabled an in-situ recovery step that sustained operation for a further 35 days, accompanied by a 14.5% increase in methane production rate. The integrated mode reduced sludge viscosity and particle size, indicating a higher mixing efficiency. Particle-image velocimetry showed higher near-membrane shear and stronger bulk circulation attributable to gas scouring and inertial effects. Scanning electron microscopy showed reduced gel-like coverage on the cake layer under the integrated strategy. Microbial sequencing identified filamentous Anaerolineae (SBR1031) as dominant in sludge and cakes, with sparging reshaping community structure. Genome-resolved metagenomics reconstructed key genomes and suggested higher representation of acetogenic and methanogenic potential under the integrated strategy. Overall, this study demonstrates a promising fouling control strategy for high-solids, viscous organic waste treatment.

ABSTRACT Unlocking the full potential of bulk transition metal oxides (TMOs) is often hindered by their limited atomic exposure and restricted tunability of active sites, which collectively lead to suboptimal catalytic activity. Herein, we present a facile ligand‐assisted metal abstraction strategy to construct an amorphous shell embedded with single Cu atoms on a crystalline CuO core. The synergistic coordination of ─COOH and ─NH 2 groups at the Cu single site promotes selective orbital coupling between Cu d xz / d yz and O p orbitals, facilitating O‐O bond cleavage of peroxymonosulfate (PMS) via electron backdonation and increasing Cu(III) selectivity from 53.9% to 90.4%. This coordination effect also demonstrates a 46.4‐fold enhancement in PMS activation efficiency over bare CuO, surpasses most state‐of‐the‐art Fenton‐like catalysts, and restricts Cu leaching to only 0.467 mg/L, 2.30 times lower than that of bare CuO. More importantly, the elevated Cu(III) redox potential upon coordination with the electron‐donating ─NH 2 group enables deep polymerization of pollutants, which generates fewer toxic oligomeric intermediates and achieves a significant reduction in the biotoxicity of treated effluent compared with the CuO/PMS system. This strategy offers a novel design approach to revitalize the site‐specific activity of TMOs for superior Fenton‐like reactions.

Radio-frequency heating (RFH) coupled with peroxydisulfate (PDS) represents a promising approach for the remediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated soil, however, its performance and enhancement mechanisms remain unclear. Here, an RFH-PDS system was systematically evaluated using benz[a]anthracene (BaA) as a representative PAH, and its applicability was further assessed in field-contaminated soils. Under temperature-matched conditions, RFH outperformed conventional heating (CH) with increasing BaA degradation rate constant by 57% and reducing the apparent activation energy by 8.72 kJ mol-1 at 50 W RF power. RFH accelerated PDS decomposition with a 1.80-fold higher rate constant and enhanced SO4•- and •OH generation, consistent with density functional theory (DFT) calculations showing RF-induced weakening of the O-O bond in PDS. The BaA desorption rate from soil was increased by 59% under RFH relative to CH, which was potentially promoted by RFH-induced dissolved organic matter release, whereas metal dissolution showed a negligible contribution. DFT and GC-MS analyses indicated that RF exposure could modify the electrostatic potential distribution of BaA and alter its degradation pathways. Overall, the temperature-matched kinetic comparison, enhanced PDS activation, and altered BaA degradation pathways suggest an RF-associated enhancement beyond bulk thermal activation. For field-contaminated soil containing eight PAHs at 402.88 mg kg-1, RFH-PDS achieved 97.15% removal and reduced the total PAHs concentration to 11.49 mg kg-1, with residual PAHs below regulatory limits. These findings demonstrate that the RFH-PDS system is an effective and potentially scalable technology for the remediation of PAHs-contaminated soils.

Fenton conditioning (FC) is a popular pretreatment method for excessive sewage sludge dewatering, but inevitably incorporates exogenous iron with uncertain effects on the derived biochar. In this study, we reveal an FC-induced trade-off between sludge dewatering performance and the catalytic activity of the sludge-derived biochar. Compared with biochar from primary sludge or other Fe-pretreated sludge, the post-Fenton biochar (FC-MSBC) showed much higher PMS activation for phenol degradation. It also markedly improved the prior sludge dewatering performance. Within an appropriate FC dosage window, the surface concentration of Fe-N sites increased in parallel with the catalytic activity of FC-MSBC. Characterization showed that moderate •OH oxidation of extracellular polymeric substances (EPS) promoted the accumulation of bound Fe(III) within sludge aggregates and accelerated the release of intercellular water. With optimized FC, the dominant oxidation pathway in the FC-MSBC/PMS system shifted from high-valent iron (Fe(IV)=O) to singlet oxygen (1O2), enabling efficient treatment of real saline coking wastewater. This study provides a full-process perspective on converting “sludge to functional materials” for green, low-carbon wastewater purification.

Real-time and reliable monitoring of nitrogen in wastewater treatment plants (WWTPs) is essential for effluent quality control and mitigation of environmental risks such as eutrophication. However, conventional online analyzers for total nitrogen (TN) and related nitrogen indicators remain costly, maintenance-intensive and difficult to deploy at high temporal resolution, especially under data-scarce conditions. To address this limitation, a hybrid soft sensing framework was developed by integrating a simplified prior model with a calibration model through a bagging ensemble strategy, based on 1068 laboratory-simulated datasets and 576 real-world observations from a WWTP. The prior model, derived from controlled water-mixing experiments, provided a constrained reference representation, while the calibration model learned the system-level discrepancy between this reference system and real wastewater observations. Using pH, electrical conductivity (EC), oxidationreduction potential (ORP), and dissolved oxygen (DO) as inputs, the proposed framework improved both robustness and predictive accuracy under data-scarce conditions. Compared with purely data-driven models, it reduced MSE, MAE, and RMSE by 41.21%, 24.31%, and 23.58% for ammonia nitrogen (NH4+-N), and by 45.79%, 25.74%, and 26.36% for TN, respectively. Reliable prediction was maintained with as little as 10% and 40% of the original training data for NH4+-N and TN, respectively. In addition, lifecycle monitoring cost was reduced by 91.34% relative to conventional online analyzers. These results demonstrate that the proposed framework offers a cost-effective and practical solution for nitrogen monitoring in WWTPs under data-scarce conditions.

The concept of converting biowaste to energy is popular worldwide; however, overcoming the trade-off between bio-oil recovery and obtaining functional biochar remains challenging. This study investigated the effects of three transition metal ions (Mn2+, Cu2+ and Fe2+) throughout the entire process of recovering 5-hydroxymethylfurfural (5-HMF) from forestry waste and on the catalytic abilities of biochar derived from the oil-extracted residue. The Cu2+, Fe2+, and Mn2+ ions significantly increased 5-HMF yields by 93- to 158-fold compared to the metal-free control. However, only marginal improvements in the catalytic ability of the residue-derived biochar for persulfate activation were observed for Cu- or Fe-doped biochar, despite the general benefit of transition metal doping for biochar functionalization. Interestingly, a dual Mn-mediated promotion was achieved beyond enhancing 5-HMF production. The Mn-doped biochar (Mn-Biochar) exhibited excellent peroxydisulfate (PDS) activation capability, enhancing the degradation of the antibiotic sulfamethoxazole (SMX) by 6.6- to 15.0-fold. Characterizations revealed that incorporated nitrogen was responsible for this enhancement. N-doping transformed the Mn species into MnO, which tripled the Mn loading capacity and enhanced the electrical conductivity of the biochar. The formed Mn-Nx structure in the biochar (Mn-N-FBBC) facilitated polarization of the OO bond and cleavage of the SO bond in PDS, generating 1O2 for SMX degradation. Life cycle assessment (LCA) indicated that this dual Mn-mediated process for 5-HMF recovery and biochar production offers synergistic benefits, realizing the “waste-resource-material-treatment” paradigm in biomass conversion.

Continuous-flow algal-bacterial systems have received increasing attention owing to their potential for efficient nitrogen removal in wastewater treatment under low aeration conditions. However, the mechanism underlying synergistic nitrogen removal by the algae-bacteria consortium during wastewater treatment remains unclear. In this study, a continuous-flow algal-bacterial system, incorporating an anaerobic-anoxic-oxic process and a rectangular sedimentation tank, was developed for municipal wastewater treatment. The results indicated that the system achieved removal efficiencies of 91.72% for chemical oxygen demand (COD), 98.05% for NH4+ -N, and 74.03% for total inorganic nitrogen. Ammonia removal mainly occurred via assimilation (55.21%+0.11%) and nitrification-denitrification (44.79%+0.11%). The aeration demand of this system was 57.14% of that of an activated sludge system. During nitrification, the cultivated microorganisms efficiently oxidized NH4+-N to NO3- -N (50.00 mg/L, 100%) at rates of 3.10 and 3.71 mg N/(g MLSS*h) under dark and 4500 lux light conditions, respectively. However, microbial sequencing analysis revealed trace ammonia monooxygenase (amo) abundance contrasted by significant hydroxylamine oxidoreductase (hao) enrichment, supporting the heterotrophic nitrification pathway. We therefore propose that NH4+-N oxidation in a continuous-flow algal-bacterial system may not solely depend on amo genes; instead, the oxidation process likely involves assimilation into glutamate, followed by heterotrophic nitrification to complete the transformation. This study provides guidance for the construction of a continuous-flow algal-bacterial system, elucidates the metabolic mechanisms of synergistic ammonia oxidation, and points toward the future development of efficient nitrogen removal by algal-bacterial systems.

The efficient recovery of tin (Sn) from acidic steel wastewater remains a critical challenge for resource sustainability and environmental protection. Herein, epichlorohydrin (ECH) cross-linked alginate fibers (ECHalginate fibers) were developed via covalent bonding between the C3-OH groups of alginate and epoxide/C-Cl groups of ECH. Unlike conventional Ca(II)-cross-linked alginate prepared in CaCl2 solutions, this ethanol-based solidification strategy avoids ion-exchange consumption of carboxyl groups, thereby preserving active adsorption sites. The resultant fibers exhibited excellent structural integrity and a high Sn(II) uptake of 497.6 +/- 92.6 mg/g at pH 2.3 within 180 min, 7.4-48.5 times higher than that of commercial carbons and ion exchange resins. Comprehensive characterization (FE-SEM, BET, XRD, FT-IR, XPS) and DFT calculations confirmed that ECH crosslinking occurred predominantly at C3-OH sites, while Sn(II) adsorption proceeded through chelation with-COO-groups and Na(I)/Sn(II) exchange, followed by oxidation to Sn(IV). A speciation-weighted adsorption energy model Eads,adj was established, showing a strong linear correlation (R2 = 0.995) with experimental capacities, enabling quantitative prediction of adsorption performance under variable pH. Moreover, the ECH-alginate fibers demonstrated rapid regeneration in 0.5 mol/L HCl with complete desorption within 5 min and minimal capacity loss after five cycles. The practical application of ECH-alginate fibers yielded a remarkable recovery efficiency of 99.7 +/- 1.0% for Sn from real Sn-plating wastewater. This work provides a mechanistically guided and scalable approach for designing durable, high performance biopolymer adsorbents for sustainable metal resource recovery.