Chlorophenols are recognized as persistent environmental contaminants due to their toxicity and resistance to biodegradation. In particular, 2-chlorophenol (2-CP) is of concern because of its high aqueous solubility and tendency to accumulate in aquatic environments. This study proposed an anaerobic removal approach for 2-CP using a tubular ceramic-supported graphene oxide membrane (TCSGoM) bioreactor, which integrates separation and biological processes in a single operational unit. Anaerobic sludge was inoculated into the TCSGoM bioreactor to establish biofilm growth and was acclimated to 2-CP before evaluation under steady-state conditions with stepwise increases in 2-CP concentration. The system achieved 100% removal at feed concentrations up to 50 mg/L, with performance gradually declining at higher concentrations, reaching 24% removal at the tested maximum concentration of 80 mg/L. The results indicate that, during the start-up phase, initial 2-CP removal is primarily driven by adsorption onto the graphene oxide layer, while sustained removal over time is attributed to biofilm-mediated processes under quasi-steady-state operation. The dominant microbial populations were identified as Comamonas and Cupriavidus, both known for their capacity to degrade chlorinated phenolic compounds. Although high removal efficiencies were achieved, transformation products were not analyzed if any were present, which limits the confirmation of the degradation pathway and the extent of mineralization. The proposed system significantly reduces the acclimation period required for conventional anaerobic reactors and has the potential to reduce or even eliminate the need for post-treatment steps, demonstrating that it is an efficient and sustainable alternative for 2-CP removal compared to conventional methods.
The increasing pollution of water sources by microplastics and cyanobacteria has promoted the formation of microplastic–cyanobacteria heteroaggregates, which can enter drinking water treatment plants. This study investigated the effects of these heteroaggregates on filtration and NaClO disinfection processes. The results showed that the interfacial interactions between microplastics and cyanobacteria increased cell membrane permeability by 19.9%–54.8% and augmented the malondialdehyde content of cyanobacteria from 9.8 nmol/mg to 46.5 nmol/mg. These interactions induced the release of intracellular substances and reduced the normalized membrane flux from 1.000 to 0.178 for microplastic–Oscillatoria heteroaggregates and from 1.000 to 0.124 for microplastic–Microcystis aeruginosa heteroaggregates. More severe membrane fouling caused by microplastic–M. aeruginosa heteroaggregates was attributed to the fact that unicellular M. aeruginosa led to more serious membrane pore blockage compared with filamentous Oscillatoria sp. After NaClO disinfection, water pollution caused by microplastic–cyanobacteria heteroaggregates became more severe than that caused by cyanobacteria alone. Specifically, the content of dissolved organic carbon increased from 7.5 mg/L to 25.2 mg/L for M. aeruginosa-containing systems and from 2.9 mg/L to 15.9 mg/L for Oscillatoria-containing systems. Meanwhile, the concentration of microcystins increased from 6.3 μg/L to 11.4 μg/L in M. aeruginosa systems, and the cylindrospermopsin concentration increased from 2.5 μg/L to 11.2 μg/L in Oscillatoria sp. systems. Furthermore, the levels of disinfection by-product formation potentials, especially the trichloronitromethane formation potential, in water containing microplastic–cyanobacteria heteroaggregates were higher than those in microplastic-free algal water. Therefore, drinking water treatment plants must fully consider the impact of microplastic–cyanobacteria heteroaggregates on filtration and disinfection processes.
Extensive application of antibiotics has led to antibiotic contamination in aquatic environments, posing global environmental and health challenges. This study pioneered periodically reversed electrocoagulation (PREC) as a process intensification strategy resistant to electrode passivation for the degradation of β-lactam antibiotics, using cefixime (CFX) as a model contaminant. Under baseline conditions (a current intensity of 0.6 A, pH of 7.0, and stirring speed of 600 r/min), Al–Zn electrodes achieved 97.4% removal of CFX (at an initial concentration of 20 mg/L). Response surface methodology (RSM) further enhanced removal efficiency to 98.8% (at a current intensity of 0.78 A, pH of 6.28, stirring speed of 613 r/min, and reaction time of 47.56 min), approaching the theoretical limits of 99.4% as predicted. Furthermore, the removal mechanisms were elucidated through analysis of flocs and CFX solutions. CFX is primarily adsorbed onto ZnAl2O4 flocs, while hydroxyl radicals (·OH) generated during the PREC process destroy aromatic rings and C=C bonds. The proposed degradation pathways involve hydroxylation, carboxylation, cleavage of C–N bonds, and benzene ring opening, followed by mineralization to H2O and CO2. Numerical simulations of the electric and flow fields revealed uniformly distributed intermediate potentials between electrodes, with electrolytic byproducts primarily accumulating near electrode surfaces. Variations in electrode configuration and flow velocity were found to affect the CFX removal efficiency. The intrinsic anti-passivation design and synergistic adsorption–oxidation of PREC provide a chemical-free and industrially adaptable solution for the treatment of recalcitrant antibiotics in water.
Composite systems of soil organic matter and iron hydroxides hold significant potential for the remediation of heavy metal pollution. However, the synergistic immobilization mechanisms of U(u2165) by humin (HM)u2014iron hydroxide composites remain insufficiently understood. In this study, goethite (Ge)u2014HM and magnetite (Mag)u2014HM composites with varying C-to-Fe molar ratios were synthesized via co-precipitation, and their adsorption behavior and underlying mechanisms towards U(u2165) in aqueous solutions were systematically investigated. The results showed that under conditions of a pH value of 5.0 and temperature of 298 K, the maximum U(u2165) adsorption capacities of Geu2014HM and Magu2014HM reached 60.56 mg/g and 64.12 mg/g, respectively, significantly surpassing those of pure Ge (39.6 mg/g), Mag (22.5 mg/g), and HM (20.2 mg/g). Kinetic studies revealed that the adsorption processes for both Geu2014HM and Magu2014HM conformed to the pseudo-second-order kinetic model, indicating chemical reaction control. Isothermal adsorption results were well described by the Langmuir model, suggesting monolayer adsorption on the composite surfaces. Crucially, characterization results elucidated distinct reaction mechanisms. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses revealed that U(u2165) primarily complexed with oxygen-containing functional groups, such as carboxyl and hydroxyl groups, on both composite surfaces, leading to stable immobilization. For Magu2014HM, a notable reduction of U(u2165) to U(u2163) was observed, with XPS U 4f spectra showing characteristic U(u2163) peaks, indicating a significant reductive immobilization pathway facilitated by the presence of both Mag and HM. In contrast, for the Geu2014HM composite with a C-to-Fe ratio of 0.5, the complete consumption of Fe(u2161) after U(u2165) adsorption, with its proportion in total Fe decreasing from 53.7% to zero, strongly suggested that Fe(u2161) played a key role in electron transfer during the immobilization process. This study elucidates the synergistic enhancement mechanisms of HMu2014iron hydroxide composites in U(u2165) removal, providing new insights for developing green and efficient materials for the remediation of heavy metal pollution.
Landslide dams constitute significant geological hazards, accompanied by challenges such as limited field data, urgent response requirements, and difficult mitigation conditions. This review systematically examines the topographic, hydrological, and geotechnical factors influencing dam formation and stability, highlighting the critical roles of material composition and internal structure in breach development. Existing methodologies for modeling dam-break scenarios, including statistical, parametric, simplified physically-based, and refined physically-based models, are critically evaluated, revealing persistent challenges such as parameter uncertainty, scale effects in physical experiments, and scarcity of field validation data. In addition, both engineering and non-engineering strategies for emergency response are reviewed. Key research gaps include an insufficient understanding of multi-phase interactions during dam failure, the potential for engineering interventions to alter failure modes (e.g., from overtopping to piping), the need for an improved dynamic risk assessment framework, and the integration of real-time data assimilation technologies. Finally, this review proposes future directions, including enhanced multi-source monitoring, machine learning-aided parameter inversion, uncertainty quantification and probabilistic forecasting, and improved dam-break models, to support effective decision-making in emergency scenarios.
