Urbanization alters hydrologic processes and pollutant transport dynamics, making the identification of critical source areas (CSAs)—where high pollutant generation coincides with strong connectivity to downstream—essential for effective urban watershed management. This study presents an integrated framework to identify and assess CSAs in urban watersheds. Using Soil and Water Assessment Tool (SWAT) modeling results, CSAs were delineated by integrating the cumulative pollutant load (CPL) method and the Getis-Ord Gi* spatial statistic with a transport factor (TF). The spatial distribution of CSAs was evaluated for the first time by analyzing their relationship with two impervious cover indicators, total impervious area (TIA) and directly connected impervious area (DCIA), and their proximity to key watershed features (e.g., centroid and outlet). The framework applicability was demonstrated in an urban watershed in Saint Paul, Minnesota. Results indicated that a relatively small fraction of subbasins contributed disproportionately to total sediment loads, e.g., 26% of the watershed area generated 50% of the load. The CPL-TF approach provided broader coverage, identifying 60 (out of 1,169) subbasins as CSAs, whereas Gi*-TF highlighted five subbasins as statistically significant hot spots. The CSA subbasins exhibited the highest DCIA among all subbasins, which was not the case for TIA, indicating DCIA as a better indicator of urban imperviousness than TIA in relation to urban stormwater runoff quality. Proximity analysis indicated central-to-downstream clustering patterns for CSAs using CPL-TF, while Gi*-TF exhibited greater CSA variability. This study advances CSA understanding in urban watersheds, supporting strategic, watershed-wide implementation of best management practices for nonpoint source-pollution control.

With inner and outer filter parts having the advantage of a more compact structure and a larger area of a single filter cartridge, a three-dimensional numerical simulation model of annular filter cartridge was constructed, and the pulsed-jet performance of annular filter cartridge with array nozzle was investigated. The spatial and temporal distribution of injection pressure in filter core was analyzed; the injection flow field, the induced ratio, and the eddy current under different number (N) of nozzles were compared. The effects of jet angle (α) and jet distance (H) on the pulsed-jet intensity and pulsed-jet uniformity were examined. The results showed that the appropriate number of outlet openings for array nozzles is 4, which corresponds to the induced ratio of 310.4%. With the increase in jet angle, the pulsed-jet intensity first increases and then decreases (the optimal jet angle is α=0°), and the pulsed-jet uniformity first decreases and then increases. With the increase of the jet distance, the pulsed-jet intensity increases first and then decreases (the optimal jet distance is H=250 mm); and the pulsed-jet uniformity was improved. Compared with N=2, the array nozzle can improve the pulsed-jet intensity by 15.5% and the pulsed-jet uniformity by 4.8 times (reducing the coefficient of variation from 0.52 to 0.09) under the optimal parameters (N=4, α=0°, H=250 mm). The research provides a reference for optimizing the performance of the dust collector with annular filter cartridges in space-constrained working environments.

Wastewater characteristics vary significantly across regions due to a combination of climatic, socioeconomic, and infrastructural factors. Understanding these variations is important for accurate influent characterization and the development of region-specific guidelines. This study investigates geographical and regional differences in wastewater characteristics by analyzing influent data from multiple locations, including a detailed comparative analysis between two distinct regions with contrasting environmental and socioeconomic conditions. A comprehensive dataset spanning several years was utilized to examine key wastewater parameters, including BOD, COD, TSS, total Kjeldahl nitrogen, and total phosphorus. To ensure data reliability, preprocessing techniques incorporating machine learning models such as principal component analysis were applied. Statistical methods, including descriptive analysis, ANOVA, and correlation analysis, were applied to assess the variability and relationships between parameters. The results highlight significant differences in wastewater characteristics, not only between geographically distant locations but also within the same country. Whereas climatic conditions influence wastewater characteristics indirectly, socioeconomic factors such as water consumption patterns, industrial activities, and waste disposal practices play a significant role in shaping influent characteristics. These findings highlight the limitations of applying standardized design criteria and regulatory frameworks to wastewater treatment systems without accounting for local conditions. The study emphasizes the necessity of adaptive approaches that integrate regional variability, ensuring more precise influent characterization and enhancing overall system efficiency.

This study developed a MnFe2O4/RHB composite catalyst through a straightforward one-step hydrothermal method, in which spinel-type manganese ferrite (MnFe2O4) was uniformly supported on rice husk biochar (RHB), effectively mitigating the agglomeration and limited active site exposure of unsupported MnFe2O4. Characterization results indicated that the composite exhibits a markedly increased specific surface area, a more developed porous structure, and a greater abundance of surface functional groups compared to pure MnFe2O4, providing enhanced active interfaces for activating peroxymonosulfate (PMS) to remove methylene blue (MB). The MnFe2O4/RHB+PMS system achieved complete MB removal within 30 min, while maintaining high catalytic activity and strong anti-interference capacity across a broad pH range and in the presence of organic or inorganic ions. The material demonstrated excellent stability, with MB removal rates exceeding 98.5% after four consecutive cycles. In a fixed-bed setup, the granular catalyst sustained over 98.8% MB removal throughout 450 min of continuous operation, indicating strong potential for practical application. Mechanistic investigation revealed that the removal process involves multiple reactive oxygen species, which jointly remove pollutants through radical (·OH, SO4−·) and nonradical (O12) pathways. Environmental safety assessments, conducted via pea seed toxicity tests, confirmed the low environmental risk of the catalyst, supporting its use as a sustainable and efficient material strategy for advanced water treatment technologies.

Preferential runoff pathways in the media of stormwater ecological treatment facilities increase pollution leaching risks, reduce contact surface area, and shorten peak emergence times, among others. In this study, tracer breakthrough tests, pollutant adsorption tests, and flow simulations were performed for four media structures in bioretention cells (BRC) and rainwater seepage wells (RSW). The results show that the structure of the upper layer with coarse particle size (RSW: 0.71–1.68 mm, BRC: 0.25–0.5 mm) and lower layer with fine particle size (RSW: 0.25–0.71 mm, BRC: 0.075–0.25 mm) formed a saturated zone between the two layers, which prolonged the tracer penetration path and time, and exhibited a superior water transport process. By changing the pressure head and relative humidity of the media, the solute penetration time is negatively correlated with rainfall intensity, and there is a positive correlation between the increase in shrinkage cracks and the decrease in water exchange between the large pore and matrix domain. The best flow state optimization for the media structure was carried out by central moment determination and HYDRUS modification. The bias of solute breakthrough curves (BTC) of the two systems after optimization was in the range of 0.005–0.009 (RSW) and 0.045–0.075 (BRC). The purification effect of the optimized model for nitrate (NO3−-N) was improved by more than 20% compared to the NO3−-N effluent results in the pollutant adsorption experiments. The results are significant for the stable, efficient operation, and accurate simulation for low impact development facilities.

Dropshafts are widely employed in urban drainage systems to convey wastewater from higher to lower elevations. To mitigate odor and corrosion issues, air circulation pipes have been installed in certain drainage networks, such as those in Edmonton, Canada. This study used validated numerical models to assess the performance of these pipes under varying inlet flow conditions. At a low inlet velocity (0.2 m/s), the pipes reduced downstream manhole air velocities by up to 43%, demonstrating significant effectiveness. However, at higher velocities (1.0 m/s), the reduction became less pronounced and even negative at specific locations. A similar trend was observed at the system level, where the air mass inflow reduction rate decreased from 38% to −17% with increasing inlet velocity. These findings highlight a velocity-dependent interaction between sewage flow and ventilation behavior, offering practical insights for the design and optimization of air circulation systems in urban drainage networks.

Nonthermal plasma (NTP) combined with selective catalytic reduction (SCR) is an innovative approach for flue gas treatment. This technology leverages the synergistic effects of NTP and SCR to produce plasma at low temperatures. The high-energy electrons, ions, and free radicals generated in this process interact with nitrogen oxides (NOx), effectively reducing their emissions. This study delves into the research progress of NTP-SCR technology, including the fundamental principles of plasma, catalyst improvements, reaction mechanisms, and numerical simulation studies, as well as the application potential and challenges of this technology in air purification. NTP-SCR efficiently reduces NOx at low temperatures, with minimal formation of harmful by-products and low energy consumption. NTP enhances catalyst performance, particularly enhancing activity and durability in low-temperature and harsh flue gas conditions. Mechanistic studies indicated that NTP can activate the catalyst surface and promote the reduction process of NOx. Meanwhile, the application of numerical simulation provides theoretical guidance for the design and operation of plasma reactors. Although NTP-SCR technology has significant potential, it still faces some challenges, including long-term stability, control of product selectivity, coking, and other issues in industrial applications. Future research focuses on developing more efficient and stable NTP synergistic catalysts, optimizing process parameters, and further exploring the synergistic mechanisms between plasma and catalysts.

The immobilization of lanthanum oxycarbonate nanoparticles on pumice [lanthanum oxycarbonate-modified pumice (LOCP)] was explored as a novel approach for enhancing fluoride removal in water treatment. Fluoride contamination in water is a significant environmental issue, and developing efficient adsorbents is crucial for sustainable remediation. Synthesized through a combined hydrothermal and annealing approach, LOCP demonstrated exceptional fluoride adsorption characteristics. Kinetic studies revealed optimal fitting with the Elovich model (R2=0.98), while adsorption isotherms followed the Langmuir model with a theoretical maximum capacity of 25.15 mg/g. The material maintained stable fluoride removal efficiency (exceeding 80%) across a broad pH range (2–10), with phosphate showing the strongest interference among coexisting anions (inhibitory order: NO3−<SO42−<Cl−<HCO3−<CO32−<PO43−). Spectroscopic analysis indicated that the adsorption mechanism primarily involves ligand exchange between fluoride ions and protonated La─ O bonds, forming stable La–F complexes. After four regeneration cycles, LOCP retained 53.9% of its initial capacity, while column tests demonstrated continuous operation for 35 h with effluent fluoride concentrations below 1 mg/L.

Landfill leachate is a source of groundwater contamination, particularly for shallow aquifers. Low-permeability vertical cutoff walls are often used to stop groundwater from flowing into contaminated areas. However, their long-term durability and performance may be adversely affected by the harsh environmental conditions they are exposed to. High-permeability barriers have emerged as a complementary technique, offering the advantage of being less sensitive to defects compared to vertical cutoff walls. Despite this advantage, limited research exists on their application in waste management. To address this gap, this study presents an experimental investigation of a high-permeability vertical barrier designed for waste isolation. To evaluate the barrier’s effectiveness in preventing flow through the isolated area, a water and salt solution was added into the sandbox model setup, and electrical conductivity sensors were placed at various locations in the experiment. An analytical solution was applied to model the flow through the barrier, demonstrating that it can reduce advective flow across the isolated area by 97.98%. Nevertheless, experimental results showed that the tracer eventually reached the points within the isolated area, albeit with lower intensity compared to the point outside the barrier. The reduction of advective flow by the barrier indicated that tracer transport to the isolated area was primarily due to diffusion, a conclusion supported by numerical simulations. In conclusion, high-permeability barriers are an effective isolation technique for reducing advective flow through a specific region. However, the barrier backfill material cannot prevent diffusive transport of contaminants. Overall, the findings of this study can guide further research to evaluate the feasibility and applicability of this isolation technique for waste management in field applications.