Water Environment Research最新文献

Petroleum oil refining industry generates complex wastewaters with toxic substances (hydrocarbons, phenols, ammonia, nitrogen, sulfur compounds, and heavy metals), posing significant environmental threats to aquatic ecosystems and groundwater. To address this, and overcome limitations of the traditional treatment methods, an innovative treatment system was developed by integrating Mn/Cu/Ni-layered double hydroxide (LDH)/magnetite (Fe₃O₄) nanocomposite (NC) into a traditional activated sludge (AS) process to enhance the performance. To the best of our knowledge, this magnetic nano-trimetal combination is investigated for the first time as an innovative alternative for the treatment of oil refinery effluents. Petroleum refinery effluent (PRE) from Alexandria, Egypt, where traditional AS treatment is adopted, was treated using two bench-scale AS basins, modified with the synthesized and characterized NC. Four trials were conducted-three in sequential batch mode and one in continuous mode. The integrated system (Trial 3) significantly enhanced contaminants removal within 45-135 min, achieving 89.0 ± 0.36%, 91.5 ± 0.44%, 87.6 ± 0.84%, and 66.87 ± 0.57% removal of total suspended solids (TSS), chemical oxygen demand (COD), oil and grease (OG), and ammonia, compared to much lower rates achieved by the unmodified AS system (Trial 2). A separate NC filter system (Trial 4) could achieve rapid removal within 2-6 min, with 83.6%, 89.8%, 87.6%, and 64.8% removal for TSS, COD, OG, and ammonia, respectively, and also improved TDS control. These findings confirm and highlight that the integrated LDH/Fe₃O₄ NC-AS system is a highly efficient, rapid, and cost-effective approach for treating refinery effluents, with the potential to meet discharge limits and enable water reuse in industrial applications.

Water contamination from petroleum-related activities remains one of the most pressing environmental and public health challenges in the Niger Delta. Yet, existing studies have largely treated heavy metals, polycyclic aromatic hydrocarbons (PAHs), seasonal dynamics, and health risks in isolation. This study assessed physicochemical parameters, arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn), and PAHs in an oil-polluted community (Ibaa, Rivers State, Nigeria) during wet (August) and dry (February) seasons. Surface waters (Ilejor River, Ibaa Rivers, and a stream along a petroleum pipeline) and groundwaters (community well and petroleum company borehole) were analyzed using standard APHA protocols, atomic absorption spectrometry, and GC-MS. Water quality was evaluated using the Water Quality Index (WQI), Heavy Metal Pollution Index, and chemometric analysis, whereas health risks were assessed via hazard quotients (HQ) and margin of exposure (MoE). Results showed that surface waters were consistently polluted (WQI > 0.5) with Pb and As MoE values well below safety thresholds, indicating risks of reduced IQ in children, elevated blood pressure in adults, and carcinogenic potential. Groundwater from the control site was of good quality in both seasons, whereas community well water met drinking standards only in the dry season. Seasonal variation significantly influenced contaminant levels, with wet-season samples showing higher nutrient and PAH load. This is the first study in the Niger Delta to merge seasonal chemometric profiling with multi-contaminant health risk analysis across water types, offering a more holistic evidence base than previously available. The results not only expose the inadequacy of current regulatory protections but also highlight the urgent need for alternative safe water sources, stronger policy enforcement, and scalable community-level treatment solutions in oil-impacted regions.

Groundwater supporting agro-pastoral regions is vulnerable to contamination from livestock effluents; this study evaluates shallow aquifers near farms in Henan Province to clarify sources and health risks of nitrate, fluoride, and manganese. We combined hydrochemical analysis with principal component analysis (PCA) and absolute principal component score-multiple linear regression (APCS-MLR) for source apportionment and applied Monte Carlo simulation (10,000 iterations) to quantify noncarcinogenic risk for children and adults via ingestion and dermal contact. Groundwater chemistry reflects carbonate weathering with contributions from evaporite dissolution and cation exchange. Source apportionment attributes ~73% of NO₃ ^- to anthropogenic inputs, ~90% of F^- to evaporitic/fluoride-bearing minerals, and ~76% of Mn²⁺ to redox-driven mobilization. Median hazard quotients (HQs) for all indicators were below 1. The median total hazard index (HI) was 1.18 for children and 0.80 for adults. At the 95th percentile, ingestion-driven nitrate HQs were 5.69 in children and 2.50 in adults, and fluoride HQs were 2.50 in children and 1.53 in adults; dermal exposure was negligible. Manganese HQs were 0.78 in children and 0.47 in adults, indicating low concern. Overall, nitrate risk reflects anthropogenic inputs from fertilizers and sanitation, whereas fluoride is largely geogenic. Management should prioritize reducing nitrate sources and, in parallel, implement feasible fluoride mitigation and removal.

The fate and transport characteristics of per- and polyfluoroalkyl substances (PFASs) in water have received considerable attention. This paper investigates the partitioning and adsorption mechanisms of PFASs in water and sediment in the Pingyin-Jinan section of the lower Yellow River. The concentration of short-chain perfluoropentanoate (PFPeA) in the body of water was found to be above the level of long-chain perfluorooctane sulfonate (PFOS). The logK_d values of PFASs were shown to be closely affiliated with the length of the carbon chain, but perfluorobutanoate (PFBA) exhibited abnormally high values in samples collected during the Spring, which might be related to water body pH. In adsorption experiments, using the kinetic model of pseudo-second order, the dominant mechanism of chemisorption was confirmed. FTIR spectroscopy revealed that hydroxyl groups and iron oxide groups in sediments enhance adsorption through electrostatic interactions. It was determined through the utilization of the intraparticle diffusion model that the adsorption process was comprised of three distinct stages: boundary adhesion, porosity diffusion, and inner surface adsorption. This study offers a theoretical foundation for the prevention and control of PFASs pollution in the Yellow River Basin.

This work reports, the fabrication of a magnetic Mg-Al layered double hydroxide (LDH) nano-bio-composite functionalized with the microalga Dunaliella salina (D. salina) for enhanced heavy metal removal from aqueous systems. Unlike conventional LDH adsorbents or biomass-based biosorbents, this hybrid design leverages the high surface area and ion-exchange capacity of LDH together with the metal-binding microalgae, D. salina, yielding a synergistic enhancement in adsorption selectivity and capacity. In multi-cation systems, the nano-bio-composite exhibited superior uptake for Pb(II) and Cu(II), with thermodynamic analysis confirming endothermic (ΔH° > 0) and entropy-driven (ΔS° > 0) processes. Kinetic studies revealed that Cu(II), Cd(II), Ni(II), and Co(II) followed a pseudo-first-order mechanism, while Pb(II) conformed to a pseudo-second-order model. All adsorption data fitted the Langmuir model, indicating monolayer coverage. The material retained its performance for Pb(II) and Cu(II) over five regeneration cycles without significant efficiency loss. This novel microalga-LDH nano-bio-composite offers a sustainable, magnetically separable, and highly reusable adsorbent platform, addressing key limitations of current heavy metal remediation technologies.

Sulfide and methane production in sewer systems poses significant operational and environmental challenges, including odor, corrosion, and greenhouse gas emissions. This study investigates the optimization of nitrate dosing strategies to mitigate sulfide generation using a laboratory-scale sewer reactor system combined with mathematical modeling. An extended kinetic model was developed, based on the Wastewater Aerobic/Anaerobic Transformations in Sewers (WATS) model, to simulate sulfide and methane dynamics, incorporating key microbial processes and nitrate-based oxidation pathways. The model was calibrated and validated using experimental data with and without nitrate dosing. A variance-based global sensitivity analysis was performed to identify influential parameters affecting model predictions. Results show that dosing location and rate substantially influence sulfide removal efficiency and residual nitrate levels. Among the tested strategies, nitrate dosing in the third reactor (out of four) at 14.5 mgNO₃-N/L offered optimal trade-offs, achieving sulfide concentrations below 0.5 mgS/L while maintaining effluent nitrate levels at 0.9 mgNO₃-N/L, representing a 42% reduction in dosing costs compared to upstream dosing. These findings provide a quantitative foundation for improving nitrate dosing strategies in sewer networks.

Conventional fluoride removal strategies predominantly target free F^- adsorption, while the impact of aluminum-fluoride (Al-F) complexation from residual aluminum ions (Al³⁺) in coagulation effluents is an often-overlooked factor compromising treatment efficiency. This study investigates how Al-F speciation regulates the performance of nano-hydrous zirconium oxide embedded in anion exchange resin (HZO-201), revealing adsorption inhibition by Al³⁺ and establishing mitigation strategies. The adsorbent achieved a dynamic adsorption capacity of 2000 bed volumes at pH 3.5 but failed completely with coexisting Al³⁺ (Al³⁺ = 6.4 mg/L, F/Al = 1:1) due to dual inhibition mechanisms: electrostatic repulsion of positively charged Al-F complexes ([AlF]²⁺ and [AlF₂]⁺) by quaternary ammonium groups on D201 and competitive site occupation. Thermodynamic and experimental analyses showed pH and F/Al ratio-controlled speciation: cationic [AlF]⁺ dominated at F/Al ≤ 1 and pH 3.5, while neutral/anionic species ([AlF], [AlF]^-) prevailed at F/Al ≥ 2 and pH ≥ 5, enabling effective adsorption. EDS mapping confirmed pore-confined nano-HZO as active sites with ligand-exchange dominating under sulfate-shielded conditions. XPS resolved distinct F1s signatures (683~686 eV for F^-, 688 eV for Al-F complexes) and Zr3d perturbation differences (Δ1.0 vs. 0.7 eV), confirming coordination-dependent adsorption pathways. This study bridges molecular-level Al-F coordination chemistry to process optimization, providing mechanistic insights into the role of Al-F charge states in defluoridation and advancing from singular fluoride targeting to multispecies cooperative regulation paradigms.

This study evaluates the performance of three constructed wetland (CW) configurations: horizontal flow (HFCW), vertical flow (VFCW), and hybrid vertical-horizontal flow (HVHCW)-for the treatment of domestic wastewater in a decentralized context in India. A pilot-scale system was operated under real wastewater loading for 8 weeks, with weekly sampling (n = 8 per system) and triplicate analysis per sample. Key water quality parameters assessed included biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonia nitrogen (NH₃-N), nitrate nitrogen (NO₃-N), and total phosphorus (TP). Analytical protocols followed APHA (2017) standard methods. The HVHCW configuration achieved the highest removal efficiencies, with mean values of 94.4% for BOD and 96.8% for TSS, outperforming both single-stage systems. One-way ANOVA revealed statistically significant differences (p < 0.05) across systems for most parameters, and Tukey's HSD post hoc test confirmed HVHCW's superiority. Nitrate removal, while observed, was not statistically significant (p > 0.05), indicating the need for design enhancements to support denitrification. These results underscore the potential of hybrid CWs as low-cost, eco-sustainable solutions for decentralized wastewater management in developing regions.

Achieving decoupling between water pollution and economic growth is a critical governance challenge in resource-based economies (RBEs). The classic environmental Kuznets curve (EKC) hypothesis often fails in such regions due to "policy trade-offs," such as the conflict between energy security and environmental protection goals. Simultaneously, existing methodologies tend to bifurcate the analysis of long-term structures and short-term shocks. This paper, using data from China's Shanxi Province (2010-2024) as a typical case, constructs a "multi-scalar diagnostic framework" that integrates principal component analysis (PCA), the EKC, and the Tapio decoupling model. Empirical results show the following: (1) During the study period, the relationship between water pollution and economic growth in Shanxi was predominantly in a state of weak decoupling. However, the Tapio model also revealed recent "expansive negative decoupling" events, indicating that short-term pressures persist. (2) The EKC analysis reveals a "differentiated path": industrial pollution indicators, including industrial wastewater, COD, and ammonia nitrogen, exhibit an inverted U-shape, suggesting industrial governance is aligning with economic growth. (3) In contrast, the EKC curve for domestic ammonia nitrogen shows a distinct N-shape, indicating that pressure from domestic wastewater discharge continues unabated. (4) Notably, this N-shaped curve appears to have passed its second turning point, with domestic ammonia nitrogen emissions showing a downward trend after peaking. This study's theoretical contribution is the revelation that the N-shaped curve is the cumulative consequence of "policy trade-offs" in RBEs. These short-term policy shocks, captured by the Tapio model, constitute the micro-foundations for the distortion of the long-term (N-shaped) EKC structure, reflecting a governance model that prioritizes industrial and energy objectives while relatively neglecting municipal environmental governance.

Replacing conventional filter media with recycled filters can enhance treatment efficiency and reduce the operational cost of vertical subsurface flow constructed wetlands (VSF CWs). This study evaluated the feasibility of using oyster shells (Crassostrea gigas) and polyethylene plastic waste as substitutes for traditional gravel media in VSF CWs treating swine wastewater. Seven media configurations were designed: CP1 (sand, small gravel [1 × 2 cm], and large gravel [3 × 5 cm]); CP2 and CP3 replaced small gravel with oyster shells and plastic waste, respectively; CP4, CP5, and CP6 used mixtures of oyster shells and plastics in varying volume ratios (1:3, 1:1, and 3:1, respectively); CP7 was a control system with no media. Four-month experiments were conducted at a laboratory scale, monitoring different hydraulic retention times (HRTs) (1, 2, 3, and 4 days) under two conditions: planted with Cyperus alternifolius and unplanted. Importantly, replacing conventional filter media with oyster shells and plastic waste did not adversely affect the growth of C. alternifolius in any of the experimental systems. The results showed that planted systems achieved 0.8%-28.7% higher removal efficiencies than unplanted ones (p < 0.05), with an optimal HRT of 2-3 days to meet QCVN 62-MT:2016/BTNMT Column B. CP1 consistently demonstrated the highest treatment efficiency. Meanwhile, CP2 and CP6 exhibited slightly lower removal efficiencies than CP1 but still achieved outstanding TP removal rates of over 70%. CP3 showed the lowest treatment performance. However, its effectiveness could be improved by blending with oyster shells at appropriate ratios. Among all experiments using recycled filter media, CP6 exhibited the most promising performance, with removal efficiencies for TSS, COD, TN, NH₄ ⁺, and TP ranging from 62.6% to 87.6%, 36.1% to 77.2%, 30.8% to 74.0%, 33.6% to 85.3%, and 29.6% to 69.0%, respectively. Substituting small gravel with recycled plastic waste and oyster shells reduces material costs by three to four times, mitigates environmental pollution, and promotes solid waste recycling toward a circular economy.