Water Environment Research最新文献

In this study, septage wastewater treatment using the flocculation/coagulation process by the natural coagulant Ocimum basilicum L. (basil) and chemical coagulants polyaluminum chloride (PAC), ferric chloride, and alum was studied. Under different conditions, the extraction of the seed of O. basilicum was done by maceration method, and SPSS 23 software was used to identify the most effective extract and chemical coagulant. The effects of five parameters-pH, coagulant dose, coagulant aid dose, rapid mixing time, and slow mixing time-on the reduction of COD, TSS, NH₄, and TP in septage samples were examined by conducting the Central Composite Design (CCD). Optimum conditions predicted by the response surface models were determined at pH 4.00, coagulant dose 498.50 mg/L, rapid mixing time 5.00 min, slow mixing time 21.60 min for natural coagulant, and pH 4.01, coagulant dose 372.88 mg/L, and coagulant aid dose 1.55 mg/L for chemical coagulant (PAC). Under optimal conditions, the reduction percentages of COD, TSS, NH₄, and TP parameters were 64.40, 87.30, 70.56, and 71.92 for natural coagulant, and 65.30, 73.42, 71.12, and 74.68 for chemical coagulant (PAC).

The pollutant removal pathways and the influencing catalysts have been assessed in benthic sediment and emergent plants-based two electroactive surface flow (SF) wetlands operated under variable wastewater contact and treated strong wastewater, that is, landfill leachate. The two SF systems achieved mean removal percentages of 68%-81% for organic matter, 33%-52% for nitrogen, 42%-70% for phosphorus, and 31%-84% for coliforms, respectively. The positive impact of electrogenic bioreactions on the removal routes in the reductive environment-dominated anode compartment, as well as the supplementary contribution from the cathode zone, improved overall organic, phosphorus, and coliform removals in the closed circuit-based (with external resistance) SF wetland. The open circuit-based SF wetland (without external resistance) achieved better nitrogen removal due to the availability of oxygen as an electron acceptor for oxidizing NH₄-N, particularly in the anode compartment. A higher wastewater contact period improved the organic removal in both systems, supporting both physicochemical and microbial-based routes. However, it also triggered oxygen consumption by the aerobic-based organic removal pathways, thereby restricting nitrification in the cathode compartments. The higher phosphorus composition of the benthic stone dust than the fresh (i.e., before being utilized as the benthic sediment) samples reflects the effect of the chemical route-based adsorption route. The mean voltage production within the two systems ranged from 50 to 215 mV; the bioenergy and wastewater contact period increments showed a positive correlation in both systems. This study investigated the interactions among benthic sediment, plants, electrodes, circuit connections, and wastewater pollutants in electrode-coupled SF wetlands operated under variable wastewater contact periods and higher influent organic strength.

On-demand purified water dispensers have been widely installed in residential communities (RCs) in China. However, water stagnation and the absence of chlorine disinfectants in these dispensers can lead to significant microbiological risks. To clarify these risks in purified water, in this study, the characteristics of the microbial community and associated microbiological hazards in 40 purified water samples from on-demand purified water dispensers in four administrative districts were investigated using quantitative PCR (qPCR) and high-throughput sequencing methods. The results revealed that the turbidity of the purified water was generally very low (< 0.28 NTU), but chlorine disinfectant was detected in more than half of the samples, indicating failure of the activated carbon process within the dispensers. Culturable bacterial counts revealed high levels of culturable bacteria in the collected water samples. Furthermore, the bacterial 16S rRNA gene copy number reached up to 6.23 Log10 Gene copies/mL. Among the seven pathogenic microorganisms detected by qPCR, Mycobacterium (95%) and Legionella (82.5%) were commonly detected with high biomass. The average gene copy number for Mycobacterium was 3.08 Log10 Gene copies/mL (0.30-4.33 Log10 Gene copies/mL), and for Legionella, it was 2.96 Log10 Gene copies/mL (0.38-4.05 Log10 Gene copies/mL). High-throughput sequencing revealed that 17 out of the top 50 microbial taxa detected at the genus level might be potential pathogens. This study demonstrates that drinking water from on-demand purified water dispensers in residential communities is associated with increased microbiological risk, necessitating enhanced monitoring and regulatory oversight.

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.