Water Environment Research最新文献

Electro-oxidation (EO) is a rapid and effective method for the elimination of organic and inorganic pollutants from wastewater. In this study, the titanium-based mesh electrodes Ti/TiO₂-RuO₂ were used for the removal of rhodamine B (RhB) azo dye in simulated water by the treated EO and EO-treated biodegradation (EO and BD) with 20 mA/cm^-2 direct current applied for the EO system, and the color removal was measured by UV-spectrophotometer. The chemical oxygen demand (COD) was greatly reduced to 78% in the EO-treated and 93% in the EO-treated biodegradation sample, respectively, and the decolorization was accomplished in 30 min in 10 ppm. The biodegradation data verify that the bacterial strain used both organic and inorganic materials. TOC (total organic carbon) in EO and EO with biodegradation were 57.2% and 86.7%, respectively. It confirms that the EO with biodegradation effectively removes RhB and aids in complete mineralization. Fourier transform infrared spectroscopy (FTIR) confirms the functional groups cleaved during the process HRMS concluded that the intermediate products NH, C-N, and C=O were generated during EO with biodegradation. The calculated toxicity of LC50 and EC50 values of RhB was observed in RhB 6 (100<) in water for fish, daphnid, and green algae. The toxicity study confirms that the majority of intermediates from EO and BD were scarcely harmful. Overall, this study concludes that RhB was effectively degraded by the EO and mineralized by the BD, and this combined treatment plays a vital role in the remediation of pollutants in the wastewater effluent treatment plant.

The revised EU Drinking Water Directive, which designates chlorate as a regulated parameter, presents a significant challenge for Hungary, where breakpoint chlorination with sodium hypochlorite is widely used for ammonium removal. Because hypochlorite decomposes during storage, half of the surveyed plants reported chlorate concentrations exceeding the national limit of 0.25 mg/L. A survey conducted on 208 drinking water treatment plants evaluated current operational practices and mitigation strategies. Chlorate occurrence was primarily associated with systems using sodium hypochlorite as the main oxidant, whereas technologies relying on chlorine gas or biological ammonium removal showed no relevant chlorate occurrence, even when hypochlorite was applied for postdisinfection. Large variability in hypochlorite handling, particularly delivery frequency, residual stock, storage volume, and cleaning practices, strongly influenced chlorate levels, with small systems being the most vulnerable. No relationship was observed between chlorine demand and chlorate concentrations, underscoring that chlorate occurrence in the finished water is governed by operational practices, hypochlorite quality, storage conditions, and dosing protocols.

Widespread chemical-enhanced phosphorus removal treatments usually result in waste activated sludge (WAS) containing excess phosphorus removal agents and byproducts. This study investigated four wastewater treatment plants (WWTPs) in China and took FeCl₃ as a representative agent to explore its effect on WAS organics dissolution and anaerobic digestion (AD). The results revealed a biphasic effect of Fe³⁺ on WAS: Disintegration dominated at low concentrations (e.g., 50-100 mg/L), and coagulation dominated at high concentrations (e.g., 1000 mg/L). High-concentration Fe³⁺ inhibited the AD performance by disrupting the system (pH and ORP), resulting in system acidification. Conversely, low-concentration Fe³⁺ promoted AD through synthetic effects (enhanced microbial activity and key gene expression, activated the DIR process, and mitigated acid accumulation), achieving maximum methane production at 50-mg Fe³⁺/L. This study enhances understanding of the effect of iron-containing phosphorus removal agents on the AD of WAS and recommends a staged dosing strategy for WWTPs to optimize performance.

Food waste (FW) is a significant renewable resource because of its high organic content and superior biodegradability. It can be effectively converted into clean energy (like methane) using anaerobic digestion technology. However, the pervasiveness of microplastics (MPs) in FW, which comes from plastic items like food packaging and throwaway tableware, not only degrades the FW's physical and chemical characteristics but also has the potential to impair the stability and effectiveness of anaerobic digestion by changing the digestion environment and microbial metabolic processes. In this paper, the occurrence characteristics and migration behavior of MPs in FW are systematically reviewed, along with the dynamic effects of the physical and chemical properties of MPs (e.g., type, particle size and concentration) on the performance of methane production, the accumulation of volatile fatty acids (VFAs), and the stability of the system during anaerobic processes. Additionally, it concentrates on examining how MPs impede activity via processes such as chemical leaching, enzyme activity interference, reactive oxygen species (ROS) induction and disruption of the microbial population. The objective of this study is to guide the effective resource exploitation of polluted organic solid waste and to theoretically support improving the tolerance of FW digestion processes to MPs stress.

Groundwater provides drinking water to approximately one-third of the global population. However, increasing population pressure and contamination from industrial discharge, agricultural runoff, and urbanization are degrading groundwater quality. Therefore, groundwater quality assessment is important for its sustainable management particularly in semiarid regions like southwestern Haryana. However, integrated multidistrict evaluations with hydrogeochemical analysis, fuzzy-based quality indexing, human health risk evaluation, and irrigation suitability mapping remain limited for this region. This study evaluates the groundwater quality across the 11 districts of southwestern Haryana by incorporating multiple analytical techniques like groundwater quality index (GWQI) and fuzzy groundwater quality index (FGWQI), hydrochemical characterization, spatial analysis, human health risk assessment, and irrigation suitability evaluation, highlighting that 15% and 8.8% of the area fall under "unsuitable" category according to GWQI and FGWQI, respectively, reflecting the smoother classification and uncertainty handling capability of the fuzzy-based approach compared to the GWQI method. Spearman's rank correlation analysis reflected a strong association between total hardness (TH), magnesium, chloride, and calcium. This suggests that hardness is influenced by natural mineral dissolution (dolomite, calcite, and gypsum) and anthropogenic inputs (industrial discharge and agricultural runoff). Hydrochemical characterization analysis reflected dominant Ca-HCO and Na-Cl water types (representing recharge-dominated and salinity-affected conditions, respectively), water-rock interaction, evaporation dominance, and underlying sodium-calcium reverse ion-exchange processes. Health risk evaluation highlighted a significant chloride and sodium contamination, and since HI values for both adults and children were above 1, there is a potential noncarcinogenic health risk, but children are more vulnerable as HI value for children is two times higher than adults. The suitability of groundwater for irrigation was tested, which indicated that most of the groundwater samples are suitable for irrigation, though isolated zones with elevated residual sodium carbonate (RSC), magnesium hazard (MH), and percent Na (%Na) may pose sodicity and permeability risks. The findings of this study underscore the need for effective policymaking and an integrated groundwater management framework, including real-time quality monitoring, regulation of industrial wastewater discharge, and precision agricultural practices, and provide a spatially explicit decision-support basis for groundwater quality zoning, risk-based resource allocation, and targeted mitigation planning for sustainable groundwater governance in southwestern Haryana.

In Bhoj Wetland, Bhopal, the presence of microplastics (MPs) in fish and water was investigated in both wet and dry seasons. Microplastic concentrations ranged from 10 ± 4 to 19 ± 4 items L^-1 during the dry season and 8 ± 1 to 15 ± 8 items L^-1 during the wet season. Among fish species, Wallago attu and tilapia showed average MP loads of 1.2 ± 1.10 and 0.8 ± 1.30 items per individual, respectively. Due to sewage, hospital waste, and tourism, higher MP levels were discovered during the dry season, particularly along Sultania Road (L1) and Masjid Lal Imli (U3). MP presence was quite low in central lake zones. Among the various shapes identified, fibers emerged as the dominant type in both aquatic samples and fish tissues. Wallago attu and tilapia showed the highest MP content, mostly made of polyethylene (PE). The predominance of black and transparent microplastic particles suggests their probable origin from degraded fishing equipment and general plastic litter. Seasonal changes influenced MP levels, with higher amounts in dry months due to less water flow and dilution. The study highlights the impact of human activities and the need for better pollution control.

Technologies based on oxidation processes, particularly ozonation, have shown great potential for microbiological wastewater (WW) treatment. Applying low-frequency ultrasound (LF-US) can cause sublethal damage to microbial cells by generating nanobubbles, potentially enhancing their sensitivity to ozonation. Thus, primary urban WWs spiked with Salmonella enterica, Escherichia coli, Enterococcus faecium, and Pseudomonas fluorescens were subjected to laboratory-scale ozonation with or without LF-US pretreatment. LF-US pretreatment increased the antimicrobial efficiency of ozonation for all targets, with the most significant increase of 5.16 ± 0.17 Log CFU/mL for P. fluorescens (LF-US 600 s followed by ozone 120 s) and 0.57 ± 0.08 Log CFU/mL for Ent. faecium (LF-US 300 s followed by ozone 30 s). By comparing individual processes with the combined treatment and using inactivation curves from laboratory experiments, it was estimated that ozone treatment following short LF-US pretreatments saved 67 ± 9% of energy and reduced costs by up to 15.1 ± 1.3 €/m³ of treated water. This highlights the potential of this sequential method for effective and cost-efficient WW sanitation.

Total reflection X-ray fluorescence (TXRF) is a well-established method to detect ultra-trace elements present in water as well as in other liquids that can be diluted into the water medium. In the present case study, we have applied the TXRF technique to analyze various elements present in the Maha Kumbh-2025 water sample, which was collected from the nose point of Triveni Sangam, at Prayagraj, India. In addition, we have also performed intercomparative quantitative analysis of other water samples collected from different water resources. Our results show that the concentrations of different elements present in the Maha Kumbh-2025 water samples are well within the acceptable limits defined by the WHO guidelines (for drinking water). Furthermore, we did not observe the presence of any heavy toxic elements (e.g., chromium (Cr), arsenic (As), mercury (Hg), and lead (Pb)) in the Maha Kumbh-2025 water sample within the range of detection limits (DL) of our technique. This case-study-based investigation provides a site-specific insight into the elemental quality of water at a location where a large mass-gathering festival is organized. It clearly demonstrates the practical applicability of TXRF as a rapid and reliable monitoring tool for assessing the quality of water from environmental pollution aspects.

Drinking water treatment plants (DWTPs) generate residues, such as filter backwash water (FBW), that can harm the aquatic environments if discharged into water sources. In this sense, FBW recycling has gained attention. Nevertheless, it requires treatment to maintain operational efficiency and water quality in the DWTP. This work analyzed the main variables interfering with Fenton treatment of FBW from a full-scale DWTP aiming at removing turbidity and microorganisms. Bench-scale tests successfully inactivated 100% of Escherichia coli. Desired removal of other parameters (99.1% of turbidity, 99.9% of color, and achieving a 2.5 log₁₀ reduction of aerobic endospores) occurred during the sedimentation stage. There was a strong influence of the pH sample and the concentration of added hydrogen peroxide on the removal of microorganisms. This study represents an initial stage that should be continued to enable the removal of resistant microorganisms through oxidation by the Fenton reaction in FBW treatment.

Vinylon industrial wastewater contains high concentrations of polyvinyl alcohol (PVA), resulting in poor biodegradability and high organic loading. In this study, an efficient pretreatment strategy based on catalytic wet peroxide oxidation (CWPO) was developed using a synergistic La₂CuO₄/activated carbon (LaCu-AC) catalyst. The catalyst was synthesized via a sol-impregnation method and characterized by XRD, FT-IR, SEM, and BET analyses, confirming successful incorporation of the perovskite phase onto the porous carbon support. Compared with bulk La₂CuO₄, LaCu-AC exhibited improved dispersion and a higher specific surface area (17.67 vs. 7.70 m²/g). Under optimized conditions (15 g/L catalyst, 1.5 Q_th H₂O₂ added in five batches, 80°C, 1 h), COD and TOC removal efficiencies reached 95% and 89%, respectively. After five cycles, the catalyst retained over 81% of its activity. The enhanced performance is attributed to adsorption-assisted radical-mediated oxidation arising from the synergistic interaction between La₂CuO₄ and activated carbon. This study demonstrates a stable and environmentally friendly approach for the pretreatment of refractory vinylon wastewater.