Environmental Science: Water Research & Technology最新文献

Per- and polyfluoroalkyl substances (PFASs) are widely used in the textile dyeing industry resulting in textile dyeing wastewater being discharged as a significant source of PFASs in aquatic environments. However, very limited information is available on the occurrence and fate of PFASs among different textile dyeing wastewater treatment processes. This study investigated thirteen targeted PFASs across 15 textile dyeing enterprises (abbreviated as A1–A15), 4 wastewater treatment plants (abbreviated as WWTPs 1–4), and 5 receiving surface waters. Specifically, WWTP-1 and WWTP-2 were equipped with an anaerobic–anoxic–oxic (A²/O) process, while WWTP-3 and WWTP-4 with an anoxic–oxic (A/O) process. Four WWTPs respectively treated raw textile dyeing wastewaters from A1–A6, A7–A11, A12 and A13, and A14 and A15 for standard emission. Results indicated that the total concentration of 13 PFASs (Σ₁₃PFASs) ranged from 23.80 to 1867.33 ng L⁻¹ in raw textile dyeing wastewaters, with short-chain perfluorocarboxylic acids (PFCAs) accounting for 60%. The comparison of two different treatment processes demonstrated that the A²/O process was more effective for the removal of long-chain PFCAs, which was attributed to the transformation of long-chain PFASs by the anaerobic environment. Moreover, the Σ₁₃PFASs in five surface waters were 235.46 to 2787.03 ng L⁻¹, and the correlation analysis revealed significant similarity of PFAS composition among surface waters with A3, A11, and WWTP-1 effluent (p < 0.01). Overall, this study comprehensively investigated the PFAS occurrence and fate in textile dyeing wastewater and receiving rivers along associated wastewater treatment processes, thus providing new insights into different textile dyeing wastewater treatment processes for PFAS dynamic alteration.

The discharge of persistent textile dyes into aquatic systems poses a major challenge for effective wastewater treatment due to their high chemical stability, toxicity and resistance to conventional remediation methods. Developing visible-light-responsive photocatalysts that achieve efficient degradation while ensuring safe mineralization remains an urgent research priority. In this work, a band-engineered CoMgAl layered triple hydroxide/CdS nanocomposite was successfully prepared through a hydrothermal treatment to fabricate a highly efficient S-scheme heterostructure photocatalyst for the degradation of textile dyes via an advanced oxidation process (AOP). The obtained samples were characterized using XRD, FTIR, SEM, HR-TEM, XPS, UV-vis DRS, PL and EIS analysis. The internal electric field (IEF) formed at the CMAC interface significantly promotes the separation of charge carriers and hinders electron–hole recombination, resulting in high visible-light absorption and a strong redox ability. Consequently, remarkably high photocatalytic degradation efficiencies of 99.5% for Auramine O (AO) and 98% for Brilliant Blue (BB) were obtained under visible-light irradiation with a low catalyst dosage and the process followed pseudo-first-order kinetics. Additionally, reactive oxygen species (ROS) have been proven to be the dominant and effective active species in wastewater treatment through scavenger experiments. LC–MS analysis was conducted to understand the degradation pathways and by-products. Toxicity evaluation using T.E.S.T. software predicted a considerable decrease in the toxicity of the intermediates obtained upon degradation. Therefore, this study reveals that the CMAC S-scheme heterojunction is an efficient, stable and environmentally safe photocatalyst, providing a promising strategy for the practical visible-light-driven removal of dyes from polluted wastewater.

This study evaluates the batch seeding of granular activated carbon (GAC) with sludge inocula and raw sewage to accelerate its transformation into biological activated carbon (BAC) and achieve rapid steady-state condition, fostering the development of microbial community and simultaneous degradation of residual organics, nitrogen, and emerging contaminants (ECs) from secondary effluents. After 7 days of seeding, pathogens dominated the surface of GAC while heterotrophs, nitrifiers, and denitrifiers were scarce. However, a sustained aerobic condition in the column shifted the community towards these beneficial microbes, enabling rapid biofilm development and attainment of steady-state conditions in the removal of dissolved organic carbon (DOC). Notably, two columns loaded with seeded GAC at food-to-microorganism (F/M) ratios of 0.8 and 0.4 reached steady-state after 4801 (50 days) and 7202 (75 days)-bed volumes (BVs), respectively, while the control required 19 206 (200 days) BVs. The seeded systems showed a higher reduction in the DOC, decreasing from 6.4 to 2 mg L⁻¹ (∼68%), meeting the USEPA DOC recommendation for drinking water. Other studies reported <50% reduction in the DOC after operating for 200 days. Additionally, NH₄-N and NO₃-N were lowered from 1.6 to 0.5 mg L⁻¹ and 5.2 to 2.6 mg L⁻¹, respectively. At a contact time of 15 min, 12 out of 17 ECs showed >70% removal, while the remaining 5 ECs showed >60% removal. A fluorescence–PARAFAC model was used to investigate the DOC removal mechanism by the BAC filters. These filters effectively reduced the total coliforms by >1.5 log₁₀ and strengthened the relationship between the functional enzymes, key metabolic pathways, and contaminant removal. Extracellular polymeric substances (EPS) from BAC were characterized to provide mechanistic insights into the enhanced attenuation of ECs.

In the biodesulfurisation process harmful sulfide is converted to sulfur by sulfide oxidising bacteria (SOB), using oxygen as terminal electron acceptor. Surprisingly, in this process sulfide is already removed before oxygen is consumed. Therefore, sulfide and/or charge is being shuttled between sulfide removal and terminal electron transfer. Previously, it was thought that the bacteria themselves were the exclusive “electron shuttlers”. Patterns in sulfide concentration and oxygen reduction potential (ORP) during anaerobic sulfide removal tests in batch confirmed that SOB remove sulfide in two steps, of which the second lowered the ORP. However, we found that aside from biomass also biosulfur and certain solutes are involved in electron shuttling. Gradual removal of sulfide by interactions between sulfide, solutes, and biosulfur caused an increase in ORP, even after all sulfide was removed. The amplitude and rate of ORP increase rose with increasing sulfide removal capacity of the process solution. We hypothesise that organic thiol/disulfide redox couples are involved in electron shuttling.

Water pollution is a significant environmental concern that necessitates the development of effective treatment techniques to mitigate the adverse impacts of water pollution on human health and ecosystems. To effectively tackle the water pollution caused by dyes, pharmaceuticals and other organic pollutants, researchers are continuously developing new technologies for wastewater treatment. This review offers a complete understanding of the fundamental principles of Photoelectrocatalytic (PEC) degradation, design strategies for photocatalysts and reactors, mechanism for the formation of reactive species, and mechanism for the degradation of target pollutants. The strategies for enhancing the performance of photoelectrocatalyts, such as doping, heterojunction formation, and morphology control, are discussed. Additionally, this review addresses the toxicity assessment of treated effluents and discusses the current challenges, including inferior material stability, limited visible-light absorption, and impediments in large-scale implementation. Finally, the factors influencing the PEC degradation of dyes and pharmaceuticals are discussed. This review will provide a roadmap for environmental researchers working in water sustainability departments to effectively design and develop new photoelectrodes and photoelectrocatalytic reactors (PECRs) to efficiently tackle water pollution.

To improve the performance of sludge pressure filtration and achieve deep dewatering, this study compared the effects of three biochar skeleton materials derived from different sources—anaerobic sludge biochar, surplus sludge biochar, and rice husk biochar—on sludge conditioning. The enhancement mechanisms were systematically investigated by analyzing changes in particle size distribution, zeta potential, and the contents of polysaccharides and proteins in extracellular polymeric substances (EPS). Experimental results showed that the addition of biochar skeletons significantly improved sludge dewatering efficiency, with anaerobic sludge biochar reducing the sludge cake moisture content to 63.98% ± 0.54% at a dosage of 50% (on a dry sludge basis). Mechanism analysis indicated that biochar skeletons neutralized surface charges, increased particle size, and adsorbed hydrophilic EPS components to promote floc formation. These effects further facilitated the construction of mechanically stable skeleton structures and stratified drainage channels, which helped maintain sludge cake permeability under high pressure, enhance filtration performance, and ultimately achieve deep dewatering. This study provides important theoretical foundations and engineering support for the development of novel sludge conditioners and the optimization of deep dewatering processes.

Pit latrines and septic systems are widely used in low-income countries across sub-Saharan Africa. Despite their critical role in providing basic sanitation, these systems face challenges in maintaining functionality due to issues such as overflowing and leakage, posing significant public health risks. This study examined operations and maintenance (O&M) factors affecting the functionality of on-site sanitation systems, focusing on overflow and leakage patterns, and explored strategies to enhance system performance. Data from 18 534 sanitation facilities across 12 countries, comprising 94% pit latrines and 6% septic systems were analyzed. Using a Bayesian Belief Network analysis, the analysis identified factors influencing system functionality, including desludging frequency, structural damage, and flood risk. Among the systems analyzed, 28% showed evidence of overflowing (29% pit latrines, 17% septic systems), and 24% showed evidence of leakage (24% pit latrines, 14% septic systems). Including flood risk in the model increased overflow rates by 1% and leakage rates by 4% in high-risk flood-prone areas. System performance was primarily influenced by desludging frequency, floor and structural integrity, and the availability of maintenance personnel. Simulations indicated that uniformly implementing frequent desludging across the network had the greatest influence, reducing overflow rates by 72% and leakage rates by 17% relative to current conditions. These findings suggest that post-construction support, such as regular desludging and access to qualified repair personnel, could substantially improve system reliability, particularly in high-risk flood-prone areas, and should be prioritized in sanitation policy and infrastructure design.

Environmental endocrine disruption, resulting from exposure to hormone-active chemicals in environmental samples, poses a significant public health risk through wastewater handling and reuse. Despite extensive surveillance globally of both health and environmental impacts, the presence of endocrine disrupting chemicals in water and wastewater has been understudied in Ghana, where greywater is commonly reused in the home. In this study, a scoping review of 87 studies was conducted to determine the most critical greywater pollutants in Ghana, greywater reuse practices, and the prevalent endocrine disorders in Ghana. Next, an in silico tool (VirtualToxLab) was used to evaluate the binding of greywater contaminants (n = 59) to 12 target proteins involved in environmental endocrine disruption to assess endocrine disrupting potential. Results showed pollutants found in greywater bound moderate to strongly to receptors involved in reproductive and metabolic disorders. Analyzing the most probable source of the pollutant (from the bathroom, kitchen, laundry), bathroom-sourced pollutants were found to exhibit the highest risk of endocrine disruption due to the presence in personal care products. This evaluation was used to assess the potential for greywater reuse considering source separation as well as the possible relationship between endocrine disorders in Ghana and exposure to greywater contaminants. Further in vivo and in vitro research into the most critical pollutants is crucial for developing effective removal technologies to treat greywater and protect public health in Ghana.

In biological wastewater treatment units, bacteria can self-assemble into flocs with heterogeneous structural characteristics. These flocs, varying in density, create dynamic microenvironments that reshape bacterial community assembly and influence the dissemination of antibiotic resistance, a process that is not yet fully understood. This study investigated the evolution of antibiotic resistance across floc density gradients to elucidate the key driving mechanisms. An increase in floc density from 1.0020 g mL⁻¹ to 1.0029 g mL⁻¹ triggered a fourfold rise in the absolute abundance of antibiotic-resistant bacteria (ARB) (p < 0.05), with their relative abundance increasing from 64% to 89%. Microbial community analysis revealed significant shifts at both the phylum and genus levels across varying floc densities (p < 0.05), likely driven by floc density-mediated changes in nutrient availability. Notably, the resource-sensitive Methylophilaceae declined in denser flocs, whereas the nutrient-tolerant Saccharimonadales and Blastocatellaceae proliferated. Furthermore, both the absolute and relative abundances of key antibiotic resistance genes (ARGs), including class 1 integron (intI1), sulfamethoxazole- (sul1 and sul2) and ciprofloxacin-related resistance genes (qnrB and qnrS), increased with increasing sludge density. Particularly, sul1 and sul2 exhibited 1.9-fold and 4.5-fold upregulations, respectively (p < 0.05). These findings highlight strong linkages among floc density, bacterial community composition and antibiotic resistance profiles, suggesting that floc density modulates resistance by reshaping the bacterial community composition in activated sludge. This study provides insights into the ecological mechanisms governing antibiotic resistance in wastewater treatment systems, aiding improved risk assessment and management strategies.

Onsite wastewater treatment systems, which collectively manage ∼12% of global wastewater, remain a preferred choice in rural and low-density communities. However, conventional systems such as septic tanks often exhibit limited treatment efficiency for nutrients and emerging contaminants and are flood prone, raising concerns about their long-term sustainability and environmental impacts. Recent advances in microbial ecology have uncovered alternative nitrogen removal processes with nitrite, iron, manganese, or sulfate as terminal electron acceptors. In this perspective, we collectively describe these processes as robust electron acceptors for nitrogen elimination from wastewater (RENEW) and evaluate their potential application in onsite wastewater treatment from thermodynamic, kinetic, and engineering standpoints. Thermodynamic calculations indicate that processes like conventional nitrification and denitrification, Anammox and Mnammox are favorable at neutral pH, while Sulfammox is unfavorable under typical wastewater conditions. Kinetic evidence highlights that Mnammox (8.15 gNH₄⁺-N gVSS⁻¹ d⁻¹) and Feammox (7.16 gNH₄⁺-N gVSS⁻¹ d⁻¹) can achieve a substantial nitrogen removal rate, with lower oxygen demand nearly 20-fold compared to traditional nitrification–denitrification. Meanwhile, microalgal photosynthesis with a higher yield (15.84 gVSS gNH₄⁺-N⁻¹) have a lower nitrogen removal rate (0.050 gNH₄⁺-N gVSS⁻¹ d⁻¹). We propose that RENEW processes could offer advantages in system footprint, climate-resilience, greenhouse gas emissions, and biosolid production. Novel onsite treatment systems can be further developed by integrating RENEW processes with artificial intelligence.