S Sethulekshmi, Pradip Kalbar, Amritanshu Shriwastav
{"title":"Investigations into the flocculent settling of microplastics.","authors":"S Sethulekshmi, Pradip Kalbar, Amritanshu Shriwastav","doi":"10.2166/wst.2026.269","DOIUrl":"https://doi.org/10.2166/wst.2026.269","url":null,"abstract":"<p><p>Sewage treatment plants (STPs) act as both significant sinks and sources of microplastics (MPs) in the environment. However, there is a lack of investigations into the flocculent settling characteristics of MPs and their removal trends in secondary clarifiers. Therefore, this study attempted to explore the flocculent settling behaviour of small-sized (15-105 μm) MPs of polymer types: nylon, polystyrene, polypropylene, and low-density polyethylene through controlled lab-scale experiments. Results showed that the MPs' removal with flocculent settling improved from 55 to over 80% as sludge mixed liquor suspended solids (MLSS) concentration increased from 50 to ∼1,000 mg/L, highlighting the importance of MLSS in MPs' retention. Furthermore, a lab-scale prototype of a secondary clarifier was used to study flocculent settling trends of a mixture of rising and settling polymers, and iso-removal plots for MPs' flocculent settling were plotted, which provide an estimation of secondary clarifier removal efficiencies. It was observed that approximately 94% of MPs were effectively removed in secondary clarifiers under optimized conditions. This study provides novel insights into the flocculent settling characteristics of MPs in secondary treatment, improving our understanding of their fate in STPs and strategies to enhance MP removal efficiency.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 9","pages":"1296-1309"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148977955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Turning waste into a resource: coal fly ash as a sustainable approach for heavy metal removal in contaminated waters.","authors":"Lesley Joseph, Sewoon Kim","doi":"10.2166/wst.2026.264","DOIUrl":"https://doi.org/10.2166/wst.2026.264","url":null,"abstract":"<p><p>Effective, low-cost water treatment approaches are needed to address increasing heavy metal contamination, particularly in the developing world. This study evaluates the use of fly ash, a waste byproduct from coal combustion, as a sustainable adsorbent to remove cadmium (Cd<sup>2+</sup>), cobalt (Co<sup>2+</sup>), and lead (Pb<sup>2+</sup>) from aqueous solutions. Two types of fly ash sourced from different power plants in the southeastern United States were evaluated in this study: Belews Creek fly ash (BFA), which was untreated, and Wateree Station fly ash (WFA), which was processed using a proprietary carbon burnout method. The removal kinetics followed the pseudo-second order model, with equilibrium being achieved within 2 h. The experimental data best fit the Freundlich isotherm model, compared with the Linear isotherm model, suggesting that multilayer adsorption occurred on the fly ash surfaces. The results showed that Pb<sup>2+</sup> exhibited the highest removal efficiency for each adsorbent (BFA: 99%; WFA: >99%), followed by Co<sup>2+</sup> (BFA: 98%; WFA: 94%) and Cd<sup>2+</sup> (BFA: 93%; WFA: 56%). Removal efficiency was influenced by pH and was negatively impacted by increasing ionic strength and total organic carbon content. The findings demonstrate that fly ash is a viable, low-cost alternative for heavy metal removal for use in resource-limited areas.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 9","pages":"1310-1327"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148978190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ziya Sing-Guang Jang, Denis Ruto, Pablo K Cornejo, Kevin D Orner, Harold Leverenz
{"title":"Evaluation of nutrients in effluent from wastewater treatment lagoons discharging to surface water in the United States.","authors":"Ziya Sing-Guang Jang, Denis Ruto, Pablo K Cornejo, Kevin D Orner, Harold Leverenz","doi":"10.2166/wst.2026.261","DOIUrl":"10.2166/wst.2026.261","url":null,"abstract":"<p><p>Wastewater treatment lagoons (WTLs) are one of the most widely used wastewater treatment technologies in the world; yet, questions remain about the best strategies to improve WTL performance, particularly for nutrient removal. In this study, 1,412 facultative and upgraded WTLs were analyzed for their average effluent quality for biochemical oxygen demand (BOD), total suspended solids (TSS), ammonia (NH<sub>3</sub>), total nitrogen (TN), nitrate (NO<sub>3</sub>), and total phosphorus (TP). The geometric means of BOD, TSS, NH<sub>3</sub>, TN, NO<sub>3</sub>, and TP facility average effluent concentrations for facultative WTLs were 11.2, 19.3, 2.5, 8.8, 0.95, and 1.9 mg/L, respectively. WTLs upgraded with sand or rock filters had a lower geometric mean of average effluent BOD and TSS compared with facultative systems (Tukey-Kramer test). WTLs upgraded with moving bed-biofilm reactors, aerated gravel filters, and complete mix converted ponds showed a significant reduction in NH<sub>3</sub> concentrations comparable to similar-sized activated sludge systems. A multi-variable regression analysis (<i>n</i> = 764, <i>R</i><sup>2</sup> = 0.35) found that temperature had a nonlinear effect on the average NH<sub>3</sub> concentration. The nitrogen surface loading rate also had a significant, but smaller, effect. Finally, the seasonal NH<sub>3</sub> variation observed in WTLs was reduced with the addition of nutrient upgrades.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 9","pages":"1241-1256"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13583163/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148977847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Microplastics in Tanguar Haor: abundance, spatial variations, and environmental risks in a Ramsar wetland of Bangladesh.","authors":"Md Fardullah, Md Rakibur Rahman, Khadigha Akther, Md Tanvir Hossain, Mohammad Saiful Alam, Md Kawcher Alam, Md Tariqur Rahaman Bhuiyan Mamun, Fataha Nur Robel","doi":"10.2166/wst.2026.266","DOIUrl":"https://doi.org/10.2166/wst.2026.266","url":null,"abstract":"<p><p>Microplastic (MP) pollution in aquatic ecosystems is an emerging global concern. This study presents the first comprehensive assessment of MP contamination in Tanguar Haor, the second-largest Haor and a Ramsar site in Bangladesh. Twenty water samples were collected from 20 locations and analyzed using optical microscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and scanning electron microscopy (SEM). MP concentrations ranged from 10 to 1,290 ± 80.9 items/m<sup>3</sup>, with an average of 353 ± 98 items/m<sup>3</sup>. Fibers dominated the MP types (72.1%), followed by fragments, films, foams, pellets, and lines. Polyethylene and polyethylene terephthalate were the most abundant polymers (each 36%). Most MPs were transparent (48%) or red (21%), with sizes mainly between 0.3 and 1.5 mm (83%). SEM analysis revealed rough and weathered surfaces, indicating long-term environmental exposure. High polymer hazard index (550-1,740) and ecological risk index (>600) identified several high-risk sites (S14 > S1 > S2 > S13 > S7), despite relatively low Nemerow pollution and pollution load indices. Major MP sources include river inflow, agricultural and household waste, fishing activities, and tourism. The findings highlight potential risks of MP ingestion and bioaccumulation, threatening aquatic biodiversity and ecosystem health. This study provides baseline data to support future research and policy development for freshwater protection in Bangladesh.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 9","pages":"1328-1345"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148978031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nerea Uri Carreno, Andreas Froemelt, Carlos Domingo-Felez, Laurence Strubbe, Narasimman Lakshminarasimman, Mirzaman Zamanzadeh, Jose Porro, Arne Freyschmidt, Saba Daneshgar, Amanda Lake, Qing Zhao, Tony Flameling, Etteke Wypkema, Mohammad Shakil Ahmmed, Shuting Wang, Gürkan Sin, Fabrizio Sabba, Giacomo Bellandi
{"title":"N<sub>2</sub>O Modeling: current solutions and new avenues.","authors":"Nerea Uri Carreno, Andreas Froemelt, Carlos Domingo-Felez, Laurence Strubbe, Narasimman Lakshminarasimman, Mirzaman Zamanzadeh, Jose Porro, Arne Freyschmidt, Saba Daneshgar, Amanda Lake, Qing Zhao, Tony Flameling, Etteke Wypkema, Mohammad Shakil Ahmmed, Shuting Wang, Gürkan Sin, Fabrizio Sabba, Giacomo Bellandi","doi":"10.2166/wst.2026.245","DOIUrl":"https://doi.org/10.2166/wst.2026.245","url":null,"abstract":"<p><p>This paper addresses the critical issue of nitrous oxide (N<sub>2</sub>O) emissions from wastewater treatment plants, which have a significant impact on climate change. The article discusses the challenges associated with measuring and mitigating N<sub>2</sub>O emissions, as well as the importance of understanding the complex pathways through which N<sub>2</sub>O is produced in wastewater treatment processes. The article places a special focus on the role of modeling tools in enhancing our understanding of N<sub>2</sub>O emissions and supporting mitigation strategies. Various modeling approaches, including mechanistic models, data-driven models, and integrated computational fluid dynamics-biokinetic models, are discussed in the context of predicting and controlling N<sub>2</sub>O emissions. Case studies and examples from real-world applications demonstrate the effectiveness of modeling approaches in identifying emission hotspots, optimizing process control strategies, and developing mitigation measures. Overall, the article emphasizes the significance of modeling in addressing the challenges of N<sub>2</sub>O emissions in the water sector and advancing sustainability goals.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 9","pages":"1195-1213"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148978058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Valeria Sandoval-García, Maria Victoria Ruano, Marion Alliet, Christoph Brepols, Joaquim Comas, Jérôme Harmand, Marc Heran, Abril Prats, Ignasi Rodriguez-Roda, Ilse Smets, Giorgio Mannina, Ángel Robles
{"title":"New framework for standardized resistance-in-series-based membrane filtration modeling in wastewater treatment.","authors":"Valeria Sandoval-García, Maria Victoria Ruano, Marion Alliet, Christoph Brepols, Joaquim Comas, Jérôme Harmand, Marc Heran, Abril Prats, Ignasi Rodriguez-Roda, Ilse Smets, Giorgio Mannina, Ángel Robles","doi":"10.2166/wst.2026.258","DOIUrl":"https://doi.org/10.2166/wst.2026.258","url":null,"abstract":"<p><p>Membrane filtration models for membrane bioreactors (MBRs) currently suffer from a lack of consistency in nomenclature and notation. This work, conducted under the umbrella of the IWA Task Group on Membrane Bioreactor Modeling and Control, aims to establish a unified notational framework that integrates existing nomenclatures to harmonize terminology and resolve inconsistencies in current modeling practices. The standardized notation encompasses state variables and model parameters, incorporating multiple levels of subscripts where necessary. Beyond improving clarity and comparability among modeling approaches, the proposed framework also helps practitioners by simplifying implementation, reducing coding errors, and improving communication. These benefits ultimately enable more effective optimization of MBR systems for wastewater resource recovery.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 9","pages":"1257-1277"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148978095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anderson Ramírez-Ramírez, Juan A Lozano-Álvarez, Jesús A Cordova-López, Florentina Zurita
{"title":"Preliminary evaluation of the treatment of raw tequila vinasse with <i>Trametes versicolor</i> immobilized on biomedia.","authors":"Anderson Ramírez-Ramírez, Juan A Lozano-Álvarez, Jesús A Cordova-López, Florentina Zurita","doi":"10.2166/wst.2026.273","DOIUrl":"https://doi.org/10.2166/wst.2026.273","url":null,"abstract":"<p><p>The aim of this study was to evaluate the treatment of raw tequila vinasse (TV) using immobilized <i>Trametes versicolor</i> in lab-scale reactors. To isolate the fungal impact on the wastewater matrix, three treatments were monitored during 10 weeks: immobilized fungus on inert biomedia (Treatment A), a biomedia-only control (Treatment B), and a raw TV control (Treatment C). The initial vinasse acidity was moderated by adjusting the pH from 3.74 to 4.52 to support fungal growth. Successful immobilization of <i>T. versicolor</i> was evidenced by both internal and external colonization of the biomedia. While fungal enzymatic activity remained relatively low, significant removal efficiencies were achieved: 13.40% for COD, 9.34% for BOD<sub>5</sub>, 33.95% for TSS, and 32.4% for turbidity. These reductions are attributed to enzymatic degradation and adsorption onto the fungal mycelium. These results demonstrate the potential for using immobilized fungi to treat raw TV with minimal pH adjustment, though further research is required to optimize treatment efficacy and increase removal rates.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 9","pages":"1228-1240"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148978066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shiguo Gu, Guangliang Li, Wei Zhu, Zhengyan Xu, Yaqing Yang
{"title":"Optimization of coagulation treatment of papermaking wastewater by magnetized polyferric sulfate and polyacrylamide.","authors":"Shiguo Gu, Guangliang Li, Wei Zhu, Zhengyan Xu, Yaqing Yang","doi":"10.2166/wst.2026.259","DOIUrl":"10.2166/wst.2026.259","url":null,"abstract":"<p><p>This study investigated the coagulation effect of magnetized polyferric sulfate (PFS) and polyacrylamide (PAM) on papermaking wastewater. Results showed that the co-magnetized PFS-PAM group (Group C) achieved significantly higher removal rates of chemical oxygen demand (COD), color, turbidity, and UV<sub>254</sub> than the nonmagnetized PFS-PAM group (Group B) and control group (Group A). Specifically, the effluent COD of Group C decreased to 46.72 mg/L, with color, turbidity, and UV<sub>254</sub> removal rates increased by 16.85, 32.38, and 10.78%, respectively, compared with Group A. The enhanced efficiency was attributed to the cutting effect of magnetic induction lines in alternating magnetic fields (AMFs), which promoted coagulation and sedimentation. AMFs converted magnetic energy into internal energy of PFS particles, increasing multinuclear polymers in PFS solutions and strengthening complexation and chelation reactions. Orthogonal experiments identified the optimal parameter combination as A3B1C1D3E3 (PFS dosage: 1,000 mg/L, PAM dosage: 1.5 mg/L, magnetization intensity: 6 mT, magnetization time: 5 min, magnetization frequency: 130 Hz), under which the removal rates of COD, color, turbidity, and UV<sub>254</sub> reached 94.2, 93.08, 90.07, and 89.35%, respectively. Importantly, PAM did not alter the magnetization effect, supporting the wide application of AMFs in wastewater treatment.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 8","pages":"1169-1179"},"PeriodicalIF":2.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147782672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Prajwal Bhattarai, Sivasankar Annamalai, Namwon Kim, Sangchul Hwang
{"title":"PFOA adsorption onto biochar derived from invasive water hyacinth.","authors":"Prajwal Bhattarai, Sivasankar Annamalai, Namwon Kim, Sangchul Hwang","doi":"10.2166/wst.2026.260","DOIUrl":"10.2166/wst.2026.260","url":null,"abstract":"<p><p>Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals widely used in consumer products, firefighting foams, and various industrial applications. These chemicals are pervasive, persistent, and degradation-resistant, posing a critical threat to human and environmental health. Currently, adsorption remains the most widely used technology for the remediation of PFAS. However, large-scale PFAS removal would require extensive usage of adsorbents such as activated carbon, which tends to be relatively expensive. Therefore, we investigated the upcycling of water hyacinth, an invasive aquatic plant, as a sustainable source for biochar production to remove perfluorooctanoic acid (PFOA), a type of PFAS. Different kinetic and isotherm models assessed PFOA adsorption to water hyacinth biochar. Pseudo-second-order kinetics and Langmuir isotherm models proved to be better fits in most experiments. Intra-particle diffusion and surface adsorption were determined to contribute to the rate-limiting step, and a monolayer distribution of PFOA through chemisorption was found to be the primary mechanism of adsorption. Water hyacinth biochar exhibited an adsorption capacity of 154.39 μg/g for PFOA removal at a solid-to-liquid ratio of 1 (in mg/mL). Experiments at different pH levels revealed that electrostatic interactions influenced PFOA adsorption, and, in acidic conditions, the removal capacity increased to 164.91 μg/g.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 8","pages":"1180-1194"},"PeriodicalIF":2.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147782833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Greywater treatment using treatment wetland systems - five cases from Northern Europe.","authors":"Ashley Hall, Åsa Davidsson, Hamse Kjerstadius","doi":"10.2166/wst.2026.254","DOIUrl":"10.2166/wst.2026.254","url":null,"abstract":"<p><p>Treatment wetlands are widely used for greywater treatment in Europe, but upcoming stricter nutrient limits in the revised EU Urban Wastewater Treatment Directive (EU 2024/3019) raise questions about their ability to meet future standards. This is especially relevant as interest increases in scaling systems beyond 1,000 PE and in reusing treated greywater, which under the EU Water Reuse Regulation (EU 2020/741) requires compliance with EU 2024/3019 effluent limits. To assess performance under these conditions, four greywater treatment wetlands and one mixed wastewater reference wetland were monitored for 18 months. All wetlands consistently produced dissolved COD below 50 mg/L, within the strictest limit of 125 mg COD/L. However, only three of the wetlands achieved total nitrogen concentrations below the required 6 mg N/L. Regarding total phosphorus, only the two wetlands, which used phosphorus adsorbing media, met the 0.5 mg P/L limit. Performance was not strongly linked to flow path design. Instead, lower nitrogen loading and use of phosphorus adsorbing media were associated with higher quality effluents. Other factors, including system age and groundwater interactions, showed no consistent influence across sites. Overall, results show that treatment wetlands can meet EU wastewater requirements for greywater, though nutrient removal may require targeted design strategies.</p>","PeriodicalId":23653,"journal":{"name":"Water Science and Technology","volume":"93 7","pages":"1100-1116"},"PeriodicalIF":2.8,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147692573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}