Water Research最新文献

{"title":"A novel framework for forward osmosis in zero- and low-flow conditions: Applicability and fundamental differences from reverse osmosis","authors":"Yinseo Song, GunYoung Kim, Min Seok Lee, Min-kyu Kim, Ji Woong Chang, Dae Ryook Yang, Kiho Park","doi":"10.1016/j.watres.2025.124717","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124717","url":null,"abstract":"Forward osmosis (FO) systems operating under low or zero cross-flow velocities present modeling challenges due to the limitations of conventional external concentration polarization (ECP) formulations, which often predict near-zero flux under stagnant conditions, contradicting experimental observations. To address this, we propose a revised ECP model incorporating an asymptotic Sherwood number that enables continuous mass transfer prediction as the Reynolds number approaches zero. The model accounts for both molecular diffusion and natural convection, allowing accurate flux prediction in spacer-free and low-flow environments. Model parameters were estimated from experimental data and validated through simulations of a hydration pack (zero flow) and a commercial FO module operating at 0–10 cm/s cross-flow velocity. Simulated results closely matched experimental trends and successfully reproduced water flux behavior across operating regimes. Sensitivity analysis revealed that baseline mass transfer parameters (<em>Sh₀, a, b, c, d</em>) had influence comparable to intrinsic membrane properties (<em>A</em> and <em>S</em>), particularly in no-spacer systems where diffusion and boundary layer resistance dominate. These findings confirm the critical role of mass transfer coefficients in FO performance. In the low cross-flow regime, analysis of the recovery–flux–velocity relationship demonstrated the feasibility of low-velocity operation and clarified key distinctions from RO. The model supports FO system design under minimal flow conditions, facilitating the development of compact modules suitable for portable and hybrid applications.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"126 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145209612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Intensification of ozone gas/liquid mass transfer and ozonation efficiency: a critical review","authors":"Xuetong Yang, Tao Zhang, Ze Liu, Rui Zhang, Changtao Chen, Zhengyao Li, Kristof Demeestere, Stijn W.H. Van Hulle","doi":"10.1016/j.watres.2025.124719","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124719","url":null,"abstract":"Ozone (O₃) is effective for degrading persistent organic pollutants in wastewater but its efficiency is limited by poor O₃ gas/liquid mass transfer (<em>k</em>_L<em>a</em>) and low O₃ utilization efficiency (typically 30%-64% in bubble columns). This review critically evaluates strategies to intensify O₃ mass transfer and enhance pollutant degradation. The <em>k</em>_L<em>a</em> and energy consumption in different commonly used ozone contactors was compared, highlighting the importance of developing enhancement methods. Based on this, four types of techniques (i.e. applying physical fields, implementing membrane technology, utilizing micro/nano bubbles, and adding additives) were evaluated using <em>k</em>_L<em>a</em> enhancement factor, pollutant degradation efficiency, and scalability as criteria. Physical methods (including ultrasound, electric field, and high gravity) enhanced <em>k</em>_L<em>a</em> by 1.3–3 times but face scalability challenges due to high energy demands. Micro/nano-bubble producing systems coupled with catalysts such as activated carbon or chemical additives achieved <em>k</em>_L<em>a</em> enhancements 3-4 times, increasing degradation of refractory pollutants by over 60% removal. However, the microbubble generation also demands additional energy and chemical additives may cause secondary pollution. Natural mineral packings provide a balanced solution, enhancing <em>k</em>_L<em>a</em> by 2.5–3 times and recalcitrant pollutant removal by 25–30% at low energy consumption without secondary separation issues. For scalability, membrane contactors and catalytic microbubble have been applied at large-scale wastewater treatment while the stability of membrane and catalysts needs to be further improved. Overall, this study identifies favorable strategy for O₃ gas/liquid mass transfer and pollutant removal for sustainable water treatment.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"102 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145209603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Comparative Study of CO₂ Nanobubbles and Macrobubbles: Effects on Water Chemistry, Microalgal Growth, and Carbon Utilization","authors":"Lili Li, Jingru Wei, Yi-Ying Lee, Yihan Zhang, Shan Xue, Sowmya Atukuri, Yantao Li, Taha Marhaba, Xuezhi Zhang, Wen Zhang","doi":"10.1016/j.watres.2025.124714","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124714","url":null,"abstract":"Algal biotechnology presents a cost-effective approach for simultaneous carbon dioxide (CO₂) capture and bioproduct generation. However, conventional gas delivery approaches (e.g., macro and micro-bubbles) suffer from low gas-liquid mass transfer efficiency (<em>K_L·a</em>) and CO₂ utilization. This study investigated the aqueous properties of CO₂ nanobubbles and impacts on the CO₂ mass transfer, utilization, and microalgal growth. Results revealed that direct injection of CO₂ nanobubbles in DI water achieved rapid CO₂ saturation (1.48 ± 0.08 g·L^-1) and nanobubble density (1.5 × 10⁸ particles·mL^-1) within 1 minute. By contrast, the circulation mode produced a higher nanobubbles concentration (2.6 × 10⁸ particles·mL^-1) after 20 min with a similar dissolved CO₂ concentration. Accordingly, the volumetric mass transfer coefficient (<em>K_L·a</em>) of CO₂ nanobubbles in DI water reached 12.41 ± 3.49 h^-1 (circulation mode) and 18.91 ± 7.68 h^-1 (direct mode), exceeding that of macrobubbles (10.18 ± 2.38 h^-1). Compared to macrobubbles, the use of CO₂ nanobubbles in <em>Scenedesmus obliquus</em> cultivation increased biomass by 10.11 ± 0.01% over 14 days and garnered carbon utilization efficiency (CUE) to 27.86 ± 0.63%, supported by the enhanced CO₂ mass transfer or carbon transfer efficiency. These findings highlight the potential of nanobubble technology in algal biotechnology applications and global CO₂ emission mitigation.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"37 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145209605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Validating a Bayesian network model to characterise faecal indicator organism loss from septic tank systems in rural catchments","authors":"Chisha Chongo Mzyece, Miriam Glendell, Zisis Gagkas, Mads Troldborg, Camilla Negri, Eulyn Pagaling, Ian Jones, David M. Oliver","doi":"10.1016/j.watres.2025.124715","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124715","url":null,"abstract":"Validating model predictions with observed data is crucial for fostering confidence in model results, yet it is often overlooked in Bayesian Network (BN) studies. This research validated a BN model designed to predict faecal indicator organism (FIO) loss from septic tank systems (STS) in rural catchments (Cessnock and Mein). Both a hybrid model (combining continuous and discrete variables) and a fully discretised model were assessed. Our approach to model validation employed four methods: (1) comparing probability distributions of simulated and observed FIO loads in the hybrid model, (2) sensitivity analysis in the discrete model to identify key variables influencing results, (3) estimating percentage bias to evaluate the average difference between predicted and observed FIO loads in the hybrid model, and (4) applying Shannon entropy to measure uncertainty in the discrete model’s spatial application. Predicted FIO loads per STS were consistent across models, with the hybrid network estimating 4.63 × 10¹⁰ cfu/yr in the Cessnock catchment and 4.36 × 10¹⁰ cfu/yr in the Mein catchment, while the discrete network predicted 3.85 × 10¹⁰ cfu/yr and 3.65 × 10¹⁰ cfu/yr, respectively, closely aligning with observed values of 6.17 × 10¹⁰ cfu/yr and 5.10 × 10¹⁰ cfu/yr. Sensitivity analysis identified STS condition and treatment level as critical factors influencing FIO loss. Shannon entropy values (1.60–1.85) revealed significant uncertainty in model predictions in the catchment where STS were associated with a variability of Hydrology of Soil Types (HOST)-derived risk factors. When applied at national scale, greater confidence in model results was associated with Central, East and West Scotland where most STS were associated with a moderate to high HOST-derived risk classification. Our research is the first to show how BN models can predict FIO pollution from STS to watercourses and the findings suggest that refining model predictions requires more accurate data on STS treatment levels and maintenance, as well as access to good quality high-resolution stream water quality monitoring data.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"4 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145209606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Enhanced venlafaxine degradation in amorphous FeS2 under redox-dynamic aqueous environments: Critical role of citrate in electron utilization for boosted hydroxyl radical generation","authors":"Yibo Yuan, Xipeng Wei, Minghan Zhu, Jiale Liu, Hua Yin, Zhi Dang","doi":"10.1016/j.watres.2025.124709","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124709","url":null,"abstract":"Pharmaceuticals and organic acids ubiquitously coexist in urban riverine environments, yet the transformation mechanisms of antidepressants like venlafaxine (VNF) in iron sulfide-rich sediments under redox-dynamic conditions remain poorly resolved. This study comprehensively analyzed adsorption/desorption dynamics and reactive oxygen species (ROS)-mediated oxidative degradation of VNF in amorphous iron sulfide (FeS_2(am)), emphasizing the role of citric acid (CA) in modifying these interactions. Our results revealed that VNF was stably adsorbed onto FeS_2(am) under anoxic conditions with no observable degradation. Conversely, exposure to O₂ triggered rapid desorption of VNF (93.58%) and its partial degradation (16.96%) mediated by hydroxyl radicals (•OH). Remarkably, CA amendment significantly promoted VNF degradation under oxic conditions, achieving 97.36% degradation and increasing the observed rate constant (<em>k_obs</em>) 17.4-fold (from 6.38×10⁻⁴ to 1.11×10⁻² min⁻¹). Mechanistically, CA optimized electron utilization efficiency in FeS_2(am) through three synergistic pathways: (i) generation of carbon-centered radicals that amplified secondary •OH production via Fenton-like chain reactions; (ii) acceleration of Fe²⁺ regeneration through enhanced electron transfer from sulfur intermediates (e.g., S²⁻, S₀) to Fe³⁺; and (iii) elevation of H₂O₂ into •OH conversion efficiency from 57.20% to 83.20%. Electrochemical analyses corroborated that CA enabled a more efficient four-electron O₂ reduction pathway, thereby enhancing electron utilization for rapid •OH generation. Density functional theory calculations combined with LC-Orbitrap-HRMS analyses identified nine distinct VNF degradation pathways. Additionally, ECOSAR results indicated a significant reduction in ecotoxicity of the transformation products compared to the parent compound. Collectively, these findings pave the way for developing ligand-enhanced in situ remediation strategies for antidepressant contaminants in redox-dynamic sediments.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"23 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145203089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Multi-Scale Spatio-Temporal Graph Neural Network for Enhanced Water Demand Forecasting","authors":"Ang Xu, Tuqiao Zhang, Xuanpeng Zhang, Yu Shao, Tingchao Yu, Shipeng Chu, Lijuan Qian","doi":"10.1016/j.watres.2025.124711","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124711","url":null,"abstract":"Accurate Water Demand Forecasting (WDF) is essential for effectively managing the Water Distribution System (WDS). Graph neural networks, which utilize pre-defined spatial graphs to model relationships among sensor nodes, have been widely applied to WDF. Existing methods typically capture temporal dependencies at a single time scale and construct static graphs representing the most dominant spatial relationships. These limitations often impair model performance, particularly under increased graph complexity and extended forecasting horizons. To address the above issues, this study proposes a Multi-scale Spatio-Temporal Graph Neural Network (MSTGNN) tailored to the hierarchical nature of water demand time series. Specifically, MSTGNN captures multi-scale demand patterns by constructing hierarchical temporal representations ranging from fine to coarse time scales. Moreover, it adaptively learns scale-specific graph structures to reflect rich inter-sensor dependencies varying across scales. Extensive experiments on a real-world WDF dataset with 54 sensors demonstrate that MSTGNN achieves superior performance over six state-of-the-art methods in day-ahead WDF at 15-minute intervals. Its strength in modeling multi-scale spatio-temporal dependencies significantly enhances forecasting accuracy and scalability, supporting advanced smart applications in WDS.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"101 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145203122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Elemental sulfur enhances autotrophic denitrifying phosphorus removal from carbon-deficient wastewater through microbial synergy and electron transfer optimization","authors":"Boyi Cheng, Jinji Jiang, Lichang Zhou, Miao Zhou, Hui Lu, Yichao Lu, Zongping Wang, Weijun Zhang, Gang Guo","doi":"10.1016/j.watres.2025.124710","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124710","url":null,"abstract":"The deficient organic carbon sources frequently constrain biological phosphorus removal in urban wastewater treatment. While elemental sulfur (S⁰) serves as an economical electron donor for autotrophic denitrification, its capacity to offer supplementary electron donor to enhance denitrifying phosphorus removal (DPR) under carbon-deficient conditions (&lt; 200 mg COD/L) remains unexplored. To address this gap, a long-term reactor with and without S⁰ supplementation was operated for 178 days. Results demonstrated that S⁰ effectively replaced partial carbon demand, elevating phosphorus removal efficiency from 93.3% (200 mg COD/L) to 95.1% under carbon-deficient conditions (150 mg COD/L + 67.5 mg/L S⁰). Sulfur conversion analysis revealed heightened S⁰ utilization during carbon limitation, corroborated by typical cycle tests. Microbial analyses indicated S⁰ enrichment of community richness (Ace: +1.14%) and diversity (Shannon: +2.0%), while molecular ecological networks exhibited enhanced complexity (connectance: +100%) and stability (robustness: +100∼206.3%). Crucially, S⁰ amplified synergistic interactions between polyphosphate-accumulating organisms (PAOs; <em>Rhodobacteraceae, Dechloromonas, Sediminibacterium</em>) and sulfur-driven denitrifiers (<em>Terrimonas, Arenimonas</em>). Random forest analysis confirmed S⁰-mediated upregulation of key functional genes: phosphorus metabolism (ppk, ppx), sulfur oxidation (soxB, dsrA), and electron transfer (nuoF, coxA, cytc), thereby optimizing electron flux and ATP synthesis for metabolic demands. This work establishes an S⁰-assisted DPR strategy that leverages synergistic microbial partnerships and enhanced electron transport to overcome carbon deficiency in wastewater treatment.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"65 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145203090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Nanoplastics Induce Prophage Activation and Quorum Sensing to Enhance Biofilm Mechanical and Chemical Resilience","authors":"Haibo Wang, Hui Chen, Chujin Ruan, Jingqiu Liao, Cory Schwarz, Baoyou Shi, Pedro J.J. Alvarez, Pingfeng Yu","doi":"10.1016/j.watres.2025.124712","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124712","url":null,"abstract":"Despite the prevalence of nanoplastics (NPs) in natural and engineered water systems and their association with microbial risks, bacterium-phage interactions have been largely overlooked in the context of biofilm formation. Here, we investigated the effects of positively (PS-NH₂) and negatively (PS-COOH) charged polystyrene nanoplastics (PS-NPs) on dual-species biofilms composed of <em>Escherichia coli</em> (λ+) and <em>Pseudomonas aeruginosa</em>. PS-NPs promoted biofilm formation and stability at environmentally relevant concentrations (e.g., 100-1000 ng/L), with PS-NH₂ exhibiting higher influence. The cellular internalization of PS-NPs increased the reactive oxygen species (ROS) levels by 2.18-2.25 folds, triggered prophage λ activation followed by lysis of E. coli (λ+) after exposure to PS-NPs. Transcriptomic analyses revealed that PS-NPs, especially PS-NH₂, activated the SOS response (2.35-2.63-fold), λ phage replication (2.68-3.97-fold), and interspecies quorum sensing (2.24-5.13-fold), which was verified by the proteomic analyses. Therefore, PS-NPs stimulated protective extracellular polymeric substances (EPS) secretion with eDNA content increased to 325.8-433.8 μg/cm². Enhanced EPS production contributed to improved biofilm mechanical properties (1.46-1.57-fold as measured by atomic force microscopy) and increased resistance to chlorine disinfection. Metagenomic analysis of pipeline biofilm demonstrated that PS-NPs promoted bacterium-phage interactions and enhanced bacterial antiviral defense systems, which stimulated multi-species biofilm formation and enhanced environmental resilience. Overall, our findings provide novel insights into the interplay between nanoplastics and bacterium-phage dynamics, highlighting increased microbial risks associated with waterborne nanoplastics.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"101 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145203121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Efficient metal removal from digested sludge and supernatant by nitrification-driven acidifying leaching and denitrification-driven alkalizing precipitation","authors":"Chenkai Niu, Tao Liu, Zheng Kong, Suicao Wang, Min Zheng, Jianhua Guo, Shihu Hu","doi":"10.1016/j.watres.2025.124707","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124707","url":null,"abstract":"The transfer of heavy metals from wastewater to sludge necessitates proper sludge management. This study proposed a two-step bioprocess, utilizing pH variations during nitrification (decreasing pH) and denitrification (increasing pH) to achieve heavy metals removal from digested sludge and supernatant, alongside simultaneous nitrogen removal in the sludge supernatant. In the first stage, digested sludge was acidified to a pH of approximately 2 through ammonia oxidation, facilitated by acid-tolerant ammonia-oxidizing bacteria (AOB). This step resulted in metal solubilization efficiencies of 84.1 ± 2.5% for Cu, 94.5 ± 2.3% for Zn, 83.9 ± 2.5% for Mg, and 72.3 ± 2.2% for Al. In the second stage, the metal ions and nitrogen-rich sludge supernatant derived from bioleaching were introduced into a hydrogen/carbon dioxide (H₂/CO₂)-based membrane biofilm reactor (MBfR). During this process, denitrification raised the pH to above 7, leading to nitrogen removal efficiencies exceeding 90% and the precipitation of over 90% of Cu, Zn, and Al. Long-term operation of the system revealed the presence of volatile fatty acids (VFAs) in MBfR, which functioned as secondary electron donors alongside hydrogen, as confirmed by <em>in situ</em> batch assays. Furthermore, microbial analysis identified denitrifiers (e.g., <em>Comamonas, Denitratisoma</em>) and fermenters (e.g., <em>Sporomusa</em>) within the biofilm, substantiating the biological processes underpinning the treatment. Overall, this two-step biological treatment effectively removed metals from sludge without reliance on external acids or alkalis, which promotes sustainable waste management practices.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"115 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145203124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Mechanical resistance of higher EPS contents in larger granules restricts anammox bacterial growth","authors":"Dongdong Xu, Tao Liu, Jiahui Fan, Wenda Chen, Yiyu Li, Meng Zhang, Ping Zheng, Jianhua Guo","doi":"10.1016/j.watres.2025.124705","DOIUrl":"https://doi.org/10.1016/j.watres.2025.124705","url":null,"abstract":"Extracellular polymeric substances (EPS) are core granular components, playing critical roles in its structural stability. However, little is known about the effect of EPS on bacterial growth due to physical and mechanical resistances posed by EPS matrix. Herein, anaerobic ammonium oxidation (anammox) granules with different sizes and EPS contents were collected from a full-scale plant. Using ¹³C isotope labelling and qPCR assays, we confirmed that larger granules with higher EPS content exhibited the higher maximum nitrogen removal activity but much lower bacterial growth yield, resulting in a significantly lower maximum specific growth rate (-26.8%), compared to smaller granules. Metagenomic sequencing revealed that anammox species were identical in different granules, and actual EPS production yields were similar in 15-day incubation, ruling out the possibility that more energy was diverted to produce additional EPS in larger granules. Interestingly, the EPS mechanical strength was significantly greater in large granules, which reduced cell membrane fluidity and severely deformed bacterial cells. These mechanical constraints imposed by the dense EPS matrix limited anammox bacterial proliferation and reduced their growth yield. Using low-intensity ultrasound to loosen EPS structure improved the growth yield of anammox bacteria in large granules, while also enhancing nitrogen removal activity. These together contributed to a substantial increase in bacterial growth rate (+153.3%). The findings highlight that physical and mechanical resistance imposed by EPS plays a previously overlooked role in bacterial growth, and provide the basis for promoting anammox bacterial proliferation within granules.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"8 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145203181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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}