Water Environment Research[JOURNAL]
Sun
200 papers
Machine Learning Assisted Modeling and Interpretation of Thermally Activated Persulfate-Based Advanced Oxidation Processes.
Zhang Y, Yang X, Wang D … +1 more , Zhang J
Water Environ Res · 2026 May · PMID 42138628 · Publisher ↗
Thermally activated persulfate oxidation is an effective advanced oxidation process for the removal of refractory organic contaminants, yet quantitative prediction of degradation kinetics and interactions between process...
Thermally activated persulfate oxidation is an effective advanced oxidation process for the removal of refractory organic contaminants, yet quantitative prediction of degradation kinetics and interactions between process parameters remain challenging due to the complicated reaction mechanisms and heterogeneity of experimental conditions. In this study, a machine learning framework was established to predict apparent degradation rate constants in thermally activated persulfate systems using a curated dataset of 580 data points collected from 53 peer-reviewed studies. Fourteen input variables were considered, with the degradation rate expressed as -log(k) as the target variable. Six supervised regression models were developed and evaluated, including CatBoost, XGBoost, LightGBM, random forest, support vector regression, and artificial neural networks. Among them, CatBoost achieved the most robust predictive performance, exhibiting high accuracy and generalization capability. Model interpretation using permutation importance, SHapley Additive exPlanations, and partial dependence plots identified temperature, initial contaminant concentration, and oxidant dose as the dominant factors governing degradation kinetics, whereas molecular descriptors played a secondary role within the studied domain. Applicability domain analysis further confirmed the reliability of model predictions across most experimental conditions. This work provides an interpretable data driven approach for analyzing and optimizing thermally activated persulfate oxidation processes in water treatment.
Sonication-Assisted Struvite Fertilizer Production From Anaerobic Granular Sludge Effluent of Seafood Processing Wastewater: An Eco-Friendly Approach for Circular Economy.
Huy NV, Hang TTT, Van Tri D … +3 more , Nhan NT, Ha CT, Le Luu T
Water Environ Res · 2026 May · PMID 42138326 · Publisher ↗
The burgeoning seafood processing industry generates nutrient-rich effluents that necessitate sustainable management to prevent environmental degradation. This study investigates, for the first time, the intensification...
The burgeoning seafood processing industry generates nutrient-rich effluents that necessitate sustainable management to prevent environmental degradation. This study investigates, for the first time, the intensification of struvite fertilizer (MgNHPO·6HO) crystallization from anaerobic granular sludge effluent of a seafood processing plant using ultrasonic irradiation. The process was systematically optimized to enhance nutrient recovery and crystal quality. Experimental results demonstrated that high-purity struvite with a well-defined prismatic morphology was successfully synthesized. Optimal precipitation conditions were identified at a Mg:NH :PO molar ratio of 1:1:1, a stirring speed of 200 rpm, and a temperature of 25°C, with a combined reaction and settling time of 2.5 h. Notably, the integration of sonication-specifically in degas mode-significantly accelerated nucleation kinetics and facilitated uniform crystal growth. Compared to conventional mechanical agitation, the sonication-assisted approach yielded higher recovery efficiencies and improved crystal size distribution by mitigating localized supersaturation and enhancing mass transfer via acoustic cavitation. These findings underscore the potential of sonochemical intensification as a green, efficient strategy for transforming wastewater pollutants into high-value fertilizers, thereby advancing the circular economy in the seafood sector.
Near-Source Wastewater Surveillance of SARS-CoV-2, Influenza A, and Respiratory Syncytial Virus With Spatiotemporal Evaluation of Pepper Mild Mottle Virus as a Fecal Indicator.
Mao Y, Liu C, Abayagunawardena R … +3 more , Desilva K, Arcellana P, Kjellerup BV
Water Environ Res · 2026 · PMID 42138300 · Full text
Wastewater-based epidemiology (WBE) is increasingly transitioning from treatment plant scale monitoring toward community-scale surveillance to provide higher spatial resolution. However, the influence of monitoring scale...
Wastewater-based epidemiology (WBE) is increasingly transitioning from treatment plant scale monitoring toward community-scale surveillance to provide higher spatial resolution. However, the influence of monitoring scale on signal stability and normalization performance remains insufficiently characterized. This study evaluated the dynamics of SARS-CoV-2, influenza A (IAV), and Respiratory Syncytial Virus (RSV) at five near-source pumping stations between October 2022 and September 2024. The monitoring sites were selected using the Social Vulnerability Index to ensure representative coverage, and the catchment populations were estimated by integrating census data with physical sewershed boundaries. Wastewater viral concentrations exhibited strong associations with clinical hospitalizations, with maximum Pearson correlations occurring at lead times of 1 day for RSV and 8 days for SARS-CoV-2. The performance of Pepper Mild Mottle Virus (PMMoV) as a fecal indicator was target-specific and scale-dependent. PMMoV normalization improved predictive correlations and extended the lead time for IAV to 7 days but reduced correlation strength for SARS-CoV-2 and RSV, suggesting that raw viral loads may better reflect community shedding for certain pathogens at the neighborhood scale. Comparison with downstream wastewater treatment plant influent revealed substantial signal smoothing at larger spatial scales, whereas upstream pumping stations exhibited higher hydraulic volatility. Small catchments serving fewer than 600 residents showed large signal instability and frequent stagnation. Significant PMMoV seasonality was observed, with consistent winter and spring peaks across sites. Together, these findings indicate that near-source WBE offers reliable neighborhood-level surveillance and that the effectiveness of normalization depends on both the viral target and catchment characteristics.
Microplastics in Aquaculture Wastewater in Southeast Asia: Sources, Fate, and Treatment Technologies: A Review.
Mohd Harun MHZ, Azam MA, Zainuddin MIF
Water Environ Res · 2026 May · PMID 42125860 · Publisher ↗
This review examines microplastics (MPs) in aquaculture wastewater across Southeast Asia, focusing on sources, occurrence pathways, fate during routine farm operations, and treatment opportunities that fit regional reali...
This review examines microplastics (MPs) in aquaculture wastewater across Southeast Asia, focusing on sources, occurrence pathways, fate during routine farm operations, and treatment opportunities that fit regional realities. The literature shows that aquaculture wastewater behaves as a connected river-canal-estuary system, with intermittent and solids-rich discharges that create short release windows often missed by routine grab sampling. Reported MP levels range from < 1 item/L in some receiving waters to > 10 items/L in aquaculture pond waters, while fishpond sediments in Hanoi, Vietnam, have been reported at 2767 ± 240 to 2833 ± 176 items/kg dry weight. Across reviewed studies, physical capture and separation provide the most consistent control: Sedimentation-based processes show reported removal ranges of 16.5%-98.4%, retention ponds retain about 88%-95% depending on particle size, and rapid sand filtration can reach 84%-98% under tested conditions. However, credible mitigation requires treatment trains rather than single-unit solutions, because many apparent removal pathways transfer MPs into sludge, scum, and backwash. Key gaps include uneven regional data, limited wastewater/sludge evidence, and a need for harmonized operations-aligned monitoring to support technology selection and policy action at scale.
Laboratory-Scale Physicochemical Simulation of Palm Oil Mill Final Effluent: Water Quality Analysis and Synthetic Wastewater Formulation.
Liew CM, Puteh MH, Othman MHD … +10 more , Kamaludin R, Jasman SM, Asogan P, Alkhadi AA, Muhammad MS, Nurul H, Samah NAA, Heng J, Gunawan T, Yoshida N
Water Environ Res · 2026 May · PMID 42125849 · Publisher ↗
This study presents a systematic and reproducible methodology for developing synthetic wastewater that mimics the bulk physicochemical characteristics of palm oil mill final effluent (SWM-POME) at laboratory scale. The f...
This study presents a systematic and reproducible methodology for developing synthetic wastewater that mimics the bulk physicochemical characteristics of palm oil mill final effluent (SWM-POME) at laboratory scale. The framework was established through four sequential phases: (1) physicochemical characterization of real POME (R-POME), (2) dose-response analysis of selected media, (3) iterative formulation of SWM-POME, and (4) stability and statistical validation. R-POME was characterized across 10 sampling events to establish baseline conditions for key parameters. Dose-response analyses of glucose, lignin, surfactant, unrefined red palm oil, and NHCl were conducted to reproduce COD, BOD, color, O&G, and NH-N contributions. Three progressively refined formulations were developed through iterative adjustments, demonstrating strong agreement between experimental results (Exp-R) and calibrated predictions (Cal-P), with deviations ranging from 0.3% to 6.3%. Statistical similarity analysis of the final SWM-POME formulation showed that NH-N, O&G, color, and turbidity closely matched the distribution of the R-POME dataset, with mean values falling within the 95% confidence interval, interquartile range, and ±10% tolerance band. These parameters also exhibited very small standardized deviations (|z| ≤ 0.2), indicating negligible differences relative to the natural variability of the field measurements. TSS met all criteria except the interquartile range (z = 0.76). In contrast, COD and BOD fell outside the central distribution metrics but remained within the observed field range (z = 1.03 and 1.52, respectively). Although formal equivalence testing using the two one-sided tests procedure did not demonstrate strict equivalence, this was attributed to the large natural variability of the field measurements. Stability assessments further confirmed the robustness of the formulation, with < 5% variation during the 5-day short-term test and only minor reductions after 3-month storage, indicating that SWM-POME provides a stable physicochemical surrogate for controlled laboratory studies.
Comparative Analysis of Machine Learning Models in Groundwater Quality Assessment: A Systematic Review.
Kumar A, Singh PK, Kumar V … +4 more , Kumar RP, Patel R, Kumari S, Saw S
Water Environ Res · 2026 May · PMID 42124483 · Publisher ↗
Groundwater Quality (GWQ) presents a significant global concern owing to extensive agricultural and industrial activities, necessitating proficient management strategies, as it constitutes approximately half of the world...
Groundwater Quality (GWQ) presents a significant global concern owing to extensive agricultural and industrial activities, necessitating proficient management strategies, as it constitutes approximately half of the world's potable water supply. Traditional methods of monitoring water quality are valuable for identifying pollution sources, but they do not adequately provide an overall view of water quality trends. Machine learning (ML) technologies provide reliable predictions of water quality by learning complicated patterns from data without preconceived equations. This paper provides a meta-analysis and bibliographic review of ML applications in GWQ assessment, evaluating the accuracy, applicability, and usability of various models including artificial neural networks (ANN), support vector machines (SVM), k-nearest neighbors (KNN), decision tree (DT), random forest (RF), and deep learning (DL) (including deep neural networks [DNN] architectures) approaches. It offers a thorough synopsis and conclusion that neural networks have traditionally been the most widely used ML model in GWQ modelling. India, China, and the United States are global leaders in groundwater modelling, benefiting from extensive historical data. The most widely modelled elements are nitrate and heavy metal pollution, which are present in about half of the studies. Despite significant progress, several research gaps remain, particularly in the modelling of lesser-explored water quality parameters and in the integration of advanced ML techniques. Emerging approaches such as physics-informed machine learning (PIML), graph neural networks (GNNs), transformer-based architectures, and large language models (LLMs) show considerable potential for improving prediction accuracy and handling complex environmental datasets. These advancements may enable more robust and integrated GWQ management frameworks in future studies.
Synthesis of MWCNTs-Polyaniline Macromolecule Nanocomposite for Doxycycline Removal From Wastewater: Modeling, Kinetics, and Thermodynamics Studies.
Ali I, Hasan SZ, Hozaifa M … +4 more , Al-Qahtani N, Danquah MK, Imanova G, Abass KS
Water Environ Res · 2026 May · PMID 42121330 · Publisher ↗
A nanocomposite of MWCNTs (40%) and polyaniline macromolecule (60%) was prepared and characterized. The doxycycline antibiotic was removed from the water using this nanocomposite. At 60 mg/L of doxycycline, 1.0 g/L of th...
A nanocomposite of MWCNTs (40%) and polyaniline macromolecule (60%) was prepared and characterized. The doxycycline antibiotic was removed from the water using this nanocomposite. At 60 mg/L of doxycycline, 1.0 g/L of the antibiotic, 60 min of contact time, and 298 K temperature, the adsorbent had an adsorption capacity of 45 mg/g. The Henry, Langmuir, Freundlich, D-R, and Temkin models were used. The best fitting model was the Langmuir model based on statistical data. According to the thermodynamic data, the adsorption occurred spontaneously and thermodynamically. A combination of external mass transfer processes and intraparticle diffusion, along with external mass transfer, led to the adsorption. The supramolecular mechanism demonstrated the adsorption of the antibiotic doxycycline through π-π interactions, hydrophobic interactions, and hydrogen bonding. The adsorbent showed good removal at natural pH 8 and is cost-effective. This method is useful in removing doxycycline from water.
Hydrogeochemical, Isotopic, and Modeling Insights Into Groundwater Salinization in a Coastal Semiarid Aquifer System.
Al-Maktoumi A, Izady A, Abdalla O … +8 more , Elzain HE, Al-Yaqoubi S, Al-Mamari H, Al-Saadi R, Al-Mahrouqi R, Al Rajhi A, Al-Wahaibi B, Al-Asmi S
Water Environ Res · 2026 May · PMID 42120074 · Publisher ↗
Groundwater salinization poses a critical challenge to water security in arid and semiarid regions worldwide. To elucidate the processes governing salinity evolution and support sustainable management, this study integra...
Groundwater salinization poses a critical challenge to water security in arid and semiarid regions worldwide. To elucidate the processes governing salinity evolution and support sustainable management, this study integrates hydrogeochemical, isotopic, and solute transport modeling analyses based on 50 groundwater samples collected from 34 wells in the Wadi Aday Basin, Oman. Total dissolved solids (TDS) range from 585 to 1926 mg/L, with chloride concentrations reaching up to 886 mg/L. The primary source of salinity is attributed to the dissolution of evaporitic sedimentary units, with secondary contributions from evaporation, soil salt leaching, and limited natural recharge. Stable isotope data differentiate deeper, isotopically depleted groundwater formed under past humid climatic conditions from shallower wells influenced by episodic surface recharge, leakage from water-supply networks, and evaporative enrichment. Most wells exceed Omani drinking water standards for TDS, Mg, and SO, although minor element ratios and vertical EC profiles indicate no seawater intrusion. Groundwater flow and solute transport models developed using MODFLOW-USG and MT3DMS, respectively, were calibrated successfully. Simulations identify an area downstream of a proposed dam as an optimal site for future development owing to higher hydraulic conductivity and enhanced recharge potential, which would help dilute salinity and stabilize water quality. Modeling shows that under "no change" (Sc1), chloride concentrations increased by approximately 11 mg/L, whereas under "construction of a new dam with increased groundwater recharge" (Sc2) concentrations remained relatively stable and were approximately 10-11 mg/L lower than Sc1 by the end of the simulation. Recommended management options include implementing managed aquifer recharge via dam construction, optimizing well design to isolate high-salinity zones, adopting blending strategies, and deepening wells to access fresher groundwater.
Perovskite Quantum Dots as Dual-Functional Nanomaterials for Sensitive Optical Detection and Photocatalytic Degradation of Antibiotics in Environmental Applications.
Al Omari RH, Zaki MEA, PadmaPriya G … +7 more , Aziz QH, Sasikumar Y, Aldulaimi A, Sharma R, Gomha SM, Noorizadeh H, Kazemi M
Water Environ Res · 2026 May · PMID 42117905 · Publisher ↗
Perovskite quantum dots (PQDs) have attracted intense interest for environmental remediation owing to their outstanding optoelectronic properties; however, their simultaneous use for both sensitive optical detection and...
Perovskite quantum dots (PQDs) have attracted intense interest for environmental remediation owing to their outstanding optoelectronic properties; however, their simultaneous use for both sensitive optical detection and efficient photocatalytic degradation of antibiotics within a single platform remains largely unexplored and conceptually fragmented. This comprehensive review examines the latest advances in PQD-based materials for antibiotic sensing and photocatalytic degradation, with particular emphasis on emerging efforts to integrate both functions into unified, dual-functional systems. We discuss synthesis strategies, surface engineering approaches for enhanced stability, lead-free alternatives, sensing mechanisms (IFE, ET, FRET, etc.), and visible-light-driven photocatalytic pathways, supported by comparative analyses of performance metrics, kinetics, and degradation routes. Although numerous studies report either excellent fluorescence sensing or high photocatalytic activity, genuine dual-functional platforms that perform both tasks effectively and recyclably under real environmental conditions are still rare. Key challenges such as aqueous instability, lead toxicity, incomplete mineralization, and lack of standardized testing in complex matrices are analyzed in detail. Finally, we outline promising directions-including heterostructuring, computational and data-driven design, and modular sensing-degradation devices-to realize practical, sustainable, and truly bifunctional PQD systems for next-generation antibiotic monitoring and remediation.
Characteristics and Source Analysis of Dissolved Organic Matter Components in the Dadu River Under Cascade Hydropower Development.
Ding Y, Zhang Y, Zhang Y … +1 more , Qiao H
Water Environ Res · 2026 · PMID 42117788 · Publisher ↗
Dissolved organic matter (DOM) plays a crucial role in aquatic carbon cycling and serves as a sensitive indicator of water quality changes, making it essential to understand its behavior in anthropogenically modified riv...
Dissolved organic matter (DOM) plays a crucial role in aquatic carbon cycling and serves as a sensitive indicator of water quality changes, making it essential to understand its behavior in anthropogenically modified river systems. This study investigated the characteristics, sources, and influencing factors of DOM in the Dadu River cascade reservoir system. Through field sampling and laboratory analysis, key physicochemical parameters were measured, and DOM composition was characterized using three-dimensional fluorescence spectroscopy combined with the PARAFAC model. Three fluorescent components were identified: two terrestrial humic-like components (C1 and C2) and one autochthonous protein-like component (C3). Results suggest that the cascade reservoir system did not fundamentally alter the dual-source (allochthonous and autochthonous) of DOM inputs but induced spatial differentiation at individual reservoir. Reservoir retention enhanced the sedimentation and in situ transformation of particulate organic matter, leading to increased autochthonous contributions in quiescent zones. Conversely, discharge operations and construction phase disturbances modified DOM transport and composition patterns. Significant correlations were found between DOM components and nutrients. Specifically, TP correlated positively with C3 but negatively with C1 and C2, highlighting the close association between DOM composition and phosphorus dynamics. However, the FI showed no significant correlation with nutrients, suggesting lower sensitivity in mountainous rivers compared to plain river systems. This study demonstrates that cascade hydropower development regulates DOM dynamics through coupled physical (retention and disturbance) and biogeochemical (microbial degradation and photochemical transformation) processes.
Fe-C Micro-Electrolysis Driven Dyeing Wastewater Purification in Constructed Wetlands.
Xu S, Hao Q, Chen X … +6 more , Wei Z, Zhang W, Li Y, He Y, Ren J, Jiang C
Water Environ Res · 2026 May · PMID 42114932 · Publisher ↗
Textile dyeing wastewater poses significant environmental threats due to high COD, persistent organic compounds, and intense color. To investigate the effects of Fe-C micro-electrolysis on wastewater treatment, greenhous...
Textile dyeing wastewater poses significant environmental threats due to high COD, persistent organic compounds, and intense color. To investigate the effects of Fe-C micro-electrolysis on wastewater treatment, greenhouse gas emissions, and microbial communities, four intermittently aerated vertical-flow constructed wetlands (CWs) were established: gravel-based (GCW), biochar-amended (BCW), zero-valent iron (ZVI) amended (ZCW), and a combined biochar-ZVI system (ICW). Results showed that all CW configurations effectively removed dyes (94%), COD (81%), and NO -N (94%). The ICW demonstrated superior and stable performance, maintaining > 85% NH -N removal under high dye loading and achieving exceptional TP removal (79.75%-96.46%, 2-3 times higher than GCW and BCW). Crucially, ICW also exhibited the lowest integrated GWP, achieving 62.75% reduction compared to GCW, with a further 31.2% reduction at higher dye concentrations. This significant greenhouse gas (GHG) mitigation originated from suppressed CH emissions (indicated by a 26-fold higher pmoA/mcrA ratio, reflecting enhanced methanotrophy and suppressed methanogenesis) and reduced NO emission, linked to an increased nosZ/(nirK+nirS) ratio (0.16 in ICW vs. 0.14 in GCW), signifying more complete denitrification (NO to N). Mechanistic analysis revealed that ICW fostered the highest microbial richness (Sobs = 1818 OTUs) and diversity, significantly enriching key functional phyla (Proteobacteria, Bacteroidota, Chloroflexi, Desulfobacterota) and genera (Flavobacterium for dyes degradation; Denitratisoma, and VadinHA17 for denitrification; Desulfomonile and Geothrix for electrogenesis). In this system, biochar promoted ammonia oxidation dominated by ammonia-oxidizing archaea (AOA) over ammonia-oxidizing bacteria (AOB), and served as an electron shuttle and carbon source, while ZVI supplied electrons for redox reactions. The synergistic Fe-C micro-electrolysis in ICW optimally integrated these functions, modulating the microbial community and enhancing key biochemical pathways. Thus, Fe-C micro-electrolysis offers dual advantages of efficient dyeing wastewater treatment and significant GHG mitigation, providing a novel low-carbon solution for the remediation of complex industrial wastewater.
Groundwater Overexploitation and Water Quality Degradation in a Typical Inland River Basin of the Agro-Pastoral Ecotone in Northern China.
Deng Q, Sun Q, Li W … +4 more , Zheng Y, Ma X, Li J, Zong Q
Water Environ Res · 2026 May · PMID 42107963 · Publisher ↗
Groundwater is the primary freshwater source in semiarid regions, yet intensive overextraction and water quality deterioration increasingly threaten agricultural production and ecological sustainability. The Angulinao En...
Groundwater is the primary freshwater source in semiarid regions, yet intensive overextraction and water quality deterioration increasingly threaten agricultural production and ecological sustainability. The Angulinao Endorheic Basin (AEB) in northern China has experienced rapid irrigation expansion, wetland degradation, and severe lake desiccation over recent decades. In this study, we integrated long-term climate and hydrology records, land-use dynamics, hydrochemical data, and regional groundwater resource balance calculations to quantify groundwater availability, quality evolution, and supply-demand relationships. Results indicate that mean annual groundwater recharge is approximately 1.04 × 10 m, whereas sustainable groundwater exploitation is limited to 4.16 × 10 m year. Projections suggest that by 2030, groundwater demand will exceed sustainable supply by 2.86 × 10 m year in normal hydrological years and up to 9.83 × 10 m year in dry years. Groundwater quality exhibits pronounced spatial heterogeneity: 55% of irrigated areas exceed nitrate (NO ) standards and 17% exceed fluoride (F) thresholds. Discharge zones are characterized by elevated total dissolved solids (TDS), NO , Fe, and Mn, reflecting combined geological controls and anthropogenic inputs, whereas elevated F concentrations are primarily associated with strong evaporation processes. These findings reveal critical risks associated with continued groundwater overextraction and quality degradation and emphasize the urgent need for integrated groundwater management strategies to ensure long-term water security and ecosystem resilience in semiarid endorheic basins.
Managing Nitrification in Secondary Water Supply Systems: Effects of Chloramine Levels and Material Choice on Nitrifying Guild Dynamics.
Li X, Cai X, Jiang K … +2 more , Xia S, Wang H
Water Environ Res · 2026 May · PMID 42104594 · Publisher ↗
Nitrification in chloraminated secondary water supply systems remains a significant challenge to maintaining drinking water quality, as it accelerates disinfectant decay and facilitates microbial regrowth. This study inv...
Nitrification in chloraminated secondary water supply systems remains a significant challenge to maintaining drinking water quality, as it accelerates disinfectant decay and facilitates microbial regrowth. This study investigated the colonization and succession patterns of nitrifying guilds in response to varying chloramine concentrations and commonly used tank and plumbing materials, using continuously operated simulated secondary water supply systems (SWSSs) over a 270-day period. Quantitative PCR analysis of nitrifier marker genes revealed that ammonia-oxidizing bacteria (AOB) were the dominant early colonizers in biofilms whereas Comammox clade A and strict nitrite-oxidizing bacteria (sNOB) became more prevalent as the biofilm matured. Notably, principal coordinate analysis (PCoA) of AOB- and NOB-affiliated operational taxonomic units (OTUs) extracted from 16S rRNA gene sequencing indicated that chloramine and material type exerted a more profound selective pressure on the AOB community than on NOB. Copper surfaces selectively promoted the enrichment of complete ammonia-oxidizing (Comammox) and sNOB, emphasizing the role of material type in shaping nitrifier assembly. Chloramine concentration had a pronounced, dose-dependent effect: Moderate levels supported AOB proliferation, whereas high levels inhibited all nitrifiers. A temporary chlorine burn reduced total bacterial abundance and coincided with a selective increase in Comammox and ammonia-oxidizing archaea (AOA), suggesting differential tolerance among nitrifying taxa. These findings provide insights into the dynamic succession of nitrifying guilds under representative SWSS conditions and underscore the importance of chloramine concentration and material selection in informing integrated nitrification control strategies.
Simultaneous Partial Nitrification, Anammox, and Denitrification Treating Mixture of Aged Landfill Leachate and Kitchen Digestate for Deep Nitrogen Removal in Microaerobic Membrane Bioreactor.
Su B, Wang J, Chen C … +2 more , Zhou X, Liu G
Water Environ Res · 2026 May · PMID 42087550 · Publisher ↗
The high ammonia nitrogen and low C/N ratio inherent in both aged landfill leachate and kitchen digestate lead to complex and costly nitrogen removal processes. In this study, the rapid start-up and nitrogen removal perf...
The high ammonia nitrogen and low C/N ratio inherent in both aged landfill leachate and kitchen digestate lead to complex and costly nitrogen removal processes. In this study, the rapid start-up and nitrogen removal performance of the simultaneous partial nitrification, anammox and denitrification (SNAD) process for treating a mixed solution of aged landfill leachate and kitchen digestate were investigated in an upflow microaerobic membrane bioreactor (UMMBR) throughout the 265-day experiment. The average removal efficiencies of NH -N and TN were 95.51% and 90.29%, respectively. A stable coexistence of red granular sludge (D₅₀ = 251.7 μm) and floc sludge was achieved with the MLSS concentration of approximately 13.54 g/L. High-throughput sequencing analysis showed that Candidatus Brocadia (9.01%) and Candidatus Jettenia (0.53%) as the functional genera of anaerobic ammonia oxidation (AnAOB) were enriched; Nitrosomonas (ammonia oxidizing bacteria, AOB, 2.1%) dominated the nitrifying microbial community. Surprisingly, nitrite oxidizing bacteria (NOB) only accounted for 0.3% of the microbial community and showed a low activity of 0.081 mg NO -N/(g MLSS·h), indicating they were effectively inhibited. Furthermore, the presence of denitrifying genera such as Phaeodactylibacter (4.67%), OLB13 (1.95%), and norank_f__PHOS-HE36 (3.01%) supported complementary nitrogen removal. This study provides a low-energy, multipathway deep nitrogen removal process for treating real wastewater with high salinity, high ammonia nitrogen, and a low C/N ratio.
Nutrient Removal and Phosphate Recovery Using Agricultural Residue Media in Denitrifying Bioreactors.
Kouanda A, Ebrahimzadeh S, Dai P … +1 more , Hua G
Water Environ Res · 2026 May · PMID 42065355 · Publisher ↗
Agricultural residues have been proposed as alternative organic carbon sources to woodchips for nitrate removal in denitrifying bioreactors. However, the phosphate removal potentials of agricultural residues have not bee...
Agricultural residues have been proposed as alternative organic carbon sources to woodchips for nitrate removal in denitrifying bioreactors. However, the phosphate removal potentials of agricultural residues have not been carefully evaluated. The objectives of this study were to determine the long-term nitrate and phosphate removal capacities of agricultural residue media in bioreactors and to evaluate the phosphate desorption potentials. Laboratory denitrifying bioreactors using corn cobs, corn stalks, barley straw, and woodchips were operated for 390 days. The reactor average nitrate load reduction rates were 57.1, 21.9, 19.4, and 10.1 g N/m/day, and the average phosphate load reduction rates were 0.35, 0.16, 0.14, and 0.05 g P/m/day for corn cobs, corn stalks, barley straw, and woodchips, respectively. Barley straw quickly lost nitrate and phosphate removal capacities over time. Corn cobs consistently removed the highest amounts of nitrate and phosphate and showed the least decline in removal performance throughout the experiment. The phosphate desorption potentials after the bioreactor experiment were in the order of corn stalks > corn cobs > barley straw > woodchips. The results of this study suggest that corn cobs can be used as bioreactor filling materials to effectively remove nitrate and recover phosphate from contaminated waters.
Hydrogeochemical Characteristics and Quality Assessment of Groundwater in Xingtai Selenium-Enriched Area, Central North China.
Zhang H, Zhang M
Water Environ Res · 2026 May · PMID 42052753 · Publisher ↗
In this study, a total of 103 groundwater samples were collected from four subareas in the Xingtai Se-enriched area, central North China to explore controlling factors of hydrochemical components and suitability for drin...
In this study, a total of 103 groundwater samples were collected from four subareas in the Xingtai Se-enriched area, central North China to explore controlling factors of hydrochemical components and suitability for drinking and irrigation purposes. The results indicate that the groundwater exhibits neutral to slightly alkaline properties. Piper diagram classifies the major groundwater types as SO-Ca and Cl-Ca·Mg. Integrated hydrochemical analyses (Gibbs and Gaillardet diagrams, ionic ratios, Chloro-Alkali Index, and Saturation Index) together with statistical approaches (Pearson's correlation analysis and principal component analysis) reveal that hydrogeochemical evolution is governed by water-rock interactions (dissolution of calcite, dolomite, fluorite, gypsum, pyrite, and halite), cation exchange, and anthropogenic influences. Nonpoint sources (fertilizers, manure, and sewage) contribute to the elevations of NO and Cl concentrations. Water Quality Index (WQI) assessments indicate 80.58% of samples are suitable for drinking. SO and NO are identified as key triggers of water quality deterioration, which are linked to carbonate rock dissolution, cation exchange, sulfur-containing minerals dissolution (gypsum and pyrite), and anthropogenic pollution (fertilizers and sewage). USSL classifications indicate 44.67% of samples are suitable for irrigation, contrasting with 1.94% deemed unsuitable, whereas Wilcox diagram categorizations show 43.68% as excellent-to-good and 2.91% as unsuitable. The findings can provide scientific guidance for rationally utilizing the valuable local Se-enriched groundwater resource on the premise of balancing exploitation with protection against hydrogeochemical and anthropogenic contamination.
Removal and Detoxification of Safranin in Aqueous Solutions Using a Betula pendula Roth Based Biomass: Isotherm, Kinetics, Thermodynamics of the Biosorption Process, and Molecular Insights Into the Mechanism of Safranin Ecotoxicity.
Karadayı M, Güllüce E, Aksu Ş … +4 more , Gülşahin Y, Tosun B, Karadayı G, Güllüce M
Water Environ Res · 2026 May · PMID 42047532 · Publisher ↗
Wastewater containing safranin from dyes used in textile industries has serious harmful effects on aquatic ecosystems and living organisms. This has led to increased interest in advanced toxicity assessment of this dye a...
Wastewater containing safranin from dyes used in textile industries has serious harmful effects on aquatic ecosystems and living organisms. This has led to increased interest in advanced toxicity assessment of this dye and the treatment of its wastewater with sustainable biological removal methods. In this study, using in vitro model systems and molecular approach, new insights into the toxicity of safranin were obtained, a sustainable biomass was developed from Betula pendula (BP) biomass, and the detoxification potential of BP biomass was investigated for the first time. Safranin application up to 10 ppm caused significant phytotoxic effects on the physiological parameters of and the anatomical parameters of Allium cepa L. After safranin treatment, significant changes in cytogenetic parameters and oxidant-antioxidant dynamics, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and malondialdehyde (MDA), were observed. Molecular interactions between Safranin and target receptors associated with in vitro parameters were determined by molecular docking analysis. BP biomass treatment significantly detoxified safranin solutions, and improvements in the values of the tested physiological, cytogenetic, biochemical, and anatomical parameters were observed. Safranin was removed by 98% from aqueous solutions by using BP biomass under optimal conditions. The Freundlich isotherm and pseudo-second-order kinetic models best fitted in isotherm and kinetic studies. Biosorption process occurred spontaneously because ∆G° values were negative in thermodynamic studies. These results suggest that BP biomass is an important biomass for safranin detoxification due to its low cost, sustainable, and effective treatment.
Mechanism of Groundwater Hydrochemical Evolution Under the Control of Land-Sea Gradient.
Zhang H, Chen J, Li J … +4 more , Zhang W, Zhao Q, Dang X, Hu S
Water Environ Res · 2026 May · PMID 42037103 · Publisher ↗
Unraveling the integrated mechanisms governing groundwater hydrochemical evolution along a complete land-sea gradient is crucial for coastal water resource management and seawater intrusion prevention and control. This s...
Unraveling the integrated mechanisms governing groundwater hydrochemical evolution along a complete land-sea gradient is crucial for coastal water resource management and seawater intrusion prevention and control. This study focused on the Bailang River Basin (southern Laizhou Bay, Bohai Sea, China). Based on 45 systematically collected groundwater samples, we integrated hydrochemical statistics, Piper trilinear/Gibbs diagrams, and ion ratio analysis to clarify the hydrochemical evolution of the research area from mountains to coast. Results show: (1) The upstream reservoir area is dominated by low total dissolved solids (TDS) freshwater (360.1-1648.7 mg/L, HCO-Ca·Mg type), which is mainly controlled by carbonate and silicate weathering; (2) midstream plain: transitional brackish-saline water (702.1-32,322.3 mg/L, shifting to Na-Ca-Cl type), affected by cation exchange, agricultural return flow, and weak evaporation; (3) coastal area: high-TDS brine (15,398.9-86,169.6 mg/L, Na-Cl type), driven by paleoseawater residual, modern seawater intrusion, and intense evaporation. This study identifies a "source-sink" evolutionary pattern controlled by the coupling of rock leaching, cation exchange, seawater intrusion, and evaporative concentration. This pattern explicitly links geomorphic gradients to hydrochemical differentiation. This work clarifies how natural processes and anthropogenic activities synergistically shape the coastal groundwater hydrochemical spatial pattern, providing a scientific basis for sustainable groundwater management and seawater intrusion control in similar regions.
Phytoremediation of Wastewater From Oil Well Drilling: Potential of Different Plant Species.
Souza TO, Mendes TAO, Monteiro LCP … +3 more , Watthier Júnior LE, Marques DDS, Borges AC
Water Environ Res · 2026 May · PMID 42036918 · Full text
This study evaluated the removal of contaminants present in wastewater from oil well drilling in the presence of three plant species: water hyacinth (Eichhornia crassipes), cattail (Typha domingensis), and purple fountai...
This study evaluated the removal of contaminants present in wastewater from oil well drilling in the presence of three plant species: water hyacinth (Eichhornia crassipes), cattail (Typha domingensis), and purple fountain grass (Cenchrus setaceus "Rubrum"). The synthesized wastewater contained potentially toxic metals (Zn, Cu, and Cr) and representative hydrocarbons (naphthalene, hexane, and hexadecane) and it was applied in hydroponic systems operating in sequential batches. Agronomic, biochemical, and water quality variables were monitored periodically. The results indicated that C. setaceus had the best overall performance, indicating its absence of mortality, agronomic stability, and statistically significant removal of color, biochemical oxygen demand, total organic carbon, total carbon, and metals. The kinetics of chemical oxygen demand removal were faster in the presence of C. setaceus, with a higher reaction coefficient and better fit of the first-order model with residual (plateau) to the data. Although they promoted the removal of some pollutants, the performance of the treatments in the presence of T. domingensis and E. crassipes was inferior to that of the treatment with C. setaceus in terms of stability, vigor, and consistency of the results. It was concluded that C. setaceus has high tolerance to contaminated environments and potential for application in constructed wetland systems for the treatment of wastewater from well drilling and is a promising alternative for sustainable phytoremediation strategies.
ORP-Guided, Temperature-Model-Based Control of Nitrification and Denitrification in SBRs and a Full-Scale UNITANK System.
Son RC, Kim KC, Hong I … +3 more , Mun GJ, Rim JH, Yim GM
Water Environ Res · 2026 Apr · PMID 42036352 · Publisher ↗
This study evaluated the efficacy of oxidation-reduction potential (ORP) as a real-time control parameter for optimizing nitrification and denitrification durations in a sequencing batch reactor (SBR) treating actual mun...
This study evaluated the efficacy of oxidation-reduction potential (ORP) as a real-time control parameter for optimizing nitrification and denitrification durations in a sequencing batch reactor (SBR) treating actual municipal wastewater. The distinct novelty of this work lies in the systematic validation of characteristic ORP inflection points using real municipal wastewater with inherent compositional variability, the derivation of temperature dependent predictive models from a robust dataset, and the successful scale-up of the control strategy to a full-scale UNITANK system bridging a critical gap between laboratory research and practical implementation. Characteristic inflection points on the ORP profile were identified: A distinct knee point within 28-80 mV indicated the completion of nitrification (> 95% NH -N removal), while a stable plateau (|dORP/dt| ≤ 0.1 mV/min) within -25 to -65 mV signified the end of denitrification (> 90% total nitrogen removal). Temperature exhibited the most significant influence on reaction rates. Linear regression models predicted phase durations: nitrification time (min) = -11.918 × T (°C) + 370.3 (R = 0.82) and denitrification time (min) = -7.363 × T (°C) + 274.93 (R = 0.75). Implementation of this temperature-model-based strategy (with ORP used only for validation and calibration) in a full-scale UNITANK system reduced aeration time and achieved annual energy savings of approximately 6000 kWh (a 25% reduction), while maintaining effluent quality. These findings confirm the feasibility and economic advantage of using ORP as a guiding rather than direct real-time control parameter for intelligent management of biological nitrogen removal.
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