Abstract: The highly efficient electrochemical treatment technology for dye-polluted wastewater is one of hot research topics in industrial wastewater treatment. This study reported a three-dimensional electrochemical treatment process integrating graphite intercalation compound (GIC) adsorption, direct anodic oxidation, and ·OH oxidation for decolourising Reactive Black 5 (RB5) from aqueous solutions. The electrochemical process was optimised using the novel progressive central composite design-response surface methodology (CCD-NPRSM), hybrid artificial neural network-extreme gradient boosting (hybrid ANN-XGBoost), and classification and regression trees (CART). CCD-NPRSM and hybrid ANN-XGBoost were employed to minimise errors in evaluating the electrochemical process involving three manipulated operational parameters: current density, electrolysis (treatment) time, and initial dye concentration. The optimised decolourisation efficiencies were 99.30%, 96.63%, and 99.14% for CCD-NPRSM, hybrid ANN-XGBoost, and CART, respectively, compared to the 98.46% RB5 removal rate observed experimentally under optimum conditions: approximately 20 mA/cm2 of current density, 20 min of electrolysis time, and 65 mg/L of RB5. The optimised mineralisation efficiencies ranged between 89% and 92% for different models based on total organic carbon (TOC). Experimental studies confirmed that the predictive efficiency of optimised models ranked in the descending order of hybrid ANN-XGBoost, CCD-NPRSM, and CART. Model validation using analysis of variance (ANOVA) revealed that hybrid ANN-XGBoost had a mean squared error (MSE) and a coefficient of determination (R2) of approximately 0.014 and 0.998, respectively, for the RB5 removal efficiency, outperforming CCD-NPRSM with MSE and R2 of 0.518 and 0.998, respectively. Overall, the hybrid ANN-XGBoost approach is the most feasible technique for assessing the electrochemical treatment efficiency in RB5 dye wastewater decolourisation.
Abstract: Bromocresol green (BCG) and malachite green (MG) are water-soluble toxic organic dyes with adverse health and environmental implications. This study presented a conjugate imprinted adsorbent (CIA) synthesized by incorporating trimethoprim vanillin ligand into a highly crosslinked polymer, designed for the efficient removal of BCG and MG from wastewater. Characterization of CIA involved X-ray powder diffraction, Fourier transform infrared, and scanning electron microscopic analyses. Batch adsorption processes were conducted to evaluate the adsorption characteristics of CIA, with focuses on the effects of contact time, initial dye concentration, pH, and temperature. The molecularly imprinted polymers (MIPs) achieved removal efficiencies of 99.27% and 98.99% at equilibrium for BCG and MG adsorption, respectively. The non-imprinted polymers (NIPs) demonstrated BCG and MG adsorption efficiencies of 51.52% and 62.90% at equilibrium, respectively. Kinetic and isotherm models were employed to elucidate the BCG and MG adsorption mechanisms. The thermodynamic results indicated non-spontaneous and spontaneous reactions for BCG and MG adsorption on MIPs under the examined temperature conditions. The adsorbent exhibited sustained high removal efficiency through five reuse cycles, with no apparent reduction in adsorption performance. Validation of the adsorbent using real textile wastewater samples achieved BCG and MG removal efficiencies of 85.5%-87.5%. The adsorbent outperformed previously reported materials in BCG and MG adsorption. The synthesized CIA is a promising adsorbent for BCG and MG dye removal, contributing to water sustainability.
Abstract: Degrading ciprofloxacin (CIP)-polluted water has recently emerged as an urgent environmental issue. This study introduced mechanochemical treatment (MCT) as an innovative and underexplored approach for the degradation of CIP in water. The influence of various additives (CaO, Fe2O3, SiO2, Al, and Fe) on CIP degradation efficiency was investigated. Additionally, six types of composite additives (Fe-CaO, Fe-Fe2O3, Fe-SiO2, Fe-Al, Al-SiO2, and Al-CaO) were explored, with the composite of 20% Fe and 80% SiO2 exhibiting notable performance. The impacts of additive content, pH value, and co-existing ions on CIP degradation efficiency were investigated. Furthermore, the effectiveness of MCT in degrading other medical pollutants (norfloxacin, ofloxacin, and enrofloxacin) was verified. The transformations and changes in the crystal structure, oxidation state, microstructure, and morphology of the Fe-SiO2 composite additive were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. This study proposed a sigmoid trend kinetic model (the Delogu model) that better elucidates the MCT process. Three plausible degradation pathways were discussed based on intermediate substance identification and pertinent literature. This study not only establishes a pathway for the facile degradation of CIP pollutants through MCT but also contributes to advancements in wastewater treatment methodologies.
Abstract: Fluoride (F-) and arsenic, present as As(III) and As(V), are widespread toxins in groundwater across India, as well as in other countries or regions like Pakistan, China, Kenya, Africa, Thailand, and Latin America. Their presence in water resources poses significant environmental and health risks, including fluorosis and arsenicosis. To address this issue, this study developed an integrated process combining biosorbents and ultrafiltration (UF) for the removal of F-, As, and turbidity from contaminated water. Laboratory-scale adsorption experiments were conducted using low-cost biosorbents with different biosorbent dosages, specifically Moringa oleifera seed powder (MSP) and sorghum bicolor husk (SBH), along with sand as a binding medium. F- and As concentrations ranging from 2 to 10 mg/L and 3 to 12 mg/L, respectively, were investigated. Biosorbents and their different combinations were tested to determine their efficacy in removing dissolved F- and As. The results showed that a blend of 10-g/L MSP with SBH achieved the highest F- (97.20%) and As (78.63%) removal efficiencies. Subsequent treatment with a UF membrane effectively reduced turbidity and colloidal impurities in the treated water, achieving a maximum turbidity removal efficiency of 95.40%. Equilibrium kinetic and isotherm models were employed to analyze the experimental data, demonstrating good fit. Preliminary cost analysis indicated that the hybrid technology is economically viable and suitable for the separation of hazardous contaminants from aqueous solutions. This study underscores the potential of inexpensive biosorption technologies in providing clean and safe drinking water, particularly in industrial, rural, and urban areas.
Abstract: Cresyl diphenyl phosphate (CDP), an emerging aryl organophosphate ester (OPE), exhibits potential toxic effects and is frequently found in diverse environmental media, thereby raising concerns about environmental pollution. Biodegradation demonstrates substantial potential for CDP removal from the environment. This study investigated the biodegradation mechanisms of CDP using anaerobic activated sludge (AnAS). The biodegradation of 1-mg/L CDP followed a first-order kinetic model with a degradation kinetic constant of 0.943 d-1, and the addition of different electron acceptors affected the degradation rate. High-resolution mass spectrometry identified seven transformation products (TPs) of CDP. The pathways of CDP degradation in anaerobic conditions were proposed, with carboxylation products being the most dominant intermediate products. The structure of the anaerobic microbial community at different degradation time points in CDP-amended microcosms was examined. The linear discriminant analysis (LDA) of effect size (LEfSe) potentially underscored the pivotal role of Methyloversatilis in CDP biodegradation. Zebrafish embryotoxicity experiments revealed both lethal and morphogenetic impacts of CDP on zebrafish embryos. The survival rate, hatching rate, and body length indicators of zebrafish embryos underscored the detoxification of CDP and its resultant intermediates by AnAS. This study offers new insights into the fate and biodegradation mechanisms of CDP in wastewater treatment plants.
Abstract: The discharge of effluents containing uranium (U) ions into aquatic ecosystems poses significant risks to both human health and marine organisms. This study investigated the biosorption of U(VI) ions from aqueous solutions using corncob-sodium alginate (SA)-immobilized Trichoderma aureoviride hyphal pellets. Experimental parameters, including initial solution pH, initial concentration, temperature, and contact time, were systematically examined to understand their influence on the bioadsorption process. Results showed that the corncob-SA-immobilized T. aureoviride hyphal pellets exhibited maximum uranium biosorption capacity at an initial pH of 6.23 and a contact time of 12 h. The equilibrium data aligned with the Langmuir isotherm model, with a maximum biosorption capacity of 105.60 mg/g at 301 K. Moreover, biosorption kinetics followed the pseudo-second-order kinetic model. In terms of thermodynamic parameters, the changes in Gibbs-free energy (△G°) were determined to be -4.29 kJ/mol at 301 K, the changes in enthalpy (△H°) were 46.88 kJ/mol, and the changes in entropy (△S°) was 164.98 J/(mol·K). Notably, the adsorbed U(VI) could be efficiently desorbed using Na2CO3, with a maximum readsorption efficiency of 53.6%. Scanning electron microscopic (SEM) analysis revealed U(VI) ion binding onto the hyphal pellet surface. This study underscores the efficacy of corncob-SA-immobilized T. aureoviride hyphal pellets as a cost-effective and environmentally favorable biosorbent material for removing U(VI) from aquatic ecosystems.
Abstract: Understanding the occurrence and characteristics of dry and wet events is crucial for effective disaster prevention, resource management, and risk reduction in vulnerable regions. This study analyzed the spatiotemporal patterns of dry-wet events and their transition characteristics in Uttar Pradesh, India. The standardized precipitation evapotranspiration index (SPEI) at a monthly timescale was utilized to identify hotspot regions vulnerable to concurrent and frequent dry and wet events and their transitions. The severity, duration, and intensity of dry and wet events were characterized with the run theory over SPEI time series data from 18 synoptic stations in Uttar Pradesh over 48 years (1971-2018), sourced from the Indian Institute of Tropical Meteorology and the India Meteorological Department. Multiple assessment methods were utilized to examine the interaction of these extreme events, considering characteristics such as wet-dry ratio, average transition time, and rapid transition times from wet to dry events and from dry to wet events. Average wet durations ranged from 1.27 to 1.58 months, and average dry durations ranged from 1.29 to 1.82 months. Rapid transition times from dry to wet events ranged from 2.5 to 4.1 months, and those for wet-to-dry events ranged from 2.1 to 5.3 months. The eastern region experienced a significantly high number of dry events, while the western and Bundelkhand regions experienced more intense dry events. In contrast, the eastern region had intense wet events. This research on the occurrence of dry-wet events and their transitions can provide valuable insights for government decision-making and disaster prevention and reduction efforts.
Abstract: Located downstream the Kupang Catchment in Indonesia, Pekalongan faces significant land subsidence issues, leading to severe coastal flooding. This study aimed to assess the impact of climate change on future flow regimes and hydrological extremes to inform long-term water resources management strategies for the Kupang Catchment. Utilizing precipitation and air temperature data from general circulation models in the Coupled Model Intercomparison Project 6 (CMIP6) and employing bias correction techniques, the Soil and Water Assessment Tool (SWAT) hydrological model was employed to analyze climate-induced changes in hydrological fluxes, specifically streamflow. Results indicated a consistent increase in monthly streamflow during the wet season, with a substantial rise of 22.8%, alongside a slight decrease of 18.0% during the dry season. Moreover, both the frequency and severity of extremely low and high flows were projected to intensify by approximately 50% and 70%, respectively, for a 20-year return period, suggesting heightened flood and drought risks in the future. The observed declining trend in low flow, by up to 11%, indicated the potential for long-term groundwater depletion exacerbating the threat of land subsidence and coastal flooding, especially in areas with inadequate surface water management policies and infrastructure.
Abstract: Accurate capture and presentation of the interactive feedback relationships among various objectives in multi-objective reservoir operation is essential for maximizing operational benefits. In this study, the niche theory of ecology was innovatively applied to the field of reservoir operation, and a novel state-relationship (S-R) measurement analysis method was developed for multi-objective reservoir operation. This method enables the study of interaction among multiple objectives. This method was used to investigate the relationship among the objectives of power generation, water supply, and ecological protection for cascade reservoir operation in the Wujiang River Basin in China. The results indicated that the ecological protection objective was the most competitive in acquiring and capturing resources like flow and water level, while the water supply objective was the weakest. Power generation competed most strongly with ecological protection and relatively weakly with water supply. These findings facilitate decision-making throughout the reservoir operation process in the region. The S-R method based on the niche theory is convenient, efficient, and intuitive, allowing for the quantification of feedback relationships among objectives without requiring the solution of the Pareto frontier of a multi-objective problem in advance. This method provides a novel and feasible idea for studying multi-objective interactions.
Abstract: Hydraulic jumps are a prevalent phenomenon in flows through spillways, chutes, and sluice gates. As hydraulic jumps exhibit substantial kinetic energy, the downstream of a hydraulic structure is prone to scour. To mitigate downstream scour and enhance energy dissipation, hydraulic jumps are often directed into stilling basins with various bed configurations, including horizontal, sloping, rough, and their combinations. This review compiles numerous analytical and experimental studies on hydraulic jumps under various bed conditions. The effect of bed roughness on sequent depth ratio, roller and jump lengths, shear stress, and energy dissipation is critically reviewed. The impacts of roughness height, flow Froude number, and bed angle on jump characteristics are discussed, substantiated by comparative analyses for distinct roughness heights. The results indicate that bed roughness intensifies shear stress, resulting in augmented energy dissipation and reductions in jump length and sequent depth. Additionally, the analytical and empirical equations proposed by researchers for different jump scenarios are discussed, and their applicability under various conditions is summarized. Finally, it suggests considering the scale effect in future research to refine the comprehension of jump stability over adverse slopes.
Abstract: The classification of dams or off-stream reservoirs concerning potential hazards in the event of failure often involves the use of two-dimensional hydraulic models for computing floodwave effects. These models necessitate defining breach geometry and formation time, for which various parametric models have been proposed. These models yield different values for average breach width, time of failure, and consequently, peak flows, as demonstrated by several researchers. This study analyzed the effect of selecting a breach parametric model on the hydraulic variables, potential damages, and hazard classification of structures. Three common parametric models were compared using a set of synthetic cases and a real off-stream reservoir. Results indicated significant effects of model choice. Material erodibility exerted a significant impact, surpassing that of failure mode. Other factors, such as the Manning coefficient, significantly affected the results. Utilizing an inadequate model or lacking information on dike material can lead to overly conservative or underestimated outcomes, thereby affecting hazard classification.
Abstract: To enhance the operational capacity and space utilization of baffle-drop shafts, this study improved the traditional baffle-drop shaft by expanding the wet-side space, incorporating large rotation-angle baffles, and installing overflow holes in the dividing wall. A three-dimensional turbulent model was developed using ANSYS Fluent to simulate the hydraulic characteristics of both traditional and new baffle-drop shafts across various flow rates. The simulation results demonstrated that the new shaft design allowed for discharge from both the wet and dry sides, significantly improving operational capacity, with the dry side capable of handling 40% of the inlet flow. Compared to the traditional shaft, the new design reduced shaft wall pressures and decreased the mean and standard deviation of pressure on typical baffles by 21% and 63%, respectively, therefore enhancing structural safety. Additionally, the new shaft achieved a 2%-12% higher energy dissipation rate than the traditional shaft across different flow rates. This study offers valuable insights for the design and optimization of drop shafts in deep tunnel drainage systems.
