ABSTRACT This study addresses the trade-off between representativeness and cost-effectiveness in urban sewer network water quality monitoring. Using the storm water management model, hydraulic and water quality models were developed for a real sewer system. A total of 6,000 Monte Carlo scenarios with randomized inflow conditions were simulated to analyze the spatiotemporal distribution of inert pollutants and the absolute relative error (RE) of instantaneous sampling relative to daily flow-weighted average concentrations (RE*). Results indicate that optimal sampling windows occur at 00:00–02:00 and 13:30–16:30, during which RE* is minimized (5–12%). Downstream nodes generally show lower RE* due to cumulative mixing effects, whereas locations right downstream of the pumping stations exhibit elevated errors caused by pump cycling, making them unsuitable for representative sampling during frequent pump cycling or idle periods. A significant negative correlation was identified between node flow rate and RE*, suggesting that high-flow nodes are preferable for representative monitoring. This study proposes a spatiotemporal dual-representativeness strategy that enhances monitoring accuracy and efficiency under limited resources, providing practical guidance for sewer network water quality management.
ABSTRACT This work highlights new insights into the performance of a hybrid TiO2/clinoptilolite (TiO2/CPL) catalyst for the photocatalytic degradation of organic water pollutants, specifically amoxicillin (AMX) and 2,4-dichlorophenol (2,4-DCP). The TiO2/CPL hybrid material was synthesized via a modified sol–gel method followed by impregnation. The TiO2 precursor was initially hydrolyzed to form Ti(OH)4 monomers within the sol–gel medium. These monomer species were separated and dispersed into a hexane suspension containing CPL powders. XRD and scanning electron microscopy analyses indicated that the hybrid material consisted of CPL and TiO2 anatase, without any impurity phases. FTIR and X-ray photoelectron spectroscopy analyses revealed that TiO2 particles are bonded to CPL via Ti–O–Si linkages. The TiO2/CPL catalyst achieved 93.5% degradation of AMX and complete degradation of 2,4-DCP within 120 min. Phytotoxicity and antibacterial assessments were also conducted to evaluate the toxicity of 2,4-DCP and the residual antibiotic activity of AMX, aiming to support water reuse and environmental protection.
ABSTRACT The textile and allied industries produce dye-containing wastewater often at high concentrations, which also contains persistent synthetic dyes, such as rhodamine B (RB), creating a need for economical and sustainable treatment materials. Yellow bluestem (YBS) (Bothriochloa ischaemum) was pyrolyzed to produce a porous carbon-based bioadsorbent and evaluated for RB removal from aqueous solution. The prepared carbon exhibits a surface area of 512 m2 g−1, total pore volume of 0.522 cm3 g−1, and mean pore diameter of 3.65 nm. Central composite design (CCD) and response surface methodology (RSM) were employed to determine the effect of initial dye concentration, adsorbent dosage, pH, and contact time. The quadratic model was highly significant (p < 0.0001), with R2 = 99.71%, an adjusted R2 = 99.41%. Numerical optimization identified selected operating condition as 80 mg L−1 RB concentration, 1.6 g L−1 adsorbent dose, pH 4.5, and 130 min contact time, with a predictive removal of approximately 96.55%. Experimental validation under these conditions in triplicate yielded removal efficiencies of 92.97, 93.56, and 93.01%, corresponding to 93.18 ± 0.33% removal and a prediction error of 1.92%. Equilibrium data were best represented by Dubinin–Radushkevich model (R2 = 0.963), with a mean adsorption energy of 0.45 kJ mol−1, supporting predominantly physical adsorption involving heterogeneous surface interactions and pore-filling contributions. Kinetic data are best described by the pseudo-second-order model (R2 = 0.997), while, intraparticle diffusion analysis indicated a multistep adsorption process. Thermodynamic analysis indicated that adsorption was endothermic and became thermodynamically favourable at higher temperature. After five regeneration cycles, the adsorbent retained 67.4% of its initial removal performance. The findings demonstrate the potential of YBS-derived carbon as a sustainable bioadsorbant for RB removal from aqueous system.
ABSTRACT The rising demand for water in Ilawe-Ekiti necessitates sustainable groundwater management, particularly within its fracture-controlled basement complex aquifer system. This study employed an integrated geospatial and geophysical approach to delineate groundwater potential zones. Four hydrogeological factors – drainage density, slope, land use/cover, and elevation – were analysed and weighted (40, 25, 20, and 15, respectively) using an expert-judgement scheme informed by similar basement terrain studies. These thematic layers were integrated within a geographical information system weighted-overlay framework to generate an initial groundwater potential map (GWPM-1). To enhance the spatial model, thirty vertical electrical soundings were conducted using the Schlumberger configuration, enabling estimation of aquifer transmissivity from resistivity and thickness parameters. These were integrated with GWPM-1 to produce an enhanced map (GWPM-2). Results classify the study area into high (36%), moderate (42%), low (19%), and very low (3%) groundwater potential zones, indicating overall moderate-to-high potential. Model validation, based on spatial agreement between classified groundwater potential zones and established transmissivity frameworks, showed agreement ranges of 52.7–64, 62–82, and 35.3–44% with Offodile, Krásný, and Jetel–Krásný classifications, respectively. The findings underscore the need for targeted groundwater conservation strategies and recommend the incorporation of additional surface indicators to further improve groundwater characterization accuracy.
ABSTRACT Graphical abstract illustrating the preparation, characterization, and chromium removal performance of ultrasound-assisted sulfuric acid-modified Salvinia cucullata biomass. The preparation involves washing, drying, and grinding the biomass, followed by treatment with 0.5 M H2SO4 under ultrasound at 35 kHz for 15 min, filtration, and oven drying. FTIR analysis identifies oxygen-containing surface functional groups, while point of zero charge analysis indicates a pHpzc of 5.21. The final schematic illustrates chromium interaction with the modified adsorbent and summarizes approximately 90% chromium removal in batch experiments. Hexavalent chromium [Cr(VI)] is a highly toxic pollutant that poses significant environmental and public health concerns because of its persistence in aquatic environments. This study investigates the potential of Salvinia cucullata (Roxb. ex Bory) as a sustainable and low-cost bioadsorbent for Cr(VI) removal from synthetic aqueous solution. The bioadsorbent was prepared from Salvinia cucullata biomass, followed by ultrasound-assisted sulphuric acid modification to enhance its physicochemical properties and adsorption performance. The prepared adsorbent was characterized using Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHpzc) analysis. FTIR analysis confirmed the presence of oxygen-containing functional groups, including hydroxyl (-OH), carbonyl (C = O), and carboxyl (-COOH), which may contribute to Cr(VI) adsorption. The pHpzc was determined to be 5.21, indicating a positively charged adsorbent surface under acidic conditions and favourable electrostatic attraction towards negatively charged chromium oxyanions. Batch adsorption experiments showed that Cr(VI) removal increased from 64.3% at 30 min to 91.9% at 90 min. At an initial Cr(VI) concentration of 10 mg/L, the removal efficiency reached 93.9%, while the highest removal efficiency of 91.10% and adsorption capacity of 5.261 mg/g were obtained at pH 5. The findings demonstrate the potential of modified Salvinia cucullata as a sustainable bioadsorbent.
