Water science and engineering最新文献

Three-dimensional (3D) porous absorbents have attracted significant attention in the oily wastewater treatment technology due to their high porosity and elasticity. Given their amphiphilic surface, they have a propensity to simultaneously absorb water and oil, which restricts their range of applications. In this study, a reduced graphene oxide and titanium dioxide nanocomposite (rGO/TiO₂) was used to fabricate an ultrahydrophobic melamine sponge (MS) through interfacial modification using a solution immersion technique. To further modify it, polydimethylsiloxane (PDMS) was grafted onto its surface to establish stronger covalent bonds with the composite. The water contact angle of the sponge (rGO/TiO₂/PDMS/MS) was 164.2°, which satisfies the condition for ultrahydrophobicity. The evidence of its water repellency was demonstrated by the Cassie–Baxter theory and the lotus leaf effect. As a result of the increased density of rGO/TiO₂/PDMS/MS, it recorded an initial capacity that was 2 g/g lower than the raw MS for crude oil absorption. The raw MS retained 53% of its initial absorption capacity after 20 cycles of absorption, while rGO/TiO2/PDMS/MS retained 97%, suggesting good recyclability. Excellent oil and organic solvent recovery (90%–96%) was demonstrated by rGO/TiO₂/PDMS/MS in oil–water combinations. In a continuous separation system, it achieved a remarkable separation efficiency of 2.4 × 10⁶ L/(m³·h), and in turbulent emulsion separation, it achieved a demulsification efficiency of 90%–91%. This study provides a practical substitute for massive oil spill cleaning.

The material mechanical parameters of the dam body and foundation will change when a dam is reinforced during the aging process. This causes significant changes in the structural state of the project and makes it difficult to ensure its structural safety. In this study, a new deformation warning index for reinforced concrete dams was developed according to the prototype monitoring data, statistical models, three-dimensional finite element model (FEM) numerical simulation, and the critical conditions of the dam structure. A statistical model was established to separate the water pressure component. Then, a three-dimensional FEM of the reinforced concrete dam was constructed to simulate the water pressure component. Furthermore, the deformation components that affected the mechanical parameters of the dam under the same amount of reservoir water level change were separated and quantified accurately. In addition, the method for inversion of comprehensive mechanical parameters after dam reinforcement was used. The influence mechanisms of the deformation behavior of concrete dams under the reservoir water level and temperature changes were investigated. A new deformation warning index was developed by combining the forward-simulated critical water pressure component and temperature component in the period of extreme temperature decrease with the aging component separated by the statistical model. The new deformation warning index considers the structural state of the dam before and after reinforcement and links the structural strength criterion and the deformation evolution mechanisms. It provides a theoretical foundation and decision support for long-term service and operation management of reinforced dams.

Numerical simulation of concrete-faced rockfill dams (CFRDs) considering the spatial variability of rockfill has become a popular research topic in recent years. In order to determine uncertain rockfill properties efficiently and reliably, this study developed an uncertainty inversion analysis method for rockfill material parameters using the stacking ensemble strategy and Jaya optimizer. The comprehensive implementation process of the proposed model was described with an illustrative CFRD example. First, the surrogate model method using the stacking ensemble algorithm was used to conduct the Monte Carlo stochastic finite element calculations with reduced computational cost and improved accuracy. Afterwards, the Jaya algorithm was used to inversely calculate the combination of the coefficient of variation of rockfill material parameters. This optimizer obtained higher accuracy and more significant uncertainty reduction than traditional optimizers. Overall, the developed model effectively identified the random parameters of rockfill materials. This study provided scientific references for uncertainty analysis of CFRDs. In addition, the proposed method can be applied to other similar engineering structures.

Constructed wetlands (CW) are well known nature-based systems for water treatment. This study evaluated the efficiency and effectiveness of seven domestic wastewater treatment systems based on horizontal flow CWs in Jarabacoa, the Dominican Republic. The results showed that the CWs were efficient in reducing the degree of contamination of wastewater to levels below the Dominican wastewater discharge standards for parameters such as the 5-day biochemical oxygen demand (BOD5) and chemical oxygen demand, but not for the removal of phosphorus and fecal coliforms. In addition, a horizontal flow subsurface wetland in the peri-urban area El Dorado was evaluated in terms of the performance of wastewater treatment in tropical climatic conditions. The concentrations of heavy metals, such as zinc, copper, chromium, and iron, were found to decrease in the effluent of the wetland, and the concentrations for nickel and manganese tended to increase. The levels of heavy metals in the effluent were lower than the limit values of the Dominican wastewater discharge standards. The construction cost of these facilities was around 200 USD per population equivalent, similar to the cost in other countries in the same region. This study suggested some solutions to the improved performance of CWs: selection of a microbial flora that guarantees the reduction of nitrates and nitrites to molecular nitrogen, use of endemic plants that bioaccumulate heavy metals, combination of constructed wetlands with filtration on activated carbon, and inclusion of water purification processes that allow to evaluate the reuse of treated water.

In this paper, we present a proof-of-concept study of the enhancement of photocatalytic activity via a combined strategy of fabricating a visible-light responsive ternary heterostructure and improving overall photostability by incorporating magnetic zinc oxide/graphene/iron oxide (ZGF). A solvothermal approach was used to synthesize the catalyst. X-ray diffraction (XRD), scanning electron microscopic, energy dispersive X-ray, transmission electron microscopic, vibrating sample magnetometric, and ultraviolet–visible diffuse reflectance spectroscopic techniques were used to characterize the synthesized samples. The obtained optimal Zn(NO₃)₂ concentration, temperature, and heating duration were 0.10 mol/L, 600°C, and 1 h, respectively. The XRD pattern revealed the presence of peaks corresponding to zinc oxide, graphene, and iron oxide, indicating that the ZGF catalyst was effectively synthesized. Furthermore, when the developed ZGF was used for methylene blue dye degradation, the optimum irradiation time, dye concentration, catalyst dosage, irradiation intensity, and solution pH were 90 min, 10 mg/L, 0.03 g/L, 100 W, and 8.0, respectively. Therefore, the synthesized ZGF system could be used as a catalyst to degrade dyes in wastewater samples. This hybrid nanocomposite consisting of zinc oxide, graphene, and iron oxide could also be used as an effective photocatalytic degrader for various dye pollutants.

It is necessary to treat textile effluents before discharging them into natural water bodies as they harm the environment. Compared to conventional treatment methods, catalytic ozonation has gained attention due to its effectiveness in removing refractory organic pollutants. In this study, the coprecipitation method was used to synthesize a composite metal oxide of silver and cerium oxide, and the synthesized catalyst was used to eliminate the Reactive Black 5 (RB5) dye. X-ray diffraction, scanning electron microscopic, and Brunauer–Emmett–Teller surface area analyses were performed to characterize the synthesized catalyst. Afterwards, relevant experimental parameters, such as pH, ozone and catalyst dosages, and initial dye concentration, were investigated. The experiments revealed that the optimal experimental conditions were a pH value of 10, a catalyst dosage of 0.7 g/L, and an ozone dosage of 60 L/h. In these optimized conditions, the RB5 dye was entirely removed, and a chemical oxygen demand removal efficiency of 88% was achieved within a reaction time of 80 min. Furthermore, the recycling potential of the catalyst was tested for three cycles, and no deterioration in its activity was observed. Additionally, studies were conducted using a hydroxyl radical scavenger in order to understand the reaction pathway of the system. As a result, the indirect pathway was more dominant than the direct pathway in the system.

Owing to extensive construction of dams, the impact of backwater on flow may lead to navigation or flood control issues in curved channels. To date, the impact of backwater on the water surface profile in curved channels remains unknown and requires investigation. In this study, experiments were conducted in a glass-walled recirculating flume with a length of 19.4 m, a width of 0.6 m, and a depth of 0.8 m, and the impact of backwater on the water surface profile in a 90° channel bend was investigated. The experimental results showed that the backwater degree had a significant impact on the transverse and longitudinal flow depth distributions in the bend. The transverse slope of the flow (J_r) increased linearly with an increase in the Froude number of the approach flow upstream of the bend. J_r increased with the longitudinal location parameter ξ when −0.2 < ξ < 0.5, and decreased with ξ when 0.5 < ξ < 1.2. Furthermore, the results showed that J_r asymptotically decreased to zero with an increase in the degree of backwater. An equation was formulated to estimate the transverse slope of the flow in a 90° bend in backwater zones.

Estimating the design flood under nonstationary conditions is challenging. In this study, a sample reconstruction approach was developed to transform a nonstationary series into a stationary one in a future time window (FTW). In this approach, the first-order moment (E_FTW) of an extreme flood series in the FTW was used, and two possible methods of estimating E_FTW values in terms of point values and confidence intervals were developed. Three schemes were proposed to analyze the uncertainty of design flood estimation in terms of sample representativeness, uncertainty from E_FTW estimation, and both factors, respectively. To investigate the performance of the sample reconstruction approach, synthesis experiments were designed based on the annual peak series of the Little Sugar Creek in the United States. The results showed that the sample reconstruction approach performed well when the high-order moment of the series did not change significantly in the specified FTW. Otherwise, its performance deteriorated. In addition, the uncertainty of design flood estimation caused by sample representativeness was greater than that caused by E_FTW estimation.

Malaysia's rapid economic and demographic development have placed negative pressure on its water supplies and the quality of the Juru River, which is close to the nation's capital and its major source of water. Healthy aquatic ecosystems are supported by physicochemical properties and biological diversity. This study evaluated the anthropogenic impacts on aquatic biodiversity, especially plankton, fish, and macrobenthos, as well as the water quality of the Juru River in the Penang area. Aquatic biodiversity and river water parameters were collected from ten sampling stations along the Juru River. Seven variables were used to assess the physicochemical environment: pH, temperature, total suspended solids (TSS), salinity, dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand. At each sampling station, the total number of plankton, fish, and macrobenthic taxa were counted and analyzed. The relationships between the physicochemical parameters and aquatic biodiversity were investigated with biotypological analysis, principal component analysis, hierarchical cluster analysis, and linear regression analysis. These analyses showed that the richness and diversity indices were generally influenced by salinity, temperature, TSS, BOD, and pH. The data obtained in this study supported the bioindicator concept. The findings, as they related to scientifically informed conservation, could serve as a model for Juru River management, as well as for river management throughout Malaysia and other tropical Asian countries.

Malachite green (MG) dye is a common industrial dye and organic contaminant that can be found in (waste)water. Textile and food industries make use of MG as dyeing and food coloring agents, respectively. However, MG is both genotoxic and mutagenic. Hence, the elimination of MG from MG-laden-wastewater is germane. This review summarizes up-to-date researches that have been reported in literature as regards the decontamination of toxic MG wastewater. Various removal methods (adsorption, membrane, Fenton system, and heterogenous and homogeneous photodegradation) were discussed. Of the two basic technologies that are comprehensively explored and reviewed, chemical treatment methods are not as viable as physical removal methods, such as the adsorption technology, due to the lack of secondary pollutant production, simple design, low operation costs, and resource availability. This review also presents various practical knowledge gaps needed for large-scale applications of adsorptive removal methods for MG. It concludes by recommending further research on the techniques of cheap and simple decontamination of MG to get clean water.