Water

Compared to a photovoltaic array, a photovoltaic/thermal concentrator module can produce thermal power for various productions in downstream cycles in addition to electrical energy. In this study, the system for the combined production of electricity, heat and cooling based on a photovoltaic/thermal concentrator has been evaluated. In this triple production system, a lithium bromide-water absorption chiller with a cooling capacity of 5 kW was used. In the organic Rankine power generation cycle, the annual exergy rate of the incoming stream was almost 48 MWh, the annual production exergy rate was about 54.4 MWh and the annual exergy destruction rate was ~43.1 MWh. According to the results, the freshwater production rate of the desalination plant was approximately 56.7 m³/year; the lowest month was 3.8 m³ in November. Full article

One of the most notable problems in the Atacama desert is the low occurrence of rainfall, which leads to a shortage of surface and groundwater for different users in the region. Therefore, the task of carrying out new exploration studies of potential groundwater zones (GWPZs) is of vital importance for decision-makers in water resources. The main objective of this research is to determine potential sources of groundwater using a Multi-Criteria Decision-Making technique with remote sensors. A method of exploration using the Analytical Hierarchy Process (AHP) techniques applied to remote sensing data is provided. The AHP method allows calculating the influence of multiple factors, and along with the GIS environment, a map of groundwater exploitation potential can be produced. The results indicating GWPZs showed four classifications of groundwater potential. The distribution shows 15.02%, 23.93%, 59.80%, and 1.25% of the total area with high, moderate, low, and very low potential, respectively. The results were validated with existing wells in the study area, offering an acceptance of 86.9%. This reveals the effectiveness and accuracy of the AHP-based GIS approach as a strategy for analyzing groundwater potential in arid zones. Similarly, the tested high GWP areas are helpful for the development and management of water resources in the Caplina basin. Full article

River bank filtration (RBF) under human supervision has been applied for groundwater recharge. This study clarified the characteristics of water composition and its origins during the reservoir water recharge RBF. The groundwater samples were collected during four periods: pre-recharge (June 2018), early recharge (November 2018), intermediate recharge (May 2019), and late recharge (October 2019). Hydrogeochemical methods (Piper diagram, chlor-alkali index, and ion correlation) and principal component analysis (PCA) were used to analyze the chemical evolution of groundwater in the aforementioned periods. TDS concentration tended to increase in the later stage due to the aggravation of carbonate rock dissolution and cation exchange adsorption. Results demonstrated a small, temporary influence of reservoir water on groundwater, characterized as the Ca–Mg–HCO₃–SO₄ and Ca–Mg–SO₄–HCO₃ types, both before and after the recharge. The research on water chemistry changes under different mixing ratios depicts that the continuation of the recharge process promotes mineral dissolution. Rock dissolution was the primary environmental control factor of groundwater components during the recharge period. This strengthened the water–rock reaction and caused potential risk impacts such as the increase of nitrate. Full article

The high water cut stage is an important stage of the water injection development of oilfields because there are still more oil reserves available for recovery in this stage. Most oilfields have experienced decades of waterflooding development and adjustment. Although waterflooding reservoirs face the problems of the seriously watered-out and highly dispersed distribution of remaining oil, they remain dominant in waterflood development. This paper investigates the current situation of high-water content reservoirs and the methods available to improve oil recovery and elaborates on the fine reservoir description. Furthermore, it analyzes the main technical measures taken during the high water cut period, namely, secondary oil recovery waterflooding technology (including layer system subdivision, well pattern infilling, strengthening of water injection and liquid extraction, closure of high water cut wells, cyclic waterflooding technology, and water injection profile control) and tertiary oil recovery technology (represented by chemical flooding and gas flooding). In addition, this study reveals the mechanisms and effects of these methods on improving waterflooding development. Finally, this paper summarizes improved oil recovery technology and discusses the key directions and development prospects of this technology in enhancing the oil recovery rate. Full article

Side orifices are commonly installed in the side of a main channel to spill or divert some of the flow from the source channel to lateral channels. The aim of the present study is the accurate estimation of the discharge coefficient for flow through triangular (Δ-shaped) side orifices by applying three data-driven models including support vector machine (SVM), least squares support vector machine (LSSVM) and least squares support vector machine improved by gravity search algorithm (LSSVM-GSA). The discharge coefficient was estimated by utilizing five dimensionless variables resulted from experimental data (570 runs). Five different scenarios were applied based on the input variables. The models were evaluated through several statistical indices and graphical charts. The results showed that all of the models could successfully estimate the discharge coefficient of Δ-shaped side orifices with adequate accuracy. However, the LSSVM-GSA produced the best performance for the input combination of all variables with the highest coefficients of determination (R²) and Nash–Sutcliffe efficiency (NSE), equal to 0.965 and 0.993, and the least root mean square error (RMSE) and mean absolute error (MAE), equal to 0.0099 and 0.0077, respectively. The LSSVM-GSA improved the RMSE of the SVM and LSSVM by 26% and 20% in estimating the discharge coefficient. Furthermore, the ratio of orifice crest height to orifice height (W/H) was identified as having the highest influence on the discharge coefficient of triangular side orifices among the various input variables. Full article

Waterlogging in agriculture poses severe threats to soil properties, crop yields, and farm profitability. Remote sensing data coupled with drainage systems offer solutions to monitor and manage waterlogging in agricultural systems. However, implementing agricultural projects such as drainage is associated with high uncertainty and risk, with substantial negative impacts on farm profitability if not well planned. Cost–benefit analyses can help allocate resources more effectively; however, data scarcity, high uncertainty, and risks in the agricultural sector make it difficult to use traditional approaches. Here, we combined a wide range of field and remote sensing data, unsupervised machine learning, and Bayesian probabilistic models to: (1) identify potential sites susceptible to waterlogging at the farm scale, and (2) test whether the installation of drainage systems would yield a positive benefit for the farmer. Using the K-means clustering algorithm on water and vegetation indices derived from Sentinel-2 multispectral imagery, we were able to detect potential waterlogging sites in the investigated field (elbow point = 2, silhouette coefficient = 0.46). Using a combination of the Bayesian statistical model and the A/B test, we show that the installation of a drainage system can increase farm profitability by 1.7 times per year compared to the existing farm management. The posterior effect size associated with yield, cropping area, and time (year) was 0.5, 1.5, and 1.9, respectively. Altogether, our results emphasize the importance of data-driven decision-making for agriculture project planning and resource management in the wake of smart agriculture for food security and adaptation to climate change. Full article

Batik is a piece of woven cloth decorated with beautiful patterns and designs and has become a signature product of the Malay Archipelago, including Malaysia and Indonesia. Batik industry consumes a large volume of water and produces a large amount of wastewater during the boiling process and dyeing process, both for hand-drawn (batik lukis) and block-printed (batik cap) batik. The release of colored effluents that contain a large number of dyes and chemicals can harm the environment and become a human health concern, particularly in south east Asian countries. Therefore, treatments of batik effluent are very crucial and have caught a lot of attention from researchers. The color removal is a major challenge, especially from this industry, as up until now there is no single and cost-effective treatment that can effectively decolorize as well as treat the dye effluent. Since batik is part of the textile industry, most treatment methods have been adapted from textile effluent treatment. Here, we review a variety of textile wastewater treatment techniques to make a good consideration of selecting the most appropriate method to be applied in batik wastewater. First, we briefly review the batik process, including the potential dyes that are mostly used in batik processing. Secondly, we describe all possible techniques and their performance to reduce dye concentration and decolorization. Finally, we review all advantages and disadvantages of these techniques for domestic and industrial applications. Full article

A hydrological–thermal coupling discrete element model depicting the unidirectional freezing process of unsaturated silty clay was developed in order to investigate the migration law of unfrozen water in unsaturated silty clay under unidirectional freezing circumstances. The model uses the contact heat transfer equation to calculate the heat transfer process while taking into account the latent heat of phase transition. To obtain the silty clay’s freezing characteristic curve, the model combines the unfrozen water content curve with the Clausius–Clapeyron equation. The water migration from the unfrozen zone to the frozen zone was calculated using Harlan’s model and the frozen fringe hypothesis. The discrete element application MatDEM 3.0 was used to incorporate the mathematical model for computation, and the output was compared to the result of indoor unidirectional freezing tests. The soil closest to the stable freezing front had the largest water content, according to the findings of numerical modeling and laboratory testing, and unfrozen water in the soil would move from the unfrozen zone to the frozen zone under the action of water potential difference. The results of laboratory tests and numerical simulations can accurately describe the temperature variation and water migration of soil during freezing, demonstrating the accuracy of the established discrete element model and proving the viability of the discrete element method in the study of frozen soil. Full article

Coastal aquifers have been extensively studied from the hydrodynamic and geochemical points of view, but there is still a significant gap in the knowledge of their microbial diversity. The bacterial communities of four coastal aquifers at different depths and salinities were studied in order to infer the anthropogenic and physico-chemical influences on groundwater microbiota. At the physico-chemical level, samples from different aquifers, but with similar salinities, are more similar than those taken within the same aquifer. The microbial community at the phylum level shows the dominance of Proteobacteria, Firmicutes, and Actinobacteria. Samples from the same aquifer, although having very different salinities, are more similar than samples with similar physico-chemical characteristics. Therefore, the taxa present in these media are resilient to environmental variations. The aquifer preserving the most pristine conditions harbors the lowest values of biodiversity, compared to those affected by anthropic activities. The incorporation of pollutants into the aquifer favors the development of a so-called “rare biosphere”, consisting of a high number of taxa which represent a low percentage (<1%) of the total microbial community. The analysis of microbial biodiversity in a coastal aquifer could be used as an indicator of the degree of anthropic alteration. Full article

In subsurface irrigation systems in desert areas, the wetting front transport pattern allows the determination of irrigation flow and timing. In this study, an indoor subsurface irrigation experiment on aeolian sandy soil is designed, and the vertical and horizontal wetting front movement distances under different irrigation flows are obtained. The dimensional analysis method was used to perform a dimensional analysis on the experimental data. An empirical setting front distance estimation model, which only considers three parameters, saturated hydraulic conductivity K_s, irrigation flow Q, and total irrigation volume V, was proposed. The model’s accuracy was statistically evaluated with the observed data and verified by a numerical simulation using HYDRUS-2D/3D. The mean absolute error (MAE) and root mean square error (RMSE) of the proposed model in the horizontal and downward directions were 0.80 and 0.95 cm, respectively, with a percentage bias (PBIAS) of −3.47 ≤ ±10 and a Nash–Sutcliffe efficiency (NSE) of 0.98, which is close to 1. Thus, this model can contribute to the selection of the appropriate depth and spacing of subsurface laterals. Full article

This paper takes the deep foundation pit project of Lanzhou Hospital of Traditional Chinese Medicine as the background. The design and construction of the foundation pit is relatively difficult due to the complex environment around the pit, the dense surrounding buildings, the complex underground soil layer and the influence of groundwater on the pit. In order to detect problems in the construction process, the pit was monitored in real time through an automated monitoring system for the whole process of excavation and backfilling of the pit. The analysis of the actual monitoring data shows that: (i) the support scheme of bored pile + prestressed anchor cable support combined with concrete corner bracing can meet the design of this type of foundation pit without causing disturbance to the surrounding buildings; (ii) combined with the actual case of the influence of groundwater on the excavation process of the foundation pit, it proves that the real-time measurement by the robot can timely detect the safety hazards caused by external factors during the construction process of the foundation pit. The project is a very important one for deep pits and complex pits. This project provides a good reference case for deep foundation pits and foundation pit projects in complex environments. Full article

Excessive discharge of ammonia nitrogen wastewater from intensive aquaculture has worsened in recent years. Therefore, there is an urgent need to develop an effective and energy-saving denitrification technology. This study intends to adopt a moving bed biofilm reactor (MBBR) to remove ammonia nitrogen through the combination of adsorption and shortcut simultaneous nitrification and denitrification (SND). The research focuses on the operational parameters and regeneration mechanism of the MBBR adsorption-shortcut SND process. The optimal operating parameters in the adsorption stage were a hydraulic retention time of 8 h and an agitation rate of 120 r/min. For the shortcut SND stage, the ideal optimal parameters were two times alkalinity and dissolved oxygen (DO) 1.0 mg/L. Under optimal operating parameters conditions, the SND rate, TN removal rate, ${\mathrm{NH}}_4^{+}$-N removal rate and nitrite accumulation rate were 89.1%, 84.0%, 94.3%, and 86.4%, respectively. The synergetic actions of ion exchange and microorganisms were the main driving force for regenerating ceramsite zeolite components. The synergistic inhibitory effect of high-concentration free ammonia and low-level DO on nitrite-oxidizing bacteria was the key to achieving stable and efficient ${\mathrm{NO}}_2^{-}$-N accumulation. ${\mathrm{NO}}_2^{-}$-N produced in shortcut nitrification entered the ceramsite through complex mass transfer, and denitrifying bacteria can reduce these ${\mathrm{NO}}_2^{-}$-N to N₂. Full article

The aim of this study was the development of a new multi-analytical approach to evaluate chemical alterations and differences in the element content in relation to arsenic (As) in the As hyperaccumulator fern P. vittata. P. vittata plants were grown on two natural As-rich soils with either high or moderate As (750 and 58 mg/kg). Dried samples from plant tissues were then analysed by means of micro-energy dispersive X-ray fluorescence spectrometry (μ-XRF), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and hyperspectral imaging (HSI) with a multivariate approach. The As and micro- and macronutrients content was evaluated by μ-XRF and a significant correlation between As, potassium (K), iron (Fe), calcium (Ca) and manganese (Mn) contents were found at both moderate and high As levels. The same samples were then analysed by ATR-FTIR spectroscopy and HSI (SWIR range, 1000–2500 nm). Interestingly, by FTIR analysis it was found that the main differences between the control and the As-contaminated samples are due to the intensity of the absorption band related to polysaccharides (i.e., cellulose, hemicellulose and pectin), lignin, lipid and amide groups. The same chemical alterations were detected by an HSI analysis and all the FTIR and HSI data were validated by a PCA analysis. These results suggest a possible complexation of As ions with the amide group. Moreover, the proposed μ-XRF, HSI and ATR-FTIR combining approach could be a promising strategy to monitor in-field phytoremediation approaches by directly controlling the As content in plants. Full article

Fish introduction into fishless high-altitude lakes has detrimental effects on biodiversity. Removal of alien fish through intensive fishing is cost-intensive and difficult to achieve in productive lakes. Lake Sulzkarsee is the only lake in the National Park Gesäuse, Austria, and was an important breeding site for amphibians until the lake was stocked with fish in the late 1970s. Salmonids were eradicated in 2005, but the lake remained degraded by the introduced minnows (Phoxinus sp.). In 2018, the lake was drained through a siphon pipe and then by pumping out water with dirt water pumps. The deepest part was treated with slaked lime, but several hundred adult minnows survived in sediment crevices and reproduced in the following season. After drainage, the phytoplankton biomass increased. Indicator species, such as Daphnia longispina and amphibians, showed signs of recovery, but they went back to an impacted state when minnows recovered after the failed eradication attempt. Purse seines proved to be the most efficient gear to catch minnows. These results indicate that deep mountain lakes are difficult to drain efficiently. Sediment treatment is required to eliminate all fish. Full article

Freshwater salinization is a growing environmental issue caused by various anthropic or natural factors that lead to changes in water chemistry and physical conditions, affecting the survival and diversity of phytoplankton. In this study, we tested the physiological, morphological and interspecific competition of the freshwater cyanobacterium Microcystis aeruginosa and the green algae Scenedesmus obliquus to salinity stress. Results demonstrated that increasing salinity had a significant negative effect on the growth of M. aeruginosa and S. obliquus. M. aeruginosa showed a decline in growth rate with increasing salinity, while S. obliquus showed a lower growth rate under salinity stress but with no significant difference between the two salinity groups. In cocultures, S. obliquus outcompeted M. aeruginosa, and the displacement was accelerated with increasing salinity. The photosynthetic performance of both algae was affected by salinity, the presence of competitors, and the cultivation time. S. obliquus showed morphological variations under salinity stress and the presence of a competitor. The study suggests that salinity stress and competition can have a significant impact on the growth and performance of algae species. The findings of our study suggest that the salinization of freshwater can impact the interspecific interactions among phytoplankton, which play a crucial role in the functioning of freshwater ecosystems. Full article

The Yangtze River Basin, one of China’s five major watersheds and a primary source of drinking water for the country, is experiencing serious environmental pollution as heavy metals are discharged into its rivers. To evaluate the water quality of the river, determined water quality parameters were compared with the maximum permissible limit values recommended by the World Health Organization and Chinese drinking water standards. Physical and chemical analyses were conducted on water samples taken from 19 locations along the river’s path. The study quantified the contents of sodium (Na), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lithium (Li), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), scandium (Sc) and mercury (Hg). The results show that the average values of Mg, Sr, Co, Cu, Fe, Mn and Sc are higher than the historical background values. Moreover, through a correlation analysis it was concluded that these nutrients and trace metals have high values due to anthropogenic pollution in the study area. The computed WQI values range between 9.59 and 20.26, indicating excellent water quality in the river basin. Finally, hazard quotient (HQ) values show that exposure to the detected pollutants will have no adverse effects on human health and does not pose a potential non-carcinogenic risk. Full article

The spatial and temporal distributions, contamination evaluation, and source apportionment of Cu, Zn, As, Pb, Cd, and Cr in the sediments of Hulun Lake were explored in this work. The pollution characteristics of six heavy metals were assessed by single factor pollution index (PI) and geo-accumulation index (Igeo). The sources of heavy metals in the surface sediments were analyzed by the positive definite matrix factorization (PMF) and Pearson correlation analysis. The sedimentary records of heavy metals in core sediments were reproduced by radioisotopes. The average concentrations of 6 heavy metals except Cd were lower than the corresponding background values. The spatial distributions of Cu, Zn, Cr, Cd and As were generally similar and showed higher abundances in the southwestern part of the lake. With the use and import of heavy metals, the concentration of heavy metals in core sediments increased with the fluctuation of years. The peak of heavy metal concentration was related to the high growth rate of gross domestic product in 2003-2008. The single factor pollution index and geo accumulation index results showed that the surface sediment was mainly polluted by Cd, followed by Zn and As. Natural parent material, agricultural activities and industrial activities were the main sources of heavy metal pollution in the sediments, accounting for 17.03%, 26.34%, and 56.63% of the total heavy metal accumulation, respectively. Pb was derived mainly from natural parent material. Cd and As were closely associated with agricultural activities. Cu and Zn were mainly attributed to industrial mining activities. Source apportionment of the ecological risks of heavy metals illustrated that industrial sources were the primary ecosystem risk sources (66.1%), followed by agricultural sources (23.75%) and natural sources (10.15%). The results will also provide reference data for future studies of heavy metals pollution in sediments from Hulun Lake and other lakes. Full article

Expansive soil is one of the most widely distributed special soils in the world. It is widely developed in Henan, Anhui, Guangxi and other places in China, and highly overlaps with densely populated and economically active areas. Expansive soil is considered a typical “problematic soil” because its mechanical behaviour is very sensitive to water content changes; such behaviour mainly manifests as swelling upon wetting and shrinking upon drying, so the presence of expansive soil is an important factor in mountain landslide disasters in southern China. Because the particularities of its constituent materials are related to typical physical and mechanical properties, forecasting the failure times of expansive soil slopes remains a global problem. In this study, a series of in situ artificial rainfall experiments were conducted on an excavated expansive soil slope; then, the digital image correlation (DIC) method was applied to monitor the slope surface deformation and crack development. Finally, the failure time of the slope was forecasted using the inverse velocity (INV) and slope (SLO) models. The study results show that the deformation and failure processes of the analysed expansive soil slope had an obvious crack control effect, and the displacement–time curve derived by the DIC method had an obvious “phased change law”. The data points calculated by the INV method were discrete and had high linear fitting requirements, resulting in large failure time forecasts. When the SLO method was used to forecast the failure time, because the values derived in the stable deformation stage were relatively concentrated in the calculation process, an obvious linear relationship was found in only the accelerated deformation stage, so the prediction results were more accurate. Therefore, the SLO method should be preferentially used to forecast the failure of expansive soil slopes with “step-like” displacement. These results enabled us to characterize slide processes and identify the mechanism responsible for the movement of a rainfall-induced expansive soil landslide. The stage deformation and failure mode of expansive soil landslide under rainfall infiltration: “slow deformation—stable deformation—accelerated deformation—instability failure” was revealed. This study is helpful for determining the deformation and failure mechanism of rainfall-induced expansive soil landslide and forecasting expansive soil landslides and providing guidance for controlling landslide hazards in expansive soil areas. Full article

The effects of earthquakes on groundwater and aquifer properties can be quantified and monitored using water-level changes produced by tides and barometric pressure. Tidal and barometric responses are particularly useful in evaluating the impacts of unexpected events, such as earthquakes, because the signals are continuously generated and recorded over large areas of the Earth’s surface. The techniques for the extraction of tidal and barometric signals from the water-level time series are described in many excellent papers, here, we focus on reviewing the hydrogeologic interpretations of, and earthquake impacts on, these responses. We review how hydrogeology and earthquakes impact the groundwater response to Earth tides, and changes in barometric pressure and barometric tides. Next, we review the current understanding of the mechanisms responsible for earthquake-induced changes in aquifer confinement and permeability. We conclude with a summary of open questions and topics for future research, notably the value in long-term monitoring and analysis of the earthquake response at multiple tidal and barometric frequencies. Full article