Optimal Pumping Rates Research Articles

A Simplified Approach of Pumping Rate Optimization for Production Wells to Mitigate Saltwater Intrusion: A Case Study in Vinh Hung District, Long An Province, Vietnam

In the investigation of optimal groundwater extraction in coastal regions, conventional assumptions typically revolve around unconfined aquifers with specified boundary conditions. In such cases, intricate solutions for groundwater management have been documented. However, within extensive delta plains, the extraction wells are frequently drilled in confined aquifers with not much variable-density flow. This circumstance, characterized by paleo-saltwater intrusion, is further complicated by the placement of wells at a considerable distance from the coastal line. As a result, the design and implementation of groundwater supply systems in these areas necessitate strategic groundwater management to optimize groundwater utilization while mitigating the potential risk of saltwater intrusion. Analytical solutions and an optimization problem approach have been applied to address this challenge and solve the differential equations governing confined aquifers with salt–freshwater interfaces. These methodologies provide simplified yet dependable conditions tailored to the study area. A case study conducted in Vinh Hung district, Long An province, is focused on determining the optimal pumping rate for production wells to forestall saltwater intrusion during groundwater extraction. Here, the focus is on the migration of older saltwater towards inland pumped wells, rather than the influence of recent seawater encroachment. The findings contribute valuable insights into achieving an equilibrium between maximizing groundwater utilization and preventing saltwater intrusion in the aquifer systems by a simplified approach.

Impact of ionic strength on goethite colloids co-transported with arsenite (As3+) through a saturated sand column under anoxic condition: Experiment and mathematical modeling

The knowledge about co-transport of goethite and As3+ to investigate the effect of goethite colloids on As3+ transport under various degrees of seawater intrusion, particular extremely conditions, in groundwater environment is still limited. The main objective is to investigate the influence of seawater intrusion on the sorption, migration, and reaction of As3+and goethite colloids into sand aquifer media under anoxic conditions by using the bench-scale and reactive geochemical modeling. The research consisted of two parts as follows: 1) column transport experiments consisting of 8 columns, which were packed by using synthesis groundwater at IS of 0.5, 50, 200, and 400 mM referring to the saline of seawater system in the study area, and 2) reactive transport modeling, the mathematical model (HYDRUS-1D) was applied to describe the co-transport of As3+ and goethite. Finally, to explain the interaction of goethite and As3+, the Derjaguin-Landau-Verwey-Overbeek (DLVO) calculation was considered to support the experimental results and HYDRUS-1D model. The results of column experiments showed goethite colloids can significantly inhibit the mobility of As3+ under high IS conditions (>200 mM). The Rf of As3+ bound to goethite grows to higher sizes (47.5 and 65.0 μm for 200 and 400 mM, respectively) of goethite colloid, inhibiting As3+ migration through the sand columns. In contrast, based on Rf value, goethite colloids transport As3+ more rapidly than a solution with a lower IS (0.5 and 50 mM). The knowledge gained from this study would help to better understand the mechanisms of As3+ contamination in urbanized coastal groundwater aquifers and to assess the transport of As3+ in groundwater, which is useful for groundwater management, including the optimum pumping rate and long-term monitoring of groundwater quality.

Research on the transport behavior of microparticle proppants inside natural fractures

As a crucial exploration technique for unconventional reservoirs, hydraulic fracturing enables the formation of complex fracture networks, thereby facilitating the flow of oil and gas. The closure of natural fractures decreases stimulation performance. Microparticle proppants are used to fill natural fractures and effectively increase the stimulation area. The 100-mesh proppant conventionally used in field operations may be insufficiently small to effectively access natural fractures. In order to effectively overcome natural fractures closure, microparticle proppants (i.e., proppants with a diameter of 75 μm (200-mesh) or less) are required. The particle size threshold test of microparticle proppants placement is conducted to determine the size threshold of proppants flowing into natural fractures. The microparticle proppants placement experiment in multi-branch fractures is conducted to investigate the volume difference of proppants in different fractures. Numerical simulations are performed to model proppant transport within fractures of actual dimensions to facilitating the optimization of stimulation parameters. The main conclusions are as follows: (1) Effective inflow of microparticle proppants requires a size threshold of proppants. For the 200-mesh proppants, the size should be less than half of natural fractures width when microparticle proppants effectively flow into natural fractures. (2) Sand concentration affects the size threshold of microparticle proppants. The size threshold should appropriately increase to ensure the inflow of proppant. (3) Difference of multi-branch fracture width has a significant effect on volume of microparticle proppants inside fractures. When the width ratio of multi-branch fractures exceeds 2, this effect becomes obvious. (4) Particle size has an effect on proppant placement. 200-mesh proppants can obtain uniform distribution of proppants among natural fractures. 140-mesh proppants can obtain maximum proppant volume among natural fractures. Sand concentration significantly affects proppant placement performance. The optimal sand concentration is 60kg/m3. The pumping rate for a single cluster fracture should not be excessively low. The pumping rate should be larger than 0.5m3/min and the optimal pumping rate 2m3/min. In this paper, the particle size and concentration of particulate proppant are optimized and the geometric characteristics of fractures are considered. These conclusions provide important practical guidance and scientific basis for the optimization and application of hydraulic fracturing technology.

Hydrogeologic Framework Model‐Based Numerical Simulation of Groundwater Flow and Salt Transport and Analytic Hierarchy Process‐Based Multi‐Criteria Evaluation of Optimal Pumping Location and Rate for Mitigation of Seawater Intrusion in a Complex Coastal Aquifer System

AbstractA series of hydrogeologic framework model (HFM)‐based steady‐ and transient‐state numerical simulations is performed first using a coupled subsurface flow‐transport numerical model to analyze groundwater flow and salt transport in an actual three‐dimensional complex coastal aquifer system before and during groundwater pumping. A series of analytic hierarchy process (AHP)‐based multi‐criteria evaluations is then performed applying a multi‐criteria decision‐making approach to determine optimal pumping location and rate for a new pumping well in the complex coastal aquifer system during groundwater pumping. The complex coastal aquifer system is composed of six anisotropic fractured porous geologic media (five rock formations and one fault) and three isotropic porous geologic media (three soil formations) and shows high geometric irregularity and significant heterogeneity and anisotropy of the nine geologic media. Results of the steady‐state numerical simulations show successful model calibration with 26 measured groundwater levels and two observed seawater intrusion front lines. The latter two are determined by spatial interpolation and extrapolation of electrical conductivity logging data and electrical resistivity survey data, respectively. Based on the status and prospect of necessary water uses and available groundwater resources, the field observations of groundwater and seawater intrusion, and the analyses of the steady‐state numerical simulation after the model calibration, six candidate pumping locations are selected for the new pumping well. In addition, from six preliminary individual transient‐state numerical simulations, maximum pumping rates at the six candidate pumping locations are calculated first, and a set of six incremental candidate pumping rates is then assigned at each of the six candidate pumping locations. Results of the transients‐state numerical simulations show that groundwater flow and salt transport are spatially and temporally changed, and seawater intrusion is further intensified by groundwater pumping. In addition, the magnitudes of such spatial and temporal changes and intensification are significantly different depending on the candidate pumping locations and rates. Results of the steady‐ and transient‐state numerical simulations also show that both complexity (geometric irregularity, heterogeneity, and anisotropy including the fault) and topography have significant effects on the spatial distributions and temporal changes of groundwater flow and salt transport in the coastal aquifer system before and during groundwater pumping. In addition, results of statistical estimations of the mesh Peclet and Courant numbers confirm acceptabilities of minimizing numerical dispersion in the steady‐ and transient‐state numerical simulations. Based on the analyses of the transient‐state numerical simulations, eight multiple criteria are chosen to judge, prioritize, and rank the six candidate pumping locations and six candidate pumping rates for optimal pumping. Results of the multi‐criteria evaluations determine the optimal pumping location and rate for the new pumping well among the six candidate pumping locations and six candidate pumping rates. In addition, results of consistency checks confirm consistencies of judgments in the multi‐criteria evaluations.

Integrating MODFLOW and machine learning for detecting optimum groundwater abstraction considering sustainable drawdown and climate changes

Detecting optimum groundwater abstraction is a challenging objective. This study proposes a new approach for identifying the optimum pumping rates by integrating MODFLOW with machine learning (ML). The adopted strategy has been applied to the Oligocene and Eocene aquifers in the western desert of Minia, Egypt. MODFLOW-2005 model has been utilized to simulate various management scenarios, including current and expected climate scenarios of two Representative Concentration Pathways (RCPs): RCP 4.5 and RCP 8.5. The steady-state and transient MODFLOW models were calibrated using the groundwater levels of 37 observation wells with a coefficient of correlation (R2) of 0.986 and 0.988, respectively. The developed model has been run for 80 years, from 2020 to 2100. The results of MODFLOW demonstrated a drawdown in the groundwater level in the two aquifers, about 40, 41, and 42 m, owing to current climate conditions and scenarios of RCP 4.5 and RCP 8.5, respectively, in 2100. Generated data based on the calibrated model has been used to develop the ML models. ML models have been applied to predict the pumping rates using the well coordinates, aquifer type, evapotranspiration, the operating period in days, and drawdown as inputs. For this purpose, four ML models, Gaussian Process Regression (GPR), Support Vector Regression (SVR), Tree, and Artificial Neural Network (ANN)) were developed and evaluated. All ML models demonstrated an effective performance during the training and validation processes, particularly the GPR model, which has the best ability to predict the pumping rates with a correlation coefficient, RMSE, and Mean Absolute Error (MAE) equal to 1.0, 6.53, and 8.04, respectively. Therefore, the GPR model has been utilized to identify the optimum pumping rates. The findings of the GPR model revealed that the optimum abstraction of the Oligocene aquifer is 602266, 625329, and 635061 m3/day, while the Eocene aquifer’s optimal groundwater abstraction is 10229801, 1027906, and 102936 m3/day, considering the current climate, RCP 4.5, and RCP8.5, respectively. Anticipated findings are supposed to be instrumental for decision-makers, offering valuable insights into sustainable groundwater management. The novel integration methodology promotes the efficient use of groundwater, contributing to achieving sustainable development goals (SDGs).

Confined aquifer dewatering optimization with a modified simulation–optimization method capable of determining the optimal well screen length and depth

Simulation-optimization methods are widely used in dewatering optimization. However, traditional simulation–optimization methods do not address the optimization of well screen length and depth. This study proposes a modified simulation–optimization method for confined aquifer dewatering optimization, which is capable of determining the optimal screen length and depth. The proposed method is based on the linear programming method, and the multivariate adaptive regression splines method is also introduced to develop the prediction model for the parameters required in the linear programming model. A hypothetical case of deep excavation dewatering was optimized using the proposed method to demonstrate its feasibility, with the optimal pumping rate, screen length and depth of each well computed. Furthermore, parametric studies were performed to investigate the effects of some key factors on the optimization results, such as the number of considered pumping wells, required drawdown, insertion ratio of the waterproof curtain, aquifer anisotropy coefficient, and prescribed well screen. The results show that optimal total pumping rate and screen length generally increase with increasing required drawdown and aquifer anisotropy coefficient, while they decrease with increasing well number and insertion ratio of the waterproof curtain. Adjusting screen length is more critical to the optimization results since lower screen depth is always preferred. Optimizing well screen is more essential for higher well number, insertion ratio of the waterproof curtain, and lower aquifer anisotropy coefficient.

An ensemble-based approach for pumping optimization in an island aquifer considering parameter, observation and climate uncertainty

Abstract. In coastal zones, a major objective of groundwater management is often to determine sustainable pumping rates which avoid well salinization. Understanding how model and climate uncertainties affect optimal management solutions is essential for providing groundwater managers with information about salinization risk and is facilitated by the use of optimization under uncertainty (OUU) methods. However, guidelines are missing for the widespread implementation of OUU in real-world coastal aquifers and for the incorporation of climate uncertainty into OUU approaches. An ensemble-based OUU approach was developed considering parameter, observation and climate uncertainty and was implemented in a real-world island aquifer in the Magdalen Islands (Quebec, Canada). A sharp-interface seawater intrusion model was developed using MODFLOW-SWI2 and a prior parameter ensemble was generated containing multiple equally plausible realizations. Ensemble-based history matching was conducted using an iterative ensemble smoother which yielded a posterior parameter ensemble conveying both parameter and observation uncertainty. Sea level and recharge ensembles were generated for the year 2050 and were then used to generate a predictive parameter ensemble conveying parameter, observation and climate uncertainty. Multi-objective OUU was then conducted, aiming to both maximize pumping rates and minimize the probability of well salinization. As a result, the optimal trade-off between pumping and the probability of salinization was quantified considering parameter, historical observation and future climate uncertainty simultaneously. The multi-objective, ensemble-based OUU led to optimal pumping rates that were very different from a previous deterministic OUU and close to the current and projected water demand for risk-averse stances. Incorporating climate uncertainty into the OUU was also critical since it reduced the maximum allowable pumping rates for users with a risk-averse stance. The workflow used tools adapted to very high-dimensional, nonlinear models and optimization problems to facilitate its implementation in a wide range of real-world settings.

ОЦЕНКА ЭФФЕКТИВНОСТИ ПОДАВЛЕНИЯ АММИАКА В ВОЗДУШНЫХ СРЕДАХ ПРОИЗВОДСТВЕННЫХ ПОМЕЩЕНИЙ С ИСПОЛЬЗОВАНИЕМ БАРЬЕРНОГО РАЗРЯДА

One of the main problems in the industrial production of livestock and poultry products is the neutralization of toxic gases in the air removed from livestock premises. Ozonation is used for this. Ozone is produced in dielectric barrier discharge installations. The disadvantages of the method include the dependence of the electrical characteristics of the dielectric barrier discharge on the parameters of the medium and the generation of nitrogen oxides. (Research purpose) The research purpose is determining the effectiveness of ammonia suppression by ozone generated in dielectric barrier discharge installations at various parameters of the generator operating mode. (Materials and methods) Established the effectiveness of ammonia suppression by ozone at various parameters of the ozone generator operation mode. A 25 percent aqueous solution of ammonia with controlled purging over the surface of the solution was used as an ammonia source. The dependences of the mass concentration of ozone (O3), nitrogen oxides (NOx) and hydrogen sulfide (H2S) at the generator output on the operating mode parameters were studied. It was shown that the range of changes in the concentration of gases varied within the following limits: ozone - from 180 to 4, ammonia - from 80 to 2, hydrogen sulfide - from 4 to 0, nitrogen oxides - from 0 to 130 milligrams per cubic meter. (Results and discussion) It was found that the concentration of ammonia decreased from 50 to 10 milligrams per cubic meter; the time to reach the specified values of the concentration of ammonia in the stream was 20-50 seconds; when ozone is generated in all operating modes, nitrogen oxides are formed in the weight ratio O3/NOx from 1.42/1 to 1/1. The dependences of the generation of ozone and nitrogen oxides on the input voltage of the generator power supply unit were determined. It was noted that the optimal pumping rate of plasma-forming gas (atmospheric air) ranged from 0.8 to 1.5 m/ s; the mass ratio of nitrogen oxides to ozone varies from 0.69 to 0.98, which is unacceptable for premises with permanent residence of animals and maintenance personnel. (Conclusions) It was stated that the results obtained in assessing the rational operating modes of ozonators allow us to formulate technical requirements for the development of a specialized ozone generator adapted for use in agricultural production.

Innovative groundwater management in industrial park: Optimization and modelling of extraction system

The research presented in this paper focuses on the optimization and modelling of an innovative groundwater extraction system and addresses the challenge of managing the increased groundwater level in Nitra Industrial Park, where the Land Rover Jaguar car manufacturer is located. The primary objective of this research was to determine the optimal pumping rate of the system, ensuring the maintenance of the groundwater level at the required elevation without depleting the surrounding water resources. To achieve this goal, a numerical groundwater modelling approach was utilized, employing the TRIWACO simulation package and the finite element method (FEM). The study involved various simulations under steady and unsteady flow conditions, using hydrological, geological and hydrogeological data, including the results of three proposed pumping tests conducted by INGEO, Ltd. Company, as well as measured groundwater level data from boreholes monitored by the Slovak Hydrometeorological Institute (SHMI). Implementing transient groundwater flow simulations considered the impact of a 1000-year flash flood wave (Q1000). This paper presents results of numerical modelling results, offering insights into maintaining the required groundwater elevation while considering key parameters and uncertainties for design purposes. Additionally, on-site optimization was performed to ensure efficient system operation and minimize associated costs. In conclusion, this research contributes to sustainable groundwater management in the Nitra Industrial Park, addressing the challenge of the increased groundwater level and providing valuable findings to optimize the extraction system’s performance.

Enhancing quantum synchronization through homodyne measurement, noise, and squeezing.

Quantum synchronization has been a central topic in quantum nonlinear dynamics. Despite the rapid development in this field, very few have studied how to efficiently boost synchronization. Homodyne measurement emerges as one of the successful candidates for this task but preferably in the semiclassical regime. In our work, we focus on the phase synchronization of a harmonic-driven quantum Stuart-Landau oscillator and show that the enhancement induced by homodyne measurement persists into the quantum regime. Interestingly, optimal two-photon damping rates exist when the oscillator and driving are at resonance and with a small single-photon damping rate. We also report noise-induced enhancement in quantum synchronization when the single-photon damping rate is sufficiently large. Apart from these results, we discover that adding a squeezing Hamiltonian can further boost synchronization, especially in the semiclassical regime. Furthermore, the addition of squeezing causes the optimal two-photon pumping rates to shift and converge.

Performance comparison of physics-based and machine learning assisted multi-fidelity methods for the management of coastal aquifer systems

In this work we investigate the performance of various lower-fidelity models of seawater intrusion in coastal aquifer management problems. The variable density model is considered as the high-fidelity model and a pumping optimization framework is applied on a hypothetical coastal aquifer system in order to calculate the optimal pumping rates which are used as a benchmark for the lower-fidelity approaches. The examined lower-fidelity models could be classified in two categories: (1) physics-based models, which include several widely used variations of the sharp-interface approximation and (2) machine learning assisted models, which aim to improve the efficiency of the SI approach. The Random Forest method was utilized to create a spatially adaptive correction factor for the original sharp-interface model, which improves its accuracy without compromising its efficiency as a lower-fidelity model. Both the original sharp-interface and Machine Learning assisted model are then tested in a single-fidelity optimization method. The optimal pumping rated which were calculated using the Machine Learning based SI model sufficiently approximate the solution from the variable density model. The Machine Learning assisted approximation seems to be a promising surrogate for the high-fidelity, variable density model and could be utilized in multi-fidelity groundwater management frameworks.

Optimization of Water Pipe Network and Formulation of Pumping Rate

Minimizing water delivery costs and increasing water supply dependability are the two key objectives in designing and operating of water distribution systems. An analytical solution for the best pipe diameters of a water distribution pipe network was created in this study. The raw water was collected from a water canal and transported to a treatment plant (WTP). The cleansed water was pushed into the water distribution network via the pumping station. The derivative approach was used in the optimization process, and the cost functions incorporating the various capital and operating expenses were used. The initial diameters were adjusted to reach the least-cost diameters. The study shows that the optimum design of a pipe network (PNW) achieves saving a total cost of about 12.3% after utilizing our unique method. The optimal pumping rate in the PNW can also be determined using an analytical approach that considers the optimum value that occurs when the minor and friction losses in the entire network are at their lowest. The analytical solution for the optimum pumping rate shows a rigid value of optimum pumping rate (Qopt) which is 5296.32 m3/day. On comparative estimates, this figure is very close to that of 5,300 m3/day interpreted from the graphical solution, with negligible deviation. The total cost and optimum pumping rate results for the analyzed PNW example demonstrate the correctness of the analytical solutions, reliability, and dependability of the assumptions.

Optimal management of coastal aquifers using artificial jellyfish search algorithm

In the current study, a simulation-optimization model is presented using a new metaheuristic optimization algorithm called artificial Jellyfish Search (JS) to develop sustainable saltwater intrusion optimal management strategies for coastal aquifers. The simulation model is based on the finite element method (FEM). The effectiveness of the proposed model is tested by application to the real aquifer system of Miami Beach aquifer, Spain with management decisions of maximizing the total economic benefit and the total pumping rate. The model is also applied to the case study of El-Arish Rafah aquifer, Egypt to maximize the total pumping rate. The results of both cases are compared to that obtained by using genetic algorithm (GA), probabilistic global search Lausanne (PGSL), shuffled frog leaping (SFL) and particle swarm optimization (PSO). The efficiency rate metric and statistical indices are used to assess the performance of the proposed model. For Miami Beach aquifer, an optimal benefit of 24.93 ($/d) was obtained and which is equivalent to that by PSO and SFLA but higher than that of GA and PGSL and with the highest pumping rate of 5544.62 (m3/s). The model also had the highest efficiency rates compared to PSO, PGSL and SFLA. For El-Arish Rafah aquifer, a maximum optimal pumping rate of 55,619.43 (m3/s) is determined. The results show that the model can be considered as an effective and efficient management tool.

Improvement of mud displacement from the annular space of the borehole in terms of the criterion of selecting washing fluids and pre-flushes

One of the most important steps in drilling the well is cementing the annular space between casing and rock formations. This process is significant because of the stabilization of the well and effectively separation of the consecutive rock horizons. It is required that cementing ensures durable and effective insulation of the rock mass. The complete displacement of the drilling fluid from the annular space is particularly important due to a number of negative phenomena related to its insufficient extrusion. The cement slurry pressed through the annular space displaces the mud but is not able to sufficiently thoroughly remove the residue left behind. The subject of the laboratory research was to check how selected washer affect the efficiency of displacing drilling fluid from the annular space of the borehole. In addition, the tests included the determination of the optimal washing time and the optimal pumping rate of the washing fluid. Moreover, the tests included the determination of the optimal washing time and the optimal pumping rate of the washing fluid.

Optimal design of groundwater pollution management systems for a decanting contaminated site: A simulation-optimization approach

Major challenges facing groundwater management arise mostly from approaches aiming at ensuring water resources sustainability, water quality protection and aquifer restoration. In many old polluted sites, the most challenging practice is the management of decanting contaminated water from flooded shaft that decants into the natural environment. Pump and treat (PAT) is one of the commonly used techniques in management of groundwater pollution problem. Simulation-Optimization (S–O) models have proven to be very useful in appropriate design of an effective PAT groundwater remediation system. In this study, simulation models MODFLOW and MT3DMS for groundwater flow and transport respectively, and a solving constraint integer program (SCIP) optimization algorithm were employed in designing of an effective system for cleaning and controlling pollution coming from hypothetical decanting site. Simulation models were used to predict the spatial and temporal variation of contaminant plumes and aquifer response to remediation measures. SCIP optimization algorithm, on the other hand, was applied to determine the optimal solution of the formulated objective function while attaining a set of water quality and head constraints as well as operation bounds. Results from this study indicated that the optimal pumping rates for the proposed pumping wells met water quality and water head requirements. Further, the obtained results demonstrate the application of SCIP in conjunction with simulation models as a capable tool in designing an effective groundwater management system and control decanting problem. The performance of SCIP is also compared with genetic algorithm (GA) and the SCIP is found to have a better convergence rate than the GA.

Investigating groundwater vulnerability variation under future abstraction scenarios to estimate optimal pumping reduction rates

Groundwater vulnerability variation over time due to groundwater depth variation caused by pumping reduction is an issue of great interest that should be properly investigated; this is because pumping reduction results in groundwater level increase on the one hand and groundwater vulnerability increase, as a result of groundwater depth decrease, on the other hand. In this context, the present study introduces a novel approach, which considers the spatio-temporal variation of groundwater vulnerability and at the same time focuses on the relationship between vulnerability change and pumping reduction to estimate the optimal pumping reduction rate (i.e. the highest rate of pumping reduction under which the highest increase in groundwater levels occurs without an increase in groundwater vulnerability taking place) in over-exploited and contaminated aquifers. In a first stage, a dynamic and time-dependent approach involving the linkage between a GIS-based DRASTIC model and a groundwater flow model was developed in order to determine groundwater vulnerability changes under different pumping reduction rates (0%, 10%, 20%, 30% and 40%), and thus to produce the necessary data sets for investigating their relationship. Subsequently, regression analysis was conducted to define this relationship and estimate the optimal pumping reduction rate. Our implementation of the methodology showed that groundwater vulnerability displays small changes during the projection period for all reduction rates, while decreasing for 0% and 10% reduction of withdrawals and increasing for 20%, 30% and 40% reduction. After finding that a quadratic equation accurately describes the relationship between vulnerability change and pumping reduction (R2 = 0.999), an optimal reduction rate of 16.4% was estimated. By confirming that no change in vulnerability occurs under this value during the projection period, the validity of the equation defined was affirmed.

Mechanisms of arsenic contamination associated with hydrochemical characteristics in coastal alluvial aquifers using multivariate statistical technique and hydrogeochemical modeling: a case study in Rayong province, eastern Thailand.

The rapid development of Rayong Province has resulted in increased demands on groundwater usage. This has potentially induced the release of contaminants such as arsenic (As), among others (i.e., NO3-, PO43-) from various land use types-especially in intensive agricultural areas and heavy industrial areas, including landfill sites. The objectives of this research are to investigate the As speciation and groundwater chemistry occurring due to different hydrogeological settings and the influence of human activities and to explain the mechanism of As release in the coastal alluvial aquifers in Rayong Province using multivariate statistical techniques and hydrogeochemical modeling (PHREEQC). Six major water facies, mainly consisting of Ca-Na-HCO3-Cl and Ca-Na-Cl, were included in the hydrochemical analysis. Arsenic levels were inversely correlated with NO3-, SO42-, DO, and ORP, confirming the reducing environment in the groundwater system. The results from the PHREEQC model show that most wells were strongly under-supersaturated with respect to arsenorite, scorodite, and arsenic pentoxide. Arsenic (As) is probably derived from the dissolution of Fe oxide and hydroxide (i.e., Fe(OH)3, goethite, maghemite, and magnetite). The multivariate statistical techniques revealed that the As species mainly consisted of As(III), governed by the reducing environment, while As(V) may be desorbed from Fe oxide and hydroxide as the pH increases. Anthropogenic inputs and intensive pumping may enhance the reducing environment, facilitating the release of As(III) into the groundwater. The knowledge gained from this study helps to better understand the mechanisms of As contamination in coastal groundwater aquifers, which is useful for groundwater management, including the optimum pumping rate and long-term monitoring of groundwater quality.

Optimized Pumping Strategy for Reducing the Spatial Extent of Saltwater Intrusion along the Coast of Wadi Ham, UAE

Many coastal aquifers are facing severe anthropogenic impacts such as urbanization, industrialization and agricultural activities are resulting in a saltwater intrusion. This establishes the need for a sustainable groundwater management strategy aimed to overcome the situation. Pumping of brackish/saline water to mitigate saltwater intrusion is a major potential approach to effectively control saltwater intrusion. However, this method has many challenges including selection of appropriate discharge rates under an optimum number of pumping wells and at specified wells distance from the shoreline. Hence, this study developed a Finite Element Flow and solute transport model (FEFLOW) to simulate three scenarios to assess the most appropriate pumping rates, number of wells and optimum well locations from the shoreline. These parameters were assessed and evaluated with respect to the change in groundwater saline concentration at different distance from the coastline. The 15,000 mg L−1 isosalinity contour line was used as a linear threshold to assess the progression of saltwater intrusion along three major locations in the aquifer. Scenario One was simulated with a constant number of wells and rate of pumping. Shifting of pumping wells to several distances from the shoreline was conducted. Scenario Two assessed the most appropriate number of pumping wells under constant pumping rates and distances from the shoreline and in scenario 3, the optimum pumping rates under a constant number of wells and distance from the shoreline were simulated. The results showed that the pumping of brackish/saline water from a distance of 1500 m from the shoreline using 16 pumping wells at a total pumping rate of 8000 m3 d−1 is the most effective solution in contrasting the saltwater intrusion in the Wadi Ham coastal aquifer.

A numerical model to optimize LNAPL remediation by multi-phase extraction

Light non-aqueous phase liquid (LNAPL) contaminated sites pose a risk to human health and the natural environment. Multi-phase extraction (MPE) is one of the most widely used technologies to remediate these sites. Thus, it is important to optimize MPE systems to improve their effectiveness and cost-efficiency. In this study, we developed a numerical model to optimize LNAPL mass removal by MPE, in which the aquifer domain was simplified as a cylinder with a single MPE extraction well located at the center. A dual-pump extraction system was applied to the model, which involved vacuum enhanced recovery to remove volatilized gaseous phase contaminants and a submerged pump to remove NAPL and contaminants in groundwater. After the model was validated with field data, the results showed that the contaminant extraction rate varied with the LNAPL thickness and submerged pump position. For benzene selected as the contaminant of concern, greater LNAPL extraction rates were achieved when the initial LNAPL thickness was large (>1.5 m) or in aquifers of high permeability (>2.45 × 10−10 m2). Importantly, it was discovered that in highly permeable coarse sand and gravel, the submerged pump ought to be placed within the LNAPL layer, whereas the pump should be placed below the water-NAPL interface in fine to medium sand aquifers. It was also found that an optimal liquid pumping rates exist, beyond which contaminant mass removal rates do not increase. Furthermore, it was found that in aquifers contaminated with thin LNAPL layers, mass transfer modelling that assumes equilibrium between the phases may greatly overestimate the accumulated mass of contaminants removed and, therefore, non-equilibrium modelling should be adopted. Finally, a cost analysis was carried out to compare the costs of remediating a contaminated site with MPE and by an alternative chemical oxidation approach. The MPE technology was found to be more cost effective when the initial thickness of LNAPL was relatively thin. In summary, the numerical model developed in this study is a useful tool for optimizing MPE system design.

Pumping optimization of coastal aquifers using probabilistic search – case study: Quaternary aquifer of El-Arish Rafah, Egypt

Abstract The increased pumping of freshwater from coastal aquifers, to meet growing demands, causes an environmental problem called saltwater intrusion. Consequently, proper management schemes are necessary to tackle such a situation and permit the optimal development of coastal groundwater basins. In this research, a probabilistic search algorithm, namely Probabilistic Global Search Lausanne (PGSL), is used to calculate optimal pumping rates of unconfined coastal aquifer. The results of using PGSL are compared with a stochastic search optimization technique, Shuffled Frog Leaping Algorithm (SFLA). The finite element method is applied to simulate the hydraulic response of the steady state homogenous aquifer. The lower and upper (LU) decomposition method is adapted to invert the conductance matrix, which noticeably decreases the computation time. The results of both the PGSL and the SFLA are verified through the application on the aquifer system underlying the City of Miami Beach in the north of Spain. Multiple independent optimization runs are carried out to provide more insightful comparison outcomes. Consequently, a statistical analysis is performed to assess the performance of each algorithm. The two optimization algorithms are then applied on the Quaternary aquifer of El-Arish Rafah area, Egypt. The results show that both algorithms can effectively be used to obtain nearly global solutions compared with other previous published results.