Uzair
Ahmad
a,
Ahmed
Abdala
b,
Kim Choon
Ng
c and
Faheem Hassan
Akhtar
*a
aDepartment of Chemistry and Chemical Engineering, Lahore University of Management Sciences (LUMS), Lahore 54792, Pakistan. E-mail: faheem.akhtar@lums.edu.pk
bCollege of Science and Engineering, Hamad Bin Khalifa University, Doha 34111, Qatar
cBiological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
First published on 13th August 2025
Membrane-based desalination technologies are critical for addressing global water scarcity; however, their performance optimization remains a complex challenge. This review explores the potential of machine learning (ML) in advancing membrane desalination, with a focus on process optimization, fouling mitigation, and performance prediction. We provide a comprehensive analysis of ML techniques, including artificial neural networks (ANNs), support vector machines (SVMs), and random forest (RF), applied to membrane systems such as reverse osmosis (RO), forward osmosis (FO), and for the treatment of produced water. The study highlights how data-driven models enhance decision-making by correlating operational parameters (e.g., pressure, temperature, feed salinity) with membrane efficiency, energy consumption, and fouling behavior. A key emphasis is placed on ANN-based frameworks for real-time monitoring and predictive control, demonstrating their superiority in modeling non-linear interactions compared to traditional mechanistic approaches. We also examine ML applications in optimizing design parameters, maintenance strategies, and renewable-energy-integrated desalination systems. Challenges such as data scarcity and model generalizability are discussed, alongside future directions for integrating ML with emerging membrane materials and hybrid processes. This review highlights ML's role in bridging theoretical and practical gaps in desalination, offering actionable insights for researchers and industry experts to deploy intelligent and sustainable water treatment solutions.
Water impactRemoving salt and other impurities from water remains a significant challenge in today's world. Machine learning notably helps to improve water treatment and desalination by making processes more adaptable, efficient and cost effective. Recent advancements in operational parameters, system optimization and membrane fouling prediction were explored. This study offers a holistic methodology to develop smart water technologies in real world applications and contribute to addressing global water issues by enhancing the performance of desalination systems using machine learning. |
Desalination, the process of purifying water by removing salt and other contaminants, can be used to lessen the impact of water scarcity. Desalination methods can be categorized into two main groups: thermal and membrane-based processes. Since the 1960s, membrane processes, such as RO, have surpassed thermal processes for new plant installations globally,4 where thermal desalination has remained the predominant technology. The primary disadvantage of desalination is associated with costs;5 30% of the total cost of desalinated water is associated with electricity for seawater desalination using RO. Increased energy consumption is accompanied by a rise in greenhouse gas (GHG) emissions.6
The overall energy demand for RO seawater desalination, encompassing both pre- and post-treatment processes, generally ranges from 3 to 6 kWh m−3.7,8 To enhance energy efficiency in RO applications, there has been a growing emphasis on utilizing feedback controls tied to the salinity of the incoming feedwater as a means to reduce desalination energy consumption.9,10 In the past few years, significant improvements have been achieved in the permeability and salt rejection capacity of membranes used to treat high salinity streams. The energy utilization for RO seawater desalination remains greater than the theoretical minimal energy demands. The average energy system use is 3.1 kWh m−3. Developments in desalination membranes hold the potential to reduce energy consumption. New desalination technologies reduce the required feed pressure while maintaining salt rejection. The global installed desalination capacity saw a significant increase from 27.05 (million m3 per day) in 2003 to 98.93 (million m3 per day) in 2023.
In recent years, ML has gained significant importance and has shown great potential in various domains, including water treatment technologies as shown in Fig. 1. ML methods, like support vector machine (SVM), artificial neural networks (ANN), and deep learning algorithms, have demonstrated the ability to extract valuable insights from complex data and optimize system performance.
The application of ML in membrane desalination offers several advantages. ML algorithms can process vast amounts of data collected from sensor arrays, monitoring systems, and historical records to identify patterns, correlations, and trends that may not be apparent through conventional analysis methods. By leveraging this data-driven approach, ML algorithms can learn and adapt to the dynamic behavior of desalination processes, enabling real-time monitoring, predictive modeling, and advanced control strategies.
ML techniques can be employed to enhance the optimization of critical operational variables, including but not limited to feedwater flow rate, pressure, temperature, and chemical dosage. ML algorithms can provide invaluable insights into the relationships between these variables and the membrane desalination system's performance by perpetually analyzing process data and environmental factors. This information can aid in decision-making and facilitate modifying operating conditions to enhance efficiency, water recovery, and fouling potential.
In this review paper, we aim to explore the current state of research and development in machine learning for process optimization and modification in membrane desalination for produced water and saline wastewater treatment as shown in Fig. 2. We will examine the various ML techniques, advantages, and limitations, demonstrating their application in real-world desalination plants. Additionally, we will discuss the challenges associated with implementing ML in desalination systems and potential avenues for future research and development.
Wastewater sources include those originating from industrial (tannery, food, paper, textile, oil and gas), agriculture activities, and domestic wastewater streams.
Saline wastewater is generated from agricultural drainage originating from saline and contains fertilizer nutrients, salt ions, herbicides, and pesticides.11 In the food processing industry, using brine and salt in processing plants that handle pickled vegetables, dairy products, seafood, and canned meats can lead to the generation of saline wastewater.12
While conducting oil drilling operations, the oil and gas sectors simultaneously produce a saline byproduct called flow back water or produced water.13 Shale reservoirs have the potential to produce a significant amount of water per well, ranging from 1.7 to 14.3 million liters, in the initial 5–10 years of production.14 The specific composition of the produced water is contingent upon factors such as geographical location, hydrocarbon classes, and reservoir age.15,16
In addition to the wastewater generated by the industries mentioned earlier, landfill leachate exhibits traits typical of saline wastewater. This is primarily attributed to ammonia, inorganic salts, organic pollutants, heavy metals, and biological organisms.17 It has been reported that as landfill leachate ages, its organic constituents will become more complex and chemically stable.18 Therefore, it is extremely difficult to treat this form of wastewater. Table 1 below shows the different compositions of saline wastewater from industrial resources. Different compositions like COD, TDS, BOD and TOC are mentioned in Table 1. Oil and gas industries have the highest amount of TDS which is 100 g L−1 followed by food industries (dairy wastewater) with the value of 48 g L−1.
Sources | Constituents | Composition, g L−1 | Ref. | |||
---|---|---|---|---|---|---|
TDS | COD | BOD | TOC | |||
Leather/tannery industries, soaking process | Salts, ammonium, phosphorus, salts, chromium, organic nitrogen, sulfide | 22–33 | 3–6 | 19 | ||
Textile industries, dyeing process | Dyes, nitrogen, salts, heavy metals (Cu, Sb, Pb, Cr), suspended solids | 1.5–4.0 | 0.4–1.4 | 20, 21 | ||
Textile industries, bleaching process | 2.5–11.0 | 1.2–1.6 | ||||
Food industries: dairy wastewater | Soluble proteins, lactose, mineral salts, lipids | 48 | 29 | 21–24 | ||
Food industries: seafood wastewater | Oils, fats, suspended solids, excess nutrients (phosphorus and nitrogen), sodium chloride, proteins | 13.18 | 3.25 | |||
Landfill leachate | Ammonia, inorganic salts, organic contaminants, heavy metals, and biological organisms | 10.7–35.8 mS cm−1 | 2.04–69.6 | 25, 26 | ||
Paper industries | Phenols, lignin, sulfur compounds, furans, chlorides, acetic acid, phosphate | 0.40–2.5 | 0.48–4.45 | 27 | ||
Oil and gas industries | Heavy metals, toluene, benzene, grease, aromatic hydrocarbons, salts, oil, carboxylic acid | 100 | 0.5–2 | 28, 29 |
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Fig. 3 Desalination using membrane techniques for wastewater treatment.31 (Copyright 2021, Elsevier). |
Given the negative effects saline wastewater has on the environment, treating it by removing salt and contaminants is essential before releasing it into the environment. If the water quality meets certain standard criteria, the treated wastewater could be further reused, offering an alternative to freshwater supplies. Because of their high permeate quality, adaptability, and desalination potential in water treatment, membrane-based technologies are currently attracting a lot of interest.32 The different membrane-based methods that have been used to treat saline wastewater are discussed below in Table 2. Different membrane processes like FO, RO, MD and MBR are discussed below. Characteristics of different saline wastewater sources are also explained, which includes COD, TOC and EC. In the case of COD and TOC rejection, the FO process shows 90% effectiveness. RO processes can achieve water recovery greater than 83%.
Saline wastewater types/source | Wastewater/feed solution characteristics | Membrane process | Performance | Ref. |
---|---|---|---|---|
Dyeing wastewater from textile and printing industries (China) | COD = 398.11 mg L−1 | FO | 90% rejection for TOC and COD | 33 |
EC > 100 mS cm−1 | ||||
TOC = 170.70 mg L−1 | ||||
Landfill leachate (Virginia, USA) | COD = 69![]() |
FO | Water recovery = 36.6% | 34 |
EC = 35.8 mS cm−1 | ||||
Landfill leachate (anaerobic landfill in Southwest China) | EC = 28.1–31.8 mS cm−1 | RO | Water recovery >83% | 35 |
EC = 0.15–0.22 mS cm−1 | ||||
Textile wastewater (Turkey) | COD = 1000 mg L−1 | RO | EC = 300 μS cm−1 | 36 |
Water recovery 70% | ||||
EC = 5500 μS cm−1 | ||||
Textile wastewater (from factory in Johor, Malaysia) | COD = 405–477 mg L−1 | MD | Rejection efficiency: COD = 89.6% | 37 |
EC = 1294–1673 μS cm−1 | ||||
EC = 93.7% | ||||
Crude olive mill wastewater (from Morocco region) | COD = 160 g L−1 | MD | Permeate flux = 3.9 LMH | 38 |
EC = 23 mS cm−1 | ||||
Textile wastewater (woolen textile dyeing factory, Turkey) | COD = 750 mg L−1 | MBR | Total phenol removal 80–87% | 39 |
EC = 3680 mS cm−1 | ||||
Total phenol = 1610 mg L−1 | ||||
Tannery wastewater (Tamil Nadu, India) | Soluble COD = 7560 mg L−1 | MBR | Permeate flux 6.8 LMH | 40 |
Bleach plant effluent (from paper/pulp industry, South Africa) | Total COD = 1700 mg L−1 | MBR | Flux = 6 LMH | 41 |
EC = 1196 mS m−1 |
This section analyzes the different types of membranes which are used for the treatment of produced water.
Membrane | Feed, ppm | Flux, L m−2 h−1 | Rejection, % | Ref. | |||
---|---|---|---|---|---|---|---|
Type | TDS | TOC | TDS | TOC | |||
Commercial RO double filtration | Synthetic PW | 37![]() |
565 | — | 99.8 | 42 | |
Commercial RO (BW-30) | Real PW | 722 | 68.8 | 30–35 | 87 | 43 | |
Commercial RO (TFC-HR) | Real PW | 5243 | >15 | 91.4 | 80.4 | 44 | |
Commercial RO (RE-4040) | Synthetic PW | 4800–5500 | 9–13 | 50.0–55.0 | 96.6 | ∼99.9 | 45 |
PSF-PAMAM + TMC | Synthetic PW | 2000 (NaCl) | 2500/5000 ppm hexadecane + 250![]() |
18.42 | 89.3 | 99 | 46 |
The efficiency of RO membranes is significantly influenced by the concentration of impurities, hydrocarbons and ions, in the PW feed solution. Furthermore, the extent of membrane fouling substantially affects both process costs and the required cleaning frequency. Nevertheless, when evaluating the quality of the treated water (permeate) produced through the RO process, it becomes evident that RO remains a reliable method for treating PW, especially when the membrane is appropriately customized.
Membrane | Feed, ppm | Draw solution | Flux, L m−2 h−1 | Rejection, % | Ref. | |||
---|---|---|---|---|---|---|---|---|
Type | TDS | TOC | TDS | TOC | ||||
TFC HF (Asahi Kasei Corp) | Synthetic PW | 14![]() |
46 | NaCl | 11 | 90 | 56 | |
TFC (Hydration Technology Innov.) | Real PW | 24![]() |
95 | NaCl | 7.2 | 95 (multivalent) | >80 | 57 |
PES-PVA-GO nanosheets | Synthetic PW | 256![]() |
2.5–100 | Na2 SO4 | 16.05 | 99.9 | 58 | |
TFC (Hydration Technology Innov.) | Real PW | NaCl | 8 | 97 | ∼99.9 | 49 | ||
TFC HF (Asahi Kasei Corp) | Synthetic PW | NaCl | 11.2 | 59 |
In addition to designing an efficient forward osmosis membrane, draw solution improvement plays a key part in enhancing the overall efficiency of the FO produced water desalination.47,48 When FO is operated as a stand-alone process, water permeates through a semi-permeable membrane, causing a rise in the concentration of the feed solution and a fall in the concentration of the draw solution. This ultimately lowers the osmotic pressure.49 Hence, DS should undergo reconcentration to restore its osmotic pressure, ensuring a viable and environmentally sustainable operation.50–52 Important criteria for DS53–55 include low molecular weight (MW), high solubility, non-toxicity, and excellent compatibility with membranes; however, the cost involved and regeneration are also essential factors to consider.
MD configuration | Membrane type | Feed | Flux (L m−2 h−1) | Rejection (%) salt |
---|---|---|---|---|
DCMD | PVDF functionalized with KOH | Synthetic PW | 45 | 99.99 |
AGMD | Commercial PVDF | Synthetic PW | 15.5 | 99.2 |
DCMD | PVDF + PVA | Real PW | 30.3 | 99.9 |
VMD | Commercial PVDF | Synthetic coal shale gas | — | 99.97 |
DCMD | PVDF incorporated with silica | Synthetic PW | 28.6 | 99.98 |
Unsupervised learning is a computational approach that utilizes unlabeled datasets for analysis without human interventions. This method is commonly used for grouping results, identifying meaningful structures and trends, and extracting generative features. Dimensionality reduction, feature learning, density estimation, and clustering are the most common unsupervised learning tasks. It discovers hidden patterns in unlabeled data but lacks ground truth validation. Semi-supervised learning operates on both unlabeled and labeled data.60 It can be defined as a hybrid of the unsupervised and supervised learning methods. Therefore, it lies between “without supervision” and “with supervision”. In numerous practical scenarios, the availability of labeled data may be limited, while unlabeled data is abundant, rendering semi-supervised learning useful.61 The objective of a semi-supervised learning model is to generate more accurate predictions than would be possible using the model's labeled data alone. It has applications in data labeling, fraud detection and machine translation.
The primary aim of supervised learning ML is to acquire knowledge of a function that establishes a correspondence between an input and an output, utilizing a set of input–output pairs as an example. The system employs a collection of training examples and labeled training data to infer a function. In a task-driven approach, supervised learning is carried out when specific objectives are to be achieved from a specific set of inputs that are identified.60 The most typical supervised activities are “regression”, which fits the data, and “classification”, which separates the data.
Another method is reinforcement learning (RL), which facilitates the automatic determination of optimal behavior for machines and software agents within a given context or environment, aiming to achieve a desired objective.62 This form of learning relies on reward or punishment. The ultimate objective of the penalty is to use insights gained by environmental activists to enhance their efforts to maximize the reward or minimize the risk.61 “It is a powerful tool for training AI models capable of boosting automation and optimizing the performance of intricate systems like robotics and autonomous vehicles. However, it finds limited application in addressing basic or uncomplicated issues within manufacturing and supply chain logistics”.
Various ML techniques can substantially impact the development of an efficient model in diverse application domains, depending upon the characteristics of the data and the intended objectives. A comparison of different ML models is given in Table 6. Different AI models like ANN, SVM, KNN, RF and DTR are compared based on applications, data needs and computational cost.
Model | Applications | Data needs | Computational cost |
---|---|---|---|
Artificial neural network (ANN) | Regression, classification | Very large | Very expensive |
Support vector machine (SVM) | Pattern recognition, regression, classification | Moderate | Medium |
K nearest neighbor (KNN) | Regression, classification | Large | Expensive |
Random forest (RF) | Regression, classification | Moderate to large | Low to medium |
Decision tree forest (DTR) | Regression, classification | Small to moderate | Low |
Various types of ANNs exist that can be classified according to their model parameters, design, and topology. The back propagation (BP) feedforward neural network, also referred to as the multi-layer perceptron (ML P), is widely recognized as the most frequently employed ANN. Additional types of ANNs include the recurrent neural network (RNN), radial basis function neural network (RBFNN), deep neural network (DNN), and Elman neural network (ENN). These types exhibit modifications in their structural composition, model parameters, and training algorithms while still belonging to the broader category of multi-layer perceptron (ML P) ANN.
A MLP comprises three essential components: input, hidden, and output layers. The number of input parameters corresponds to the number of neurons in the input layer, while the number of output parameters matches the neuron count in the output layer. Depending on how well-designed the ANN model is, one or more concealed layers may be composed of multiple neurons. The weights provided to each neuron during training set the hidden layer and output layer values. Each neuron in the hidden and output layers also receives a weighted unit input with a constant value called the threshold value or bias. Fig. 5 shows the basic layout of the ML P.
![]() | ||
Fig. 5 A single hidden layer ML P structure having 4 inputs, 4 hidden layers and 2 output neurons (4–4–2). (Copyright 2021, Elsevier). |
The radial basis function neural network (RBFNN) modeling technique can be considered an alternative to ANNs. The network resembles an ML P, structured as a feedforward network comprising input, output, and hidden layers. The output of each neuron is dictated by a basis function that exhibits radial symmetry. The RBFNN exhibits the ability to achieve universal approximation while avoiding the presence of local minima issues.66
In addition, it has a simplified structure and converges faster than other neural networks. Instead of employing inputs and their respective weights, the training procedure of the RBFNN relies on the standard Euclidean distance, which measures the distance between inputs and the network's center points. This approach effectively maps input neurons to a hidden layer that exhibits non-linear characteristics. An activation function is then applied to compute the value of each node within this hidden layer. Like an ML P, the network's output is computed as a weighted sum of the hidden neuron activations. The hidden neuron numbers are established through the training process. In each iteration, one RBF neuron is gradually integrated into the network. A single RBF neuron is incrementally incorporated into the network during each iteration. This process continues until either the error aim is achieved or the maximum allowable number of neurons67 is reached. Fig. 6 shows an RBFNN model.
Using a year's worth of operational data, Lee et al. have developed an ANN model to enhance the operation of a seawater RO desalination plant, using temperature control.69 Due to the difference in variance between the outputs, the model demonstrated the capability to determine permeate TDS with greater accuracy than flow rate. The researchers utilized the model to examine the impact of temperature, facilitating the development of an optimization method. This technique involved implementing a linear increment in feed temperature control to get the minimum permeate TDS concentration. Righton created a neural network model for RO groundwater and wastewater treatment.70 Furthermore, the ANN technique was employed to model two RO desalination techniques, resulting in accurate salt rejection and permeate flux predictions (Fig. 7).
The study conducted by Libotean et al.71 provides evidence that implementing an ANN model effectively predicts the operational efficiency of an RO plant. This prediction is made by considering the changes in salt passage and permeate flux. The study assessed the efficacy of three forecasting methods: the marching forecast, sequential forecast and the standard time-series correlation (STSC). A comparative analysis was conducted between the ML P model and SVR model. Using short-term memory intervals of up to 24 hours, the study demonstrated that it was possible to make reasonably accurate forecasts using the models.
Barello et al. conducted a modeling analysis of an RO desalination process to predict water permeability by considering membrane type, salinity, pressure, and contamination.72 To facilitate the training of the ANN, the researchers carried out an extensive study to evaluate the impact of various parameters, including the number of hidden layers, number of neurons, and choice of transfer function, on the selection of an ideal network configuration. The performance of a model utilizing a tan-sigmoid transfer function and the minimum number of hidden layers was improved. Examining the quantity of neurons in the layer exhibited oscillatory phenomena; nevertheless, it was observed that a concealed layer consisting of 20 neurons yields a minimal error. Furthermore, the ANN calculated water permeability was verified by comparing it with correlations reported in the scientific literature.
Farahbakhsh et al.73 applied ANN modeling to a RO process to investigate the antifouling properties of a membrane prepared by merging polypyrrole (PPy)-coated multiwalled carbon nanotubes (MWCNTs). For both unprocessed and oxidized MWCNTs-PPy membranes, two neural networks were constructed. The model demonstrated that the oxidized MWCNTs-PPy membrane generated higher water flux with a constant trend. Additionally, the aggregation of molecules on the membrane's surface was predicted to reduce salt rejection and water flux. Table 7 below shows the different features of ANN models developed for membrane processes. MLP with Levenberg Marquardt as a training algorithm shows the highest value of R2 which is 0.9964. The input parameters for this study were membrane type, salinity, time and operating pressure while the output was water permeability.
Process | Method | Input | Output | Activation | Training algorithm | Result | Ref. |
---|---|---|---|---|---|---|---|
Groundwater desalination plant | RBFN | — | Permeate TDS, permeate flow rate | — | — | Error = 1.73 | 74 |
RO desalination plant | ML P | Flow rate, pressure, pH, temperature | Product conductivity, product flux | tan-sigmoid | Gradient-descent algorithm | R 2 = 0.916 | 74 |
RO water desalination unit | ML P | Temperature, pressure, and salt concentration | Permeate rate | log-sigmoid | Levenberg Marquardt | R 2 = 0.988 | 68 |
Separation of CaCl2 and NaCO3 | ML P | Feed concentration, flow rates, pressure | Solute rejection percentage, permeate flux | log-sigmoid | Levenberg Marquardt | R 2 = 0.9889 | 70 |
Seawater desalination plant | ML P | Feed TDS, temperature, flow rate, TMP, time, | Flow rate, permeate flux | log-sigmoid | Back propagation algorithm | R 2 = 0.96 | 69 |
Brackish water desalination plant | ML P | Conductivity, flow rate, pressure, temperature, pH | Salt passage, permeate flux | tan-sigmoid | Levenberg Marquardt | Error = 0.9% | 71 |
RO desalination process | ML P | Membrane type, salinity, time, operating pressure, | Water permeability | tan-sigmoid | Levenberg Marquardt | R 2 = 0.9964 | 72 |
Small and large-scale brackish water desalination | RBFN ML P | Conductivity, temperature, pressure, pH | Permeate flow, TDS | tan-sigmoid/Gaussian kernel | Levenberg Marquard | R 2 = 0.9873 | 75 |
Brackish water desalination plant | — | TMP, time, temperature, concentration | Water flux | Levenberg Marquard | R 2 = 0.9947 | 73 | |
Bench-scale FO unit | ML P | FS viscosity, osmotic pressure difference, DS viscosity, DS temperature, FS temperature | Membrane flux | tan-sigmoid | Levenberg Marquard | R 2 = 0.9803 | 76 |
System type | Data driven method | Dataset size | Inputs | Outputs | Main remarks | Ref. |
---|---|---|---|---|---|---|
RO | ML PANN, RBFANN | — | Pressure, temperature, conductivity, pH | Permeate TDS, permeate flowrate | The data set is divided into two parts: 70% training and 30% testing | 75 |
When it is trained using LM algorithm, the performance was seen to be better | ||||||
RBF network is trained using OLS backpropagation model | ||||||
RO | ML PANN | 97–129 | Temperature, influent concentration, influent flow, recovery percentage | Effluent TDS | The behavior of RO membranes was predicted to be using computational models | 82 |
LM algorithm is used to train the neural network | ||||||
The neurons in the first and second hidden layers ranged from 4 to 6 and 8 to 13, respectively | ||||||
Multi-stage flash (MSF) | RBFANN | 380 | Salinity, boiling point temperature | Temperature elevation | The structure of the ANN is defined as a 2–12–1 configuration | 83 |
The data has been split into three partitions: 70% for training, 15% for validation, and 15% for testing | ||||||
The RBFANN model had superior prediction performance when compared to the ML PANN model, thermodynamic models, and empirical correlations | ||||||
RO | ANN | 9 | TDS inlet, inlet concentration, time | Permeate flow | The dataset was divided into three parts for training, validation, and testing, with a split ratio (SR) of 33.3% for each | 84 |
Four neurons made up the first hidden layer, while three neurons made up the second | ||||||
The artificial neural network (ANN) utilizing a fitness approximation network achieved the lowest mean squared error (LMSE) and R2 | ||||||
RO | ML PANN with GA | 70 | Inlet pressure, inlet flow rate, inlet temperature, inlet concentration | Response parameter of chlorophenol rejection | The data has been split into three partitions: the training set consisting of 68.57% of the data, the validation set consisting of 15.71% of the data, and the test set consisting of 15.71% of the data | 85 |
The model's performance was assessed by testing it with two distinct hidden layer configurations: one containing 2 neurons and the other containing 8 neurons | ||||||
RO | ANN | 63 | Feed pressure, salt concentration, temperature | Water permeate rate | The first and second hidden layers consist of 3, 5, 10, and 15 neurons respectively | 68 |
RO | ML PANN | 1806 | Raw water salinity, plant location, plant type, plant capacity | Capital cost of plant | The suggested model has the potential to be utilized to generate a rational approximation of the investment expenses associated with future RO plant developments | 86 |
MD | ANN | 252 | Feed salt concentration, vacuum pressure, feed flow rate, feed salt concentration | Permeate flux | The data has been split into three sets as follows: the training set, accounting for 66% of the data; the validation set encompasses 17% of the data, and the test set likewise comprises 17% of the data | 87 |
RO | SVR | 3990 | Flow rate, conductivity, pressure | Permeate conductivity, permeate flow rate, retentate conductivity, retentate flow rate | The data was divided into two sets, with 60% allocated for training purposes and 40% reserved for testing | 81 |
The construction of steady state and transient models for a RO facility was undertaken | ||||||
A proposed approach for time forecasting was introduced to demonstrate the temporal variation in conductivity during transient operation | ||||||
MD | ANN | 38 | Feed inlet temperature, vacuum pressure, feed inlet temperature, feed salt concentration, feed flow rate | Permeate flux | The design of the ANN under consideration follows a 4–3–1 configuration | 78 |
The data has been divided into three sets based on the following split ratio: 70% for training, 15% for validation, and 15% for testing | ||||||
The parametric research conducted | ||||||
using the constructed ANN model revealed that the permeate flux was most significantly influenced by vacuum pressure and feed input temperature | ||||||
RO | ANN | 436 | Dipole moment, molecular width, molecular length, molecular weight, salt rejection, pressure, surface membrane charge | Rejection rate | The data was split into three sets: the training set, representing 80% of the data; the validation and testing set, comprising 20% of the data; the BANN model demonstrated superior performance compared to both the single neural network and BA ML R techniques | 78 |
RO | ANN, RF, SVR | — | Feed conductivity, feed temperature, electrical power | Feed flow rate, pressure, permeate conductivity, permeate flow rate, water productivity | Random forest (RF) and support vector regression (SVR) models demonstrate superior predictive capabilities in relation artificial neural networks (ANN), with statistical significance at a 5% level | 88 |
RO | SVR, ANN | 10 min steps for 3 months | Feed pressure, feed conductivity, feed flow rate, feed temperature, permeate pressure, permeate flow rate, permeate conductivity | Salt passage, permeate flux | The data has been divided into three sets with the following split ratios: 40% for training, 10% for validation, and 50% for testing | 89 |
The findings demonstrated strong predictive validity in projecting short-term memory time intervals ranging from 8 to 24 hours for permeate flux and salt passage, with a forecasting horizon of up to 24 hours | ||||||
RO | ML PANN-PSO, DT, SVM | 150 | Temperature, feed pressure, conductivity | Permeate flow rate, permeate TDS | The architecture of the artificial neural network (ANN) is structured as a 4–3–1 configuration | 71 |
The hybrid ML PANN-PSO model demonstrated superior performance compared to the DT and SVM models | ||||||
The hybrid model demonstrated a reduction in uncertainty when applied to the simulated data |
Although artificial neural networks (ANNs) are extensively utilized, various ML models have also been employed to predict the efficiency of different desalination systems. Pascual et al.,81 for instance, used support vector regression (SVR) to forecast the efficiency of an RO plant. Their findings concluded that SVR exhibits the potential to predict crucial parameters like conductivity and flow rate for both retentate and permeate streams, achieving impressively low average absolute relative errors ranging from 0.70% to 2.46%.
In Table 8 various ML models, such as support vector machines (SVM), artificial neural networks (ANN), and random forest (RF), were studied for different membrane processes, including RO, multi-stage flash (MSF), and membrane distillation (MD). Different output parameters were analyzed, and these models were used to optimize the operational parameters of the respective processes.
System type | Data-driven method | Data set size | Inputs | Outputs | Main remarks | Ref. |
---|---|---|---|---|---|---|
HDH (solar seawater greenhouse) | ANN | 66 | Roof transparency | Water production rate | The structure of the ANN is specified as 4–9–1 | 91 |
One often employed approach for hyperparameter tuning is the trial-and-error method | ||||||
The dataset was divided into 3 subsets for training, validation, and testing purposes. The training set accounted for 70% of the data, while the validation set comprised 15% and the test set consisted of 5% | ||||||
The LM algorithm emerged as the most effective training method | ||||||
Length, width and height of front evaporator | ||||||
RO | RBFANN | 304 | Model parameters (fractional pore area, potential parameter, average pore length) | Pure solvent flux, separation factor, total flux | The architecture of the artificial neural network (ANN) is structured as a 9–20–1 configuration | 90 |
The data was divided into two sets, with 80% allocated for training purposes and 20% reserved for testing | ||||||
Membrane properties (friction constant between solvent, solute and membrane, pore radius) | ||||||
The performance of RBFANN was superior to that of the previous methods (mathematical and mechanistic-based models) | ||||||
Operational parameters (temperature, pressure) | ||||||
HDH (seawater greenhouse system) | SVR | 66 | Roof transparency, first evaporator height, greenhouse length and width | Water production | The dataset was divided into two subsets for the purpose of training and testing the model. The training set consisted of 70% of the data, while the remaining 30% was allocated for testing | 92 |
The constructed model was utilized to examine the impact of each input parameter on consumption of energy and water production | ||||||
HDH (seawater greenhouse system) | ML PANN | 30 | Roof transparency | Power consumption | The dataset was divided into two subsets: the training set, which comprised 70% of the data, and the test set, which comprised the remaining 30% | 93 |
Height, width and length of first evaporator | ||||||
The RVFL-AEO model exhibited superior performance in comparison to the RVFL model, suggesting that the inclusion of AEO plays a significant role in achieving optimal RVFL parameters that ultimately improve the accuracy of the model | ||||||
MD (VMD) | ANN | 36 | Membrane length, feed flow rate, feed inlet temperature | Specific heat energy consumption, permeate flux, heat consumption | The design of the artificial neural network (ANN) under consideration follows a certain configuration, denoted as 3–7–1 | 94 |
The data was divided into three sets with the following split ratios: 70% for training, 10% for validation, and 20% for testing | ||||||
The increase in feed flow rate and feed inlet temperature resulted in an increase in permeate flux. Moreover, as the length of the membrane increased, there was a decrease in the permeate flux |
Various ML models, such as artificial neural networks (ANN), support vector regression (SVR), RBFANN, and ML PANN, were studied for different membrane processes, including RO, HDH (solar seawater greenhouse), and membrane distillation (MD). Different output parameters were analyzed, and these models were used to optimize the design parameters of the respective processes.
Iranmanesh et al.90 conducted a comparative analysis of model parameters and operational variables, highlighting the critical importance of precise hyperparameter tuning techniques in machine learning approaches for evaluating the performance of humidification–dehumidification (HDH) systems. Their results highlighted that combining the random vector functional link (RVFL) model with an artificial ecosystem-based optimization algorithm significantly improved model accuracy. Furthermore, another research effort88 investigated the utilization of the SVR model in evaluating the efficiency of a seawater greenhouse system. This study unveiled the impressive predictive capacity of the SVR model in forecasting both freshwater production rates and energy consumption.
In the case of multi-effect distillation (MD) systems, one study focused on considering the membrane length in a vacuum membrane distillation (VMD) configuration, along with operational parameters like temperature and feed mass flow rate, as inputs for modeling an ANN model. This investigation unveiled the substantial influence of membrane length on both energy consumption and permeate flux, emphasizing the critical significance of including membrane length as an input parameter when employing data-driven (DD) methods for model development.
System | Data-driven method | Data set size | Input | Output | Main remarks | Ref. |
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RO | ANN | 1197 | Temperature, pressure, conductivity | Flow, pressure | The ANN architecture employed for flow prediction is structured as follows: 3 input nodes, 38 hidden nodes in the 1st layer, 4 hidden nodes in the 2nd layer, and 1 output node. Additionally, another ANN architecture uses 3 input nodes, 69 hidden nodes in the 1st layer, 13 in the 2nd layer, and 1 in the output node | 96 |
The ANN architecture employed for pressure prediction is specified as 3![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
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ANNs were employed to control the variable functioning of an RO plant effectively | ||||||
ANNs effectively managed the unpredictable and diverse range of electrical power resources | ||||||
ANN models created set points for operating pressure and feed flow | ||||||
RO | RNN (LSTM) | 1871 | Feed pressure | Permeate concentration, permeate flow rate | The LSTM model was employed as a robust predictive controller model | 99 |
RO | DRL | 8760 | Electricity price, water demand, PV output | Pollution cost, cost of battery storage system, operating cost | The data was divided into two sets, with 90% allocated for training and 10% reserved for testing | 97 |
The study focuses on the optimal control objective of managing energy in a hybrid energy system, considering several targets and constraints | ||||||
The information entropy theory is employed to determine the weight factor that facilitates the assessment of the trade-off among several aims. According to the paper, a proficiently trained agent can offer an enhanced control policy, resulting in a potential cost reduction of up to 14.17% compared to alternative approaches | ||||||
MD (solar PGMD) | ANN | 540 | Feed flow rate | Distillate flow rate | The artificial neural network (ANN) architecture is structured as a 1–5–1 configuration | 98 |
One often employed approach for hyper-parameter tuning involves trial and error | ||||||
The dataset was divided into 3 subsets for training and evaluation. The training set comprised 80% of the data, while the validation set accounted for 15%, and the remaining 5% was allocated to the test set | ||||||
A dynamic artificial neural network (ANN) control system was designed to optimize the distillate flow rate | ||||||
Implementing the adaptive control system resulted in a 17.2% increase in daily productivity | ||||||
MSF | ANN | 4500 | Set point, blow down flow rate, mass flow rate of the heater vapor | Brine salinity, level of last stage, top brine temperature | This study's artificial neural network (ANN) architecture follows a 3–12–1 configuration. The hyper-parameter tuning approach employed was trial and error. 75% of the data is allocated to the training set, and the remaining 25% is designated for the test set. Comprising 25% of the data | 100 |
Three controllers utilizing an ANN model were evaluated to regulate the top brine temperature, salinity, and the level of the last stage | ||||||
The findings indicate that implementing a control mechanism in MSF desalination systems is feasible | ||||||
RO | GA AND ANN | 474 | Flow rate, conductivity, time | Permeate conductivity, permeate flow | The data was partitioned into three distinct sets: the training set, comprising 60% of the data; the validation set, consisting of 20% of the data; and the test set, which likewise constituted 20% of the data | 101 |
The investigation focused on examining long-term forecasting and control strategies for the RO system for 5000 hours of operation | ||||||
By employing control measures, conductivity permeability can be declined in both the model and experimental prediction phases |
Various ML models, such as ANN, RNN (LSTM), and DRL, were studied for different membrane processes, including RO, MD (solar PGMD) and MSF. Different output parameters were analyzed, and these models were used to optimize the process control of the respective processes.
However, it is evident from Table 10 that there is a notable gap in the literature regarding the use of DD control methods to enhance performance and reduce costs in renewable-based desalination systems, although solar and wind energy sources exhibit intermittent characteristics. For instance, Cabrera et al.96 showcased the remarkable capabilities of ANN models in effectively regulating a wind-powered RO desalination facility with intermittent operations. In another study,95 the implementation of a reinforcement learning model resulted in a substantial 14% cost reduction in a RO desalination system powered by renewable energy. Similarly, Gandhi et al.97 reported successful outcomes using the sequential extreme learning method for improving performance and reducing costs in a solar still (SS) desalination system. Furthermore, Porrazzo et al.98 achieved a notable approximately 17% increase in the productivity of daily freshwater of the pressure retarded osmosis (PRO) desalination system by employing adaptive control of the feed mass flow rate with an ANN model.
System type | Data driven model | Dataset size | Input | Output | Main remarks | Ref. |
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RO | CNN | 13![]() |
Image | Flux decline, fouling growth | The present study explores various methodologies employed in conjunction with the convolutional neural network (CNN) model to detect and analyze fouling phenomena | 102 |
Regarding performance, CNN exhibited superior results compared to mathematical approaches | ||||||
RO | ANN | 6 years process data base | Water quality parameters (total ammonia and chlorine, turbidity), hydraulic parameters (pressure and flow rate) | New calculated pressure index | A total of 59 hydraulic and water quality measures were employed to assess and quantify the underlying factors contributing to membrane fouling within an RO system | 103 |
For the initial validation of the generated model, a substantial dataset was utilized | ||||||
The identification of the most accurate indicators of fouling was achieved by the utilization of ANN. The study demonstrated the potential application of the model in mitigating fouling rates | ||||||
MD (VMD) | ANN | 149 | Feed side temperature, time, feed flow rate, pressure | Permeate flux | The architecture of the ANN is specified as a 5–10–1 configuration | 104 |
75% of the data used for training; 15% for the validation and 15% for testing | ||||||
The study focused on the impact of membrane fouling operational parameters | ||||||
The ANN model that was constructed was integrated with the GA optimization method to identify the optimal values for the operational parameters | ||||||
Membrane fouling was seen to occur more prominently under elevated feed temperatures and reduced vacuum pressures. Moreover, elevated feed solute concentrations were found to be associated with increased membrane fouling | ||||||
MD | ANN | 229 | Raw water turbidity, permeate flow rate, operating time | Transmembrane pressure drops | The architecture of the ANN is specified as 3–5–1 | 105 |
One often used approach for hyper-parameter tuning is the trail-error method | ||||||
A comparative analysis was conducted to evaluate the predictive capabilities of mathematical models and artificial neural network (ANN) models in the context of membrane fouling investigation | ||||||
The ANN demonstrated significant superiority in predicting the total market performance (TMP) compared to the use of blocking rules across all trial periods | ||||||
ED | ANN | 22 | Salt concentration, current, crossflow velocity | Stack resistance | According to the report, this model has the capability to accurately forecast the fouling rate, even when provided with a restricted amount of experimental data | 106 |
The study demonstrated that neural differential equations exhibit strong extrapolation capabilities when applied to simulate colloidal fouling in electrodialysis | ||||||
The Sobol sensitivity analysis reveals that the crossflow velocity has a direct, linear effect of 41%, whereas the current and salt concentration have effects of 18.6% and 13.1% respectively |
Various ML models, such as ANN and CNN, were studied for different membrane processes, including RO, MD (VDM), MD and ED. Different output parameters were analyzed, and these models were used to optimize the maintenance of the respective processes.
Fouling mechanisms are generally characterized by the undesirable accumulation of materials such as solid particles in the biological substances, ions, and feed stream both on the surface of the membrane and within its pores. This gradual accumulation leads to a decline in permeate flux over time, resulting in higher expenses for producing purified water.
Traditional mechanistic modeling methods have encountered challenges in accurately forecasting fouling mechanisms in various membrane-based desalination technologies. These challenges primarily stem from the dynamic nature of fouling phenomena, the intricacies inherent in mathematical modeling, and the necessity of making simplified assumptions during model development. As a result, researchers have increasingly shown interest in DD approaches as a viable alternative to providing more precise predictions of fouling mechanisms.
Based on the analysis, it can be concluded that within the field of ML techniques, ANN and RSM emerged as the most often utilized methods. Furthermore, the findings presented in several studies demonstrate the effectiveness of alternative ML techniques, including support vector machines (SVM), adaptive neuro-fuzzy inference systems (ANFIS), and random forest (RF), in accurately analyzing desalination systems. These results demonstrate the need for further research in exploring additional traditional ML methods for analyzing various desalination technologies.
Despite the present advancements in this domain, additional comprehensive research and investigations are required to enhance desalination efficacy and propel the commercialization of this technology. The choice of the desalination method should rely on the characteristics and quality of the produced water. Furthermore, it is imperative that the studies prioritize the examination of the financial aspect and the potential for maintaining the effectiveness of the treatment to ensure its viability for industrial implementation.
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