Lead Removal by Reverse Osmosis: Seeking Sustainability in the Operation of Advanced Technologies: A Preliminary Study

Abstract

Nowadays, stricter control and rigorous landfill standards are being promoted in industries that produce liquid discharges into the environment. The development of innovative and sustainable technologies to remove lead from water is of great importance in all aspects, with safe recycling practices, especially with high lead concentrations, such as in mining activities. The experiment was conducted at a reverse osmosis (RO) pilot plant, operated at low impact pressures and designed to optimize energy savings without compromising separation efficiency. By reducing energy consumption, the process not only lowers operational costs but also minimizes the environmental impact associated with high energy consumption. The results show that RO operated at low pressures successfully removed 99.75% of lead at a pressure of 10 bar and a flux of 67.44 L/m²·h, demonstrating a practical and sustainable solution for lead removal at pressures of 5, 7.5, and 10 bar, which are considered low pressures since they are below 1.0 MPa. In addition to its high removal efficiency, the process offers significant advantages in terms of energy efficiency and a reduced carbon footprint. Enhancing the efficiency of this technology is crucial, not only to decrease operational costs but also to reduce environmental impact.

1. Introduction

The importance of water as a vital resource is undeniable. Population growth and anthropogenic activities contribute to water pollution. This increases the need to find economical and safe methods for its treatment to give it some other use or for its return to the environment without generating negative impacts on local inhabitants [1]. It is also essential to reduce energy consumption and enhance sustainability in pollutant removal technologies, as this contributes to the achievement of several Sustainable Development Goals (SDGs). Particularly, Goal 6: Clean Water and Sanitation, specifically Target 6.3, which aims to improve water quality by reducing pollution, eliminating dumping, and minimizing the release of hazardous chemicals and materials, as well as halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally. It also supports Goal 7: Affordable and Clean Energy, particularly Target 7.3, which seeks to double the global rate of improvement in energy efficiency. Additionally, it aligns with Goal 12: Responsible Consumption and Production, especially Target 12.4, which focuses on the environmentally sound management of chemicals and all wastes throughout their life cycle, according to agreed international frameworks, to significantly reduce their release into the air, water, and soil, thereby minimizing their adverse effects on human health and the environment [2].

Among the most prevalent contaminants in water are coliform bacteria, organic matter, suspended solids, fertilizers, pesticides, and, significantly, heavy metals [3]. Mining can significantly impact water quality and aquatic ecosystems through several mechanisms, with acid mine drainage (AMD) being one of the most well-known and harmful. This acid leaches heavy metals from surrounding rocks, creating a toxic, acidic runoff that can enter nearby rivers, lakes, and groundwater. AMD severely lowers pH levels in water, harming aquatic life and contaminating drinking water sources [4]. Lead in water has led to worrying situations worldwide, affecting public health. In 2014, the city of Flint, Michigan, experienced a crisis when changing the source of its water supply, and the Flint River water began to corrode lead pipes, releasing high levels of the mineral in water and affecting the health of thousands of residents, especially children [5]. Lead poisoning is a major global health concern, particularly affecting children. Lead exposure has resulted in the poisoning of one-third of children globally, with the primary sources being the use of lead pipes and activities related to mining [6]. According to a 2020 study published by the United Nations Children’s Fund (UNICEF), an estimated 800 million children worldwide have blood lead levels at or above five micrograms per deciliter (µg/dL). This report was the first to comprehensively assess the global scale of childhood lead exposure [7]. In

Table 1. World refined lead supply and usage 2020–2025 (×10³ tonnes).

Year	Month	Mine Production	Metal Production	Metal Usage
2020	January–December	4437	12,545	12,392
2021	January–December	4552	13,039	12,995
2022	January–December	4433	12,829	13,006
2023	January–December	4459	13,271	13,104
2024	January–December	4511	13,029	13,000
2024	January–March	1035	3236	3171
2025	January–March	1028	3258	3242
2025	January	352.1	1068.3	1063.0
2025	February	308.2	1058.5	1040.8
2025	March	367.3	1131.6	1138.3

, data on lead global production and usage are shown [8].

Lead represents one of the main minerals produced in Bolivia, giving rise to considerable lead emissions into the environmental matrices in areas close to mining operations, especially near roads, fruit orchards, and industrial zones [9,10]. This phenomenon affects the flora, fauna, and inhabitants who reside near production areas or lead deposits [11]. Lead can be absorbed into soil or contaminate water, affecting vegetative species and other living beings [12]. Lead bioaccumulation in the soil, water, and air produces an increase in environmental pollution rates [13]. There is an alarming situation regarding lead in different bodies of water, reaching a wide presence like other heavy metals [14]. The production volumes of lead extracted in Bolivia since 2010 are shown in

Table 2. Lead production in Bolivia in metric tons.

Period	Lead
2010	72,803.32
2011	100,051.09
2012	81,095.06
2013	82,135.56
2014	76,005.85
2015	75,272.70
2016	89,510.02
2017	111,566.08
2018	112,047.20
2019	88,341.69
2020	64,619.23
2021	93,246.38
2022 p	90,257.68
2023 p	102,958.88
2024 p	112,808.84
2025 p	25,957.96

^p preliminary.

[15].

The exploitation of lead in San Cristóbal mine (one of the largest mine facilities in Bolivia) could last up to 147 years [16]. According to the International Lead and Zinc Study Group (ILZSG), global lead production continues to remain elevated, highlighting the ongoing demand for and extraction of lead worldwide [8]. In Bolivia, this trend is likely to continue, with lead mining operations potentially expanding, which in turn could lead to further contamination of local water sources. This persistent production and extraction of lead contribute to both global pollution and localized environmental challenges, particularly in water quality, exacerbating the risk of lead contamination for surrounding communities.

Given the problems caused by heavy metals, various technologies have been developed for their elimination or inactivation. Some removal methods are membrane filtration, ion exchange, adsorption by activated carbon, and coagulation–flocculation, among others [17].

Research on membrane filtration technology is constantly growing and has yielded positive results [18,19,20]. The study by Vera et al. involved using osmosis membranes to remove Pb and Cd from mining wastewater. The study achieved an osmosis rejection of 98.77% for Pb and 98.30% for Cd [19]. Another successful experience was recorded in the removal of metal ions such as lead, achieving removal percentages of 98.9% and 98.7% using RO and nanofiltration (NF), respectively [19]. Reverse osmosis membranes have demonstrated high efficiency in removing not only lead but also other toxic metals, reinforcing their potential as a versatile and reliable water treatment technology. In the case of arsenic, removal rates ranging from 90% to 99% have been achieved, while tests involving hexavalent chromium have shown removal efficiencies as high as 99.9% [21]. In addition, Villena Martines et al. reached a rejection rate greater than 99% using heavy metals such as arsenic and lead [22]. On the other hand, low-pressure reverse osmosis studies were addressed, showing effective results on municipal wastewater treatment [23]. The use of low pressures in reverse osmosis obtained percentages of rejection greater than 90% in anionic pollutants from wastewater [24], showing that low pressures confer a reduction in environmental impact while minimizing energy consumption [25]. The objective of this research was to optimize the working pressure range for RO, using a pilot plant to remove lead and seeking to maintain high metal removal with more sustainable energy costs. With the demand for the removal of heavy metals, such as lead from water, the need arises to obtain high efficiencies with existing technologies and at the same time a low energy cost, aiming at sustainability.

2. Materials and Methods

To ensure a reliable and comprehensive assessment of lead removal through reverse osmosis, a full factorial experimental design was developed using Minitab 19 software, followed by preliminary tests in the pilot plant, synthetic water preparation, systematic experimentation under varying conditions, and statistical evaluation of the results. The methodological sequence used to develop this research is detailed in Figure 1.

2.1. Experiment Preparation

2.1.1. Experiment Design Development

A general full factorial design was used in planning the experiments. This experimental design was generated to obtain statistically robust results that cover the variables studied. The statistical program used, MiniTab 19, developed by LLC, State College, PA, USA [26], is a user-friendly interface with powerful statistical tools and facilitates data manipulation in this type of design. In Figure 2, the interface for creating factorial designs within the program is shown.

The experimental design incorporated two input variables: pressure and average inlet flow. Response variables included analytical mean flux, conductivity rejection, and lead rejection rate. The conductivity rejection acted as a guiding parameter that is similar to the percentage of conductivity removal of lead ions from a contaminated solution [27]. On the other hand, flux is considered a crucial parameter in understanding the production of treated water [28,29,30]. The lead rejection rate indicates the amount of lead removed from the water with respect to an initial amount [31]. These indicators allowed the evaluation of removal technology, seeking sustainable conditions, since, according to previous experiences, less energy is consumed with low pressures of less than 1 MPa (10 bar) [30]. Industrial conditions of pressure commonly range from 10 bar to 70 bar, which means that the present study considers pressures under these parameters [32].

2.1.2. Initial Tests in the RO Pilot Plant

Preliminary tests were carried out prior to experimentation with the RO pilot plant. Thanks to this, it was possible to determine the initial conditions provided by the membrane without coming into contact with the metal under study. These tests consisted of executing the established runs with the parameters used according to another study carried out with the same membrane, that is, at a pressure of 10 bar and a frequency of 20 Hz. The plant was operated under these conditions for a period of 20 min, during which the stability of the permeate and concentrate flow rate data was monitored. Temperature correction is necessary to consider the dependence of permeability on temperature [22], and results are not affected by the increase in temperature that occurs due to the heating of the water pump within a closed system in which water recirculates. This correction involves the Arrhenius equation:

ln(Ap) = ln(A) − Ea/R · 1/T

(1)

where

• Ap = apparent permeability [L/(m²·h·bar)];
• A = pre-exponential factor;
• Ea = activation energy;
• R = ideal gas constant;
• T = temperature [K].

Flux is the permeate flow rate, Qp, obtained at the membrane outlet, divided by the membrane surface [33]:

J = Qp/S

(2)

where

• J = flux [L/(m²·h)];
• Qp = permeate flow rate [L/h];
• S = surface area [m²].

Permeability, Ap, is given by Equation (3) [34,35]:

Ap = J/P

(3)

where

• Ap = Apparent permeability [L/(m²·h·bar)]
• J = Flux [L/(m²·h)]
• P = Pressure [bar]

Subtracting the final state, 2, from the initial state, 1, using Equation (1) and substituting Equations (2) and (3) into it, the following is obtained:

J₂/S₂ = J₁/S₁ · e^(−Ea/R · (1/T₂ − 1/T₁))

(4)

By having the same membrane area, this data is eliminated, and the term Ea/R is a constant, which will be called K. Finally, the equation is

J₂ = J₁ · e^(−K · (1/(273 + t) − (1/293))

(5)

where

• J₂ = flux corrected with respect to temperature [L/(m²·h)];
• J₁ = flux without correction [L/(m²·h)];
• K = Ea/R = 3573.2 = correlation constant with respect to different temperatures, obtained for the plant’s working conditions.
• t = Temperature [°C]

2.1.3. Preparation of Synthetic Waters

A total of 40 L (V_d) of lead solution with a concentration of 1 ppm or mg/L(C_d) was prepared. The synthetic water was prepared by adding a lead standard solution from Inorganic^TM Ventures with a concentration of 1000 ug/mL (C_s) in distilled water. The lead standard solution is composed of a 0.5% v/v in a medium of HNO₃.

This procedure was carried out to establish an initial concentration that exceeded by 20 times the limits allowed by various organizations, as established by Bolivian regulations (0.05 mg/L) from the Regulation on Water Pollution—RMCH [36]. This lead limit is aligned to the limit established by the European Union (EU) [37]. The purpose of this choice was to evaluate the effectiveness of lead removal until reaching the permissible limits.

A volume of 40 mL of the standard solution was used to prepare 40 L of synthetic water with a final lead concentration of 1 mg/L (1 ppm). Serial dilutions were performed to calibrate the multiparameter equipment and observe the behavior of conductivity and pH at different concentrations. These parameters give a method to measure the quantity of lead ions present in the water. For the measurement, the Hach brand multiparameter model HQ40d was used.

2.2. Experimentation

The experimentation consisted of varying the parameters of pressure, average inlet flow and average analytical flux, measured through sensors. The opening of the valves and frequency were varied according to the limits to achieve each of the desired experimental scenarios.

2.2.1. Reverse Osmosis Pilot Plant Operation

The pilot plant operation was carried out with 40 L of synthetic water with lead solution at 1 mg/L. Figure 3 presents the scheme of the RO pilot plant.

The pilot plant, based on a cross-flow system, is shown in Figure 3. It has a Keensen-brand aromatic polyamide semipermeable membrane, Changsha, China, model ULP-2540, and Wave Cyber 2540-300-1 casing, Shangái, China, presenting a contact area of 2.5 m². The movement of water within the plant is driven by a multistage centrifugal/electric LEO pump, model 2ACM150H, Wenling, Zhejiang, China with a power of 2HP and 40 bar of pressure, with its filter regulated through a pressure valve. In addition, it has flow sensors at the entrance and exit of the membrane in [L/min], an integrated circuit for turning the plant on and off, and a frequency regulator on the control panel. Additional characteristics are shown in

Table 3. Characteristics of membrane ULP-2540 [38].

Specification	Parameter
Active Membrane Area ft2 (m2)	27 (2.5)
Max. Working Pressure	600 psi (4.14 MPa)
Max. FeedWater Temperature	45 °C
pH Range of Feed Water During Continuous Operation	3–10
Permeate rate	2.84 m3/d
Minimum concentrate ratio	8%
Max. Pressure Drop of Single Membrane Element	15 psi (0.1 Mpa)

.

The pressure and flow levels were adjusted according to the operating parameters of the reverse osmosis pilot plant and the maximum frequency levels in Bolivia (50 Hz) [39]. Pressure levels were categorized as low (5 bar), medium (7.5 bar), and high (10 bar), taking into account that these pressures are considered low pressures when it is possible to reduce energy consumption [22,30]. Regarding the flow parameters, an average inlet flow was established and divided into two levels: low (290–320 L/min) and high (350–380 L/min), considering that 40 L is the minimum capacity of the plant.

2.2.2. Calculation of Response Parameters

The percentage of conductivity rejection and lead rejection rate were calculated. The conductivity rejection (R%) of the metal ion and lead rejection rate (C%) are determined by replacing the values into Equation (6) [27]:

V% = (V_i − V_f)/V_i · 100%

(6)

where

• V_i = initial value;
• V_f = final value.

With a simple mass balance of the system, Equation (7) is obtained in terms of concentrate (C₁) and permeate (P₁).

C₁ = F₁ − P₁

(7)

Flow data was taken every 6 s, through the sensors at the inlet (F₁) and outlet of the plant module (P₁ + C₁). On the other hand, a sample of the feed was taken at the beginning of the tests and permeated at both 10 min and 20 min to take the in situ parameters of conductivity and pH, using a Hach-brand multiparameter, model HQ40d, while lead concentrations were measured through a Perkin Elmer-brand atomic absorption spectrophotometer, model AAnalyst 200, which allows a single measurement of the UV lamp.

2.3. Statistical Evaluation for the Results

The data was entered into Minitab 19 for statistical analysis. As a result, a parametric ANOVA (Analysis of Variance) table was generated to determine the significance of the control variables, pressure and flow rate, on the response variables, analytical flux and conductivity rejection. The ANOVA obtained was normally distributed thanks to the stability of the process and the results measured. In addition to the ANOVA output, Minitab provided main effects plots and interaction graphs, which allowed for a deeper understanding of how each factor independently and jointly influenced the system’s performance. These visual tools made it possible to observe the behavior of the response variables across different levels of pressure and flow, revealing not only the individual impact of each parameter but also how their interaction affects the overall efficiency of lead removal. This analysis is essential for identifying optimal operational conditions and supports the development of more energy efficient and sustainable treatment strategies.

In Bolivia, there are companies that offer energy consumption prices depending on the quantity of kWh consumed. For this study, the prices given by the DELAPAZ company refer to 0.969 BOB (0.14 USD) per kWh consumed [40].

2.4. Calculation of Costs

To estimate the energy cost associated with the operation of the reverse osmosis pilot plant, the total electrical consumption during the experimental runs was considered. Calculations were taken into account along with the operating conditions and electricity tariff.

The energy consumed by the pilot plant is calculated using a general formula, shown in Equation (8):

E = Qp·P·t/η

(8)

where

• E = energy consumed [kWh];
• Qp = permeate flow rate [m³/h];
• P = operating pressure [bar];
• T = operating time [s];
• η = pump efficiency.

This analysis allows for quantifying energy consumed per volume of treated water and evaluating the economic feasibility of the process [41].

3. Results

3.1. Initial Test Results

After operating the membrane system for 20 min (1200 s) at a pressure of 10 bar and a frequency of 20 Hz, the permeate flow rate was obtained. The distribution of the data is presented in Figure 4.

As seen in Figure 4, this provides an indicator to take into account membrane fouling, playing the role of a control mechanism to clean the membrane after its use. So, it would be used after prolonged use of the pilot plant, meanwhile it did not show significant variation.

A temperature correction was carried out during the preliminary tests. This correction took into account the minimum temperature recorded in the laboratory, from 15.5 °C to 26.1 °C, that was reached during the run.

Regarding temperature correction, once Equations (1)–(3) were applied to the recorded temperatures, pressures, and flux, the results were graphed with a linear trend. The obtained data is presented in Figure 5.

3.2. Experimentation Results

The following section presents an analysis of the experimental data obtained from the reverse osmosis pilot plant trials, designed to assess the efficiency of lead removal under different operational scenarios. Key response variables such as flux, conductivity rejection, and lead removal rate were examined to understand the influence of pressure and flow conditions. The results obtained for removing lead by filtration with membrane RO are presented in

Table 4. Summary table of lead removal experimentation by reverse osmosis.

Test Number	Control Variables		Response Variables
	Pressure P [bar]	Average Inlet Flow [L/h]	Average Flux (Analytical) [L/m2 h]	Conductivity Rejection [R%]	Lead Rejection Rate [C%]
1	5 (low)	290–320 (low)	40.61	92.98	99.02%
2	5 (low)	350–380 (high)	40.29	94.04	99.12%
3	7.5 (medium)	290–320 (low)	53.38	94.11	99.45%
4	7.5 (medium)	350–380 (high)	51.89	95.76	99.53%
5	10 (high)	290–320 (low)	64.62	96.13	99.68%
6	10 (high)	350–380 (high)	67.44	95.66	99.75%

.

Table 4 shows that the conductivity rejection and lead rejection rates are consistently high in all tests, exceeding 99% and 92.98%, respectively. Conductivity serves as a secondary measurement parameter to support removal percentages due to the conductivity of the solution including not only lead ions, but also nitrate ions.

3.3. Statistical Evaluation of the Results

Once the results were entered into the Minitab 19 statistical program, an ANOVA table was extracted for the proposed experimental design, which is presented in

Table 5. ANOVA table for RO factors.

	Source of Variation	DF	Sum of Squares	Mean Squares	F-Ratio	p-Value
Analytical mean flux	Pressure	2	654.974	327.487	132.19	0.008
	Flow rate	1	0.175	0.175	0.07	0.815
	Error	2	4.955	2.477
	Total	5	660.104
% Conductivity rejection	Pressure	2	5.7556	2.8778	4.82	0.172
	Flow rate	1	0.8450	0.8450	1.41	0.356
	Error	2	1.1944	0.5972
	Total	5	7.7950

.

The data obtained from Table 5 indicates that pressure has a significant impact on analytical mean flux, since its p-value is less than 0.05. On the other hand, the variation in flow does not present a significant effect, since its p-value is greater than 0.05. Furthermore, according to the analysis, neither pressure nor flow rate shows significance in the rejection of conductivity.

The effects of analytical mean flux concerning pressure and flow are presented in Figure 6.

As seen in Figure 6, the variation in average analytical flux depending on pressure is notable, while flow does not generate much apparent change in the flux.

In Figure 7, the variation in pressure and flow does not generate a wide range of changes in mean conductivity rejection. Despite this, in all cases, a rejection rate exceeding 90% was recorded.

According to Figure 8, (a) an increase in average analytical mean flux is observed as both pressure and flow rate increase for both flow levels. This results in greater flux under high-pressure and -flow conditions; (b) at lower levels of flow and pressure, a slight increase in conductivity rejection is achieved. However, this trend is reversed by increasing both flow and pressure, thus reaching maximum rejection in the latter scenario.

During the testing of the reverse osmosis pilot system, both advantages and disadvantages were observed. While the cost is a drawback, it can be reduced by regulating the pressure, which lowers the environmental impact, reduces energy consumption, and enhances sustainability. Conducting this experiment with RO pilot plants is essential to replicate real operational conditions, allowing accurate and sustainable data on process behavior and scaling.

3.4. Results of Calculation of Costs

The present study measured an efficiency of 0.8 due to the pump of the pilot plant being a new machine without any problems during its operation [41]. Each run’s duration was 20 min, which is 0.333 h. The results obtained are shown in

Table 6. Energy and costs consumed during the study.

Essay	Pressure [bar]	Permeate Flow [m3/h]	Energy [kWh]	Cost Per Month [$US]
1	5	0.06702	0.13963	0.99736
2	5	0.07155	0.14906	1.06471
3	7.5	0.07942	0.16546	1.18186
4	7.5	0.08173	0.17027	1.21621
5	10	0.08773	0.18277	1.30555
6	10	0.09198	0.19162	1.36871

.

Table 6 presents the results obtained after substituting permeate flow, pressure, and time data into Equation (8). Once the energy results were obtained, we used the electricity tariff of the DELAPAZ company from Bolivia to calculate the costs of operation for each essay.

4. Discussions

4.1. Discussions of Results

Membrane filtration technology, particularly in the context of RO systems, offers several significant advantages. These systems are compact, requiring minimal operating space, and are known for their ease of operation and quick processing capabilities [18,42]. They can also be integrated into both parallel and series configurations to enhance performance, providing flexibility in various applications. Additionally, membrane filtration systems boast an impressive lifespan of 15 to 20 years, with stable efficiency over extended periods. When operated under controlled conditions, these systems can also deliver notable energy savings [23,30]. However, this technology does come with some challenges. The initial cost of equipment and installation is relatively high, though the prices of key components have been decreasing [25,43]. Furthermore, certain compounds may accumulate on the membrane surface, leading to fouling and reduced performance [23,30]. To mitigate this, pretreatment of the feedwater or ensuring the water quality is sufficient is essential to prevent premature clogging and damage to the membrane [17,23]. Notably, the lack of an energy recovery device in some original designs limits the potential for optimizing energy usage [42].

On the one hand, this study shows that energy savings can be achieved even when operating at the maximum pressure selected for the experiment (10 bar). Therefore, operating costs can be reduced, along the same lines as indicated in [30]. Furthermore, high Pb removal rates were achieved under unconventional pressure conditions below 10 bar, as was also seen in the study by Villena et al., where similar removal percentages were achieved [22]. This aspect makes the RO process operated under low-pressure conditions while maintaining separation efficiency a more sustainable and environmentally friendly option. On the other hand, the solute transport permeability adhered to an Arrhenius type correlation, as pointed out in [19,44]. This made it possible to examine how temperature influences the performance of the reverse osmosis process. According to [43], there is a possibility of decreasing the total energy consumption in a range of 47% to 53.8% when the variables are controlled, compared to the calculation for the original design that lacks an energy recovery device.

As mentioned in [45], conducting experiments with reverse osmosis pilot plants becomes essential to replicate operating conditions that resemble reality. This approach is crucial to obtain accurate and sustainable information to scale the process behavior. In general, the main disadvantage of RO is the cost of both implementation and operation. Still, this work presents preliminary studies demonstrating that it is possible to remove lead from synthetic waters operating under unconventional pressure conditions, which translates into optimizing the RO operating cost. This is reinforced by the study by Leon et al., where it was presented that the optimization of RO operation can reduce the cost per cubic meter of produced water and thus reduce the carbon footprint of the process [45].

4.2. Energetic and Circular Economy Reflections

The present study shows high rejection rates for Pb obtained at low operating pressures, which means energy savings. The above is aligned with a study that used RO membranes at different sizes, which showed an improvement in the energy efficiency of the system even at low pressures, saving operation costs and reducing the carbon and ecological footprints in the Canary Islands [44]. Energy savings shown in this study are a good reference based on the comparison with other conventional treatments of surface water. In general, RO systems consume 0.2–0.4 kWh, and the average flux produced is about 25 L/m²·h [25]. On the other hand, the present study ranged from 0.13963 to 0.19163 kWh (Table 6). Concerning average flux, the study turns into a competitive stage, producing from 40.61 to 67.44 L/m²·h.

This is an important step for developing countries such as Bolivia because it includes economic savings in the water treatment. At the same time, the use of less energy implies that the process is eco-efficient and sustainable, which coincides with the research [22,43]. The present work as a preliminary study opens the doors to future investigations where greater scalability can be applied at the industrial level and with real water conditions.

In countries like Bolivia, where mining is one of the main economic activities, it is necessary that the metals removed during the water purification process return to the productive chain. For this purpose, the recovery of Pb through other methods of extraction, such as chemical precipitation or electrodialysis, will be a good opportunity to take advantage of trace amounts of Pb trapped in the reverse osmosis process [46]. However, a deeper investigation into metal recovery methods within the mining sector is necessary to accurately evaluate the actual recovery rates achieved and to identify the operational and technical limitations that may hinder the efficiency and sustainability of these processes.

5. Conclusions

The negative impact of lead on the environment and public health is of great concern. Like other heavy metals, lead is mined in large quantities and released into the environment, often without undergoing any treatment process. Illegal mining emerges as a significant source of lead contamination of water resources. There are active technologies that achieve high removal rates, close to 100%, but high operating costs limit their application. This research offers a vision of the Bolivian context and the danger that the world faces due to the presence of lead in water.

Experimentation through RO membrane filtration has yielded promising results. The conductivity rejection percentages in membrane tests ranged between 92.98% and 96.13%. Regarding the lead rejection rate concerning the lead concentration, significant values were obtained, all around 100%, with a maximum rejection rate of lead of 99.75%.

The use of technology such as membrane filtration contemplates various potential applications in different industrial sectors. Significant advances and improvements in this technology allow for the regulation of more environmentally friendly working conditions without compromising removal efficiency. During experimentation, it was highlighted that controlling conditions on a pilot scale contributes to reductions in operational failures and continuous monitoring of removal performance. The process reduced energy consumption by 30% compared to conventional operation conditions. At the same time, the average flux produced almost tripled with respect to that when normal conditions for RO are used.

RO emerges as a quick solution to address the contamination of water bodies, which demands immediate action. RO is a great precedent to begin decontaminating mining liabilities in different regions of the world. Although this article focuses on lead removal, the use of membranes can cover a large number of contaminants present in bodies of water. The results obtained are a contribution to the SGDs, specifically Goal 6 Target 6.3, because the present study address future research to minimize and remove hazardous chemicals such as lead in untreated wastewater from mining, Goal 7 Target 7.3, because reducing energy costs involves increasing energy efficiency, and Goal 12 Target 12.4, on the management of chemicals—in this case, lead—to significantly reduce their release into water and minimize their negative impacts on human health and the environment.

Although our study with a single heavy metal, lead, had good results, the proposal for optimization and reduction in energy costs must continue to be evaluated using in situ contaminated water. Future research should focus on the application of conditions found for the removal of other metals separately, as well as on sets of heavy metals present in reality. It must be evaluated whether, under similar conditions or other conditions, there are high removals with low pressures. This will allow a set of sustainable parameters to be evaluated using reverse osmosis membranes in conditions closer to reality.