State of the Art of Desalination in Mexico

Abstract

This research paper presents a review of the state of the art of desalination in Mexico, with the aim of clarifying the main challenges and opportunity areas for desalination as the main solution to overcome water stress. First, the current situation and forecasts on the availability of water resources in Mexico are described, followed by the main economic, social, and legislative issues of desalination. Mexico’s installed capacity for the different desalination technologies and their evolution in recent years was investigated, followed by a comparison with global trends. The current state of research and development in desalination technologies carried out by Mexican institutions was also studied. The results show that membrane technology plants account for 88.85%, while thermal technology plants account for the remaining 11.15%. Although Mexico presented a 240% increase in its desalination capacity in the last 10 years, it has not been enough to overcome water stress, so it is concluded that in the future, it is necessary to increase its capacity in greater proportion, specifically in the areas with greater scarcity, which can be achieved with the joint participation of academy–industry–government through the creation of autonomous organizations, social programs, and/or public policies that promote it.

1. Introduction

Water is a crucial element for the development and survival of living beings; its availability declines as the population increases and as a consequence of climate change [1]. In the last decades, the percentage increase in water use worldwide has doubled the percentage increase in population [2]. It is estimated that if the current rate of exploitation continues, in the year 2030, there will be a 40% water deficit worldwide, a deficit predicted to be greater in arid regions [3]. It is worth noting that, according to regional forecasts, the regions with greater solar radiation—Mexico, for instance—are the ones that will face severe droughts [4].

Since the sixteenth century, water desalination systems have been developed; nevertheless, those early systems were unable to produce water that could be used for human consumption [5]. Desalination technologies are classified into two categories: thermal (phase change) and membrane desalination [6]. Currently, membrane desalination technologies are the most widely used due to the expansion of Reverse Osmosis (RO) technology. However, thermal technologies are attractive because of their potential for integration with thermal energy sources such as waste heat and/or renewable energy sources, and they also perform better for the desalination of high-salinity water [7].

For the year 2022, the worldwide installed capacity percentages for membrane technologies are the following: Reverse Osmosis (RO), 70%; Nanofiltration (NF), 4%; and Electrodialysis (ED), 2%. It is worth noting that the high percentage of membrane desalination systems’ installed capacity is closely related to the rise of RO technology since its installed capacity has significantly increased in comparison to the rest of the membrane technologies. The worldwide installed capacity percentages for thermal desalination systems are the following: Multi-Stage Flash (MSF) at 17%; and Multiple-Effect Distillation (MED) at 6%. The remaining 1% is distributed among the rest of the technologies; Membrane Distillation (MD), Vapor Compression (VC), Freezing (FR), Humidification-Dehumidification (H-DH), and Solar Still (SS) [8]. Thermal technologies, also known as phase-change technologies, were the pioneers in the desalination area, and they dominated the world’s installed capacity until the year 2000 when Reverse Osmosis technologies reached the same installed capacity [9].

Since 2010, the percentage increase in capacity and installation of new desalination plants worldwide has been 6.8% per year (4.6 million m³/d per year). According to Zotalis et al. [10], in 2012, the worldwide desalination capacity was 79 million m³/d. Four years later, Catrini et al. [11] reported that the worldwide installed desalination capacity in the year 2016 was 88.6 million m³/d, resulting in a 12.15% increase. In 2018, the total capacity reported was 92.5 million m³/d, representing a 4.4% increase. In 2019, Jones et al. [9] reported an installed capacity of 95.37 million m³/d, a 3.1% increase. In the year 2020, Eke et al. [12] reported an installed capacity of 97.5 million m³/d, representing a 1.9% increase.

The worldwide desalination installed capacity for the year 2022 is 115.62 million m³/d, distributed in 20,956 desalination plants, presenting an increase of 18.9% with respect to the year 2020 [8]. This is a considerable increase with respect to those obtained in previous years; even though the increase spans over two years, the yearly percentage increase is approximately 9%.

An analysis of the worldwide installed capacity indicates that the country with the largest installed capacity is Saudi Arabia, with 14.58 million m³/d, followed by the United States of America, with 11.90 million m³/d, and by the United Arab Emirates, with 9.47 million m³/d. Membrane desalination technologies amount to 88.96% of the worldwide desalination capacity, while thermal (phase change) technologies amount to 10.56%. The remaining percentage (≈0.5%) corresponds to hybrid and/or unknown technology plants [8].

The installed capacity percentages of membrane and thermal technologies worldwide are mostly similar at a country level. Nevertheless, in the Persian Gulf region, the percentages are inverted; thermal technologies amount to 85% of the total installed capacity. This is due mainly to the availability of fossil fuels in oil-producing countries, where the residual heat of electrical energy generation processes is used to activate desalination systems, mainly through MED or MSF technologies. It is also worth noting that these two technologies easily adapt to the high salinity and high-temperature conditions of the Persian Gulf’s water. Furthermore, MED and MSF systems are more robust for the desalination of water with a proliferation of marine biology, which is highly detrimental to RO technology [13].

Dévora-Isiordia et al. [14] conducted a comparative evaluation of the desalination processes used in Mexico in terms of production costs (USD/m³) and energy consumption (kWh/m³). The authors report that the most widely used desalination technology in Mexico in 2013 is reverse osmosis, and the results of their evaluation support this fact because this technology consumes 2 to 2.8 kWh/m³ at the cost of 0.6 USD/m³, while its direct competition (MED and MSF) consume between 3.4 to 4 and 5 to 8 kWh/m³ at the cost of 1.5 and 1.1 USD/m³, respectively.

In summary, reverse osmosis technology is the current leader in the desalination area. However, there are factors that potentialize the implementation of thermal technologies, such as thermo-physical conditions of the water to be desalinated or the availability of energetic resources (waste heat, electrical energy, renewable sources) for the activation of desalination systems. Another potential area of improvement that can accelerate the growth of thermal desalination technologies is their hybridization with cooling [15,16,17,18] and/or electrical energy generation systems [19,20,21].

Despite having a water availability of 3620 m³ per capita per year, Mexico is a country that faces a severe water shortage, mainly due to its territorial extension, because the concentration of water resources is located in the southern part of the country, while the main industrial activity is carried out in the north (which presents scarcity conditions). The distance and the technical limitations of transporting water between the northern and southern zones make water desalination the main tool to combat water stress in Mexico.

RO technology is currently the most widely used; however, Mexico has some bodies of water with high salinity and a high potential for biofouling, factors that limit the proper performance of RO technology. In addition, there is a great diversity of renewable energy sources, such as solar, geothermal, and biomass, that can directly activate thermal desalination systems. For this reason, it is of interest to know the state of the art of the different desalination technologies used in Mexico and their respective advances in technological development to increase their viability. Additionally, modifications or hybridizations with other systems allow the cogeneration of electrical energy and/or cooling.

This research paper briefly and concisely analyzes the current state of desalination worldwide and focuses on the study of the state of the art of desalination plants in Mexico in order to clarify the main challenges and opportunity areas of desalination as the main solution to overcome water stress. The current conditions in Mexico are analyzed, beginning from the water availability for each administrative hydrological region (AHR), the main socio-economic issues of desalination, and the existing public policies/development programs, as well as those in the process of consolidation. Mexico’s installed capacity for the different desalination technologies and their evolution in recent years was investigated, followed by a comparison with global trends. It also reports some of the research and development work applied to desalination technologies carried out by researchers affiliated with Mexican institutions. Finally, the authors present their perspective on the current situation and future challenges of desalination in Mexico as the main way to solve the problem of water stress. The main contributions of this work, which have not been presented before, are the following:

• The evolution of desalination in Mexico is analyzed in terms of its total capacity and percentages by technology.
• The main contributions and findings of R&D of Desalination in Mexico are reported.
• The main limitations for desalination in Mexico to be a sustainable solution to overcome water stress are defined.
• An overview of existing and ongoing regulations is given, as well as program and policy options proposed by the authors.

2. Current State of Desalination in Mexico

2.1. Water Availability in Mexico

The population growth rate in Mexico has caused its population to quintuplicate in the time lapse between 1950 and 2020 [22]. In the same period, its per capita (pc) amount of available water has decreased by almost 80% [23], mainly due to the decrease in annual precipitation in some regions of the country and to its extraction rate. The average annual precipitation in Mexico is 718.3 mm, which presents a decrease of ≈7% from the year 2000 to date. However, in regions such as the Baja California peninsula, the average annual precipitation is ≈168 mm, which presents a decrease of 10% with respect to the year 2000 and is 77% lower than the national average. It is worth noting that Mexico rates as the fourth country with the largest water extraction (88.84 × 10⁹ m³/year), only below China, the United States of America, and Indonesia [24].

The Water Stress Indicator (WSI) was proposed by Falkenmark and Lindh in 1974 [25] and is currently the most utilized indicator to measure water scarcity [26]. This method defines water scarcity in terms of the total amount of water available for the population of a delimited region. Therefore, it is expressed as the amount of renewable drinking water available for each person every year [27].

Table 1. Water scarcity-level classification in accordance with the Water Stress Indicator.

WSI (m3/pc/Year)	Category
WSI < 500	Absolute scarcity
500 < WSI < 1000	Chronic scarcity
1000 < WSI < 1700	Regular scarcity

shows the limits established for the classification of the level of water scarcity.

The national average per capita (pc) water availability in Mexico reported for the year 2019 is 3620 m³/pc/year. However, there is a marked disparity in the per capita water availability among the administrative hydrological regions (AHR) in Mexico. In the Northern, Central, and Northeastern regions, the water availability is 1558 m³/pc/year, while in the Southern region of the country, it is 10,508 m³/pc/year [28]. Therefore, currently, the largest part of the country is under regular scarcity conditions, although there are regions that present chronic and absolute scarcity conditions. Figure 1 shows that AHRs 1 (Baja California and Baja California Sur) and 6 (Chihuahua, Coahuila, Nuevo León, and Tamaulipas) are facing regular scarcity, and the forecast is that, in the year 2030, they will be under chronic scarcity conditions. AHR 13, located in the central zone of Mexico, presents conditions of absolute scarcity and is forecast to remain in this status until 2030, this is due to the fact that AHR 13 has the second largest population (23,721,664 inhabitants) only behind AHR 8 (24,981,524 inhabitants), but its territorial extension is 957.23% smaller.

It is worth emphasizing that the Northern, Central, and Northeastern zones of Mexico cover 78% of the national territory, host 77% of the Mexican population, and contribute 83% of the Gross Domestic Product (GDP). In these regions, there is a larger population concentration and, therefore, greater activity in the agricultural, industrial, and services sectors, which results in a greater water requirement in the zones with less availability [29]. The economic sectors with the largest water consumption are the following: agricultural (75.7%), public supply (14.7%), industrial (4.9%), and electrical energy generation (4.7%). It should be noted that human consumption through public supply should be the main usage of water and that in some AHRs that have water scarcity, there have been shortages reflected in supply cuts for the housing sector [30]. There have also been socio-hydric problems derived from the population’s disapproval of the construction of new industrial plants with high water-consumption processes.

Throughout the different AHRs, 1186 monitoring points have been installed. Their purpose is to assess the quality of underground water in terms of their total dissolved solids (TDS). Their results for the year 2018 show that in the Northern, Central, and Northeastern zones of Mexico, 78.53% of the underground water is sweet water, 13.42 is slightly brackish, 7.92% is brackish water, and 0.11% is saline water. In the Southern zone of the country, 81.58% of the underground water is sweet water, 13.92% is slightly brackish, 4.48% is brackish water, and there is no presence of saline water (or saltwater intrusion).

It is projected that the population of Mexico will increase by 10% in the year 2030, 141.8 million inhabitants, even though the growth rate tends to reduce. It is estimated that 56% of the population growth will occur in the Central and Northern regions of the country, which currently have low water availability. This will worsen their status, moving from regular scarcity (WSI ≈ 1000) to chronic or absolute scarcity (WSI ≈ 500), as shown in Table 1.

2.2. Desalination Plants in Mexico

Mexico’s installed desalination capacity in the year 2022 is 749,751 m³/d, distributed throughout 351 desalination plants located in 28 of its 32 federative entities—also called states. The federative entity with the largest installed capacity is Mexico City, located in AHR 13, with 276,453 m³/d, followed by Baja California, located in AHR 1, with 97,382 m³/d, and Quintana Roo, located in AHR 12, with con 63,523 m³/d. Mexico City’s desalination capacity is 183.89% higher than Baja California’s, but its WSI is 91.28% lower. Therefore, this can be interpreted as a response to the absolute scarcity faced by AHR 13. Another factor to take into account is that Mexico City (and all of AHR 13) is located far from the coastline; therefore, its main feed waters are brackish, river, and wastewater. Figure 2 shows the installed desalination capacity in Mexico compared to the five countries with the largest installed capacity in the world.

The increase in desalination capacity in Mexico from 2013 to 2022 is 240% (2.4 times) [14]. Until 2013, only 19 of the 32 federative entities in Mexico had desalination plants (59% of the federal entities); in 2020, 28 federative entities had desalination plants (87.5%). Figure 3 shows the number of desalination plants per federative entity. Considering the federative entities that already had desalination plants, those with the largest increase in capacity during the last 10 years are Nuevo Leon, with 1734%, Tamaulipas, 666%, and Jalisco, 595%. It is worth mentioning that Nuevo Leon is one of the entities with the lowest WSI (839 m³/hab/year), the highest industrial activity, and, therefore, the highest contribution to GDP. Currently, its government continues to seek to increase its desalination capacity despite its distance from the coast.

The number of installed desalination plants that use membrane technology in Mexico amount to 85.7% of the total plants; the plants based on thermal (phase change) technology amount to 14.3% [8]. However, in terms of installed capacity, membrane technology plants amount to 88.85%, while thermal technology plants amount to the remaining 11.15%. These percentages are similar to those of worldwide installed capacity, where membrane technology amounts to 90%, while thermal technology amounts to 10%. Figure 4 shows the percentages of installed capacity in Mexico and in the rest of the world. In Figure 4a), the category -Other- groups; forward osmosis (FO), freezing (FR), humidification–dehumidification (HDH), membrane distillation (MD), solar still (SS), and vapor compression (VC), due to their low percentages of installed capacity worldwide. In Figure 4b), the category -Other- groups; humidification–dehumidification (HDH) and solar still (SS) due to their low percentages of installed capacity in Mexico.

The technologies used in the desalination plants in Mexico are the following: electrodialysis (ED), electrodeionization (EDI), reverse osmosis (RO), multiple-effect distillation (MED), multiple-stage flash (MSF), and vapor compression (VC). Within the category -others- we can find humidification-dehumidification (HDH) and solar distillation (SS) technologies, which present a lower capacity and efficiency compared to the rest of the desalination technologies. However, they are appropriate for the satisfaction of low water demand (1–100 m³/d) [31] and highlight their low and null electrical energy consumption required for their activation, respectively [32]. Figure 5 shows the installed capacity (m³/d) per type of technology in Mexico.

The number of desalination plants installed in the Northern and Southern zones of the country is similar; however, in terms of installed capacity, the Northern zone has a larger capacity. For instance, AHR 1, which corresponds to the Baja California Peninsula, whose population is 4,672,579 inhabitants, has 91 desalination plants and an installed capacity of 161,470 m³/d. On the other hand, AHR 12, which corresponds to the Yucatan Peninsula, whose population is 4,857,556 inhabitants, has 91 desalination plants and a capacity of 81,480 m³/d. This shows that in the Southern zone of the country, there are more low-capacity installed plants, a situation that could be related to the installation of autonomous desalination systems by the private, touristic activities-related sector in the Yucatan Peninsula.

AHR 4, which covers the northern states of the country, has regular scarcity conditions, and it is expected that in 2030 it will be in chronic scarcity conditions, with WSI levels similar to those in AHR 1. However, Nuevo León, the most affected federative entity belonging to AHR 4 is approximately 300 km away from the coast of Tamaulipas, where seawater desalination plants could be installed. Regardless of having the second largest number of aquifers (102), only below RHA 6, AHR 4 has the second lowest per capita water availability in Mexico (Figure 1). To solve this problem, aqueducts are needed for either the transportation of water from zones with availability or for the transportation of desalinated water from the coasts near the urban zones, as proposed by Roggenburg et al. [33].

The difference in per capita water availability between the AHRs in Mexico is an indicator of the need to increase per capita water availability in the Northern, Central, and Northeastern zones of the country. This has induced federative entities governments, as well as members of the private industry, to continue pursuing the construction of desalination plants under the BOT scheme in order to guarantee a continuous supply, especially in the federative entities of Nuevo Leon, Baja California, Baja California Sur, and Mexico City.

2.2.1. Reverse Osmosis

In the 1980s, derived from the Sonntlan project, a reverse osmosis desalination plant was constructed in the fishing community of Barrancas, which belongs to the municipality of Comondú, Baja California Sur. It had a capacity of 20 m³/d and was activated using solar PV energy, as well as a backup diesel generator. The project worked for some time, but nowadays, it is abandoned.

Currently, the largest reverse osmosis desalination plant has a capacity of 94,500 m³/d, 12.6% of the total desalination capacity in Mexico, and is located in Mexico City, where it desalinates brackish water. It started operations in 2011 and is still in operation. The second largest reverse osmosis desalination plant, with a capacity of 29,184 m³/d, is located in the municipality of Cadereyta, in the federative entity of Nuevo León, where it desalinates wastewater to be used in industrial processes. It started operations in 2015 and is still in operation. The third place in installed capacity (21,600 m³/d) belongs to the Ensenada desalination plant located in the federative entity of Baja California, which started operations in 2011 and still operating to desalinate seawater to be used for human consumption.

2.2.2. Electrodialysis

The electrodialysis desalination plant with the largest capacity is located in Mexico City. It has a capacity of 29,331 m³/d, started operation in 2001, and desalinates brackish water for human consumption. The second largest plant is located in Zacatecas, has a capacity of 6480 m³/d, started operations in 1995, and is still in operation. The third largest plant is located in Veracruz, has a capacity of 6240 m³/d, started operation in 1996, and is still operational.

It is worth noting that Mexico has a high percentage of electrodialysis technology installed capacity (14.72%) compared to world averages (2%). This is due to the fact that Mexico is a country with a high level of beer production, and this industry usually uses electrodialysis to desalinate water for its processes [34].

2.2.3. Electrodeionization (EDI)

The only electrodeionization technology plant is located in Mexico City; it has operated since 1999 with a capacity of 1091 m³/d, desalinating drinking water to be used as distilled water for industrial processes.

2.2.4. Multi-Stage Flash

In the 1970s, a collaborative project between the governments of Mexico and Germany resulted in the construction of a 10 m³/d MSF desalination plant in the municipality of La Paz, Baja California Sur. This MSF plant started operations in 1980, and it used a 194 m² field of flat plate solar collectors and a 160 m² field of 2-axis parabolic trough channel concentrators for activation. In addition, it had 324 m² of flat-plate solar collectors to heat a working fluid and store thermal energy to ensure continuous operation of the plant for 28 h.

The Federal Electricity Commission (CFE) operates the MSF desalination plants with the largest capacity. The largest plant has a capacity of 28,388 m³/d, is located in the municipality of Rosarito, Baja California, started operations in 1966, desalinates seawater, produces distilled water for electrical energy generation processes, and is still in operation. The plant with the second largest capacity (4800 m³/d) is also located in Rosarito, started operations in 1987, and is still in operation. In the third place of MSF desalination capacity, there are two 2400 m³/d plants; one is located in the municipality of Tuxpan, Veracruz, and the other in the municipality of Manzanillo, Colima. Both plants started operations in 1985, are still in operation, and desalinate seawater, generating distilled water for electrical energy generation processes.

2.2.5. Multiple-Effect Distillation (MED)

The MED desalination plant with the largest capacity (10,900 m³/d) is located in Mexico City, started operation in 1998 (is still in operation), and desalinates wastewater, producing distilled water for industrial use. The plant with the second largest capacity (2424 m³/d) is located in Topolobampo, Sinaloa, started operations in 1991, is still in operation, administered by the CFE, and desalinates seawater for electrical energy generation processes. The third place in capacity (2400 m³/d) is shared by two plants, both located in the municipality of Tuxpan, Veracruz. One of them started operations in 1991, is still in operation, and desalinates seawater for human consumption. The other plant started operations in 1993, is still in operation, and desalinates seawater for industrial processes.

2.2.6. Vapor Compression (VC)

There are six vapor compression desalination plants in Mexico. The one with the largest capacity (772 m³/d) is located in the municipality of Rosarito, Baja California, has been in operation since 1999, is managed by the CFE, and desalinates seawater in order to produce distilled water for electrical energy generation processes. The second place of installed capacity (768 m³/d) is shared by two plants, both controlled by the CFE. These plants desalinate seawater in order to produce distilled water for electrical energy generation processes. One is located in the municipality of Ciudad Victoria, Tamaulipas, and has been in operation since 2003. The other plant is located in Mazatlán, Sinaloa, and has been in operation since 2005. The plant with the third largest capacity (360 m³/d) is located in Rosarito, Baja California, and has been operated by a private company since 2007. It desalinates seawater for electrical energy generation processes.

2.3. Social, Economic, and Legislative Scenario for Desalination in Mexico

2.3.1. Social

Due to its large extension (1,964,375 km²) [35], Mexico has a large number of remote rural communities without access to the water distribution network. Even though the national percentage of access to water is 97.4% in urban areas, only 88% of the population in rural areas have access to drinking water [28]. Some of these remote communities are located near 11,122 km of the Mexican coastline; therefore, water desalination is an attractive solution to this problem. However, it is necessary to conduct the corresponding environmental, economic, and technical feasibility studies in order to compare the cost of the process to that of extending the water distribution network from the closest interconnection point.

Overall, rural communities have a low number of inhabitants, which results in a low water demand—or decentralized demand (<100 m³/d). The market-leading desalination technologies (RO, MED, MSF) have more feasibility when used on a large scale [36]. It is common for rural populations to be in conditions of social marginalization and without access to the electrical energy transmission grid. Such is the case of Puertecitos, Baja California, and Punta Chueca, in the Seri indigenous community of Sonora, just to list a few examples. For these reasons, it is complicated to make the initial investment required to install a new desalination plant without external investment (government or private). Moreover, the activation and continuous operation of the plant could be affected by the lack of a continuous and reliable supply of electrical energy, as well as qualified personnel for preventive and/or corrective maintenance and for in site decision making regarding the plant’s operation.

The National Hydric Policy (2019–2024) [37] sets as its priorities to progressively guarantee the human right to water access, to make more efficient use of water in order to contribute to sustainable development, and to reduce vulnerability during droughts, especially for indigenous populations. In remote coastal communities with decentralized demands, it may be more feasible to implement thermal desalination systems such as humidification-dehumidification or distillation, to mention a few examples. For this reason, it is of national interest to advance in the technological development of emerging or not commercially mature technologies and their implementation in demonstration projects or pilot plants. In addition, the availability of renewable energy sources in almost all territorial extensions can increase the feasibility of implementing decentralized desalination systems activated with renewable energy in remote or indigenous communities. Rural, indigenous, or remote communities usually access drinking water by exploiting underground aquifers. These, when exploited at a rate greater than their natural renewal rate, start to present a decrease in their availability, an increase in the depth in which the phreatic water is found (static level), or changes in the physical-chemical composition of the water. For instance, aquifers close to the sea may present marine intrusion, which increases the salinity of the aquifer to levels inappropriate for direct consumption. The number of aquifers with marine intrusion in Mexico has increased, mainly in the Baja California Peninsula, where there is a convergence of low rainfall rate, high levels of solar radiation, and the presence of high-salinity congenital water and easily soluble evaporitic minerals [28]. In these cases, the implementation of reverse osmosis desalination systems could represent an attractive solution because the energy consumption of this technology is proportional to the salinity of the water, which is generally found in brackish water conditions. In addition, the membrane lifetime, which is usually a limiting factor for the viability of this technology, is longer compared to its lifetime when desalinating seawater directly.

2.3.2. Economic

When there is no nearby aquifer, the population carries water in containers in order to have access to it. Worldwide, millions of women and children travel approximately 6 km in order to have access to water, and Mexico is not an exception [38]. Furthermore, there are people that commercialize water carriage in containers from a site with availability to remote communities in which it is scarce. Some documented cases reach costs of 40 USD/m³, a price above that reported by IDA (2017) of 15 USD/m³ of desalinated water. Moreover, this carriage is conducted using trucks with metallic containers in which iron sediments that damage the quality of the water and, consequently, human health have been found [14]. Furthermore, water carriage in vehicles that use internal combustion engines causes a greater environmental impact due to the emissions caused by the consumption of the fuel required to carry large amounts of water, which also increases the economic cost of water with the aim of seeking business profitability.

Being a medium-low-income country, most of the desalination plants installed in Mexico have been built and operated by private sector companies in alliance with state and/or municipal governments in the BOT (building, operating, and transfer) modality. The private company is in charge of the plant’s building and operation, obtaining an economic remuneration for the water produced for an agreed-upon number of years (≈20 years); after this period, the plant is transferred to the government to be managed through its Public Services State Commissions. This is the case of the first desalination plant installed in the state of Sonora, which has a capacity of 200 L/s.

Another factor to take into account in the economic aspect is the operating cost of the desalination plants; although the reverse osmosis technology leads the market, it shares with the rest of the technologies the limiting factor of the specific energy consumption, to reduce it, it has been proposed; The integration of energy recovery devices, the activation with energy coming from renewable energy sources, the hybridization with systems for cooling and/or electric energy generation and the high-pressure pump with solar thermal energy, etc. In some regions of Mexico, as in AHR 1, the availability of electricity is a problem for the industrial, commercial, and residential sectors. For this reason, the construction of desalination plants must have correct energy planning that does not compromise the availability of electricity for other sectors. Some of the measures to reduce the energy consumption of desalination plants may mean a higher initial investment, but if they significantly reduce the cost of operation, they may be more economically viable.

Desalination continues to be a technologically viable solution, but its economic viability is still a limiting factor; for this reason, it is most widely used in developed countries. On the global scale, the cost of producing desalinated water dropped by 50% from 1985 [39]; nonetheless, studies in California and Mexico identify desalination as having the highest marginal costs among all realistic water-supply alternatives [40]. The final USTDA (2009) report estimates that Puerto Peñasco, Mexico, could build a plant with the capacity to produce 0.5 m³/s in the first phase, with the expected expansion of up to 2 m³/s by 2020 at the cost of 2.29 USD/m³ (not including conveyance and storage). This is approximately seven times more expensive than the current cost of water production and delivery (0.339 USD/m³) (USTDA, 2009) [41]. For this reason, in countries such as Mexico, the economic impact derived from the investment required to build high-capacity plants is minimized because the design, construction, and operation are carried out jointly with private industry under the BOT modality.

With respect to environmental impact, the greatest challenge of desalination at present is the disposal of brine since it is usually discharged directly into seas and oceans near the coast; in Mexico, there are draft standards that establish guidelines for desalination plant discharge works, but they are in the process of being approved (PROY-NOM-013-CONAGUA-2015) [42]. However, Mexico has water bodies with different hydrodynamic characteristics; information reported in the literature indicates that the environmental impact caused by brine discharge is lower in water bodies with turbulence (waves and currents), such as the Pacific Ocean, but discharging brine in calm seas such as the Sea of Cortez has a greater environmental impact [43]. Therefore, the discharge work must be carried out in accordance with the regulations (when approved) and considering the characteristics of the water body in question. In second place are the emissions of gases into the atmosphere derived from energy consumption.

To cite a recent example reported by Wilder et al. [44] on the Puerto Peñasco desalination plant project, which could produce 0.5 m³/s of freshwater (in its first stage), an estimated 0.73 m³/s of brine concentrate will be produced. Project engineers recommend discharging near the surface to take advantage of prevailing winds and stronger currents to help disperse the brine concentrate [42]. An environmental impact assessment was initiated but not completed [45]. In addition, energy use at the desalination plant would likely come from fossil fuel sources that produce GHG emissions.

2.3.3. Legislative

Regarding legislation, the 1992 National Water Law established that the exploitation of national water will be conducted through concession titles emitted by the National Water Commission (CONAGUA, by its Spanish acronym). Therefore, in order to install a desalination plant, a concession for the water extraction is required, whether from the sea –direct intake–or from underground aquifers –wells–. For the rejected water discharge, as is the case of brine, discharge permission emitted by the same institution is also required.

Other Official Mexican Norms (NOM, by its Spanish acronym) applicable for desalination are the following. NOM-001-SEMARNAT-2021 [46] established the maximum level of pollutants allowed for wastewater discharge into national waters, which applies to the discharge of brine from desalination plants. NOM-003-CONAGUA-1996 [47] established the requirements for the construction of water extraction wells looking for the prevention of aquifer pollutants, which applies in the case of the construction of an extracting well for a desalination plant. NOM-006-ENER-2015 [48] established the energetic efficiency required for pumping systems for water extraction wells in operation, limits, and testing method, which applies to the selection of the pumping equipment used in desalination plants that extract water from underground wells.

In 2015, the Mexican Official Norm project PROY-NOM-013-CONAGUA-2015 [42] was proposed. This project seeks to establish specifications and requirements for the extraction and discharge works that must be met in desalination plants or processes (public or private) that generate brackish or saline rejection waters and discharge them to the coastal, marine, and/or continental environment, in order to protect the environment. The Norm project was presented by the National Consultative Committee for Standardization of the Water Sector, with the collaboration of private sector organizations, institutions, and companies.

Regarding the quality of the product water obtained from desalination plants, NOM-0127-SSA1-2004 [49], originally published in 1994, establishes the maximum permissible levels that produce water should meet for human consumption. This norm determines that water for human consumption should have a maximum of 1000 ppm of TDS.

3. Mexico’s Research and Development in Desalination

The main barrier that has limited the widespread of desalination technologies is the production cost (USD/m³), which is mostly (50–60%) dependent on the energy consumption during the process (kWh/m³) [50], for this reason, the efforts of different desalination research groups have been focused on reducing energy consumption, initial investment and increasing the useful life of the components involved in the different desalination technologies. This section summarizes the research and development work focused on optimizing the process of different desalination technologies published by researchers from Mexican institutions.

According to the extended citation index (SCI-EXPANDED) of the Web of Science (WOS) Core Collection database, from 1980 to 2022, 352 papers related to desalination have been published with total or partial participation of researchers from institutions located in Mexico. These papers have been cited 4084 times and 3865 times without considering self-citations, giving an average of 11.6 citations per article, with an h-index of 32.

Figure 6 shows that research in Mexico started in 1981, although with occasional publications, one in 1989 and another in 1992. It was from the year 2000 when the rate of publications increased, reporting approximately three publications per year, until 2009, when 16 papers were published. From that year, the publication rate increased considerably; from 2015, approximately 30 papers per year began to be published, obtaining a maximum record of 50 publications per year in 2020. As well as the publication rate, the number of citations to Mexican papers has increased considerably, reaching a maximum record of approximately 750 citations in 2021.

3.1. Membrane Technologies

3.1.1. Reverse Osmosis (RO)

One of the main areas of improvement in the reverse osmosis desalination process is the optimization of the membrane; most of the efforts are focused on increasing the efficiency of the membrane, reducing its fabrication cost, increasing its useful lifetime, and/or reducing the frequency of maintenance. This section shows some of the main research papers published by researchers and/or research groups affiliated with institutions in Mexico.

Armendariz-Ontiveros et al. [52] studied the effectiveness of adhering to a coating formed by iron nanoparticles on the membrane of a reverse osmosis system in order to avoid biofouling. Under laboratory conditions, they compared the performance of the coating using seawater from two sites: Mar de Cortés, Mexico, and Playa del Sol, Chile. According to their results, the coated membranes presented greater biofouling (>74%) with water from the Sea of Cortez due to the differences in temperature and pH, but at the same time, the coating presented a greater biocide effect under these conditions. The authors concluded that temperature, dissolved oxygen, and pH have a more significant effect than salinity on the biofouling of membranes coated with iron nanoparticles.

Murillo-Verduzco et al. [53] manufactured a pulsation valve that generates pressure variations to a water flow in ranges previously defined by simulations. They studied pressure levels between 4826 and 6205 kPa, volumetric flow rates from 0.6 to 1.2 L/min, and frequencies from 10 to 45 Hz, with the purpose of increasing the permeate flow in reverse osmosis desalination systems. The authors report that they obtained their best results when operating at a pressure of 6205 kPa, a volumetric flow rate of 0.6 L/min, and a frequency of 40 Hz in a non-turbulent flow regime.

Kitano et al. [54] studied the hydraulic compaction process in nitrogen-containing carbon-based reverse osmosis membranes at a laboratory scale using cross-flow membrane desalination systems. Their results show that high water pressure induces an overall reduction of interstitial spaces in the amorphous carbon structure. They also noted that the nitrogen-containing carbon-based membrane performed better in salt rejection and water permeability compared to the carbon-based membrane. The authors attribute the improved performance to the higher mechanical stability of the carbon structure due to the presence of nitrogen sites.

Feria-Díaz et al. [55] conducted a review study on the most recent publications focused on the hybridization of the reverse osmosis process with other desalination technologies in order to reduce the weaknesses and improve the strengths of each technology. For example, they mentioned RO hybridization with MED to initially desalinate seawater with the RO process and later use the reject as the feed stream of a MED system. The authors conclude that activating RO systems with renewable energy and implementing strategies to achieve zero liquid discharge (ZLD) and/or minimum liquid discharge (MLD), as well as the use of valuable products obtained from the brine, are strategies to reduce the environmental impact of reverse osmosis desalination.

Rodríguez-López et al. [56] evaluated the energy consumption of RO desalination systems under different feedwater concentrations (5000–36,000 mg/L), maintaining a constant feed volumetric flow rate of 14.4 m³/d. The authors considered three solar PV systems (fixed, single-axis tracking, and dual-axis tracking) for the power supply. With this study, it is possible to verify that the specific energy consumption per unity of produced water increases as the salinity of the feed stream increases; their results show that it varied from 2.33 to 3.83 kWh/m³.

Torres-Valenzuela et al. [57] developed and characterized a new composite membrane for reverse osmosis desalination systems. A commercial TFC membrane was modified by impregnating silver nanoparticles on its surface (5, 10, and 15 mg per 100 mL of distilled water) via interfacial polymerization in order to improve resistance to biofouling. Their results show that the salt rejection was 97.6, 97.8, and 96.7%, with a reduction in total cell layer and organic carbon of 72, 48, and 45%, using 5, 10, and 15 mg of AgNP, respectively.

3.1.2. Electrodialysis (ED)

In Mexico, the electrodialysis process is most commonly used to separate specific compounds or ions from process water and/or groundwater. Lambert et al. [58] studied the separation of Chromium (III) present in high concentrations in effluents from the tanning process in the textile industry in order to reduce the environmental impact of this industry in Guanajuato, Mexico. Ortega et al. [59] studied a hybrid process of electrodialysis with ion exchange to reduce the concentration of dilute solutions of As (V) ions in water destined for human consumption to values below the limit (10 μg/L) recommended by the United Nations (UN). Arreola-Castro et al. [60] proposed an electrodialysis process to remove iron from an aqueous solution, effluent from the mining industry in Durango, Mexico. They obtained an iron removal of 97.15%.

Enciso et al. [61] studied the hydrodynamic behavior and mass transfer in a filter-press type ED reactor using computational fluid dynamics (CFD) and validated their results with experimental data. Their theoretical data presented a good correlation with respect to those obtained experimentally for hydrodynamics, which made possible the validation of mass transfer and electrode potential distribution. The authors performed a second validation comparing the theoretical mass transfer coefficients with those obtained experimentally, presenting a maximum error of 16%.

Dévora-Isiordia et al. [62] studied the effect of temperature on the final concentration of the product water of a batch electrodialysis reversal (EDR) process, varying the input voltage and feed water concentration in order to reduce specific energy consumption (kWh/m³) and the economic cost of the diluate (USD/m³). The variations were concentrations of 2000 and 5000 mg/L; temperature of 25, 30, and 35 °C; and input voltages of 10 and 20 V. The authors mention that temperature has a positive effect on the EDR process, especially at 10 V, where increasing 10 °C increases the efficiency by 10.83 and 24.69% for the 2000 and 5000 mg/L samples, respectively.

3.1.3. Nanofiltration (NF)

The studies published by Mexican institutions on nanofiltration desalination technology are mainly focused on the incorporation of thin films of different chemical compounds in order to improve their permeability and salt rejection properties. A case study of pilot plants of the technology is also presented, using a small-scale desalination system activated with renewable energies.

Pérez-Moreno et al. [63] studied the performance of ceramic membranes modified with metal impregnation for nanofiltration desalination on the Mexican Pacific coast. The authors report that the impregnation of metals in the membrane increases approximately 20% the rejection of TDS compared to conventional membranes, and in terms of divalent ions, the rejection was 60–80%, values close to those obtained with polymeric membranes in a reverse osmosis desalination process. The authors conclude that nanofiltration technology can be used for partial seawater desalination or as the main process in the separation of specific ions.

Flores-Prieto et al. [64] proposed a solution to treat brackish groundwater using low-pressure solar PV nanofiltration (LP-PV-NF). The study site is located in the desert of Chihuahua, where the groundwater presented high sulfate content (1863 mg/L) and 2195 mg/L TDS. The authors reported that sulfates and TDS were reduced by 98.21 and 75.15%, respectively, under solar radiation equal to or greater than 750 W/m², with an energy consumption of 1.94 kWh/m³. Their experimental results show that the production of their system was 3.2 m³/d for an average insolation time of 6.3 h/d.

García-Picazo et al. [65] studied the effect of incorporating chemically modified graphene oxide (GO) as a crosslinking agent in thin film nanofiltration membranes for water desalination applications. They studied the effect of GO on membrane properties and performance; they also analyzed the chemical and morphological composition of the GO surface on the membrane by thermogravimetric analysis. Their results show that the membranes present an increase in permeability from 1.12 to 1.93 L/m²-h-bar and also in salt rejection; Na₂SO₄ from 95.9 to 98.9% and NaCl from 46.2 to 61.7% at 2000 ppm, compared to conventional membranes.

Ounifi et al. [66] studied a synthesis of novel polyamide composite nanofiltration membranes (NF-TFC) for water purification. The polyamide was deposited on a synthetic cellulose acetate (CA) supported by the interfacial polymerization method. The membranes were characterized by scanning electron microscopy (SEM) and Fourier transform spectroscopy (FT-IR). The authors studied the effect of varying CHMA concentration (0.2–2 wt %) on the morphology, porosity, water permeability, and rejection properties of the proposed membranes. The membrane water permeability ranged from 36.02 to 17.09 L/h-m2-bar. The rejection of Na₂SO₄ and NaCl salts increased from 9 to 68% and from 38.41 to 89.4%, respectively, by increasing the CHMA concentration from 0.2 to 2 wt %.

3.1.4. Electrodeionization (EDI)

Electrodeionization technology has been studied in Mexico by Alvarado et al. [67] with the purpose of removing chromium (VI) from synthetic solutions with pH 5; their results show that an EDI process with an anionic bed is capable of removing 97.55% of chromium (VI) with an energy consumption of 0.91 kWh/m³, while an EDI process with a mixed bed is capable of removing 99.8% of chromium (VI) with 0.167 kWh/m³. Alvarado et al. [68] proposed a continuous ion exchange and electrodeionization process to remove chromium (VI) from effluents from the mining and electroplating industry. The authors report that the implementation of anionic resin combined with a strongly acidic macro reticular cation exchange resin continuously removes 98.5% of chromium (VI) in the electrodeionization process.

Huang et al. [69] studied the use of activated carbon modified with nitric acid as electrodes in a desalination process of aqueous electrolyte solutions by capacitive electrodeionization. Their experimental results show that the modification they proposed can significantly increase the removal of salts from the solution because the desalination efficiency increases by approximately 15%, and the desalination kinetics improved in the form of a rate constant from 0.09208 to 0.09922. The authors found that the modification greatly increased the oxygen-containing functional groups on the activated carbon surfaces, which resulted in increases in capacitance and reduction in charge resistance, which is reflected in the improvement of the desalination process.

Otero et al. [70] experimentally studied the electrodeionization process to desalinate brackish water using a 4-compartment EDI cell. The authors proposed a mathematical model to analyze the distribution of current density in the EDI cell and its effect on ion removal in order to identify the ineffective regions of the cell. Their results show that the model they proposed is able to describe the effect caused by changes in concentration (0.01 and 0.02 M) and cell voltage (7, 10.5, and 14 V) on current density and desalination flux.

3.2. Phase Change Technologies

3.2.1. Multi-Stage Flash

Although MSF technology arrived in Mexico in the 1980s [71] and, nowadays, there are several large-scale desalination plants that use this technology, research for the improvement of some point of this process or cases of study are limited.

Priego et al. [72] proposed different configurations to activate two thermal desalination systems (MSF and MED) by steam extraction in nuclear reactors, comparing them by means of exergy and thermoeconomic analysis. The evaluation proposed by the authors considers the reduction in electrical energy generation due to steam extraction at different positions in the secondary circuit of the nuclear reactor and the implications of the cost of electrical energy in each case. The performance of both desalination technologies was analyzed for GORs of 5, 10, and 15. Their results show the economic competitiveness and feasibility of nuclear desalination using the reactor steam mainstream. A GOR of 15 produces the highest amount of product water for all possible extraction positions in both desalination technologies. The authors conclude that the MSF technology offers the lowest cost for water production.

3.2.2. MED

One of the thermal technologies that in recent years has gained interest in the area of thermal desalination research and development is the Multiple-Effect Distillation technology. López-Zavala et al. [15] studied a modified single-effect absorption cooling system (23 kW) with a novel energy and mass integration to a FLASH/MED desalination process that allows desalinating water and using it as a coolant to increase the cooling capacity. The proposed integration increases the cooling capacity from 23 to 2012 kW and increases the COP from 0.72 to 6.15.

Aguilar-Jiménez et al. [21] proposed a novel energy integration between a MED desalination system and an Organic Rankine Cycle (ORC) for the cogeneration of water and electrical energy. The thermal energy to activate both systems is supplied at the evaporator of the MED system, while the ORC is activated by a fraction of the steam produced in the first effect of the MED. A hybrid MED/ORC system producing 50 kW of electrical energy is 22% more efficient than a MED system without integration and requires only a 6.9% increase in the heat transfer area.

3.2.3. Humidificación-Deshumidificación (HDH)

In 1963, the University of Arizona, in collaboration with the University of Sonora, developed a system for the desalination of seawater activated with low-temperature solar energy. Hodges et al. [73] report that the system is composed of a flat plate solar collector field with a plastic cover (836 m²), a packed tower humidifier with a height of 14.32 m and a diameter between 1.21 and 1.52 m, and a finned tube heat exchanger used as a dehumidifier through which 13.62 m³/h of seawater circulates. The seawater to be desalinated is used as a cooling medium in the dehumidifier and then transported to the solar collector field to increase its temperature by between 5 and 10 °C. Finally, it is atomized in the humidifier to evaporate and diffuse into the air stream, entering the dehumidifier to produce between 9.46 and 10.92 m³/d of distilled water.

Martín-Dominguez et al. [74] studied a solar-activated HDH system designed to meet water demand in rural communities. Their system had two solar collectors, one for heating water and the other for heating the air before both entered into the humidifier. They also optimized the dehumidifier by incorporating a heat pipe to keep the condensation temperature close to the ambient temperature. Using a simulator, they concluded that it is recommendable to use the maximum amount of solar radiation available to heat the seawater and air previous to the evaporation process to produce about 7.5 kg/m²d.

Tariq et al. [75] proposed a novel humidifier based on the Maisotsenko cycle for being integrated into an HDH desalination process. Their air saturation process included flow infiltration from the dry channel to the wet channel; their results show that for infiltration of 0.6 (60%), the maximum amount of water evaporation is obtained. The authors report that their proposed humidifier increases; by 30% water production, 46% recovery ratio, and 11% GOR compared to an HDH desalination system with direct contact humidifier.

Álvarez et al. [76] numerically studied a direct contact humidification-dehumidification system with open air and water cycle (OAOW). Their system does not use any type of packing material in the humidifier or dehumidifier; instead, it humidifies the air by atomizing hot water over it, and subsequently dehumidifies it by atomizing cold (distilled) water over it, both processes occur under counter-current flow patterns. They studied the influence of geometry by varying the height of the humidifier and dehumidifier. Their results show that water production is benefited by reducing the diameter and velocity of the atomized water droplets and increasing the temperature and flow rate of seawater. Their maximum production obtained is 242.2 kg/h with a height ratio of 2 between the humidifier and the dehumidifier. Their system did not present any type of energy integration; therefore, the maximum GOR obtained was 0.58.

3.2.4. Solar Still

The implementation of solar stills in Mexico began during the 1970s in the fishing villages of Puerto Chale and Punta Eugenia (1 and 1.5 m³/d, respectively), both located in the federative entity of Baja California Sur, funded by the Commission for the Exploitation of Saline Waters (CAAS, by its Spanish acronyms) for research purposes.

Later, in the 1980s, the Centro de Investigaciones Biológicas del Noroeste (CIBNOR) developed and tested—channel solar stills—built with concrete and glass cover with an inclination of ≈30°. Its first prototype had 54 m² of the collection area and produced approximately 0.2 m³/d. The same prototype was installed in Puerto Chale, Baja California Sur, with a catchment area of 300 m² consisting of 6 solar channel stills with the aim of producing 1 m³/d. The best production recorded for this plant was 1.6 m³/d [73].

The Autonomous University of Baja California Sur (UABCS) also conducted research in the area of solar stills, studying prototypes similar to those built by CIBNOR, but their increased dimensions made them choose to call it a long-section solar still (LSSS). The dimensions of the prototype were 5 m wide, 10 m long, and 2.5 m high; their system produced 0.175 m³/d in a typical day. An LSSS system was built and put into operation at El Partido Island, Baja California Sur, in 1993 [73].

Aguilar Castro [77] experimentally studied three configurations of a solar still under the climatic conditions of Ensenada, Baja, California, Mexico. The first configuration consisted only of the solar still, the second configuration included a solar collector as a water preheater, and the third configuration included a condenser external to the solar still. The maximum production obtained with each configuration was 3.86, 4.74, and 5 L/m², with thermal efficiencies of 48.8, 60.1, and 66.8%, respectively.

Feria-Díaz et al. [78] studied the performance of a solar still using the model proposed by Dunkle and validated it with an experimental study on the coast of Veracruz, Mexico. They studied different operating parameters and variations in climatic conditions, obtaining an average production of 1.57 L/m²d. The authors conclude that solar distillation is a viable solution to meet low potable water demands in remote coastal populations.

4. Conclusions, Outlook, and Future Challenges of Desalination in Mexico

Desalination capacity has increased by 46.35% worldwide from 2013 to 2022, while in Mexico, it has increased by 240% during the same period of time. This increase can be interpreted as a response to the water scarcity faced by Mexico in recent decades and to its coastline length, which allows the availability of space not to be a constraint for the installation and/or expansion of desalination plants. The main limitation of the expansion of desalination plants in Mexico is the initial investment. The main operators of desalination plants belong to the private sector, which generally has capital from external investment.

Desalination technologies began to be applied in Mexico at the end of the last century; however, there is still a lack of regulations for water extraction and brine discharge, which is a vital point to ensure that the desalination plant process does not have a negative environmental impact on nearby ecosystems. There are proposals for official Mexican standards (NOM) that were proposed more than 7 years ago by groups of experts, but they are still in the evaluation stage by the responsible agencies. Despite the fact that desalination capacity has increased significantly and thus brine production, the authorities have not expedited approval of the initiative, which helps to regulate the environmental impact caused by existing plants and future plants to be built. It is important to mention that brine discharge is generally carried out in coastal lines that receive tourist activity, having a negative impact on their flora and fauna due to the lack of environmental impact studies.

It is also important to create or update existing regulations on water exploitation in the sectors with the highest water consumption. In the agricultural, aquaculture, and livestock sectors, verify that the requirements for granting concessions of aquifer exploitation are met and increase the thoroughness of audits to ensure that the concessions granted are being carried out within the established limits. Seek to ensure that subsidies are granted preferentially to crops that are destined for national food security and not to private companies that base their profits on export sales. In this way, water will be used in the national territory, avoiding its virtual transfer [79].

In the industrial sector, promote the installation of new industries with high water consumption in the southeast region to increase its GDP, and not in the northern and central regions of the country, where it has the highest impact due to water stress. Increasing industrial activity in the southeast region implies an increase in the cost and time of exportation; however, it also implies a positive impact on the phenomenon of migration to the North of the country, which is currently a problem. Likewise, identify the existing industries that currently contribute the highest percentage to the water stress present in the north and center regions of the country, and propose their total or partial relocation gradually and/or their expansion towards the southeast zone, where their consumption does not compromise the availability of water for human consumption. In addition, this contributes to homogenizing the WSI in all the AHR of Mexico. Finally, establishing that the high consumer will have high tariffs or penalties when exceeding a permissible limit of consumption and/or failing to pay during a determined period of time, thus aiming to give greater value to water and promote its conservation as a good of national interest.

On the other hand, looking for the direct participation of research groups focused on optimizing water consumption in industrial processes similar to the already established water-intensive companies, with the purpose of making their processes more efficient or proposing alternative processes for obtaining water such as desalination, purification and/or potabilization on site. Furthermore, it is expected that these activities will increase the economic profitability and reduce the environmental impact of these industries, as well as increase their autonomy for water supply, reducing dependence on external factors that could compromise their reliable and continuous supply. Another intrinsic result is the increased training of personnel as a result of collaboration and interaction with groups of academic experts. In order to achieve a triple helix of academy–industry–government, it is necessary to promote the creation of programs or organizations with long-term projection and total autonomy to plan, manage and execute water and energy projects independently of the government in turn.

In the residential sector, state or municipal operating agencies should improve drinking water distribution networks to reduce leakage and spills (≈30%) because increasing desalination capacity and, thus, the availability of water in such places increases the waste of the latter.

Solar energy resources are abundant in most of Mexico’s land area and other renewable energy sources, such as biomass or geothermal energy, are available in some regions. Different studies at the pilot plant scale have demonstrated the technical feasibility of developing desalination plants activated by renewable energy sources. In order to develop them quickly and efficiently, the combined participation of the academic, governmental, and industrial sectors is required, promoting common projects and/or economic incentives that can increase their socio-economic feasibility.

In Mexico, spatially and temporally isolated efforts have been made to satisfy the water demand of remote communities with medium and low-capacity desalination systems mostly powered by renewable energy due to the unavailability of access to the electrical grid. Successful pilot plant projects, such as the one reported by [80], should be taken as a model to replicate in remote coastal communities because the characteristics are similar. There are such projects, such as the case of the community Punta Chueca, Sonora, which has a PV-RO system with a capacity of 150 m³/d. The government should consider the construction of desalination plants ideal to satisfy low capacities with low energy consumption. No matter how much the desalination capacity per federal entity is increased, if it is installed only in urban centers, it will have no impact on the quality of life of remote communities.

According to the latest projections on global water scarcity reported in the literature, Mexico is within the most affected zone. Therefore, it is necessary to improve water resource management and increase the installed desalination capacity in order to overcome the predicted water stress. The AHR 6, which includes most of the federative entities located in the north region of the country, currently presents the greatest water scarcity, together with low aquifer availability and remoteness from the coastline, which requires the installation of desalination plants and transport networks, the latter can be activated with renewable energy to seek self-sustainability, as proposed by Roggenburg et al. [33].

Based on the aforementioned, it is demonstrated that the 240% increase in desalination capacity during the last 10 years was not enough to overcome the water stress of recent years in Mexico, so it is necessary to seek greater increases through public policies that promote:

• Academy–Industry–Government joint participation.
• The improvement of the infrastructure of water transport/distribution networks to avoid water waste.
• Spatial homogenization of industrial activity to reduce consumption in water-stressed areas and increase GDP in the southeast regions.
• The implementation of new desalination plants powered by renewable energy in areas with energy deficits, primarily in remote communities.
• The value of water through rate increases or penalties in cases of excessive consumption and/or in the event that water is used for purposes other than those previously established.
• Seeking the sustainability of the virtual transfer of water carried out through the export of agricultural and industrial products.