This planned desalination plant in Los Cabos, the construction of which was finally approved in October 2020, will have a capacity of 250 liters of water per second and will cost more than $ 55 million, according to the government of the state of Baja California Sur. CREDIT: Baja California Government SurMEXICO CITY, Jan 31 (IPS) – Mexico is attempting to alleviate water scarcity in part of its extensive area by expanding desalination plants through the use of seawater. However, this solution has an exorbitant cost and significant environmental impact.
Gabriela Muñoz, a researcher at El Colegio de la Frontera Norte public university, highlighted the benefits of these water treatment systems as the expansion of water sources and the production of water for human consumption.
In her conversation with IPS, however, she also underlined the disadvantages of these systems, such as the high energy demand, which is made worse when the energy comes from fossil sources. high costs; and the production of brine and wastewater.
To illustrate the cost: One of the desalination plants approved by the National Water Commission (CONAGUA) in the northern state of Baja California in 2014 cost around $ 35 million to process 250 liters per second (l / s). Another plant with the same capacity, which was finally approved in October 2020 in the neighboring state of Baja California Sur, requires an investment of more than $ 55 million.
In Mexico, “there are no regulations on the disposal of the brine. Most of the time it is dumped on the beach. We have to be careful how we handle the brine as it is toxic to the ecosystems. It is also not installed.” Capacity to treat all wastewater. For certain areas, desalination shouldn’t be the first option, “said Muñoz of the northern border town of Tijuana.
Between 2012 and 2020, environmental agencies approved at least 120 desalination plants, rejected six applications, and another five are currently under review. This is evident from data that IPS received upon request from public information. Most of the new projects are located in three states with acute water scarcity: the northwestern states of Baja California and Baja California Sur and the southeastern state of Quintana Roo.
However, in Mexico, which has more than 400 such plants, no environmental impact studies have been conducted, as confirmed by IPS, with the exception of the “Desalination of Water” study published in 2000 by the Mexican Government Water Institute .
A basic desalination technique is thermal distillation, in which seawater is heated until it evaporates, the vapor condenses to fresh water, and the remaining liquid is discarded as a concentrated salt solution.
Another is reverse osmosis, in which water is filtered and then pumped under high pressure through thin membranes through which only the liquid can pass and hold back the salt.
In 2019, the study, “The State of Desalination and Brine Production: A Global Outlook,” by the United Nations University Institute for Water, Environment and Health in Ontario, Canada, warned of the growing brine generation and its grave impact on the world Environment. An estimated 142 million cubic meters (m3) of waste were accumulated worldwide from the extraction of brine this year.
According to the latest data from the International Desalination Association, there are 18,214 desalination plants worldwide with an installed capacity of 89 million m3 per day, serving more than 300 million people. For every liter of desalinated water, one liter of salt solution is produced.
These plants are part of a trend to introduce this technology in areas of water stress or water scarcity.
President Andrés Manuel López Obrador (C) visited Los Cabos on the southern tip of the Baja California peninsula on the northwest tip of Mexico in August, where he confirmed the construction of the larger of two new desalination plants in the state of Baja California Sur. Mexico already has 400 seawater treatment plants, but experts warn of excessive costs and environmental impacts. CREDIT: Government of Baja California SurWater Availability in Mexico
Mexico, Latin America’s second largest economy, covers an area of 1.96 million square kilometers, 67 percent of which is dry and semi-arid land.
According to CONAGUA, the availability of water in this country with 129 million inhabitants varies greatly, as it is scarce in the north and abundant in the south.
Of 100 liters of precipitation, 72 return to the atmosphere through evapotranspiration, 22 flow into rivers and streams and six feed 653 aquifers, 108 of which were overfished, 32 had salty soils or brackish water and 18 due to seawater infiltration rising sea levels and seepage into the groundwater level.
Although Mexico had low national water stress in 2017 – 19.5 percent – the risk of water stress is high, according to the Aqueduct platform developed by the Aqueduct Alliance, which is made up of governments, companies and foundations.
In fact, Mexico is the second most water-stressed country in America after Chile. Water stress could be a problem from the center in the north of the country by 2040.
Meanwhile, the extreme northwest is at medium to high risk of aquifer depletion, and virtually all of the Gulf of Mexico and the Caribbean Sea are at medium to high risk of drought, right where most desalination plants are.
The aqueduct takes into account 13 indicators of water stress such as groundwater availability and depletion.
In the past five months, the drought in Mexico – the third worst record of the century – has worsened as a result of the climate crisis, according to the National Weather Service.
Mexico’s water consumption is intense and is reflected in its water footprint – the impact of human activities on water – of 1,978 m3 / person per year, compared to a global average of 1,385.
As a result, national and regional authorities have their sights set on seawater, as Mexico is bounded by the Pacific Ocean to the west and the Atlantic Ocean to the east, and there are a total of 150 municipalities with a coastline totaling 2,466 under the National Policy for Mexico’s Seas and Coasts.
This screenshot from a video of the Baja California Sur government in northwest Mexico shows the location of the new Los Cabos desalination plant by the sea, including details of the various processes used to make the water from the Pacific fit for human consumption. CREDIT: IPSScalable model
This year, Héctor Aviña, a scientist at the Engineering Research Institute of the National Autonomous University of Mexico, is planning his prototype of a geothermally powered desalination plant in the city of Los Cabos in Baja California Sur, around 1,650 kilometers northwest of Mexico City.
“I don’t know if it’s the best option because of the brine production and exploitation of wells, but it’s a good alternative. Many areas are already under water stress. In these places, desalination and beach wells can help aquifers recover “Aviña told IPS from Mexico City.
The $ 500,000 plan provides for the modernization of a pilot plant from the current four m3 per day to 40 m3 and, if possible, to 400 m3. This is to be developed as part of an initiative with the Mexican state center for innovation in geothermal energy.
The project will use nearby hot water wells to generate water and geothermal energy.
With this technology, the cost per cubic meter of water is between 0.8 and 1.3 dollars, compared to 0.6 to 1.00 dollars for reverse osmosis.
The national infrastructure investment agreement signed in November 2020 between the federal government and members of the business community covers the foundations for four desalination plants in Baja California, Baja California Sur and Sonora with an investment of 643 million dollars and a capacity of 650 l / s.
However, Muñoz suggested eliminating poor irrigation practices, leaks, and aging infrastructure before desalination.
“Before considering desalination, priority should be given to measures such as saving water, investing in green infrastructure, harvesting rainwater and reusing treated water. We also need to compare the cost of building desalination plants with alternatives,” she said.
In 2014 Aviña designed a reverse osmosis model with solar panels and batteries that is competitive in cost.
“In other areas the energy source needs to be checked. Mexico will have water problems, it is a situation we have to live with. If we study it well, if we manage it well, desalination is a good alternative,” he argued.
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