Desalination technology promises to provide fresh water for millions. Can we mitigate its negative effects?

In our last episode, we discussed the basics of desalination technology and how it is being used to address water shortages. Find that episode here -    • Is Desalination the Solution to the W...  

Desalination is powerful technology, but it's not without drawbacks. It has a large energy footprint, it sends mineral-laden waste water into the ocean, and it negatively affects marine life at both ends of the process.

Most desalination plants still run on fossil fuels. Facilities fueled by renewable energy exist, but for now are limited to small-scale operations. Solar, wind, and geothermal energy are viable options for powering new desalination plants. Solar is the most common. When solar production fluctuates, a hybrid method that alternates renewable sources such as wind and solar may prove more reliable. Scientists are studying ocean power for desalination, as well as other ways to improve energy efficiency.

One promising technology, forward osmosis, separates water from dissolved solutes using a semipermeable membrane and the natural energy of osmotic pressure, requiring far less energy than the hydraulic pressure of reverse osmosis.

Another method uses low-temperature thermal desalination, which evaporates water at lower, energy-saving temperatures before reconstituting it into liquid form. But saving energy doesn't address another major issue: more than half of the seawater used in desalination is recirculated as briny wastewater laced with toxic chemicals added during the purification process. This brine is flushed back into the ocean by high-pressure jets, endangering sea life.

A recent study indicates that desalination wastewater is 50% brinier than we initially thought. Standards for releasing wastewater into the ocean vary greatly, and desalination plants frequently are clustered together in regions such as the Persian Gulf, the Gulf of Oman, the Red Sea and the Mediterranean, all continuously discharging warm brine into shallow coastal waters. This can increase seawater temperature and salinity while decreasing overall water quality, negatively impacting coastal marine ecosystems.

The plants' initial intake of seawater also endangers marine life. Drawing water from the sea kills fish, larvae, and plankton that are inadvertently siphoned into the desalination plant. Each year, millions of sea animals are sucked into desalination plants or trapped on their intake screens. Smaller fish pass through the screens and enter the system, perishing during the chemical processing of salt water.

Reducing the volume of wastewater that flows into the ocean, and dispersing it more efficiently, can further reduce negative effects on marine life. But full adoption and good enforcement are necessary for these treatments to be effective.

California has added a Desalination Amendment to its ocean water quality control plan. The amendment establishes a standardized permit process for desalination facilities that includes particular site, design and operating standards, limiting harm to marine life.

Desalination is expensive, it has negative environmental effects, and it doesn't ensure an abundant supply of freshwater for the world's expanding population. To avoid waste in the agricultural, residential, extractive, and industrial sectors, desalination must be paired with intelligent water conservation systems.

Investments in water conservation are a more environmentally friendly alternative. Worldwide, cities with limited water resources are demonstrating how conservation may be achieved by limiting consumption through cutting-edge techniques like wastewater reuse and greywater recycling. For instance, in 2021, as Lake Mead, its primary water source, dropped to dangerously low levels, Las Vegas banned ornamental grass permanently, one of many water consumption restrictions the city has imposed. Las Vegas also uses a cutting-edge wastewater treatment procedure to clean greywater and sewage for use on golf courses, parks, and businesses. Some of the clean water is then returned to Lake Mead for future use.

To guarantee a safe, consistent supply of water for a burgeoning population, humanity will need to employ every trick in the book, and likely use a few we haven't thought of yet.

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