What Is Desalination? Definition, Pros and Cons.

View all blog posts under All Engineering | View all blog posts under Articles | View all blog posts under Environmental Engineering

We are in the midst of a global crisis, with billions of people lacking safe, reliable access to a fundamental necessity of life: clean water.

A water resources engineer examines piping at a plant.

The reasons behind water scarcity vary by region, but the primary factors include insufficient water infrastructure and ecological conditions. Climate change, which plays a role in lengthening and strengthening droughts and rising temperatures, only exacerbates the problem.

As drinking water becomes more scarce, finding new sources has become a top priority around the world. One promising technology to help address this challenge is desalination. Market research firm Arizton predicts the global desalination market will grow to $28.1 billion by 2026, up from $16.5 billion in 2020.

What is desalination? In the simplest terms, desalination is the process of removing salt from seawater, which offers the potential to generate billions of gallons of potable water. However, it comes with its own challenges. The process is energy-intensive, and that energy is often derived from fossil fuels, making it expensive and harmful to the environment.

But there are solutions. Knowledgeable professionals with expertise and an advanced education in engineering can help balance meeting human needs and protecting the environment.

Desalination Explained

The desalination process removes dissolved salts from water. This can include seawater, water from inland seas, mineralized groundwater, and municipal wastewater. The aim is to convert seawater into fresh water that’s safe for drinking, irrigation, and other uses.

Desalination is far from new. Ancient civilizations used various methods for desalination, including distillation and sedimentation. For example, in the fourth century B.C., the Greek city of Cyrene used a complex system of cisterns and filters to supply water to the city.

The widespread use of desalination originated in the mid-20th century. New technologies such as reverse osmosis, thermal distillation, and electrodialysis have made distillation more cost-effective.

In the modern era, desalination is an increasingly important solution amid the climate crisis, which has led to decreased precipitation. Desalination is helping meet the growing demand for water in many areas of the world where freshwater resources are scarce.

How Does Desalination Work?

For engineers who want to help solve the water crisis, understanding how desalination works is critical. The process involves separating salt molecules from water molecules. Several desalination methods can accomplish this, each with a different approach. For example, membrane processes are a class of water treatment technologies that use permeable membranes to separate salts and other impurities from water as it passes through. The two main types of membrane processes are reverse osmosis and electrodialysis. Below are descriptions of several different desalination methods.

  • Reverse osmosis is a filtration process that uses a semipermeable membrane. The process, which involves pushing water through the membrane, leaves dissolved salts and other impurities behind. It achieves this by using pressure to drive water through the membrane, which acts as a barrier to trap salts and other contaminants. Most of today’s desalination plants use reverse osmosis.
  • Electrodialysis uses an electric current to separate ions in salt water. An electric field applied across a series of ion-exchange membranes attracts and separates ions based on their charge. This separates the ions, creating two streams of water: one containing dissolved salts and another that is much less saline.
  • Thermal distillation involves boiling seawater, collecting the steam, then cooling the steam and condensing it into fresh water. This process removes dissolved salts and other impurities.
  • Solar desalination uses energy from the sun to heat water, leading to evaporation and condensation, separating salt and other minerals from the water. Solar desalination offers a sustainable and cost-effective solution that helps to reduce dependence on nonrenewable energy sources and lower greenhouse gas emissions.

Pros and Cons of Desalination

Desalination can increase water security, turning seawater into a dependable local source of water for drinking and irrigation. This is particularly helpful in regions with limited water resources that are facing droughts.

Desalination can also make communities less reliant on distant sources of fresh water, reducing the need to extract and transport water over long distances. In turn, this minimizes the need for heavy machinery and vehicles for transport, reducing carbon usage.

But despite what desalination can help accomplish, it also has drawbacks. For example, it can be expensive, requiring building and maintaining plants. It is also highly energy-intensive, which makes it cost-prohibitive in some regions.

Desalination processes also generate brine, a highly concentrated and salty waste product. The disposal of large volumes of brine can have negative effects on the marine environment and coastal ecosystems if not properly managed.

However, water resources engineering efforts targeting issues such as brine disposal and energy usage aim to enhance desalination processes and mitigate its damaging effects. These strategies use engineering equipment, facilities, and techniques to manage desalination processes. Water resource engineers help ensure that water is safe for humans, plants, and animals.

Be Part of the Solution to the Water Crisis

More than 70% of the planet is covered in water, but just 2.5% of that is fresh water, of which only a small part is drinkable by humans. Desalination has already yielded positive results around the world, providing a steady source of clean drinking water to areas that have experienced droughts or natural disasters, as well as in arid regions without regular access to water. Desalinated water can also be used for irrigation and livestock, making it a valuable resource for farmers.

While drawbacks to the desalination process can include negative impacts on the environment and coastal ecosystems and heavy use of fossil fuels to run desalination plants, efforts are underway to improve the technology and minimize its negative effects. If you’re interested in gaining a better understanding of what desalination is and being part of this solution, explore the online Master of Science in Engineering at the University of California, Riverside, which includes a specialization in environmental engineering.

Find out how the program can help put you on the path to finding solutions to the global water crisis.

Recommended Readings

What Is Clean Energy?

The Growing Need for Advanced Water Treatment

What Can You Do With An Engineering Degree?

Sources:

The American Society of Mechanical Engineers, “8 Engineering Challenges for Desalination Technologies”

Arizton, Water Desalination Market  — Global Outlook & Forecast 2021–2026

Britannica, Desalination

Council on Foreign Relations, “Water Stress: A Global Problem That’s Getting Worse”

Danfoss, “A Brief History of the Energy Intensity of Desalination”

Danfoss, “The Four Global Trends That Will Impact Desalination in 2022”

Keiken, “Is Solar Distillation Right for Efficient Desalination Plants?”

Livestrong.com, “Why Is Water So Important to Life on Earth?”

Multipure, “The Increasing Demand for Water”

National Geographic, “Why Is America Running Out of Water?”

Pure Water Group, “Electro Dialysis

Rainman, “Desalination Theory — How Desalination Works”

Treehugger, “What Is Desalination? How Does It Impact the Environment?”

United Nations, “Five Things to Know About Desalination”

The Washington Post, “Desalination Can Make Saltwater Drinkable — But It Won’t Solve the U.S. Water Crisis”

Water Defense, “What Is Desalination & How Does It Work?”

Water Supply, “Management of Reverse Osmosis Concentrate by Solar Distillation”