Brine facts for kids

For other uses, see Brine (disambiguation).

Brine is simply water with a lot of salt dissolved in it. Think of it as super salty water! The most common salts in brine are sodium chloride (table salt) or calcium chloride.

The amount of salt in brine can vary a lot. For example, regular seawater is about 3.5% salt, which is a type of brine. But some brines can be much saltier, up to 26% salt, meaning the water can't dissolve any more salt.

Brine can form naturally when salty water evaporates, leaving the salt behind. It's also made when we mine for salt. People use brine for many things, like preserving and cooking food, melting ice on roads, and in various industrial processes. Sometimes, brine is a leftover product from factories, like those that remove salt from seawater (desalination). When this happens, it needs special handling to protect the environment.

How Brine Forms in Nature

A NASA technician measures the concentration level of brine using a hydrometer at a salt evaporation pond in San Francisco.

Brine appears in nature in several interesting ways.

Evaporation: When seawater or salty groundwater evaporates, the water turns into vapor, but the salt stays behind. This makes the remaining water much saltier, creating brine. Over long periods, this can form thick layers of salt deposits, like those found in salt mines.
Dissolving Salt: Sometimes, water flows through underground salt deposits. As it moves, it dissolves the salt, turning into brine.
Freezing: When seawater freezes, the salt doesn't become part of the ice. Instead, it gets pushed out into the surrounding water, making that water super salty and very cold. This cold, dense brine can sink and create amazing formations called brinicles, which look like icy "fingers of death" freezing everything they touch on the seabed!
Salty Springs: You might find natural saltwater springs, sometimes called "licks" or "salines," where brine comes up to the surface from underground.
Underground Water: Brine can also be found deep underground. Water with a very high amount of dissolved solids (more than 100,000 milligrams per liter) is considered brine.

Cool Ways We Use Brine

Brine is incredibly useful in many industries and even in our daily lives!

Extracting Important Elements

Brine is a valuable source for getting important elements like iodine and bromine.

Iodine: This element is vital for human health. We get it from brines rich in iodide. Factories use a special process with chlorine to turn the iodide into iodine, which is then collected.
Bromine: Like iodine, bromine is also taken from brines. Chlorine helps change bromide in the brine into bromine, which can then be separated.
Lithium and Magnesium: Many large deposits of lithium are found in brines. Magnesium is also made from brines, often as a leftover from other processes. These metals are then extracted using electricity.

Making Chlorine Gas

Brine is key to making chlorine gas, which is used in many products like cleaning supplies and water treatment. This process uses electricity to split the salt and water in brine. It creates chlorine gas, hydrogen gas, and sodium hydroxide (a strong chemical).

The overall process looks like this: 2 NaCl + 2 H
2O → Cl
2 + H
2 + 2 NaOH

Keeping Things Cold

Brine is a great coolant! Adding salt to water makes its freezing point much lower. This means brine can stay liquid at very cold temperatures.

It's used in large refrigeration systems to move heat around.
Some fishing boats use brine spray to quickly freeze fish, keeping them fresh.
However, because brine can be corrosive (it can rust metals), other liquids like ethylene glycol are sometimes used instead in modern systems.

Cleaning and Softening Water

Brine plays a role in making our water cleaner.

It's used to "recharge" special beads called ion-exchange resins in water softeners. These beads remove hard minerals like calcium and magnesium from water. When the beads are full, soaking them in brine helps them release those minerals and get ready to clean more water.

Cooking and Preserving Food

Brine is a superstar in the kitchen!

Preservation: Brining is a traditional way to preserve foods like vegetables, cheeses, fruit, and some fish. This process is often called pickling.
Flavor and Tenderness: Soaking meat and fish in brine for shorter times can make them more tender and flavorful. It also helps them stay fresh longer.

Melting Ice on Roads

You've probably seen brine in action during winter!

Salty brine solutions are sprayed on roads and sidewalks to melt ice or prevent it from freezing. This makes surfaces safer for walking and driving.

Hardening Metals

In metalworking, brine is used in a process called quenching.

When hot metals like steel are quickly cooled in brine, it helps to harden them evenly.

Desalination: Turning Saltwater into Fresh Water

Desalination is a process that removes salt from seawater or brackish water to create fresh water that we can drink or use. A lot of brine is produced as a leftover product during this process.

Marine brine discharge in Chile with its surrounding marine life

What is Desalination Brine Like?

The brine that comes out of a desalination plant is usually much saltier than the original seawater. In some cases, it can be twice as salty! However, modern desalination plants often release brine that is similar in temperature and dissolved oxygen to the surrounding seawater.

Are There Other Chemicals in Desalination Brine?

Sometimes, small amounts of chemicals are used in the desalination process to help it work better. These chemicals are mostly used up during the process. Any tiny amounts that remain in the brine are usually diluted very quickly when released into the sea. This means they generally don't harm marine ecosystems.

What About Metals?

Modern desalination plants use materials like stainless steel and non-metallic parts that resist rusting. This helps prevent harmful heavy metals from getting into the brine discharge. The levels of metals in the brine are usually very low and not enough to cause environmental problems.

How is Desalination Brine Released?

The salty brine is typically returned to the sea through underwater pipes or released along the coast. Because brine is denser (heavier) than regular seawater, it tends to sink. To prevent it from just sitting on the bottom, special diffusers are used. These diffusers help mix the brine with the surrounding seawater quickly, so it gets diluted and spreads out.

Protecting the Marine Environment

If not managed carefully, very salty brine could affect sea creatures that live on the seabed, especially those sensitive to changes in salt levels. This could impact their numbers and variety. However, many countries, like Spain, Israel, Chile, and Australia, use smart methods to reduce any potential harm. These methods ensure that desalination can happen without causing big problems for marine life. Older plants that didn't use these methods sometimes saw more effects on the environment. Today, with proper measures, the salty plume from brine discharge usually mixes and becomes harmless within a short distance from the release point.

Ways to Protect the Environment

Here are some ways we protect marine environments from brine discharge:

Smart Discharge Systems: Using well-designed pipes and diffusers helps mix the brine quickly with seawater.
Environmental Studies: Before building a plant, experts study the area to find the best place to release the brine. They look at things like ocean currents and the shape of the seabed to ensure fast mixing.
Monitoring Programs: Regular checks are done to make sure the desalination plants are working correctly and not harming the environment. This helps catch any potential problems early.

Rules and Regulations

Many countries have strict rules for desalination plants. They require detailed environmental impact assessments before construction and during operation. These rules make sure that plants are built and run in a way that protects the environment. Regular monitoring programs are also put in place to check the water quality and marine life around the discharge areas.

Brine as Wastewater

Brine can also be a leftover from many other industrial processes, not just desalination. For example, it comes from power plant cooling towers, oil and natural gas extraction, and some chemical factories. This kind of brine can contain not only salts but also residues from cleaning chemicals or even heavy metals from corroded equipment.

This wastewater brine can be harmful to the environment if not handled properly. The high salt content can damage soil and water, and other chemicals in it can be toxic.

Brine from desalination plants and cooling towers that isn't polluted can often be returned to the ocean. To reduce its impact, it might be diluted with other water streams, like treated wastewater. Since brine is heavier than seawater, it needs to be released in a way that ensures it mixes well, often using underwater diffusers. Other ways to manage brine include drying it in large evaporation ponds, injecting it into deep underground wells, or storing it to reuse for things like irrigation, de-icing, or controlling dust.

For polluted brine, special technologies are used to treat it. These include advanced filtration systems, ion exchange processes, or evaporation methods that separate the water from the salts and other chemicals. New methods are always being developed to treat brine more efficiently and reduce its environmental impact.

What's in Brine and How We Clean It

Brine is mainly a concentrated solution of sodium (Na⁺) and chloride (Cl⁻) ions. Other common ions found in different brines include potassium (K⁺), magnesium (Mg²⁺), calcium (Ca²⁺), and strontium (Sr²⁺). Magnesium and calcium can be problematic because they can form scale (hard deposits) and react with soaps.

Besides chloride, brines sometimes contain bromide (Br⁻), iodide (I⁻), and sulfate (SO₄²⁻). To purify brine for specific uses, unwanted substances are often removed. For example, calcium oxide can be added to make solid magnesium hydroxide and gypsum (CaSO₄) precipitate out, which can then be filtered. Further cleaning can be done by a process called fractional crystallization. The very pure salt that results from this is called evaporated salt or vacuum salt