Brackish water isn’t quite fresh, but it’s not full-on seawater either. It sits in the middle, typically with 1,000 to 10,000 parts per million (ppm) of total dissolved solids (TDS). You can’t drink it untreated because it’s too salty. But it’s also not salty enough to be seawater, which means it needs its own specific treatment. That’s where brackish water reverse osmosis systems come in, they’re the go-to for industries and cities using these water sources.

You’ll often find brackish water where rivers meet the ocean, in coastal aquifers that have seen saltwater creep in, in farm drainage systems, and in “produced water” from oil and gas operations. If your industrial facility or city draws from these sources, that salinity level means you need a treatment approach built just for it.

How Brackish Water Differs from Seawater

Seawater has about 35,000 ppm TDS. Brackish water is much less salty, anywhere from 3% to 29% as saline. That difference is huge when you’re designing a treatment system. A seawater reverse osmosis (SWRO) system needs 800-1,200 psi of feed pressure. A brackish water RO (BWRO) system, though, usually runs at just 150-400 psi. Lower pressure means you use less energy. Often, it’s 0.5-1.5 kWh per 1,000 gallons for brackish RO, compared to 3-6 kWh for seawater RO. The U.S. Environmental Protection Agency even calls brackish groundwater a key alternative water source in places struggling with water.

Effective Treatment Methods for Brackish Water

Reverse osmosis is the gold standard for purifying brackish water. A well-designed BWRO system will pull out 95-99% of dissolved salts, heavy metals, nitrates, and most organic contaminants in one go. The main things we consider when designing are the source’s TDS, how clean you need the water to be, and how much water you need.

Pre-Treatment Requirements

Before the water hits the RO membranes, we usually pre-treat it. This often includes multimedia filtration to catch suspended solids, activated carbon to strip out chlorine and organics that could damage the membrane, and antiscalant dosing to stop calcium carbonate and sulfate from building up on the membrane surface. The American Water Works Association (AWWA) suggests SDI (Silt Density Index) testing before you size any membrane system.

Two-Pass RO for High-TDS Sources

Got really high-TDS brackish water, above 5,000 ppm? A two-pass RO setup might be what you need. This means running the water from the first membrane stage through a second set of membranes. It helps you get super clean water, like what’s used in pharmaceuticals or for boiler feed.

Ion Exchange as a Polishing Step

Ion exchange is another option for smaller jobs or for a final polish after RO. It’s especially useful when specific ions, like nitrates or hardness minerals, are your main concern. NSF International certifies both RO membranes and ion exchange resins under Standards 58 and 44, respectively.

Brackish Water vs. Seawater: Which System Do You Need?

Parameter	Brackish Water RO	Seawater RO
Source TDS	1,000-10,000 ppm	30,000-45,000 ppm
Operating Pressure	150-400 psi	800-1,200 psi
Energy Use	0.5-1.5 kWh/1,000 gal	3-6 kWh/1,000 gal
Salt Rejection	95-99%	99-99.8%

Industrial Applications for brackish water treatment

• Municipal water supply: Coastal cities are boosting their freshwater with treated brackish groundwater.
• Power generation: Boilers need low-conductivity water, and brackish treatment helps deliver that.
• Food and beverage: Process water and ingredient water need consistent TDS levels.
• Pharmaceutical manufacturing: We build USP purified water systems using brackish sources.
• Agricultural irrigation: Treated brackish water helps salt-sensitive crops thrive.

AMPAC USA Brackish Water RO Systems

AMPAC USA builds industrial brackish water reverse osmosis systems for everything from small communities needing 500 gallons per day to massive industrial plants that use millions of gallons. We design each system specifically for your source water’s actual TDS profile. There’s no single solution for brackish sources, as their ionic makeup can vary a lot based on geology, how close they are to the coast, and even farm runoff.

If you’re thinking about a brackish water treatment project, the first step is to get a full analysis of your source water. Our engineering team can look at your water quality data. Then, we’ll recommend the right membrane setup, pre-treatment train, and recovery ratio for what you need. Want to learn more? Check out our commercial RO systems or browse our water treatment blog for more technical guides.