Clewas

Israel has one of the most ambitious desalination programs in the world. With five massive plants operating along the Mediterranean coast, the country now produces 75-85% of its domestic drinking water from the sea. That’s roughly 600 million cubic meters of fresh water every year enough to fill about 240,000 Olympic-sized swimming pools.

But here’s the challenge: for every liter of drinking water these plants produce, they create nearly a liter of super salty brine as a byproduct. So where does all that brine go? The short answer is: back into the Mediterranean Sea. The more detailed answer involves sophisticated engineering, extensive environmental monitoring, and some important questions about long-term impacts that scientists are still working to answer.

The Scale of the Challenge

To understand what Israel is dealing with, you need to grasp the sheer scale of the operation. The country currently operates five major desalination plants:

Ashkelon (opened 2005): Produces 118 million cubic meters per year
Palmachim (2007): An early adopter of advanced diffuser systems
Hadera (2009): Produces 137 million cubic meters annually
Sorek (2013): The largest when built at 150 million cubic meters per year
Ashdod (2015): Uses state-of-the-art offshore diffusers

And that’s just the beginning. Two more enormous plants are under construction (Sorek B and Western Galilee) which will add another 300 million cubic meters of capacity annually. By 2050, Israel plans to more than double its current desalination capacity along its 190 kilometer Mediterranean coastline.

What makes this situation unique is the concentration. Unlike other countries that spread their desalination plants across thousands of kilometers of coastline, Israel has packed multiple mega-facilities into a relatively small area. Some plants are less than a kilometer apart. This density creates environmental management challenges that few other nations face.

The Brine Itself: What Are We Talking About?

Before diving into disposal methods, let’s understand what desalination brine actually is. When seawater enters a reverse osmosis desalination plant, high-pressure pumps force it through membranes that filter out salt and other minerals. What comes out the other side are two streams: fresh water and brine.

The brine is essentially concentrated seawater. Normal Mediterranean seawater has a salinity around 40 parts per thousand (ppt). The brine leaving Israeli desalination plants typically measures around 80 ppt; exactly twice as salty. It also contains polyphosphonate-based chemicals used to prevent scale buildup in the membranes, and in some cases, it’s warmer than ambient seawater.

This isn’t toxic waste, but it’s not harmless either. The higher salinity affects marine life, especially organisms living on the seabed that can’t simply swim away from areas of elevated salt concentration.

Two Sophisticated Disposal Methods

Israel uses two primary approaches to manage this brine, depending on the plant’s location and infrastructure.

Method 1: Mixing with Power Plant Cooling Water

Two of Israel’s plants (Ashkelon and Hadera) sit adjacent to electrical power stations. These power plants need massive volumes of seawater for cooling, which they draw in, circulate through cooling systems, and discharge back to the ocean slightly warmer than when it arrived.

Here’s where the clever part comes in: the desalination plants mix their concentrated brine with this huge flow of cooling water before discharge. The cooling water volume is so large that it dilutes the brine dramatically. By the time the mixture reaches the ocean, the salinity is only 5-10% higher than normal seawater, around 45 ppt instead of 40 ppt.

This mixing also changes the brine’s physical properties. Pure brine is denser than seawater, so it would naturally sink to the ocean floor and creep along the bottom as a “density current.” But when mixed with warm cooling water, the resulting discharge is actually buoyant. It floats near the surface where it disperses quickly, preventing the formation of those problematic density currents along the seabed.

This method has proven highly effective, but it comes with a dependency issue. When Hadera’s adjacent power station, Orot Rabin, began converting from coal to natural gas in recent years, it no longer needed the same volume of cooling water. This forced a major redesign of Hadera’s disposal system; a 2-kilometer offshore tunnel with a new diffuser system that cost significant time and money to implement.

Method 2: Offshore Diffusers at Depth

The other three plants (Palmachim, Sorek, and Ashdod) use marine outfalls with sophisticated diffuser systems. Think of these as underwater sprinkler systems designed for maximum dispersion.

Brine flows through pipes extending offshore, then gets discharged through multiport diffusers at about 20 meters depth. These diffusers spread the brine over a large area through multiple nozzles or ports, creating immediate dilution in what engineers call the “near-field.” The diffuser at Hadera, for example, was recently optimized from 60 meters down to just 18 meters in length through advanced computational fluid dynamics (CFD) modeling; a 70% reduction while still achieving better environmental performance.

Because this brine isn’t mixed with warm cooling water, it remains denser than the surrounding seawater. It sinks to the ocean floor and begins creeping along the bottom as a density current. These currents are a key concern because they can propagate tens of kilometers along the continental shelf, carrying elevated salinity far from the discharge point.

What Environmental Studies Have Found

Israel has conducted extensive environmental monitoring of its desalination operations, including a comprehensive six-year study of the Sorek and Palmachim outfalls. The findings paint a nuanced picture.

In the near-field (within hundreds of meters of discharge points):

Salinity increases by 4.3-9.1% above ambient levels
Temperature can rise up to 0.7°C near outfalls
The affected area ranges from 2 to over 13 square kilometers, depending on conditions
Brine plumes extend from 1.75 to more than 4.4 kilometers
Importantly, brine is dispersed near the bottom and NOT detected near the surface

What’s NOT affected:

Oxygen saturation levels remain normal
Water turbidity is unchanged
pH levels stay stable
Chlorophyll levels (indicating algae and phytoplankton health) show no impact
Metal concentrations remain unaffected
Most nutrients are unimpacted

The exception? Total Organic Phosphorus (TOP) from the antiscalant chemicals correlates with areas of excess salinity. Overall, the studies concluded there is “almost no impact on seawater quality.”

But here’s where it gets more complicated: studies of benthic organisms (creatures living on the ocean floor) show measurable impacts. Certain species, particularly organic-cemented agglutinated benthic foraminifera (tiny organisms crucial to the marine food web), show sensitivity to the elevated salinity. The impact zone typically extends tens to hundreds of meters from discharge points.

The Far-Field Mystery: Density Currents

The most concerning aspect of Israel’s brine disposal isn’t what happens right at the outfalls—it’s what happens farther away. Sophisticated modeling studies have revealed that density currents from diffuser-equipped plants don’t just dissipate quickly. They propagate as “small but robust salinity anomalies” that can travel tens of kilometers along the continental shelf.

These currents behave differently depending on the season. In winter, they’re relatively focused and propagate to greater distances and depths as they flow downslope. In summer, they mainly spread along the shoreline at shallower depths.

Here’s what makes this particularly complex: the brine plumes from different plants don’t exist in isolation. The density currents from Ashdod, Palmachim, and Sorek mix together and spread along the shelf as one intact plume. You can’t assess the environmental impact of individual plants separately when they’re this close together—you have to consider the cumulative effect.

Interestingly, the plants using power plant cooling water mixing (Ashkelon and Hadera) don’t create these far-field density currents at all. The mixing compensates for the brine’s negative buoyancy, preventing the formation of creeping bottom currents. This is one reason power plant co-disposal is considered highly effective—though, as we’ve seen, it depends on the continued operation of those power plants.

Strict Regulatory Oversight

Israel doesn’t take brine disposal lightly. Every desalination plant operates under strict permits from the Ministry of Environmental Protection (MOEP). These permits require:

Comprehensive environmental impact assessments before construction
Continuous monitoring programs throughout operations
Regular water quality sampling at multiple points
Benthic organism surveys to track ecosystem health
Salinity plume tracking using sophisticated instruments
Temperature monitoring
Chemical analysis of discharge water

The Hadera redesign demonstrates how this regulatory framework works in practice. When the power plant cooling water became unavailable, the new diffuser system had to meet stringent criteria. Through CFD modeling and design optimization, engineers reduced excess salinity at the seabed from 9.8% to 7.1%; a significant environmental improvement. They also halved the construction disturbance to the seabed by reducing excavation and backfill volumes by 20,000 cubic meters.

This kind of iterative improvement, driven by monitoring data and regulatory requirements, represents responsible environmental management at scale.

The Big Unknown: Long-Term Cumulative Effects

Here’s where we need to be honest about what we don’t know. The environmental studies to date, while extensive, are relatively short-term spanning six years for the most comprehensive research. As the scientists themselves noted: “It is unknown if the results of this short term study represent a steady state, with temporal variability, or the beginning of a slow incremental impact.”

This matters enormously because Israel isn’t maintaining current capacity; it’s planning to more than double it by 2050. That means more than doubling the volume of brine discharged into the Mediterranean along that 190-kilometer stretch of coastline.

Consider the implications:

Multiple density currents mixing and interacting in ways we don’t fully understand
Unprecedented concentration of mega-desalination plants in a small area
Potential cumulative effects that only manifest over decades
Marine ecosystems adapting (or failing to adapt) to persistently elevated salinity

No other country operates at this scale and concentration. Israel has essentially become a real-world laboratory for understanding the long-term marine impacts of massive desalination operations.

How This Compares to Global Best Practices

Israel’s approach largely aligns with international best practices for brine disposal, with some innovations:

Submerged offshore diffusers are considered the gold standard globally, and Israel uses them at three of five plants. These maximize initial dilution and reduce near-field impacts compared to simple shoreline discharge.

Co-disposal with power plant cooling water represents an effective strategy that prevents far-field density currents. This approach is used where feasible, though it creates dependency on power plant operations.

Continuous monitoring and adaptive management put Israel ahead of many nations. The willingness to redesign systems based on monitoring data (like Hadera) demonstrates commitment to environmental responsibility.

What Israel doesn’t use: zero liquid discharge (ZLD) systems that evaporate brine to produce solid salt. While these eliminate marine discharge entirely, they’re prohibitively expensive for the volumes involved in seawater desalination. They’re more common for inland brackish water treatment where marine disposal isn’t an option.

The Path Forward

As Israel moves toward producing nearly 100% of its domestic water from desalination, the importance of understanding and managing brine impacts only grows. The scientific community and regulatory authorities recognize that what’s needed is:

Long-term monitoring programs that extend for decades, not just years, to understand whether current impacts represent equilibrium or the beginning of incremental degradation.

Advanced predictive modeling that can forecast cumulative impacts before they occur, allowing for proactive management rather than reactive responses.

Adaptive regulations that evolve as scientific understanding improves, ensuring environmental protection keeps pace with expanded capacity.

International collaboration to share findings and best practices, since many nations face similar challenges as climate change drives increased reliance on desalination.

A Model for Responsible Desalination at Scale

So, what does Israel do with its desalination brine? The answer is: it manages it with sophisticated engineering and extensive environmental monitoring, using methods aligned with international best practices while acknowledging uncertainties about long-term cumulative impacts.

After 20 years of operation, studies show that immediate impacts are largely limited to near-field areas, with surface waters unaffected and overall seawater quality maintained. Regulatory oversight ensures continuous improvement, as demonstrated by system redesigns that reduce environmental footprints.

At the same time, the propagation of density currents tens of kilometers from discharge points and the unknown long-term effects of doubling capacity represent genuine environmental questions that require continued research and vigilance.

As one industry expert noted, “20 years of responsible desalination demonstrate the legitimacy of seawater as an alternative water source that can co-exist in harmony with the environment.” Scientists add the caveat: “A long term, adaptable program, in conjunction with specific research and modeling, should be able to assess and predict the impact of large scale brine discharge on the marine environment.”

For other nations considering large-scale desalination and with climate change driving water scarcity worldwide, many will need to; Israel provides both a model and a cautionary tale. The model shows that responsible, well-monitored brine disposal at massive scale is technically feasible. The caution reminds us that we’re still learning about long-term impacts in an unprecedented situation.

The Mediterranean isn’t a dumping ground, it’s a carefully managed receiving environment for a vital water supply system. Whether this balance can be maintained as capacity doubles remains one of the key environmental questions of our water-scarce future.

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