‘Extremely rare event:’ Miles-long microalgae bloom knocks out most of Israel’s desalination plants

By Laura Paddison, CNN

(CNN) — A miles-long microalgae bloom in the Mediterranean Sea has been blamed for temporarily knocking offline many of Israel’s major desalination plants this week, threatening its main source of drinking water.

Five of the country’s six coastal desalination plants — which convert seawater into drinkable water — shut down on Sunday, according to Mekorot, Israel’s national water company. Since then, some of these facilities, which are privately owned and operated, have partially resumed operations, but only one was operating at full capacity on Thursday.

“An event of this kind has never occurred before in Israel … it was an extremely rare event,” said Lior Gutman, a spokesperson for Mekorot, although he stressed in roughly 99% of cases, there has been no drinking water shortage.

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Still, it’s an alarming situation given the country’s heavy dependence on desalination for drinking water. Israel is arid and has neither big rivers nor abundant rainfall, but its mastery of this technology has made it a water superpower. Desalination now provides at least 65% of its drinking water, with most plants located on the Mediterranean coast.

The problems started at the weekend, as a “sporadic, vast event of contaminates occurred across the Israeli coastline,” said Edo Bar-Zeev, an associate professor in water research at Ben-Gurion University, in Israel. When he and other scientists looked closer, they discovered it was microalgae, tiny organisms that feed on sunlight, carbon dioxide and nutrients in the water — and which can grow rapidly.

The microalgae bloom — stretching more than a dozen miles at least, according to Bar-Zeev — is believed to have originated in the Nile Delta and traveled northward with the sea’s currents up Israel’s coast. This is “the first time I saw something in this extent,” said Bar-Zeev, who has been testing the coastal water for 20 years.

The country’s desalination facilities mostly use a technology called “reverse osmosis,” where water is pre-treated to remove larger contaminants, before it’s pushed through membranes which filter out salt, bacteria and other molecules to leave clean drinking water.

Algae, and the substances they produce, can foul and damage the membranes, said Michael Christopher Low, director of the Middle East Center at the University of Utah. If there’s too much suspended material in the water, the treatment processes cannot keep up.

It’s happened before. A severe “red tide” — a harmful algae bloom — in the Gulf of Oman in 2008 and 2009 affected many desalination plants in that region.

In Israel, the government water system has “stepped in to close the gap” caused by the plant closures, Mekorot’s Gutman said. This has included pumping water from the Sea of Galilee, activating groundwater wells and using national water reserves.

Some cities have faced short-term local restrictions, including on garden irrigation and filling swimming pools, but the the main limitations affected farmers who use drinking water-quality water for irrigation, as opposed to those who use recycled water, Gutman said.

The timing compounded the problem. It happened in summer “when water demand in Israel is at its highest,” he said, adding “the situation has been challenging.”

A bloom occurs when the right combination of environmental factors in the water come together that allow the algae to grow rapidly, said Tamar Guy-Haim, a marine ecologist at the Israel Oceanographic and Limnological Research Institute. These include nutrients, temperature, light, currents and mixing.

Mekorot said this recent bloom was part of “very unusual combination of factors,” including a sea storm that increased turbidity — the amount of suspended matter in the water — and raised sea temperatures to 86 Fahrenheit (30 degrees Celsius) and above.

The extent of the disruption is striking. Desalination facilities have been forced to close before due to algae or jellyfish, “but multiple facilities over the large portion of our coast is something that is definitely abnormal,” Ben-Zeev said.

It’s something the country needs to figure out how to deal with — and will, he added. “It’s a fair estimation that this will not be a once-in-a-lifetime kind of event … you can assume that this will occur more and more through climate change.”

As the planet heats up, driven by humans burning fossil fuels, the oceans are changing. Temperatures are at record highs, currents are shifting and stronger storms wash more pollutants into the water, including sewage and fertilizers, which can trigger huge algae blooms.

This temporary crisis also exposes a broader concern, experts say.

Desalination is becoming increasingly popular, especially as the climate crisis drives more severe heat and drought, undermining water security. But this growing dependence on a centralized, technical solution carries risks. “This event is causing considerable alarm and even some criticism that the system is too vulnerable to a dramatic disruption,” Low said.

This could be natural or climate change-driven events, but there’s also the possibility of military and cyber threats. Desalination plants in the Gulf have been targeted and damaged during the US-Iran war, raising significant alarm in a region that depends overwhelmingly on this technology. Hackers have also targeted water facilities, including in the US.

Oil spills are another big concern. “It’s not if, it’s just when an oil spill in the vicinity of desalination facilities will occur,” Ben-Zeev said. A lot of plants are in water-scarce countries that are also big oil producers, such as the Gulf states.

A spill could potentially take plants offline for a much longer time than this microalgae bloom, he added. “That to me is way more worrying.”

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