Mediterranean microalgae populations caused most Israeli desalination plants to shut down

Microalgae populations tens of kilometers long in the Mediterranean caused most of Israel's desalination plants to stop operating, affecting the nation's domestic water supply.

Mekorot, Israel's national water company, said on September 3 that 5 of the country's 6 coastal desalination plants had to be urgently closed after discovering giant microalgae mats drifting along the coastline. By September 4, some private facilities had partially reopened, but only one factory was operating at full capacity.

"This type of incident has never happened in Israel," said Mr. Lior Gutman, representative of Mekorot. However, he noted that the incident has not caused a shortage of drinking water sources.

Experts assess this as a red alert situation for this Middle Eastern country. As a dry land without major rivers, Israel has emerged as a "water technology superpower" thanks to its desalination system.

About 65% of Israel's domestic water supply currently depends on seawater filtration plants along the Mediterranean coast. Unusual signs began to appear late last week, said associate professor Edo Bar-Zeev, a water research expert at Israel's Ben-Gurion University.

Analysis results showed that an outbreak of microalgae, a type of single-celled organism that reproduces extremely quickly thanks to sunlight and nutrients in the water, was the cause of the incident.

Most Israeli desalination plants use "reverse osmosis" (RO) technology, in which seawater is pretreated before being passed through a microfiltration membrane to remove salt and bacteria. However, the density of microalgae is too high and the substances they secrete cause blockage and risk of damage to the filter system.

This microalgae carpet stretches at least 20 km, originating from the Nile Delta in Egypt and then following ocean currents drifting north to the Israeli coast. Mr. Bar-Zeev, who has 20 years of research into coastal seawater, affirmed that he had never seen a microalgae bloom on such a large scale.

To compensate for the water shortage, the Israeli government had to increase pumping capacity from Lake Galilee, reopen underground wells and release water reserves. Some localities have applied regulations restricting watering plants, pumping water into swimming pools and cutting off clean water sources used in agriculture.

According to the Israel Meteorological and Oceanic Agency, this outbreak is the result of sea storms that upset the sediment layer, making the water turbid, combined with sea temperatures soaring above 30 degrees Celsius.

Global climate change is identified as the core cause of this phenomenon appearing with greater frequency. This crisis also exposed water security vulnerabilities in countries that depend on desalination technology.

Focusing on a single technical solution makes the system vulnerable to natural disasters, oil spills or even cyber and military attack threats.

"Oil spills are the biggest concern. It's not a matter of 'will it happen', but 'when will it happen'. An oil spill can paralyze the entire water filtration plant for a much longer period of time than this microalgae carpet," Mr. Bar-Zeev warned.