By John — Desalination News
Ten days into the worst seawater contamination event in Israel’s history, two of the country’s six large Mediterranean desalination plants remain completely offline, and an attempt to treat the algae bloom at sea has failed to bring relief. The setback complicates the more optimistic picture painted earlier in the week, when officials had suggested the crisis was beginning to ease.
Ashkelon and Ashdod, near the Gaza border, stayed shut as of September 8 because of persistently high seawater turbidity, while the Palmachim, Sorek A and Sorek B plants south of Tel Aviv continued running at reduced output. Only the Hadera plant, roughly 25 miles north of Tel Aviv, is operating at full capacity. Together, the affected facilities normally supply a large share of a country that draws about 80% of its drinking water from desalination.
Aerial Spraying Didn’t Work
Authorities had hoped that dispersing copper-based compounds by aircraft along roughly 5.6 miles of coastline near Ashkelon would break up the bloom. Energy Minister Eli Cohen said on September 7 that turbidity levels showed no significant improvement following the treatment, and Israel’s Ministry of Health has since recommended a temporary fishing ban in the area.
With chemical treatment offline as an option, national water company Mekorot is now studying whether intake pipelines could be extended further offshore, beyond the zone of highest algae concentration. Cohen said a recommendation is expected within days, though no cost estimate has been produced yet.
Membranes at Risk
The bigger concern for plant operators is equipment damage. Reverse-osmosis membranes normally rated to run for around seven years could foul and fail far sooner under current conditions, according to Cohen. The Water Authority and Energy Ministry are now moving to build up a reserve of replacement membranes so that damaged units can be swapped out quickly rather than taking a plant fully offline.
Household and agricultural supply has held up despite the shutdowns, with lost desalinated output made up through increased pumping from the Sea of Galilee, groundwater wells, and Mekorot-managed reservoirs. But the strain on that backup system is one reason experts have flagged the country’s heavy reliance on a handful of large coastal plants as a structural vulnerability.
Origin Still Contested
Researchers at Israel Oceanographic and Limnological Research say the microalgae bloom likely originated near Egypt’s Nile Delta and drifted north on Mediterranean currents, consistent with the marine contamination already identified as the trigger for the shutdowns. Warm seawater — at least 86°F — and storm-driven mixing are cited as contributing factors.
A separate question is how much untreated sewage from Gaza fed the bloom. The UN reported that more than 39.6 million gallons of untreated wastewater a day was being discharged while repairs continue on a damaged treatment facility there, and Israeli environmental group Zalul has pointed to sewage as one contributing factor. Cohen has rejected a direct link, citing satellite imagery pointing to a Nile-region origin, and says the question remains under scientific investigation.
A 2024 State Comptroller audit had already found 14 seawater-contamination events disrupting Israeli desalination production between 2007 and 2023, and warned that climate change could make such events more frequent. Israel is pursuing a long-term desalination expansion — including a planned near-doubling of the Ashkelon plant’s capacity — but the national water-sector master plan flagged as overdue in that audit remains unfinished.