Five of Israel's six desalination plants along the Mediterranean coast have been operating at reduced capacity or not at all since Monday after an unusual microalgae bloom originating in the Nile Delta fouled seawater intakes, the Water Authority has confirmed. On 2 September 2026 CTech reported that three of the five affected plants had received approval on Tuesday to resume partial operations as authorities struggled to predict when the bloom would end.
Key takeaways
- Five of six Israeli desalination plants halted or reduced operations after a Nile Delta microalgae bloom, on 2 September 2026 (CTech).
- About 80% of Israel's drinking water comes from large desalination plants (CTech).
- The Water Authority has halted irrigation of public gardens and instructed farmers in the south to stop irrigating, while household supply continues normally (CTech).
- Alon Zask of the Israel Oceanographic and Limnological Research Institute called the bloom "unprecedented" in scale along Israel's coast (CTech).
- Three plants received approval on Tuesday to resume partial operations despite the risk of membrane damage costing several million shekels to replace (CTech).
What happened
About 80% of Israel's drinking water is produced by large desalination plants, and some farmers in the south also depend on desalinated water for irrigation as the Kinneret, the coastal aquifer and other natural sources have yielded less water over time, particularly during prolonged droughts (CTech). Israel entered the current episode with groundwater reserves depleted and the Kinneret below its red line, and operational water reserves were also not full when the disruption began (CTech).
The trigger was an unusual marine event following stormy weekend weather. Turbidity in the Mediterranean, combined with a bloom of microalgae originating in the Nile Delta, forced the plants to suspend normal operations, with the bloom spreading across dozens of kilometres (CTech). The algae are small enough to pass through the filtration systems at the seawater intakes, and continuing to run under those conditions could eventually damage the plants' reverse-osmosis membranes, potentially requiring replacements costing several million shekels (CTech).
On 2 September 2026 CTech reported that three plants had been cleared the previous day to resume partial operations in a trade-off between maintaining production and avoiding membrane damage, and that the state will compensate operators if membranes are damaged. The Ministry of Energy and Infrastructure, the Water Authority and Mekorot said the water system is "excellently prepared for these scenarios," with household and industrial supply continuing while agriculture faces restrictions (CTech). The Water Authority has halted irrigation of public gardens and instructed farmers in the south to stop irrigating fields (CTech).
Alon Zask, director of the Israel Oceanographic and Limnological Research Institute, said: "We know for certain that these are algae. This is an unprecedented event. I've never seen anything like it. I haven't seen a bloom at this intensity along Israel's coast." Zask added that it is impossible to predict how long the phenomenon will last and that, if turbidity remains high, Israel will need a way to reduce it sufficiently to allow desalination to continue (CTech). He also warned that warmer water linked to climate change could make such blooms more frequent.
The Israel Farmers Federation said damage to many crops is already severe and irreversible, particularly for vegetables and orchards days from harvest, and called on the government to act immediately (CTech). The Water Authority is examining whether dissolved-air flotation-style pretreatment used at the Kinneret — adding a coagulant and pumping millions of tiny air bubbles to lift algae to the surface — could be deployed ahead of desalination intakes (CTech).
Specification read
Reported scale: about 80% of Israel's drinking water from large desalination plants (the source does not give a total flow in m³/day, so a class range applies below). Treating that share against Israel's population and typical per-capita demand, a national desalination train of this class is on the order of 1.6 million m³/day, or roughly 6 million population equivalent (general industry range, not from the sources). The disruption touched five of six plants, so the at-risk capacity is effectively the whole fleet except one site.
Treatment train: Mediterranean SWRO at this scale typically runs screening → coagulation / DAF or dissolved-air flotation pretreatment → cartridge or multimedia filtration → high-pressure reverse osmosis → post-treatment remineralisation and disinfection. The event bears directly on the pretreatment stage, where algae, turbidity and organic loading are removed before they foul RO membranes, and on the membrane stage itself, which the source says can be damaged if raw water carrying the bloom is processed without adequate pretreatment.
Buyer implication: if your plant looks like a large-scale seawater RO site in the tens of thousands to hundreds of thousands of m³/day range, drawing from warm coastal water with variable turbidity and seasonal algal loading, and you supply potable water and/or irrigation to downstream users with tight continuity expectations, this event is a reminder that pretreatment robustness — DAF or bubble-flotation capacity, redundant intakes, membrane protection protocols — is now a procurement specification, not an option. For buyers running brackish or reuse plants, the same pretreatment logic applies when feed water carries algal or organic spikes.
For pretreatment and biological-stage equipment used to buffer these feed conditions, see our Water Purification hub and the Industries We Serve index. For context on membrane-based biological trains that pair with RO pretreatment, see the related comparison MBR vs Conventional Activated Sludge for Mining Wastewater in Smyrna, US (2026 Guide) and our prior write-up of this same event, Israel desalination plants shut by microalgae bloom, September 2026.
FAQ
What triggered the shutdowns of Israel's desalination plants on 2 September 2026? An unusual microalgae bloom originating in the Nile Delta, combined with Mediterranean turbidity after stormy weather, forced the plants to suspend operations because the algae are small enough to pass through the seawater intake filters and could damage RO membranes (CTech).
How much of Israel's water supply is at risk from this kind of event? About 80% of Israel's drinking water comes from large desalination plants, so any prolonged interruption has national reach, even though household supply was maintained during this episode through reserve management (CTech).
What is the likely cost exposure if RO membranes are damaged by the bloom? Membrane replacement is described in the source as running to several million shekels per plant, with the state expected to compensate operators if damage occurs (general industry range for SWRO membrane replacement on large trains: USD hundreds of thousands to low single-digit millions per train, not from the sources) (CTech).
What pretreatment upgrade should a buyer specify to protect a coastal RO plant from algae events? The source points to dissolved-air flotation / bubble-flotation pretreatment already used at the Kinneret — adding a coagulant and pumping millions of tiny air bubbles to lift algae to the surface — as the option Israel is now examining for its seawater intakes (CTech).
