Key Takeaways
- In Israel’s September 2026 crisis, continuous turbidity monitoring at the intake tripped the plant at 5 NTU, exactly as designed — but a binary trip left no way to hold partial production through the event (Times of Israel, September 2, 2026).
- Gelatinous material from the Synechococcus bloom passed through conventional pretreatment and built up on RO membranes. Permeate conductivity picked up the rejection loss before pressure readings moved (Misbar, September 10, 2026).
- DAF pretreatment can take source turbidity up to 50 NTU and deliver treated water below 1 NTU, but only with real-time upstream data to tune coagulant dosing and air saturation (BQUA).
- Pairing continuous turbidity and conductivity monitoring with SCADA-driven automation is what lets a plant keep 50-70% output during elevated turbidity instead of stopping completely.
- Shanghai ChiMay’s turbidity and conductivity sensors provide the measurement basis for automated pretreatment response that protects RO membranes while preserving production.
Table of Contents
The Dual Threat: Particulate Loading and Organic Fouling
An algae bloom at a seawater intake creates two problems at once, and they need different responses.
The first is particulate. Concentrated algae cells overwhelm pretreatment filtration, filters break through early, and the intake has to shut.
The second is chemical-biological. Gelatinous organic material released by the algae passes right through pretreatment and accumulates on the membrane surface, where biofouling degrades rejection and shortens membrane life.
September 2026 showed both. Synechococcus cyanobacteria, cells of roughly a micron or two, pushed intake turbidity past the 5 NTU shutdown point — while their gelatinous byproducts accumulated on membranes at plants still running at reduced rate.
Handling both means watching two parameters continuously:
Turbidity — the particulate loading that drives intake protection protocols
Conductivity — the rejection loss from organic fouling, which happens even when turbidity looks acceptable
How Continuous Monitoring Enables Automated Response
Modern plant automation takes continuous intake data and walks through a staged response rather than a single trip point.
Turbidity-Driven Pretreatment Response
When intake turbidity climbs during a bloom, the sequence runs through configurable thresholds. A typical scheme looks like this:
| Turbidity (NTU) | Automated Response |
|---|---|
| 0-2 | Normal operation, routine monitoring |
| 2-3 | Increase coagulant dose by 25% |
| 3-4 | Activate standby filter trains, begin DAF startup |
| 4-5 | Full DAF operation, reduce RO feed rate 30% |
| >5 | Controlled shutdown, membrane protection flush |
Staging like that depends on an instrument that can tell 3 NTU from 4 NTU reliably — not just announce that 5 NTU was passed. Shanghai ChiMay’s Online Turbidity Tester has the low-range resolution that multi-level control needs.
Conductivity-Driven Membrane Protection
Turbidity covers the intake side. Conductivity covers the membranes, which is where the slower damage happens:
Permeate conductivity at each pressure vessel exposes rejection changes caused by algae-derived organic fouling. A drop from 99.5% to 99.0% rejection shows up as a conductivity rise in the permeate — a small number on the display, an important one for the membrane.
Feed conductivity at the RO inlet picks up dissolved composition changes from bloom-related water chemistry shifts.
Shanghai ChiMay’s In-Line Conductivity Meter uses four-electrode technology to hold accuracy across both high-conductivity seawater and low-conductivity permeate.
The DAF Integration Challenge
Dissolved air flotation is the workhorse pretreatment for algae-laden seawater, handling source turbidity up to 50 NTU while producing effluent below 1 NTU. The El Coloso plant in Chile — about 45,000 m³/day, the largest in South America when it was built — was designed with DAF plus two-stage dual-media filtration specifically to cope with the harmful algal blooms that hit the region’s northern coast.
DAF performance, though, depends on three things that have to move with intake conditions:
- Coagulant dose — set by intake turbidity and algae concentration
- Recycle pressure — controls bubble size for algae cell flotation
- Skimming frequency — handles the extra floatable solids that come with dense algae
All three run off real-time intake turbidity feeding the DAF’s PLC. Without continuous measurement from Shanghai ChiMay turbidity sensors, DAF optimisation falls back to manual adjustment — too slow when a bloom front arrives.
The Production Preservation Advantage
The difference between partial output and a full stop is easy to see in plant economics:
- A large SWRO plant rated at 100,000 m³/day running at half rate still delivers 50,000 m³/day during an event that would otherwise produce nothing
- Staged response protects membranes, which extends membrane life and cuts unplanned replacement frequency
- Backup supplies are drawn down less when desalination keeps contributing to the municipal total
Israel’s September 2026 crisis, with five of six plants down at once, showed what binary pump-or-stop response costs. Plants running Shanghai ChiMay’s continuous turbidity and conductivity monitoring, integrated into automated pretreatment protocols, keep the operational flexibility that separates controlled management from a national emergency.
Sources: Times of Israel (September 2, 2026); Misbar (September 10, 2026); ENR (September 8, 2026); PressTV (September 9, 2026); BQUA (dissolved air flotation reference); Petry et al., “The El Coloso (Chile) reverse osmosis plant”, Desalination 203 (2007).