4-Log Removal in RO Membranes: A New Era of Microbial Monitoring

Introduction

In the world of water treatment, verifying the removal of microbial contaminants is both critical and notoriously difficult. While reverse osmosis (RO) systems are known for their exceptional filtration performance, accurately and continuously validating that performance has remained a challenge — until now.

Orb's latest pilot, conducted in partnership with the U.S. Bureau of Reclamation and the Orange County Water District (OCWD), has demonstrated something unmatched in the industry: a verified 4-log reduction of a key microbial fluorescence marker in RO membranes, measured in real time.

This milestone is not just another performance metric. It sets a new benchmark in the field of drinking water safety, showing that water operators can achieve and verify high levels of microbial and organic compound removal with instant clarity.

The Need for Real-Time Biological Monitoring

Water operators must meet strict safety and compliance standards, especially as they integrate more advanced reuse technologies. Traditional microbial testing methods, particularly culture-based techniques, have limitations: they are slow (often taking 2–3 days to deliver results), labor-intensive, and incapable of capturing dynamic, real-time changes in microbial activity. In a system where bacteria can double every 20 minutes, such time lags translate directly into risk.

RO systems, which provide an assumed multi-log removal of microbes, are often conservatively credited with only 2-log removal due to the absence of continuous verification tools. This conservative assumption is not due to underperformance but to measurement limitations. This is where Orb's innovation comes into play.

Orb’s Innovation: A New Way to See Microbial Risk

For this pilot, Orb’s monitoring technology used autofluorescence — light emitted by specific organic molecules naturally present in microbial cells. When exposed to high-energy UV light, these molecules emit a distinctive fluorescence signal. This allows Orb sensors to detect microbial presence continuously, with no reagents or sample preparation required.

During the pilot study, Orb probes were installed at the OCWD Advanced Water Purification Facility, downstream of the RO treatment barrier. The goal was to evaluate whether Orb’s sensor could reliably and continuously track microbial reduction through the RO membrane system. The results exceeded expectations.

Unmatched Performance: 4-Log Reduction, Verified in Real Time

Orb’s system captured a 4-log reduction across the RO membrane — equivalent to 99.99 percent removal — in real time, without reagents, lab work, or delays.

To put this in context: current industry tools do not allow online validation of microbial removal at this resolution or speed. Flow cytometry, one of the most advanced lab-based methods, still requires time-consuming sample handling and expensive reagents. And while total cell counts provide insight into microbial abundance, they do not offer high temporal resolution or practical operational feedback.

Orb’s probe achieves this with ultra-low detection limits and sub-second feedback, opening new opportunities for operational excellence in water treatment.

Beyond Performance: What This Means for the Industry

This achievement is more than a technical milestone — it’s a gateway to smarter, more sustainable water management.

• Automated log crediting: Real-time microbial quantification means operators can gain regulatory recognition for actual removal performance, continuously validated in-line.

• Faster anomaly detection: If microbial fluorescence levels rise unexpectedly, operators get immediate alerts, allowing proactive responses instead of delayed action after lab confirmation.

• Resource efficiency: No reagents. Minimal maintenance. No lab overhead. The Orb platform turns a slow, reactive process into a fast, autonomous, data-driven one.

Backed by Credibility

The pilot was not only funded by the Bureau of Reclamation — one of the most respected names in water reuse innovation — but was also executed at OCWD’s flagship Advanced Water Purification Facility. Independent experts reviewed the data with the rigor expected from a government-funded evaluation.

This level of oversight and real-world validation sets Orb apart from technologies that have only been tested in controlled lab settings. Orb has proven its performance on full-scale assets under real operating conditions.

Conclusion: A New Standard in Water Monitoring

Orb’s demonstration of a real-time, 4-log reduction across an RO membrane marks a historic shift in how microbial water quality can be measured and managed. It proves that operators no longer have to choose between precision and practicality. With Orb, they get both.

For regulators, this opens the door to smarter crediting schemes. For operators, it means better control and faster responses. For everyone, it means safer water.

Orb’s sensors, powered by autofluorescence and informed by deep microbial science, are more than tools — they are a new lens through which to see, understand, and safeguard the microbiological integrity of our water systems.