ROTEC Presents on High-Recovery RO at the AWWA & AMTA Membrane Technology Conference
ROTEC recently presented at the Membrane Technology Conference, hosted by American Water Works Association and American Membrane Technology Association, where our team shared insights and data on how Flow Reversal Reverse Osmosis (FR-RO) continues to push the limits of high-recovery RO performance across industrial and municipal applications.
Across two technical sessions, ROTEC engineers explored both next-generation closed-loop FR-RO system design and field-proven HERO retrofits, highlighting how Flow Reversal helps overcome scaling, fouling, and hydraulic constraints that typically limit RO recovery.
Innovating High-Recovery RO with Closed-Loop Flow Reversal
Presented by Sapir Regev
In her session, Sapir Regev, Process Engineering Lead at ROTEC USA, introduced a closed-loop, multistage Flow Reversal RO strategy designed to enable ultra-high recovery while maintaining hydraulic balance and membrane stability.
The presentation addressed a key limitation of conventional high-recovery RO systems: as recovery increases, brine flow decreases, leading to concentration polarization, scaling risk, and hydraulic imbalance across stages. By combining block rotation, periodic flow reversal, and controlled concentrate recirculation, closed-loop FR-RO redistributes scaling stress and maintains minimum flow conditions even at recoveries approaching 90% and beyond.
Pilot results shared during the session demonstrated:
- Stable operation at ~90% total recovery
- Consistent permeate conductivity despite dynamic operation
- Improved flexibility compared to traditional RO and CCRO configurations
These findings point to closed-loop FR-RO as a promising path forward for water reuse, industrial wastewater treatment, and high-recovery RO systems constrained by scaling and hydraulics, with ongoing testing focused on expanding operating envelopes and feedwater variability.
Enhancing HERO Performance with Flow Reversal RO
Presented by Max Finder
In a second session, Max Finder, Head of U.S. Sales at ROTEC, presented operational data from a HERO retrofit at a zero liquid discharge (ZLD) combined-cycle power plant in the Southwestern United States.
The case study focused on integrating FR-RO into an existing HERO treatment train to address chronic fouling, frequent clean-in-place (CIP) events, and recovery instability caused by high silica, elevated iron, and variable pretreatment performance.
Post-retrofit results showed:
- Stable operation at ~86% RO recovery under high-TDS conditions
- Extension in CIP intervals
- Reduced chemical usage and lower operational complexity
- Decreased discharge to evaporation ponds, improving overall ZLD economics
- Increased permeate availability for boiler feed and makeup water
The presentation highlighted how Flow Reversal’s resistance to scaling and fouling allows HERO systems to operate more reliably, even when pretreatment performance is less than ideal, making FR-RO a practical upgrade path for inland power plants facing tightening water and discharge constraints.
Thank you to the American Water Works Association and the American Membrane Technology Association for their collaboration in hosting the Membrane Technology Conference and fostering meaningful technical exchange within the membrane community.