PFRO Technology: Enhancing Water Treatment Efficiency and Sustainability

PFRO: Pulse Flow Reverse Osmosis is a new, creative technique for running Reverse Osmosis water reuse systems that allow for high recovery, high flux, and Chloramine-free operation.

While chloramine can help preserve the RO membrane from biofouling, it has certain unfavorable side effects.

Chloramine causes disinfection byproducts to develop, which is a hazardous chemical and a possible human carcinogen.

PFROTM’s continuous changes considerably reduce biofouling and scaling in osmotic and hydraulic conditions.

PFRO discharges brine in a pulse flow regime, with brief, powerful surges, instead of the continuous brine discharge mode used by traditional RO.

This surge delivers a high shearing velocity, cleans the membrane and allows for faster recovery in a single-stage operation.

Pulse flow reverse osmosis rapidly increases brine flow concentration during production (Dead-End 100% recovery) and rapidly decreases brine flow concentration during short-term rejection flush.

How PFRO Works?

Contrary to typical RO systems, PFRO operates in an intermittent regime. Approximately 95% of the time, the water flows in a dead-end mode, where all the feed water passes through the membrane, and the brine valve is closed. During the remaining time, the brine valve opens, and a high-velocity brine flow flushes the system, creating high-shear forces. This periodic flushing eliminates the need for a constant brine flow, making the staged design of traditional RO systems unnecessary.

Two cycles of PFRO operation

The PFRO procedure is divided into two stages: the first stage is the Manufacturing cycle and the second is the rinsing cycle.

The brine valve (connected to the leftover brine flow) is closed during the manufacturing cycle, and the brine is not drained.

The translucent side receives 100% of the feed stream. On the supply membrane side, the salt concentration builds up. During the flushing cycle, the brine valve is opened briefly and the brine is emptied quickly.

In these cycles, the following activity occurs: Brine is provided in brief, intense pulses, and only the most concentrated brine is expelled.

During the flush process, the pressure decrease in each vessel increases.

The shear produced by high brine flow is many times greater than that produced by standard RO.

Pressure strokes and micro-shaking are caused by the brine valve’s rapid opening and shutting.

Membrane cleaning has a synergistic cleaning effect because of the combination of shear rates, membrane shaking, FO backwash and alternating osmotic and positive pressure.

Membrane components function as tensioned micro-drumheads.

The water hammer that happens when the brine valve is rapidly closed at the end of each flash cycle is thought to generate the vibration of these drumheads.

The production and flushing cycle in the commercial-size RO train is spread in the pressure vessel so that the overall supply, permeate and brine flow is practically constant over time.

Pressure vessels are classified. Each group has a single brine valve that regularly opens and closes.

As a result, only a small percentage of the PV is always in flush mode.

As a result, the high-pressure pump maintains a steady working point.

PFRO in wastewater

Traditional water treatment technologies have limitations in terms of high recovery.

The water properties of industrial and municipal wastewater are often highly demanding.

While each situation is unique, such water typically contains a variety of sparingly soluble salts, metals and organics.

When those components are concentrated in a reverse osmosis (RO) system, they tend to generate scale, fouling and bio-fouling, which risk membrane integrity.

Traditional RO works in steady hydraulic and osmotic conditions, which increases the likelihood of scaling and fouling.

Furthermore, the stable conditions allow bacteria to grow on the RO membranes, resulting in biofouling.

IDE Technologies’ proprietary Pulse Flow Reverse Osmosis (PFRO) technology, on the other hand, solves these fundamental RO issues through mechanical and chemical processes.

It accomplishes this by constantly adjusting the flow regime, as well as the osmotic and hydraulic pressures.

The PFRO system achieves this by boosting water recovery without increasing membrane cleanings or replacements.

PFRO in Brackish Water Desalination

PFRO technology is not limited to wastewater treatment but also finds applications in brackish water desalination. A case study conducted at a BWRO desalination facility in Abilene, TX, demonstrated the effectiveness of PFRO in treating brine from the plant’s 3rd stage and producing additional permeate. The study compared the performance of PFRO with standard RO and highlighted the advantages of PFRO in terms of high recovery and minimized scaling issues.

The PFRO unit in Abilene operated dynamically, constantly changing the osmotic and hydraulic conditions to achieve high recovery rates. This approach significantly reduced biofouling and scaling, allowing for higher product yield while minimizing discharge. The study also considered the technological and economic aspects of specific energy and capital expenses, further reinforcing the benefits of PFRO in brackish water desalination.

Advantages of PFRO technology

PFRO offers several advantages over traditional RO systems. Firstly, the constantly changing hydraulic conditions make it difficult for microorganisms to thrive, reducing the risk of biofouling formation. This allows PFRO to operate at very high flux, around 50% higher than normal, resulting in significant capital expenditure (CAPEX) savings.

Furthermore, PFRO eliminates the need for chloramine dosing, a common practice in traditional RO systems to control biofouling. Chloramine dosing can lead to the formation of disinfection byproducts, some of which are suspected carcinogens. By operating without chloramine, PFRO produces permeate with a high Ultraviolet Transparency (UVT) value, making the subsequent UV/AOP (Ultra Violet/Advanced Oxidation Process) stage more energy-efficient.

Future Prospects

PFRO technology has demonstrated its potential to address the challenges associated with traditional RO systems in wastewater reuse and brackish water desalination. Its ability to operate with high recovery rates, high flux, and chloramine-free operation positions it as a sustainable and cost-effective solution for water scarcity and water management concerns.

As further research and development continue, PFRO holds the promise of even greater efficiency and widespread adoption. With its ability to reduce biofouling, minimize scaling, and optimize the overall water purification process, PFRO is poised to play a significant role in meeting the world’s growing water needs in an environmentally-friendly manner.

References

[1] Treating wastewater with pulse flow reverse osmosis, 7 March, (online) available at: https://www.watertechonline.com/wastewater/article/14235101/treating-wastewater-with-pulse-flow-reverse-osmosis

[2] Pulse Flow RO – The new RO technology for the waste and brackish water applications, 1 April, (online) available at: https://www.sciencedirect.com/science/article/pii/S0011916419317096

[3] Pulse flow RO, 2 April, (online) available at: https://www.wwdmag.com/advanced-oxidation-systems/pulse-flow

[4] Potential Applications of Pulsed Flow for Minimizing Concentration Polarization in Ultrafiltration, 23Oct, (online) available at: https://www.tandfonline.com/doi/abs/10.1080/01496399008050393

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