Talkin About Regeneration

Oct. 9, 2003
Membrane regeneration facility in Bakersfield, Calif., boasts quick turnaround time; customers agree

About the author: Tim Gregorski is editorial director of WWD.

Imagine a situation in which you can take advantage of a cost-effective way to maximize your reverse osmosis system's performance while minimizing operating costs.

The opportunity is available and it is known as membrane regeneration--a process that extends membrane life and increases the time interval between cleanings at a fraction of the cost of membrane replacement. In many cases, membrane regeneration can double or triple membrane element life, significantly reducing replacement costs while effective restoring plant performance parameters.

It seems simple enough--make use of membrane regeneration and save money.

Ironically, it has long been known that many reverse osmosis membrane elements are thrown away too soon, essentially eliminating any opportunity for cost savings.

Fortunately in August 2002, a new facility designed specifically for regenerating membrane separation elements opened in Bakersfield, Calif.

Engineered for applications wherein the elements can no longer be cleaned effectively in the field and for those with operating budgets that do not provide for the purchase of new elements, the Bakersfield membrane regeneration facility is an economical and practical way for membranes to be regenerated to maintain full productivity.

Located at the production complex for GE Betz, the membrane regeneration facility can restore quality performance, extend membrane life and increase the time interval between cleanings at a fraction of the cost associated with membrane replacement.

This state-of-the-art facility has the ability to process up to 60 membranes continuously for 24 hours a day, which allows the facility to produce better than average turn-around times when compared to other regeneration facilities in North America.

"What makes us unique is the volume of membranes we can treat, meaning a quick turnaround time and the automated equipment that gives us more control over the process which improves our ability to clean membranes when others cannot," Brian Banerdt, plant manager of the Bakersfield complex told Water & Wastes Digest.

Additionally, the facility can help to increase permeate flow by incorporating a corresponding decrease in differential pressure. This helps the off-site cleaning process minimize downtime and eliminate chemical purchase, handling and disposal problems.

In discussions with WWD, Banerdt emphasized that the Bakersfield regeneration facility has been specifically engineered to decrease turn-around times and improve restoration effectiveness, a process that has been utilized often.

Within the past year, Banerdt acknowledged that the GE Betz facility has worked with numerous customers, each of which have their own specific requirements according to their needs, a few of which WWD reviews in this article.

Customer applications

While researching this article, Banerdt offered WWD a number of different testimonials touting the Bakers-field membrane regeneration facility. WWD examines four of these applications, each of which exemplify the diverse customer needs addressed at the facility.

The first application involves the city of Calpine, Ala., which sends the Bakersfield facility 50-100 membranes every 3-4 months. According to Banerdt, the facility preserves the membranes and returns them regenerated within a 2-3 week period. Calpine city officials are satisfied with the service because in addition to their membranes being cleaned, their contract price includes shipping costs.

Another application involves Ionics Ahlfinger Water, which has been a customer of membrane regeneration for over five years but has been specifically using the Bakersfield plant the past year. Again, Ionics is content with the service due to quick turn around time and pricing, but it is their close proximity to the Bakersfield plant that allows for the membranes to be shipped directly back to Ionics' customers.

The Tennessee Valley Authority (TVA) is one the Bakersfield facility's larger customers as they send an average of 100 membranes every month to be cleaned. The Bakersfield facility cleans membranes for four different TVA locations: Cumberland City, Tenn.; Gallatin, Tenn.; New Johnsonville, Tenn.; and West Paducah, Ky. Each of these locations consistently averages about 50-100 membranes every 1-2 months.

The final application is unique, as it is located outside of the U.S., in Saskfreco, Canada. The facility's most frequent membrane cleaning customer from Canada tried a number of different membrane regeneration plants before settling on the quality and performance delivered by the Bakersfield plant.

Plant capabilities

As part of the membrane regeneration process, the Bakersfield facility can process spiral wound, thin film, and cellulose acetate reverse osmosis, ultrafiltration and nanofiltration elements from all major suppliers in a full range of sizes.

According to GE Betz, the regeneration involves both physical and chemical processes. In a typical sequence, the elements are soaked in proprietary chemicals and cleaners followed by treatment in the regeneration loop. This recirculates heated cleaning solutions through membrane feed passages while importing high shear forces to the membrane surfaces, restoring performance to even the most severely fouled elements. The plant incorporates automated equipment with the ability to control all aspects of the regeneration process such as temperature, flow and flow pressure for example.

"Our closely controlled temperatures and proprietary mechanical features and specialty chemicals can provide results compared to the use of clean-in-place equipment at the customer's site," Banerdt told WWD.

After cleaning, the elements are wet tested using dechlorinated, municipally treated water, and performance results are normalized to the element manufacturer's standard test conditions.

Traditionally, membrane fouling reduces permeate flow and salt rejection, and increases differential pressures. Studies show that regeneration typically results in a 40% increase in permeate flow, a 38% decrease in differential pressure and a 3% increase in salt rejection. For a system containing these elements, operating pressure could be reduced by 100% to maintain an equivalent pre-regeneration permeate flow. If the same system were operating at a 75% recovery on a feed stream that contained 1,000 ppm total dissolved solids, permeate salt passage would decrease from 3.3% to 0.4% following regeneration.

When regeneration is combined with effective pre-filtration, field cleaning and antifoulant use, significant cost savings are possible. The more effective the pre-treatment process, the greater the savings because the frequent of regeneration is reduced.

European application

Recently, the membranes used in a reverse osmosis program at a Belgian chemical plant were so fouled that normal cleaning procedures could not restore their effectiveness. The company was faced with the prospect of having to buy 92 new membranes at a total cost of $92,000.

GE Betz recommended shipping the membranes to their membrane regeneration facility in Edinburgh, Scotland, which offers similar capabilities to the plant in Bakersfield.

After a visual inspection, weighing and wet testing, it was determined that 89 elements would benefit from a proprietary cleaning process for restoring quality performance and extending membrane life. At the end of the process, 83 membranes were judged sufficiently regenerated to be used again in the system. Only six elements had to be rejected because they still exhibited high differential pressures.

After deducting the shipping and regeneration costs, the cost avoidance saving for not having to replace 83 membranes was $61,455.

More information on GE Betz's Membrane Regeneration Facility can be found at

About the Author

Tim Gregorski

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