Bottling membranes need that ‘TLC’

Oct. 13, 2010

Checking the pressure in a cars tires or the smoke detector batteries in a home are chores people often overlook.

Checking the pressure in a car’s tires or the smoke detector batteries in a home are chores people often overlook, despite the critical role these devices play in ensuring their safety.

The same can be said for the well-being of a membrane treatment system used in bottled water production, which relies on regular upkeep to ensure high-quality water.

Unfortunately, only a small percentage of membrane users regularly maintain their systems, according to Steve Felling, a reverse osmosis (RO) expert at CUNO Inc.

"The most important thing people can do to ensure the optimal performance and longevity of their equipment is to devote a few minutes a day to look at a few key operating parameters," Felling said.

Starting your checks
By checking pre-treatment devices (such as softeners) and examining the system’s operating pressure, product flow rate and reject flow rate, the user can quickly be alerted to a problem.

Felling noted that a bottled water production system’s larger components, including softeners, backwashing filters, ultraviolet (UV) indicators, and storage and repressurization devices, generally require weekly inspections. Annual inspections of UV bulbs and pre-filters are also a good idea, he said.

Some ultrafiltration membrane systems used in bottling water perform automatic maintenance procedures, such as back-flushing, that are conducted several times each day as part of the system’s operational cycle, Jim Vecchio, marketing manager for Koch Membrane Systems, pointed out.

Regular procedures
"There are also cleaning procedures that can be done monthly or bi-monthly, depending on the nature of the feed water," Vecchio said.

These procedures include flushing the system with a caustic or acid solution and ensuring there are no contaminants on the surface of the membrane, Vecchio said.

Keeping a log of all maintenance performed on a system has two advantages, Felling noted. It is not only an excellent tool for ensuring regular upkeep is conducted, it also provides reference data in the event that a system crashes.

System lifespan
The longevity of a membrane treatment system can be influenced by a number of factors, most notably the nature of the feed water challenging the system. A system that is required to work harder to treat water will simply wear more quickly than one which works less, Felling said.

The continuous use of feed water containing a lower concentration of contaminants can extend the lifespan of a system by several years, Vecchio added.

"Most manufacturers are looking for five to 10 years for use of the membrane before it needs to be replaced," he said.

Mandated water quality thresholds can also dictate how often an individual bottler has to replace a system to maintain high-quality water. States with low prescribed levels of total dissolved solids (TDS) in bottled water will require bottlers to use their systems with more rigor than states with higher allowable TDS levels, according to Felling.

Finally, the system’s engineering and maintenance play a crucial role in prolonging its life. Even with first-class maintenance, a poorly designed system can only go so long, Felling said.

"All membranes will die; it’s just a matter of when and by what means," he said.

Picking ‘the right membrane’
The majority of membranes used for bottled water applications have a thin-film composite (TFC) construction, which Felling said tends to be more resistant to higher pH levels than cellulose triacetate (CTA) construction, the alternative choice.

"The TFC membrane is fairly bulletproof in all regards except its ability to deal with pre-chlorine on a long-term basis," Felling said. "You have to be fairly meticulous at making sure that the carbon filter in front of the RO system is properly sized and is changed whenever you see any breakthrough of pre-chlorine."

Because the condition of source water varies, bottlers should select a membrane material that fits the water in their geographic region, Vecchio noted.

"If you’re bottling water in Arizona, you’re going to need a different set of membrane treatment technologies than if you are bottling water in the Northeast," he explained. "In the Southwest, for example, you have a high salt content in the water, so you typically would want to do some deionization of the water using reverse osmosis or nanofiltration."

Maintenance training
Performing a routine check of the treatment system’s operating features is a task any bottler can handle, but more in-depth maintenance should be left to trained pros, Vecchio said.

Despite the intricacies involved in maintaining membrane treatment systems, Felling pointed out that some people who work on them do not have the required knowledge.

"It’s amazing that in the bottled water industry, and in the water treatment industry in general, the level of expertise in RO is a lot lower than it was 10 or 20 years ago," he said.

Although there is no definitive reason for the proficiency decline, Felling speculated that an influx of professionals from other industries has diluted a membrane treatment trade once comprised largely of water conditioning dealers whose businesses rested on an understanding of the equipment they were selling.

Vecchio said, "Each system has its own set of problems and criteria, so training is required to learn how these different systems are operated and maintained."

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