When describing a reverse osmosis system to customers, dealers might casually explain that RO is simply a filter that allows water to pass through the membrane’s tiny pores while salts and contaminants are rejected or not allowed to pass through. As water treatment professionals, we all know that RO filtration technology has been among the most disruptive technologies that have changed the point-of-use (POU) and point-of-entry (POE) industry over the past 60-plus years.
It is a rather diverse technology — in its treatment capabilities — that produces purified water for many types of problem water and it is an innovation that continues to make improvements. RO also continues to be widely used across the world by municipalities, bottlers, homeowners and many other types of customers.
But, during your sales and marketing pitches, what should you and your customers focus on when talking about today’s RO units and membranes?
Customers who are interested in RO are mostly likely already aware of the potentially harmful contaminants in their water and they value their health as well as their families’ or employees’ health. In addition to an initial water test, setting up an effective RO system will include a pump, membrane, vessels and proper plumbing.
However, according to Peter Waldron, vice president of marketing and sales for Toray Membrane USA Inc., removing key contaminants before they enter an RO system is even more critical. Although some membrane manufacturers are treating their membranes today to reduce fouling, pretreatment to RO is still vital to overall performance, operating costs and return on investment.
“The better the pretreatment you have, the longer the membrane life,” says Waldron. According to Waldron, the industry standard is a three-year warranty, but without proper pretreatment or cleaning regimen can be less. However, there are examples of facilities where a membrane life of seven to 10 years has been documented with effective pretreatment and proper cleaning. For residential settings, where membranes are more compact and cost effective and do not require cleaning, the average lifespan is about one to two years.
It is known that ineffective pretreatment is the most common cause of failure of an RO application. Chlorine, for instance, is a widely known adversary to RO’s polyamide thin-film membranes, which are common in many systems. When exposed to chlorine, membrane damage occurs and worsens if iron or other transition metals have fouled the membrane as well.
Free chlorine, even at low levels, will cause oxidation damage to the membrane. Two common pretreatment methods for reducing chlorine levels are by absorption with activated granular carbon filter media or by a chemical reducing agent like sodium bisulfite.
Setting up an RO system the right way and knowing all the factors to consider, including pretreatment, cleaning opportunities and sizing options, is critical to overall performance. Water Technology has published several articles throughout recent years on the subject of RO setup, cleaning and maintenance and protecting membranes. Here are just a few examples and for more you can visit WaterTechOnline.com and search “reverse osmosis”:
- “The smart approach to reverse osmosis,” by Wes Byrne. https://www.watertechonline.com/articles/the-smart-approach-to-reverse-osmosis.
- “Saving customers’ money through membranes,” by Jessica Rhodes. https://www.watertechonline.com/articles/167341-save-customers-money-through-membranes.
- “The benefits of reverse osmosis membrane cleaning,” by Norm Marowitz and Matthew Unger. https://www.watertechonline.com/articles/166278-the-benefits-of-reverse-osmosis-membrane-cleaning.
- “Taking advantage of low pressure membranes in commercial systems,” by Bill Loyd. https://www.watertechonline.com/articles/166542-taking-advantage-of-low-pressure-membranes-in-commercial-systems.
Dealers selling RO to municipal sites can also provide ongoing service to the membranes after the sale. According to Waldron, telltale signs of when a municipality might need to consider a cleaning of membranes is when the system’s net driving pressure increases or when there is an increase of salinity in the permeate water.
Today’s membranes, continues Waldron, are designed to require as little cleaning as possible since “the less you have to clean, the longer the membrane life,” he says, adding that inevitably a municipality’s RO membranes will need to be cleaned about every six to eight weeks on average.
Depending on the foulants on the membrane, either a high pH or low pH chemical cleaning is required. For mineral scale, adds Waldron, usually an acidic cleaning is required; for organic fouling, usually a high pH is called for.
Reversing operating cost and other common concerns
“The biggest change and the biggest development [in the RO membrane product category] has been the trend toward lower energy and lowering the overall operating costs of these systems,” says Waldron. He adds that some manufacturers have been able to lower operating costs because they have increased the square footage of the elements and by doing so, they have been able to reduce the size of the system by 10 percent or more in some cases.
“In addition, you are getting more through-put per element,” explains Waldron. “You’re being able to drive more water [through a similar system] as you could five to 10 years ago.” He also credits the emergence of energy recovery devices, which entered the market about 10 years ago and has helped address energy demands.
“A combination of the improvements in the membranes and the energy recovery devices has really been able to lower costs. Certainly, it is an exciting time and the market is growing. You do see more municipalities considering RO,” adds Waldron. “There’s also growing interest for wastewater reuse, especially in areas suffering from droughts.”
Along with the growing popularity of this filtration technology has come misunderstanding and bad information, typically found online from non-water treatment professionals. Typically, this information is spread by customers who have had bad experiences with RO, including being sold systems without proper education.
Oversizing RO equipment and over-treating a customer’s problem water is not recommended. For many residential settings, whole-house RO might not be appropriate. Instead, Waldron advises, RO level of treatment is recommended at the point-of-use serving drinking water faucets/coolers and certain appliances or HVAC equipment such as water heaters.
When selling and servicing RO units and membranes the right way, dealers have a unique opportunity to educate customers on the factual developments and trends that are happening with this disruptive technology. Also remember, what goes into an RO membrane is as important as what comes out so make sure customers invest in proper pretreatment and cleaning.