This article originally appeared in the Water Quality Products December 2019 issue as “Every Drop Counts.”
Nearly every day it seems we are introduced to a new chemical that has been used for many years but now is being exposed as detrimentally harmful; so harmful that it could cause serious health effects, including cancer or death. Fortunately, standard writers create testing protocols that will define which products are capable of removing these harmful contaminants from drinking water, and certifiers use these protocols to provide assurance that the products are doing what they say they will. It does not stop there, though. With standards in hand or sometimes working simultaneously, the drinking water treatment industry manufacturers work diligently to create products that will help eliminate these types of chemicals from being part of consumers’ water.
This course of action is commendable and sustains opportunities for the average citizen to have cleaner drinking water. However, these actions do not address the full spectrum of issues revolving around drinking water. While it is important to have clean water, if there is not enough water to support the population the efforts will be for naught. Water scarcity is a worldwide problem, as well.
Are RO Systems Water Efficient?
Reverse osmosis (RO) technology is a way to eliminate a plethora of harmful contaminants from water. It comes, however, at a cost and we are in a time where every drop counts. Traditional ROs are known to be one of the least efficient treatment products on the market. This is true because all of the precious water that enters into the system does not come back to the user as drinkable. In fact, traditional ROs typically send at least 3 gal of water to the drain for every single gallon produced as treated water. As a result, the drinking water treatment unit industry collaborated to develop RO products that were far more efficient than their past counterparts, thus creating systems that achieve water devoid of the chemicals mentioned above, as well as those that do not waste water while we are doing it. Problem solved, right?
Well, not really. Due to the way RO technology works, often the tweaks that manufacturers rely on to create these systems to be efficient water production machines cause the membrane to foul quickly. Most manufacturers recommend a longer replacement interval for the membrane element. The typical time a manufacturer recommends that a user change out the RO membrane can range between one and three years. Replacing membranes 10 to 35 times more often can lead to other monetary and environmental concerns. In order to ward off potential push back from the consumer and regulatory stakeholders, the drinking water treatment industry opted to be proactive and create a new standard for RO systems.
A New Standard Emerges
The production process for ASSE 1086 emerged. (Note: ASSE Intl. is a business unit under The IAPMO Group). It is an efficiency standard for RO systems. Another standard, NSF/ANSI Standard 58, allows companies the opportunity to gain certification to validate the claims they make on their products. Certainly, one might be confused that the two standards overlap. On the contrary, the group that convened to create ASSE 1086 was deliberate to ensure that the standards had vastly different scopes. The NSF/ANSI Standard 58 focuses on the testing protocols associated with the reduction of chemicals that commonly are reduced through RO technology. ASSE 1086 focuses on the environmentally friendly aspect of the treatment technology, while also ensuring that efficiency is not compromising membrane life.
Ultimately, the new standard focuses on three things: One, it must complement the existing NSF/ANSI Standard 58. ASSE 1086, in fact, requires that to qualify a RO as fully compliant or become certified to ASSE 1086 it must also be compliant with the requirements of NSF/ANSI Standard 58.
Two, the system must meet a minimum efficiency rating when tested in accordance with the NSF/ANSI Standard 58 protocol. Because the 58 standard is not an efficiency standard, while the testing protocol is present there are no minimum requirements to meet with respect to efficiency. While it may seem outrageous that no minimum requirements are established in NSF/ANSI Standard 58, it makes sense because NSF/ANSI Standard 58 is a performance standard and not an environmental standard. To be compliant with ASSE 1086, an RO must be at a minimum of 40% efficient.
Three, because the manipulations made to RO systems rendering them efficient often cause membrane fouling, it was imperative for the group to develop new testing protocols that replicated a years’ worth of use to ensure that the newly designed system would not cause premature membrane plugging.
To ensure membranes would continue to function for long periods of time, a membrane life test was created. This test simulates a year’s worth of use and the challenge water focuses on creating a Langelier Saturation Index (LSI) of 0.7. The LSI number is an indicator of how well the water will form calcium carbonate scaling. Scaling will instigate membrane fouling. The test runs for a minimum of 20 days, with a total minimum volume of 1,000 gal of water passed through. On each day, water is run through the system for four hours, at which point sample readings are taken. The system is then run for a continuous 12 hours with the outlet open and provided an eight-hour rest period at the end of each day. While the standard is in its final stages of completion, slight modifications may be realized following the review period. To pass the membrane life test three requirements must be met:
- The flow rate cannot decrease by more than 50% of the day-one flow rate throughout the duration of the testing. Flow rate was chosen because it is a quick, reliable way to determine if a membrane is becoming clogged.
- TDS (total dissolved solids) reduction throughout the duration of testing must be at least 75%.
- The recovery rating must average a minimum of 40%. One-tenth of the sample readings are allowed to be less than 40%, but the final recovery measurement cannot exceed 40%.
Comparison testing recently concluded to confirm the theoretical assumptions made by the group. Testing was conducted on systems modified for efficiency and unmodified systems. The results of the comparison testing confirmed that the traditional RO plugged after only a few days of testing. This was critical research because it verified that a traditional RO system could not pass the rigorous membrane life test.
ASSE 1086 is in its final stages of completion and once finalized with the standards writing group will become an ANSI accredited standard. Stay tuned for a release date and be sure to reach out if you have interest in demonstrating that your products meet the new efficiency protocol.
About the Author
Tina Donda is vice president-water systems for IAPMO R&T. Donda can be reached at [email protected] or 708.995.3018.
Reprinted with permission from Water Quality Products: wqpmag.com.