ASSE International recently published ASSE 1086, Performance Requirements for Reverse Osmosis Water Efficiency – Drinking Water. The standard was developed in response to the increased water shortage crisis that many parts of the U.S. and world continue to experience. Reverse Osmosis (RO) drinking water treatment is an excellent technology to reduce numerous contaminants found in drinking water. It has quickly become the water treatment technology of choice for China and India. Although RO water treatment systems reduce numerous contaminants, it comes at a cost. Traditional residential ROs are known to be one of the least efficient treatment products on the market. Traditional ROs typically send at least 3 gallons of water to the drain for every gallon produced.
ROs use a semi-permeable membrane to separate purified water from concentrated wastewater using pressure. Product modifications that manufacturers use to improve the water efficiency can cause the membrane to foul very quickly, typically in 3 to 4 weeks. Fouled membranes no longer function and must be replaced for the RO to produce purified water. Most manufacturers recommend replacing RO members at intervals of 1-3 years. Replacing a RO membrane every month would be very costly and could cause other environmental waste concerns. Based on these concerns, the ASSE 1086 standard includes testing to simulate a one-year life for the RO membrane with a minimum water efficiency of 40%.
The performance tests in ASSE 1086 focus on water efficacy and membrane fouling tests. Also, ASSE 1086 references the NSF/ANSI 58 standard for material safety, contaminant reduction, and structural integrity testing. The 1086 standard focuses on three things: 1) it requires compliance with the testing requirements of NSF/ANSI 58; 2) the system must meet a minimum efficiency rating of equal to or greater than 40%; 3) the RO membrane or system must comply with the membrane fouling test protocol that was developed to simulate a minimum one-year membrane life using an aggressive (high potential to foul) challenge water.
To ensure membranes will continue to function for at least one year, the membrane life test was created. This test simulates a year’s worth of drinking water use and the aggressive challenge water used requires a Langelier Saturation Index (LSI) of 0.7. The LSI number is an indicator of the water potential to form calcium scaling. The most common source of membrane fouling is a result of calcium scale building up on the membrane surface. The 1086 life test runs for a minimum of 20 days, with a minimum volume of 1,000 gallons of permeate water produced. Assuming 40 percent efficiency, 2,500 gallons of challenge water would be processed through the RO for this test. Each day, challenge water is processed through the system for four hours, then the first sample is taken. The system is then run continuously for an additional 12 hours followed an eight-hour rest period at the end of each day. The following criteria are evaluated each day of testing.
- The flow rate cannot decrease by more than 50% of the day-one flow rate throughout the duration of the testing. Flow rate reduction is a tool to determine membrane fouling.
- TDS (total dissolved solids) reduction throughout the duration of testing must be at least 75%. TDS reduction is another tool used to evaluate the membrane’s performance.
- The average recovery rating must be a minimum of 40%. One-tenth of the sample readings can be less than 40%, but the final recovery measurement must meet or exceed 40%.
Several working group members plan to share the standard with local jurisdictions around the country and globally. ASSE commends the work that the RO industry has done to design new highly efficient membranes and new residential RO systems that can operate significantly more efficient. Billions of gallons of drinking water can be saved in the U.S. if consumers switch to ASSE 1086 certified efficient ROs. Assume 10 million residential ROs are in use in the U.S. with an average efficiency of 15%. For each RO to produce 1,000 gallons of drinking water each year, they will each use approximately 6,666 gallons of water. If consumers switch to ROs certified to ASSE 1086 we could save 4,166 gallons of water each year per RO – assuming 10 million residential ROs are in use today in the U.S., over 41 billion gallons of total water could be saved each year. To help prevent water shortages, we encourage ASSE Members to promote the new ASSE 1086 standard. Remember ASSE’s motto, “Prevention Rater Then Cure.”
