One of the common technologies used for water treatment are Reverse Osmosis systems. (From this point forward referred to RO.) The EPA WaterSense has recently been focused on developing water efficiency specifications for point of use RO systems that connect to a single fixture (commonly a kitchen sink). POU units can be found under the counter or on the countertop.
WaterSense is a voluntary program within the U.S. Environmental Protection Agency. WaterSense is a partnership of industry and user stakeholders with the common objective of conserving water. With the help of its partners, WaterSense has developed product specifications, services, and programs with the goal of reducing water usage by 20 percent. Products are certified to WaterSense specifications and provide an easily recognizable mark that identifies the more water efficient products. This gives the consumer the ability to make informed decisions when purchasing products.
RO systems work by the use of a differential pressure across a semi-permeable membrane. The higher pressure forces water through the membrane, while the contaminates do not pass through. The rejected concentrate of contaminates is directed to waste. RO systems can significantly reduce contaminants such as total dissolved solids (TDS), heavy metals, volatile organic compounds (VOC), bacteria, and viruses.
Clearly the benefit is the ability to improve water quality by the reduction of many different types of contaminates. While RO systems can improve water quality, these systems can also generate a significant amount of water waste when operated. A typical system can generate 5 gallons of wastewater for every gallon of treated water produced. There are systems on the market with even higher inefficiencies.
Recent technology has improved such that some RO systems can operate where there is only 1 gallon of waste for each gallon of clean water produced. Hence with the availability of more efficient products in the marketplace. WaterSense saw a need to create an efficiency specification for RO devices. In January of 2022, WaterSense published a notice of intent to develop the Efficiency Specification for POU Point-of-Use Reverse Osmosis Systems.
Currently, there are no federal requirements that regulate the RO systems. However there are two product standards that are specific to RO systems.
- ASSE 1086-2022, Reverse Osmosis (RO) Water Efficiency – Drinking Water
- NSF 58-2020, Reverse Osmosis Drinking Water Treatment Systems
These standards were important in the development of the WS specification.
The current draft of the WaterSense specification for RO Systems requires the compliance of devices to NSF 58. It utilizes the methodology of ASSE 1086 for the determination of performance of the RO system. The acceptance criteria to be eligible for certification to the WaterSense specification is a minimum efficiency of 30%.
According to WaterSense, “a WaterSense labeled model will reduce water use on average by nearly 3,200 gallons of water per year — or 48,000 gallons of water over the system’s lifetime.” This saving is for a single household. When extrapolated to saving across the county, WaterSense states that nearly 3.2 billion gallons of water could be saved per year!
Once the WaterSense specification is published and listed products are on store shelves, a consumer will be able to look for and install WaterSense labeled efficient RO systems. These RO systems will produce 2.3 gallons or less of wastewater for every gallon of treated water it produces.
ASSE, WaterSense, and its partners continue to look for ways to conserve water while maintaining an acceptable level of performance. ASSE 1086, Reverse Osmosis (RO) Water Efficiency – Drinking Water, and the soon to be released WaterSense Efficiency Specification for POU Point-of-Use Reverse Osmosis Systems, are examples of this commitment.
