From November 2018, the water purification industry's first mandatory national standard—GB 34914-2017 Minimum allowable values of water efficiency and water efficiency grades for reverse osmosis drinking water treatment units (the "Water Efficiency Standard")—formally took effect.
Implementation of the Water Efficiency Standard means the state will impose compulsory water-saving requirements on the production and sale of reverse-osmosis (RO) water purifiers. After hygiene/safety and product quality, this is another national requirement for RO units.
What is water efficiency? It is how efficiently an RO water purifier uses water, expressed as a percentage. Under the test conditions in the standard, within the unit's rated total purified-water capacity, it is the ratio of the total purified water produced to the total source water consumed. The higher the water efficiency, the better the unit utilizes water.
Because of cross-flow filtration, RO purifiers necessarily discharge concentrate (reject water). Before the standard was published, the industry usually described utilization with a "wastewater ratio." So how does "water efficiency" differ from that familiar "wastewater ratio"?
1. Different test conditions and rigor
The "wastewater ratio" was self-declared by manufacturers, often without strict testing—only an approximate figure. "Water efficiency" may only be claimed after testing under the conditions specified in the Water Efficiency Standard.
2. Different labeling requirements
The "wastewater ratio" was optional; there was no national mandate to display it. After the standard took effect, every RO water purifier must carry a water-efficiency label in a conspicuous place.
3. Different forms of expression
The "wastewater ratio" is a ratio—for example, producing one part purified water and discharging three parts concentrate is shown as 1:3. Water efficiency is a percentage—for example, 60% means 60% of the source water becomes purified water and 40% is discharged as concentrate.
4. Different meanings
Water efficiency measures resource utilization: purified water obtained versus total water consumed, including water used for flushing/rinsing the unit.
The "wastewater ratio" only compares purified-water flow to concentrate flow during RO membrane production; flush water is ignored no matter how much is used. It therefore does not reflect true water-resource efficiency—only an operating parameter of the RO unit.
As living standards rise, people care more about drinking-water quality, and demand for purifiers keeps growing. RO units are especially popular for their high product-water quality. The Water Efficiency Standard will further raise overall RO product quality in the market and help these products win even wider favor.