When selecting membrane elements, the desalination rate is a crucial guiding factor. However, when considering the desalination rate, other important indicators characterizing system performance should also be taken into account.
1. Definition of desalination rate
Desalination rate is a measure of a membrane element’s ability to retain soluble substances. Reverse osmosis elements can remove many different types of ions. Generally, reverse osmosis performs worst in removing monovalent ions. If a membrane exhibits excellent removal efficiency for NaCl, it will likely have better removal efficiency for divalent ions and small molecules. Therefore, NaCl is widely used as a standard substance for evaluating the ion removal performance of reverse osmosis membrane elements.
2. Determination of desalination rate
The rate of salt transfer through the membrane is measured as mass-volume concentration. Existing instruments can measure the specific conductivity (i.e., conductivity) of the permeate, which can be converted into milligrams of salt per liter of the permeate. The desalination rate is expressed as a percentage using the following formula:
Desalination rate (%) =(Influent salinity – Product salinity)/Influent salinity*100%
Due to the various factors affecting the desalination rate of membrane elements mentioned above, the formula for calculating the desalination rate is only meaningful under specific pressure, temperature, and concentration conditions. Slight deviations in the testing environment require corresponding compensation coefficients for correction; these coefficients are often provided by the supplier after extensive testing.
3. Standardized Desalination Rate Testing
The desalination rate typically provided by manufacturers is based on data obtained from the membrane element’s factory quality assurance inspection. During the membrane element manufacturing process, quality assurance (QA) inspection is required, especially in precision manufacturing environments, to ensure the integrity of the manufacturing process and to determine the element’s fundamental performance under specified test conditions.
Jozzon Company’s manufacturing process and equipment have good stability, and the overall performance of the membrane elements produced is also excellent. However, we believe that the desalination rate and other performance characteristics obtained under standard brine conditions cannot truly and completely reflect the quality of the membrane element. Therefore, our company, through its strong technical support platform, uses the stability data of membrane elements used in different environments as a reference for product quality labeling, and the obtained data has good reproducibility.
