Since the reverse osmosis process is the concentration and discharge of dissolved solids and the utilization of fresh water, when the water is concentrated, inorganic salts will crystallize out, forming carbonate scale (CaCO3, MgCO3) and sulfate scale (CaSO4, MgSO4). In particular, sulfate crystals (such as BaSO4, SrSO4), because its crystals are often with sharp corners, will Pierce the semi-permeable film, causing concentrated water to leak through the film surface, unable to reach the purpose of desalination. This phenomenon is most likely to occur on the concentrated water side of the last membrane element of the second segment, because this place has the highest concentration of concentrated water.