RO膜元件類型
最常見的 RO 膜元件類型是咸水、海水和納濾 (NF)。要確定最適合您系統的膜,請考慮您的給水來源、所需的回收率、水質和能源需求。
RO brackish membranes are typically used with brackish feedwaters containing a relatively low (TDS) compared to seawater. They require a low amount of pressure (125 – 250 psi) while maintaining a high salt rejection (>95 – 99%(取決于特定條件)且系統回收率高,大于或等于 75%。
Seawater membranes are used with seawater or feedwaters with a high TDS. Since those feedwaters have a TDS of 35,000 mg/l or greater, seawater membranes require a much higher pressure to operate (800 – 1200 psi) and can maintain a high rejection (>99.5%);但其回收率低于咸水膜,在 50 – 70% 之間。
NF is a similar technology to RO but it has a lower rejection of monovalent ions such as sodium chloride. It rejects divalent ions such as CaSO4 very effectively and organic macromolecules to varying extents depending on the model. For example, some NF membranes can reject >硫酸鎂(MgSO4)的溶解度為97%,而氯化鈉(NaCl)的溶解度僅為85%-95%。這是因為NaCl比MgSO4小。
然而,有些硫酸鹽排斥膜只能排斥約 25% 的氯化鈉,因此 NF 的特性非常多樣化。在相同的進水中,運行 NF 膜所需的壓力低于 RO 膜,因為單價離子沒有被完全排斥。