RO膜元件类型
最常见的 RO 膜元件类型是咸水、海水和纳滤 (NF)。要确定最适合您系统的膜,请考虑您的给水来源、所需的回收率、水质和能源需求。
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%(取决于特定条件)且系统回收率高,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% 之间。
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 >硫酸镁(MgSO4)的溶解度为97%,而氯化钠(NaCl)的溶解度仅为85%-95%。这是因为NaCl比MgSO4小。
然而,有些硫酸盐排斥膜只能排斥约 25% 的氯化钠,因此 NF 的特性非常多样化。在相同的进水中,运行 NF 膜所需的压力低于 RO 膜,因为单价离子没有被完全排斥。