While a fourth method,which relies on high pressure,is called reverse osmosis. 第四种方法则是靠高压，叫反渗透法。
This paper emphatically introduces the design and application of two-stage RO process in the preparation of pure water for pharmaceutical purpose. 本文重点介绍了制药用纯水制备中二级反渗透法系统的设计和应用。
