High Efficiency Operation of Pressurized Ultrafiltration for Seawater Desalination Based on Advanced Cleaning Research

This paper discusses a method to operate polyvinylidene difluoride (PVDF) fibers based on outside-in pressurized ultrafiltration (pUF) membranes at high efficiency used as a pretreatment in seawater desalination. Backwash sequence was initially identified as the key contributor to the process efficiency yield. Backwash duration is reduced from 170 to 100 s, eliminating three redundant cleaning steps from an original sequence of five steps. Backwash frequency is decreased from once every 30 mm to once every 90 mm. These two optimizations result in an efficiency increase of 10% (from 88% to 97%). Thanks to this higher efficiency operation, it is possible to save 1.4 m(3) of ultrafiltrated water per day and filtering 96 extra minutes per day. A 14 days side by side validation is performed to validate the optimized conditions. In addition, the data is analyzed in order to prove that both backwashes have the same cleaning strength in reducing the trans-membrane pressure (TMP). A model to predict TMP evolution over time is presented and validated against the real plant performance during the validation period. This model is based on analyzing TMP increase during filtration cycle, TMP recovered during backwash cleaning and TMP recovered during chemical enhanced backwash (CEB).