Pilot Study Report on Using UF Membranes as a Pretreatment to an SWRO System
By Charan Rajan and V.J. Nathan
Hollow fiber ultrafiltration (UF) membranes made from polyethersulfone material (PES) were tested in a pilot unit at a power generation station. The pilot studyﾒs goal was to examine the performance of the hollow-fiber membrane as a precursor to a seawater reverse osmosis (SWRO) system. The source of water at this facility was raw seawater from an open intake. The wide variation in feedwater turbidity made this a challenging application. The current pretreatment for SWRO system consists of seawater chlorination, a solid contact clarifier, and a two-stage media filtration. The system has been in operation for more than 10 years. This pilot studyﾒs objective was to examine the performance and efficacy of these hollow fiber membranes as pretreatment options to SWRO systems at a real operating facility under varying conditions, and for different models of these UF membranes. Since the feedwater to the RO generally has a silt density index (SDI) of less than 3, the main parameters on which the performance of the UF was studied were product turbidity and SDI. Another objective was to optimize the UF operation with regards to service time, flux, and frequency of chemically enhanced backwash (CEB). For these purposes, process parameters like transmembrane pressure (TMP) and flows were studied throughout the pilot testing period.
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