Pretreatment options for large scale SWRO plants: case studies of OF trials at Kindasa, Saudi Arabia, and conventional pretreatment in Spain

Kindasa Water Services (KWS) currently operates an RO facility at Jeddah Port on the Red Sea in Saudi Arabia, using conventional pre-treatment, to provide a 14 mld output. Due to an increasing requirement for treated water services, a contract has recently been placed with Weir Westgarth for a new desalination facility to expand the capacity of RO treated water from 14 to 40.5 mld (3.7 to 10.7 MGD). The original system has operated well for most of the time since it was brought into supply in 2000. However, occasional poor quality conditions have occurred during storms, or periods of algal bloom, which have resulted in SDI's to the RO exceeding target levels. Accordingly, an interest was expressed in utilizing ultrafiltration (UF) as an alternative to conventional pre-treatment, to improve RO feed quality, and guarantee on-stream time. The UF trial was highly successful in achieving stable membrane permeability and a consistent filtrate SDI when operated under optimized process conditions. Utilizing ferric chloride dosing, with acidification, the trial has operated at a flux of 95 LMH, and at a transmembrane pressure of 0.15–0.20 bar. The recovery was 94%. An average SDI of 2.2 has been obtained in the UF filtrate, approximately 2 units better than the existing conventional treatment. By utilizing an air enhanced backwash on a regular basis, the trial has shown that filtrate SDI's of less than 3.0 can be obtained at all times, even under the poor feed quality conditions that occur during algal blooms. In the final phase of the trial, we have been able to obtain UF filtrate SDI values well below 2. Hydranautics has gained experience with UF pre-treatment to RO in 3 other case studies in the Gulf of Mexico, the Red Sea, and the Mediterranean. In each case, OF was demonstrated to provide excellent pre-treatment to RO, with no RO cleaning required in 6-month trial periods. In addition, the Integrated Membrane System guarantee offered by Hydranautics for the UF-RO system minimizes process risk for all parties. This paper will review the data from the UF trial at Kindasa, and from the three other case studies mentioned above. The benefits for the RO facility at Kindasa will be quantified with regard to both technical and commercial parameters. We will also mention the experiences encountered in Spain in different sites as Carboneras 123,000 m 3/d SWRO with conventional pre-treatment and Las Palmas 371,000 m 3/d SWRO with conventional pre-treatment.