An experiment with different pretreatment methods

Abstract

The use of reverse osmosis (RO) method for the desalination of seawater to produce fresh water is gaining momentum over the last decade. Although there have been considerable improvements in membrane materials, the fouling of membrane creates a significant problem yet to be overcome. Performance of systems employing different pretreatment methods used in the RO desalination process was investigated experimentally. Field tests included advanced membrane filtration techniques: ultrafiltration (UF) and microfiltration (MF). During the pilot testing, silt density index (SDI) of the filtrate samples were regularly measured to quantify the performance of pretreatment systems. Measurements of other important parameters included filtrate flux, transmembrane pressure (TMP), total suspended solids, colloidal silica, total organic carbon, etc. Test results showed that membrane pretreatment consistently produced filtrate of a good quality. SDI of the filtrate produced by membrane pretreatment method was consistently below 3.0, a prerequisite for proper operation of a RO desalination plant. Improved maintenance procedures, such as filtrate backwashing and air scouring coupled with periodic use of chemicals, resulted in significant flux and pressure recoveries during the pilot tests. Ease of operation of the membrane pretreatment systems was also noted by the authors.