Upgrading and capacity extension of old brackish water desalination plants

Abstract

In some cases upgrading and extension of old BWRO plants is far more economic in comparison with the development of new plants. This is especially true at sites where expenses related to the infrastructure are high and increase the cost of new installations. Another aspect is technological - usually the operation in the old systems requires excessive energy due to the old generation membranes that are installed that should anyhow be upgraded to reduce the energy cost. The concept will be demonstrated by describing the upgrading and extension of a 17-year old 10,000 m3/day BWRO system operating in Eilat. The system desalts a source of 6,000 ppm brackish water with high content of calcium-sulphate at 63% product recovery. The redesign of this plant comprises replacement of the 12-year old RO membranes by a set of new high permeability membranes and addition of a second desalination stage. As a result, the capacity increased to 18,000 m3/day at 80% recovery and the specific energy consumption has been reduced from 1.0 kWh to about 0.80 kWh at full capacity operation, and to less than 0.65 kWh, when operating at a partial load of 12,000 m3/day. Due to the existing infrastructure and the increase of the recovery, the required investment in the extension and the old membranes replacement has been relatively low and the pay back time is of less than 4 years.