Importance and impact of post treatments on design and operation of SWRO plants

The permeate quality of seawater reverse osmosis (SWRO) plants is suitable neither for drinking water nor for irrigation purposes. Thus, treatments must be adjusted to decrease boron concentration and post-treatments are required to improve water mineralization in order to correct its corrosiveness. Several chemical strategies were studied, and the evolution of different indicators including Leroy and Larson ratios were analyzed to evaluate the quality of the product water before distribution. Corrosive quality of the permeate remains the critical factor because of its high chloride concentration. Different strategies can be used to produce drinking or irrigation water from seawater. Chemicals added to the permeate must be carefully chosen if one pass only is used for reverse osmosis. In the case of two passes, the problem is less critical, but still remains important.