Performance study of an industrial RO plant for seawater desalination

In this work, an approach to study the long-term performance of an industrial water desalination plant is described. Operational data corresponding to the time period of 454 days were analysed and from the results obtained it was found that the normalized water permeability coefficient declined by about 7%. Due mainly to the temperature effects, the salt permeability coefficient exhibit significant changes only during the summer period. The equations used allowed a good description of the performance of the plant.

Using a simple calculation methodology that combines semi-empirical equations with the classical film theory model, it has been possible to evaluate the performance of an industrial desalination plant which uses spiral wound membranes. For an operational time of 454 days, the normalized water permeability coefficient A25/A720 decreased by about 7%. This happened because the chemical cleaning of the membranes was not performed during the considered period. The salt permeability, B2, increased significantly during the summer period due mainly to the temperature effect; however, only slight differences were observed in the values of B2 at the beginning and end of the period of operation. Even at high salt permeability values, the permeate quality was maintained within specifications according the Portuguese legislation. The specific energy consumptions obtained in this work are in the range of typical values found in the literature [11,13] and they did not exhibit any significant changes during the time period studied. The approach used allowed a good description of the performance of the plant analyzed and can be applied to the other RO desalination systems operating under similar conditions.