12-06: Forward Osmosis Applied to Evaporative Cooling Make-Up Water

Modern Water is in the process of developing a number of manipulated / forward osmosis based technologies, ranging from desalination to power generation.  This paper outlines the progress made to date on the development and commercial deployment of a forward osmosis process applied to evaporative cooling tower make-up water.  This new technology shows significant promise in allowing various raw water sources, such as seawater, to be used directly in the manipulated osmosis step, thus releasing the use of scarce and valuable higher grade water for other more important uses.  The paper presents theoretical and operational results for the process, where it is shown that the process can produce make-up water at a fraction of the apex of conventional processes.  In particular power consumption which in some cases may be as low as 15%, compared to competing processes.  Chemical additives to the cooling water (osmotic agent) are retained within the process, thus reducing their overall consumption.  Furthermore, the chemistry of the cooling water does not support the growth of Legionella pneumophila.