(29f) A Novel Method to Manage the Concentrate Disposal of Desalination Units

Scarcity of clean water is a great dilemma today and needs better management. About 1.2 billion people are living in areas where water is physically scarce and also 1.6 billion encounter economic water shortage. Population growth, climate change, and inappropriate use of available resources are the chief factors that worsen the current condition. Given that the amount of water on the earth has remained quite constant over time, it is crucial to desalinate saline and brackish waters. However, cost and concentrate stream of desalination units are two major issues that have restricted expansion of inland water desalination technologies.  The salinity of concentrate stream which is sent to disposals increases with each succeeding separation step and causes environmental issues resulting in confining practical deployment of desalination units. Cultivation of microalgae in concentrate disposal is a new method which could contribute to solving these problems inasmuch as microalgae have been considered as excellent candidates being capable of removing ions and salts existing in concentrate stream. In addition, the derived dry biomass could be used as a feedstock for biofuel production. To examine this idea, a full factorial experiment with completely random design (CRD) was conducted aiming to investigate the growth of two strains of marine algae, Dunaliella tertiolecta and Nannochloropsis oculata, in three different media including concentrate, artificial seawater medium, and a 50-50 combination of these two under 16 hours of illumination in 25^oC. Furthermore, Nitrate, Phosphate, Sodium, and potassium removal were measured everyday to characterize the trend of removing ions and salts from media. Results revealed that both strains of algae can grow fairly well in concentrate and have significant effect on removing salts and ions from concentrate disposal.