Reuse of SWRO brine for the production of carotenoids from Dunaliella salina and removal of macronutrients

Abstract

This research determines the advantages of the use of brine from reverse osmosis seawater desalination processes as hypersaline culture media to grow Dunaliella salina. In this work, we evaluated the growth of a new strain of D. salina (Ds. Janubiense-ITC5.105) cultured in residual brine and in artificial hypersaline media compared with the productivity of a well-established strain of this species (Ds. BCA421-ITC5.003). Parameters such as concentration of chlorophylls a and b and total carotenoids accumulated by the two strains throughout the cultivation course were established. The results show maximum biomass yield of 26.44g m-2 d-1 for Ds. BCA421-ITC5.003 grown in a controlled media with similar salinities to that of desalination brine; and maximum carotenoids productions of 20.93 mg m-2 d-1 for Ds. Janubiense-ITC5.105 grown in brine from seawater desalination processes. This SWRO brine would be an ideal medium to grow this kind of species at low cost in areas with seawater desalination plants. Moreover, the growth of D. salina offers a high rate of nutrient fixation, such as NO3- and PO43-, of up to 99 and 71%, respectively. Due to the fact that desalination brine contains certain amounts of these nutrients in its composition, its use as culture media requires a lower reagent expense. The cultivation also favors the complete removal of these ions from brine, thus improving the quality of the final disposal.