Evaluation of physicochemical treatment conditions for the reuse of a spent growth medium in Arthrospira platensis cultivation

quantity of alkaline medium with high salinity that could pollute the environment if discharged with no further treatment. The combined effects of the physicochemical processes of flocculation and adsorption were applied to reuse the spent modified Schlosser medium for seven days of A. platensis fed-batch cultivation using urea as nitrogen source. Different concentrations of both powdered activated carbon and ferric chloride were evaluated at different contact times to remove organic matter and pigments from the spent medium. The efficiency of the process was measured by evaluating the removal of both organic matter and pigments. The best conditions of treatment that maximized the cell growth were 24.4 mg L-1 powdered activated carbon, 20.3 mg L-1 ferric chloride and 30.4min of contact time. Under such conditions, organic matter removal was 92.3 +/- 0.6%, pigment removal was 95.3 +/- 0.6% and the maximum cell concentration was (4.89 +/- 0.03) x 10(3) mg L-1, approximately 135% higher than in the standard medium[(2.09 +/- 0.05) x 10(3) mgL(-1)]. This biomass had 36.1 +/- 0.6% protein content, which was also higher than those values obtained in the standard medium (25.8 +/- 0.9%). (C) 2015 Elsevier B.V. All rights reserved.