Cultivation of Arthrospira platensis in non-conventional water resources: A comparative analysis of biomass productivity and chemical constituents

This study addresses the significant freshwater requirements for industrial-scale Spirulina cultivation by investigating the potential of reverse osmosis reject (ROR) water and air conditioner condensate water (ACW) as alternative growth media components. Varying proportions of ROR and ACW combined with standard Spirulina medium (SM) were employed to evaluate biomass production, biochemical composition, pigment, energy, CO₂ fixation rates, high heating value (HHV), FTIR, and TGA. The cost savings and potential applications of Spirulina biomass were also assessed. Results indicated that while 100SM yielded the highest biomass (122.85 mg L⁻¹ d⁻¹) and protein (78.06 mg L⁻¹ d⁻¹) productivities, specific combinations incorporating ACW (25ACW+75SM and 50ACW+50SM) and ROR (25ROR+75SM) demonstrated comparable growth and protein yields. Notably, 50ACW+50SM exhibited the highest lipid (23.02 mg L⁻¹ d⁻¹) and carbohydrate (23.46 mg L⁻¹ d⁻¹) productivities. Energy content across all treatments ranged from 340.89 to 499.41 kcal 100 g⁻¹. The highest CO₂ fixation rate was obtained in 100SM (0.25 g CO₂ L⁻¹ d⁻¹), followed by 25ACW+75SM (0.23 g CO₂ L⁻¹ d⁻¹). The maximum HHV was observed in SM (25.42 kJ g⁻¹), comparable to 25ROR+75SM (23.6 kJ g⁻¹) and 50ACW+50SM (22.55 kJ g⁻¹) growth media. These findings provide empirical evidence supporting the feasibility of utilizing non-conventional water sources like ACW and ROR in Spirulina cultivation, offering a sustainable strategy to mitigate freshwater dependency, potentially reduce nutrient input, and enhance the economic viability of demonstration-scale Spirulina production.