PhotoBioValue project: Linking N:P Ratios and Nitrogen Sources to Microalgae-Based Wastewater Bioremediation and Biomass Valorisation

Microalgae-based systems offer potential for wastewater bioremediation by extracting nutrients while producing biomass for various uses. However, variations in wastewater properties, particularly the source of nitrogen and phosphorus, their concentration, and the N:P ratio, impact treatment efficiency. This study aimed to evaluate the combined effects of different N:P ratios and nitrogen sources on biomass composition, wastewater treatment, and Chlorella vulgaris growth. Three sources of nitrogen (NO3-, NH4+, and both) have been studied alongside four N:P ratios (9, 14, 20, and 27). All synthetic effluents were suitable for C. vulgaris growth, and the N:P ratio of 9 with NH4+ as the only nitrogen source had the greatest specific growth rate. Nitrogen was entirely removed at a N:P ratio of 9, with NH4+ being the preferred source. When both sources were available in the media, NH4+ was consumed first. The removal of phosphorus reached 99 %. Nitrogen constraints reduced the biomass's protein concentration while increasing its lipid and carbohydrate contents. Combining NO3- and NH4+ boosted protein content compared to the use of NO3- and NH4+ alone. These results show that the microalga can effectively treat diverse wastewaters with different compositions, reaching optimum growth and nutrient removals at a N:P ratio of 9.