Municipal and industrial wastewater blending: Effect of the carbon/nitrogen ratio on microalgae productivity and biocompound accumulation

• Published in: Journal of environmental management 2024-11, Vol.370, p.122760, Article 122760
• Main Authors: Pereira, Alexia Saleme Aona de Paula, Magalhães, Iara Barbosa, Silva, Thiago Abrantes, Reis, Alberto Jose Delgado dos, Couto, Eduardo de Aguiar do, Calijuri, Maria Lucia
• Format: Article
• Language: English
• Subjects: Biological Oxygen Demand Analysis; Biomass; C/N ratio; Carbon - metabolism; Microalgae; Microalgae - growth & development; Microalgae - metabolism; Nitrogen - metabolism; Nutrients removal; Resource recovery; Waste Disposal, Fluid - methods; Wastewater - chemistry; Wastewater treatment
• ISSN: 0301-4797; 1095-8630; 1095-8630
• DOI: 10.1016/j.jenvman.2024.122760

Municipal wastewater (MW) and industrial wastewater from juice processing (IWJ) were blended in different proportions to assess the effect of the carbon/nitrogen (C/N) ratio on pollutant removal, microalgal biomass (MB) cultivation, and the accumulation of carotenoids and biocompounds. MB development was not observed in treatments with higher C/N ratios (>30.67). The wastewater mixture favored the removal of dissolved organic carbon (75.61 and 81.90%) and soluble chemical oxygen demand (66.78–88.85%), compared to the treatment composed exclusively of MW (T7). Treatments T3 and T6 (C/N ratio equal to 30.67 and 7.52, respectively) showed higher Chlorophyll-a concentrations, 1.47 and 1.54 times higher than T7 (C/N ratio 1.75). It was also observed that the C/N ratio of 30.67 favored the accumulation of carbohydrates and lipids (30.07% and 26.39%, respectively), while the C/N ratio of 7.52 improved protein accumulation (33.00%). The fatty acids C16:0, C18:1, C18:2, and C18:3 had the highest concentrations. Additionally, increasing the C/N ratio can be an efficient strategy to improve the production of fatty acids for biofuels, mainly due to the increased concentration of shorter-chain fatty acids (C16:0). These findings suggest that blending wastewater not only enhances treatment performance but also increases the accumulation of valuable carbohydrates and lipids in MB, and optimizes fatty acid production for biofuel applications. This research represents significant progress towards feasibility of using MB produced from wastewater. [Display omitted] •Municipal and industrial wastewater were blended to assess different C/N ratios.•The blend favored C removal, with 81.90% for DOC and 88.85% for SCOD.•T3 (C/N = 30.67) favored carbohydrate (30.07%) and lipid accumulation (26.39%).•The highest protein content (33.00%) was achieved at a C/N ratio of 7.52.•T3 exhibited peak levels of beta-carotene (13.55 μg g−1) and lutein (537.59 μg g−1).