Agro-industrial wastewater-grown microalgae: A techno-environmental assessment of open and closed systems

• Published in: The Science of the total environment 2022-08, Vol.834, p.155282-155282, Article 155282
• Main Authors: Magalhães, Iara Barbosa, Ferreira, Jéssica, Castro, Jackeline de Siqueira, Assis, Letícia Rodrigues de, Calijuri, Maria Lúcia
• Format: Article
• Language: English
• Subjects: Algal biomass; Biomass; Bubble column reactor; High-rate ponds; Life-cycle assessment; Microalgae; Photobioreactors; Scenedesmus; Waste Water; Wastewater treatment
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.155282

Microalgae-based treatment can be applied to the bioremediation of agro-industrial wastewater, aiming at a circular economy approach. The present work compared the technical-environmental feasibility of operating a bubble column photobioreactor (PBR) and a high rate pond (HRP) for microalgae biomass production and wastewater treatment of a meat processing facility. The comparison was made regarding biomass productivity, phytoplankton composition, treatment efficiency, life cycle assessment, and energy balance. The daily yields of total biomass and the maximum specific growth rates were 483.33 mg L−1 d−1 and 0.23 d−1 for PBR and 95.00 mg L−1·d−1 and 0.193 d−1 for HRP, respectively, with a predominance of the species Scenedesmus acutus. The treatment efficiency of COD (~50%) and phosphorus (100%) were similar in the two reactors. However, the PBR showed greater assimilation of ammoniacal nitrogen (100% removal) due to the higher microalgal biomass productivity. Environmental impacts were assessed through the ReCiPe methodology for midpoint and endpoint levels. Results revealed that CO2 supply was the most impactful process for both systems (>60%), but HRP reached lower environmental burdens (−105.90 mPt) than PBR (60.74 mPt). Energy balance through the Net Energy Ratio also resulted in the HPR advantage over the PBR (NER = 14.23 and 1.09, respectively). Still, both reactors present advantages when applied to different valorization routes. At the same time, both present room for improvement in the light of bioeconomy and biorefineries, aiming at sustainable wastewater treatment plants. [Display omitted] •Open (high rate pond - HRP) and closed systems (bubble column PBR) were compared.•Comparison was made for treatment, biomass yield, life cycle and energy balance.•PBR had higher biomass yield and N removal; HRP had lower impacts and higher NER.•Hybrid systems and two-stage cultivation are proposed to overcome major impacts.•Different recovery routes are proposed to best suit each systems' advantages.