Recycling industrial wastewater for improved carbohydrate-rich biomass production in a semi-continuous photobioreactor: Effect of hydraulic retention time

• Published in: Journal of environmental management 2021-04, Vol.284, p.112065, Article 112065
• Main Authors: Sánchez-Contreras, Ma. Isabel, Morales-Arrieta, Sandra, Okoye, Patrick U., Guillén-Garcés, Rosa Angélica, Sebastian, P.J., Arias, Dulce María
• Format: Article
• Language: English
• Subjects: Bioenergy; Biofuels; Biomass; Bioreactors; Carbohydrates; Cyanobacteria; Microalgae; Mixed effluents; Photobioreactors; Raceways; Resource recovery; Waste Water
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2021.112065

This study aimed to investigate a mixed microalgae culture's capacity to simultaneously remove nutrients and organic matter from industrial effluents while producing carbohydrate-rich biomass. A culture initially dominated by filamentous cyanobacteria Geitlerinema sp. was inoculated in a lab-scale stirred tank photobioreactor, operating at 10, 8, and 6 days hydraulic retention time (HRT). The results show that different HRT led to different inorganic carbon profiles and N:P ratios in the culture, influencing microbial changes, and carbohydrate content. Hence, higher N–NH4+ removal efficiencies were obtained at HRT of 10 d and decreased with decreasing HRT. Whereas, complete depletion of P-PO43- was achieved only at HRT of 8 d and 6 d. Also, the highest COD removal efficiency (60%) was achieved at 6 d of HRT. The maximum accumulation of carbohydrates was achieved at HRT of 8 d, which presented an N:P ratio of 22:1 and carbon availability, recording a constant carbohydrate content of 57% without any additional carbon source. Furthermore, this operational condition reached the best biomass production of 0.033 g L−1d−1 of easy-settling cyanobacteria dominated culture. According to the results, this process presents an alternative to recycling industrial effluents and, at the same time, grow valuable biomass, closing a loop for sustainable economy. •Industrial effluents were used to produce carbohydrate-rich biomass.•Filamentous cyanobacteria could efficiently treat industrial wastewater.•HRT controlled the carbon and nutrients availability, thus carbohydrate accumulation.•P limitation and high N:P ratios promoted a constant carbohydrate content of 57%.