A study of photosynthetic biogas upgrading based on a high rate algal pond under alkaline conditions: Influence of the illumination regime

• Published in: The Science of the total environment 2017-08, Vol.592, p.419-425
• Main Authors: Franco-Morgado, Mariana, Alcántara, Cynthia, Noyola, Adalberto, Muñoz, Raúl, González-Sánchez, Armando
• Format: Article
• Language: English
• Subjects: Alkaliphilic algal-bacterial consortium; Biofuels; Biogas desulfurization; Biomass; Light/dark cycles; Lighting; Microalgae - physiology; Photosynthesis; Ponds
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.03.077

Microalgal-bacterial processes have emerged as environmental friendly systems for the cost-effective treatment of anaerobic effluents such as biogas and nutrients-laden digestates. Environmental parameters such as temperature, irradiation, nutrient concentration and pH effect the performance of the systems. In this paper, the potential of a microalgal-bacterial photobioreactor operated under high pH (≈9.5) and high alkalinity to convert biogas into biomethane was evaluated. The influence of the illumination regime (continuous light supply vs 12h/12h light/dark cycles) on the synthetic biogas upgrading efficiency, biomass productivity and nutrient removal efficiency was assessed in a High-Rate Algal Pond interconnected to a biogas absorption bubble column. No significant differences in the removal efficiency of CO2 and H2S (91.5±2% and 99.5%±0.5, respectively) were recorded regardless of the illumination regime. The high fluctuations of the dissolved oxygen concentration during operation under light/dark cycles allowed to evaluate the specific growth rate and the specific partial degradation rate of the microalgae biomass by photosynthesis and respiration, respectively. The respiration reduced the net microalgae biomass productivity under light/dark cycles compared with process operation under the continuous light supply. [Display omitted] •Microalgal photosynthesis effectively regenerated the culture broth alkalinity.•H2S & CO2 were effectively removed as a result of the high culture broth alkalinity.•The illumination regime did not impact the removal of H2S & CO2.•The fate of C, N, P and S was significantly influenced by the illumination regime.•Endogenous microalgal respiration in the darkness decreased biomass productivity.