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Irradiance penetration distribution and flashing light frequency simultaneously affected with microalgal cell absorption and CO 2 bubble scattering in a raceway pond.
- Source :
-
The Science of the total environment [Sci Total Environ] 2023 Mar 15; Vol. 864, pp. 160988. Date of Electronic Publication: 2022 Dec 16. - Publication Year :
- 2023
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Abstract
- In order to investigate light penetration and flashing light frequency for microalgal cell-CO <subscript>2</subscript> bubble culture system in a raceway pond, user-defined function for CO <subscript>2</subscript> mass transfer and bubble scattering models coupled with discrete ordinates radiation model were adopted to clarify simultaneous effects of microalgal cell absorption and CO <subscript>2</subscript> bubble scattering. Light intensity along the microalgal suspension depth attenuated more rapidly with increased biomass concentration, decreased bubble generation diameter, increased CO <subscript>2</subscript> gas content and incident light intensity. Ratio of light zone decreased from 81.13 % to 20.00 % when biomass concentration increased from 0 to 0.4 g/L because of light absorption and shading effects of microalgae. When bubble generation diameter increased from 0.1 to 1.6 mm, ratio of light zone increased from 37.95 % to 42.64 %, while microalgal flashing light cycle first decreased to a valley of 1.81 s at 0.8 mm and then increased. Local light intensity in the upper layers was more enhanced due to lots of CO <subscript>2</subscript> bubbles gathering and reflecting more light with decreased bubble diameter and increased gas content. Light attenuated more rapidly in microalgal suspension with decreased bubble generation diameter and increased CO <subscript>2</subscript> gas content because of increased bubble diffraction coefficient and contact area. When initial CO <subscript>2</subscript> volume fraction increased from 0.02 to 0.2, flashing light frequency of microalgal cells decreased from 0.55 to 0.29 Hz and light zone time ratio φ decreased from 36.90 % to 18.40 %. At a biomass concentration of 0.1 g/L and a bubble flow rate of 0.1 m/s, the maximum light penetration and microalgal growth rate was achieved when bubble diameter, incident light intensity and gas content were optimally at 0.8 mm, 200 W/m <superscript>2</superscript> and 0.02, respectively. This work provides data support and theoretical guidance for photobioreactor design and optimization of light energy utilization.<br />Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.<br /> (Copyright © 2022 Elsevier B.V. All rights reserved.)
- Subjects :
- Ponds
Photobioreactors
Light
Biomass
Carbon Dioxide metabolism
Microalgae metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1879-1026
- Volume :
- 864
- Database :
- MEDLINE
- Journal :
- The Science of the total environment
- Publication Type :
- Academic Journal
- Accession number :
- 36535475
- Full Text :
- https://doi.org/10.1016/j.scitotenv.2022.160988