Abstract
Microalgae can be a future source of biomass with a wide range of applications, including its use to solve current environmental issues. One of the main variables for microalgal cultivation is the light supply: (i) its intensity that often does not present a uniform spatial distribution inside the culture; (ii) photoperiod; and (iii) spectrum. Therefore, this study aims to evaluate the growth of the microalgae Chlorella vulgaris in a tubular photobioreactor with compound parabolic collectors (CPCs) under outdoor conditions. The effect of ultraviolet and visible radiation on biomass productivity and nutrients (nitrogen and phosphorus) uptake was assessed. The maximum biomass productivity was (5 ± 1) × 10−3 g·L−1·h−1, and the specific growth rates ranged from (1.1 ± 0.3) × 10−2 to (2.0 ± 0.6) × 10−2 h−1. Regarding nutrient uptake, initial removal rates of (0.9 ± 0.4) mg N·L−1·h−1 for nitrogen and (0.17 ± 0.04) mg P·L−1·h−1 for phosphorus were reached. These values increased with visible and ultraviolet irradiance until certain values (143 WVIS·m−2 and 9 WUV·m−2 for biomass productivity; 101 WVIS·m−2 and 6 WUV·m−2 for nutrient removal) and then decreased for higher ones due to the photoinhibition phenomenon. Therefore, the application of CPCs to photobioreactors (PBRs) may be beneficial for microalgal culture in countries with higher latitude (with lower solar irradiance levels).
Highlights
Microalgal cultures have been recently studied for environmental applications, such as CO2 capture, wastewater treatment, among others [1,2,3]
This work aims to assess the effect of ultraviolet (UV) and visible light on microalgal growth and nutrient uptake from a synthetic effluent under outdoor conditions in a tubular photobioreactor with compound parabolic collectors (CPCs), which enable a more uniform spatial distribution of light inside the culture medium
Temporal variation of UV and visible radiation, pH, and temperature for all assays are presented in Figures S2 to S9
Summary
Microalgal cultures have been recently studied for environmental applications, such as CO2 capture, wastewater treatment, among others [1,2,3]. Their use at the industrial level is still not economically viable due to high operational costs. Nitrogen, and phosphorus are essential macronutrients for microalgal growth These nutrients can be found in wastewaters of different sources [1,7,8,9]. Using these effluents as microalgal cultures, the addition of fertilizers may be significantly reduced, and no freshwater is needed.
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