Biotechnology and Bioprocess Engineering

, Volume 6, Issue 3, pp 194–199 | Cite as

Effect of light/dark cycles on wastewater treatments by microalgae

  • Kwangyong Lee
  • Choul-Gyun LeeEmail author


Chlorella kessleri was cultivated in artificial wastewater using diurnal illumination of 12 h light/12 h dark (L/D) cycles. The inoculum density was 105 cells/mL and the irradiance in light cycle was 45 μmol m2 s−1 at the culture surface. As a control culture, another set of flasks was cultivated under continuous illumination. Regardless of the illumination scheme, the total organic carbon (TOC) and chemical oxygen demand (COD) was reduced below 20% of the initial concentration within a day. However, cell concentration under the L/D lighting scheme was lower than that under the continuous illuminating scheme. Thus the specific removal rate of organic carbon under L/D cycles was higher than that under continuous illumination.

This result suggested thatC. kessleri grew chemoorganotrophically in the dark periods. After 3 days, nitrate was reduced to 136.5 and 154.1 mg NO3 -N/L from 168.1 mg NO3 -N/L under continuous illumination and under diurnal cycles, respectively. These results indicate nitrate removal efficiency under continuous light was better than that under diurnal cycles. High-density algal cultures using optimized photobioreactors with diurnal cycles will save energy and improve organic carbon sources removal.


microalgae nitrogen removal diurnal cycle wastewater 


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Copyright information

© The Korean Society for Biotechnology and Bioengineering 2001

Authors and Affiliations

  1. 1.Institute of Industrial Biotechnology, Department of Biological EngineeringInha UniversityIncheonKorea

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