Chlorella sorokiniana for integrated wastewater treatment, biomass accumulation and value-added product estimation under varying photoperiod regimes: A comparative study

Abstract

This study aimed at investigating the effect of varying light/dark (L/D) regimes and different tertiary wastewater types (synthetic and real) on the biomass production, nutrient removal, photosynthetic pigments (chlorophyll and carotenoids), and production of value-added products of Chlorella sorokiniana. Algae culture was grown at pH 7, 140–150 rpm agitation, and with controlled temperature (25 °C) under continuous illumination of 140 μmol m−2 s-1. The highest amount of biomass productivity (548 ± 20 mg/L/d), nitrogen and phosphorus removal (60 % and 85 %), the percentage increase in total chlorophyll (63 %), and total carotenoids (Carot) accumulation (11 mg/L) were observed in real wastewater (RWW) under 24/0 h (h) L/D cycles. C. sorokiniana showed autotrophic growth as biomass increased in the light phase and decreased in the dark phase for all culture conditions. Among all the cultivation conditions, a maximum increase in the protein content was 15 % in RWW (24/0 h) and an increase in the carbohydrate content was 6.5 % in synthetic wastewater (SWW) (24/0 h) showing that prolonged light phase positively affects the treatment efficiency. Furthermore, this study demonstrated that biomass productivity reached a threshold and then started to decline after 24 h and 30 h in RWW and SWW under both light regimes. The conditions of the RWW 24/0 h L/D regime with RWW media were found to give the maximum tertiary treatment efficiency, suggesting that selected microalgae cultured under these conditions would be best suited for integrated wastewater treatment.