Capability of Phytoplankton (Chlorella Vulgaris) Cultivation in Wastewater From Grease Trap

The aim of this research was to treat wastewater from grease traps by cultivating Chlorella vulgaris, a valuable commercial phytoplankton in biodiesel production and aquatic animal feeding. However, there is lack of information about its cultivation capability. Therefore, the most suitable medium and optimal inoculum cell density for its cultivation were examined. Chlorella vulgaris was cultured in pre-treated grease trap wastewater that had undergone sterilization and sedimentation with the addition of three different medium formulations. Then, the initial cell densities were varied to 5 × 10⁴, 5 × 10⁵, and 5 × 10⁶ cells/mL. Cell density analysis was conducted daily for 7 days. Water quality parameters such as pH, temperature, dissolved oxygen (DO), chemical oxygen demand (COD), nitrate, and phosphate were measured before and after cultivation. The results showed that the medium with the addition of calcium hydroxide 1 g/L supported the highest algal specific growth rate at 0.318 day^-1. An initial quantity of 5 × 10⁶ cells/mL yielded the highest algal growth and density. During cultivation in all experiments, the water temperature remained stable at 25°C. DO concentrations and pH ranged from 5.82-9.82 mg/L and 5.49-8.82, respectively. After the cultivation period, COD decreased from an initial range of 228.00-276.80 mg/L to 66.67-212.80 mg/L. Nitrate and phosphate were removed at 91.03% and 75.36% from the initial concentration, respectively. Finally, it can be concluded that to improve the growth efficiency of C. vulgaris in wastewater from grease traps, the addition of a nutrient medium consisting of calcium hydroxide with an initial algal density of 5 × 10⁶ cells/mL should be provided. This inoculum condition offers potential applications in microalgal biotechnology and sustainable wastewater treatment.