Determination of Minimum Inhibitory Concentration of Chromium and Salinity on Chlorella vulgaris

Heavy metal pollution, particularly chromium (VI) contamination, is a significant issue in Indonesian waters due to numerous chromium-producing industries. Research conducted in the downstream waters of Wonorejo found Cr(VI) levels ranging from 0.0025 to 0.018 mg/L, exceeding Indonesia’s quality standard of 0.002 mg/L. Thus, it is crucial to treat industrial wastewater containing Cr(VI) before disposal into water bodies. One alternative for treating Cr(VI) waste is using biological agents like microalgae. Chlorella sp. was chosen for this study due to its abundance in Indonesian waters. The study aims to determine the minimum inhibitory concentration (MIC) of Chlorella vulgaris against Cr(VI) and salinity variations. The research involved propagating the microalgae to analyze growth rates and conducting MIC tests against salinity for 14 days with variations of 0, 20, 30, and 40 ppt. MIC tests against Cr(VI) were then performed using the optimal salinity (20 ppt) with variations of 0, 5, 10, 20, 30, and 40 mg/L. Results showed that C. vulgaris can thrive in salinities up to 40 ppt, with the optimal salinity being 20 ppt. The optimal Cr(VI) concentration for growth was 5 mg/L, resulting in a growth rate of 1.17 cells/mL/day. Based on statistical analysis only concentration of Cr(VI) that affected C. vulgaris cell density and not the salinity.