Chlorella vulgaris as a potential bioremediation agent of aquaculture waste from Marine Science Techno Park, Diponegoro University

Abstract

Aquaculture activities that produce liquid waste from leftover feed can pollute aquatic ecosystems because this waste contains phosphate and nitrogen. One alternative that can be an asset is to employ Chlorella vulgaris as a bioremediation agent. The purpose of this research is to evaluate the potential ability of C. vulgaris in bioremediation of aquaculture waste based on the C. vulgaris cell density growth and the water parameter tests, including nitrate and nitrite. This research design uses a Completely Randomized Design (CRD) with six treatments with different aquaculture waste concentrations: K (0 mg/L), P1 (10 mg/L), P2 (20 mg/L), P3 (30 mg/L), P4 (40 mg/L), and P5 (50 mg/L). The research data results include C. vulgaris cell density, measurement, and test parameters of water quality, such as temperature (℃), pH, salinity (ppt), nitrate (mg/L), and nitrite (mg/L), which were carried out by descriptive analysis. The concentration of aquaculture waste at 20 mg/L on day 5 had the highest C. vulgaris cell density of 717 × 10^4 cells, indicating the exponential phase; meanwhile, the lowest C. vulgaris cell density was 32 × 10^4 cells at 30 mg/L on day 6, indicating the senescence phase. The C. vulgaris potential in bioremediating the aquaculture waste at a concentration of 10 mg/L of nitrate was 27.27%; meanwhile, nitrite was 50%. Moderate wastewater concentrations enhanced microalgal growth and nutrient uptake, whereas higher concentrations inhibited cell proliferation, likely due to nitrogen-related toxic stress. These findings demonstrate the potential application of C. vulgaris for wastewater polishing in sustainable aquaculture systems, particularly Recirculating Aquaculture Systems (RAS) and Integrated Multi-Trophic Aquaculture (IMTA).