Growth of Chlorella vulgaris using wastewater from Nile tilapia (Oreochromis niloticus) farming in a low-salinity biofloc system

Abstract

The present study aimed to analyze the growth of Chlorella vulgaris in the effluent of a Biofloc Technology (BFT) system used in the Nile tilapia fingerlings farming. The conditions were cultivated by 10 days at 25 ± 2ºC, 90 μmol photons m^−2 s^−1 irradiance, under constant aeration (without addition of CO₂), and with different BFT effluent proportions (0, 50, and 100%). After 24 hours of the inoculation that marked the beginning of the experiment, the development and multiplication of the cells were verified, demonstrating that the BFT effluent used in the Nile tilapia farming was favorable for the cultivation of the microalga Chlorella vulgaris. As expected, the Provasoli culture medium presented the best performance (1,520 ± 75 10⁴ cells mL^-1) in relation to the growth of the microalga. However, during the first four days of cultivation, C. vulgaris showed higher growth in treatments containing BFT effluent. C. vulgaris removed 93.6% of the nitrate contained in the BFT effluent. The results of the present study showed the potential use of C. vulgaris on Integrated Multi-Trophic Aquaculture with Nile tilapia fingerlings. In addition to removing nitrate and other nitrogen compounds, C. vulgaris biomass could be used to feed zooplankton or Nile tilapia larvae.