Hydrocarbon removal during the cultivation of marine microalgae in petroleum-produced water.

The presence of hydrocarbons in industrial effluents poses a threat to marine ecosystems, particularly in coastal regions influenced by agro-industrial and petroleum activities. Among these contaminants, polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) are notable for their environmental persistence, toxicity, and potential for bioaccumulation, entering marine environments via the discharge of contaminated effluents. In this context, microalgae offer a sustainable biological alternative for the removal of organic pollutants. This study evaluated the potential of the marine microalga Halamphora coffeaeformis to remove PAHs and TPHs from petroleum-derived produced water and poultry processing effluent for biostimulation. Cultivation was carried out in photobioreactors with an 800 mL working volume under mixotrophic conditions for 21 days, comparing two treatments: produced water from the petroleum industry (PW) and poultry effluent (PE), both used entirely as the culture medium. Experiments were conducted under a light intensity of 2,500 lux, a 12h light/12h dark photoperiod, a temperature of 26°C, and continuous aeration at 2.4–3.0 L min⁻¹. At the end of the cultivation period, contaminants were extracted via liquid-liquid extraction using dichloromethane as the solvent and p-terphenyl as the recovery standard. The extracts were analyzed by GC-MS, enabling determination of initial and final PAH and TPH concentrations and calculation of removal efficiency. The results demonstrate that the microalga exhibited a high capacity for contaminant removal in both matrices, although differences were observed between the treatments. Regarding PAHs, poultry effluent showed the highest removal efficiencies, ranging from 88% to 98% for compounds of varying molecular weights, with a total removal of 97%; in contrast, produced water showed removal rates between 56% and 79%, with a total removal of 70%. Low-molecular-weight PAHs generally exhibited higher removal rates, a pattern associated with their greater bioavailability, although significant removal was also observed for high-molecular-weight PAHs. Regarding TPHs, produced water showed a reduction from 22,552.80 to 3,157.39 µg L⁻¹, corresponding to 86% removal. In poultry effluent, the concentration was reduced from 2,955.20 to 1,723.70 µg L⁻¹ (42%). The high removal of PAHs and TPHs in poultry effluent may be linked to the greater availability of nutrients, particularly nitrogen and phosphorus, which foster microalgal growth and the assimilation and biodegradation of these compounds. Conversely, the high salinity and presence of toxic compounds in produced water may limit metabolic activity. The results demonstrate the potential of H. coffeaeformis as a sustainable biotechnological tool for hydrocarbon removal and for reducing organic loads in effluents that could otherwise impact coastal and marine environments.