Phycoremediation of tetracycline via bio-Fenton process using diatoms

The presence of antibiotics in wastewater poses serious environmental and health risks. As common wastewater treatment technologies are not effective in antibiotic removal from wastewaters, techniques such as ozonation, photo-Fenton process, and adsorption have been employed. However, studies are relatively scarce on the bio-Fenton process, in which aquatic plants have been used for the successful removal of pollutants. Many aquatic phytoplankton are capable of producing hydrogen peroxide (H₂O₂). Hence, in this study we identified the bio-Fenton reaction in diatoms: degradation of hydrogen peroxide produced by diatom cells to the hydroxyl radical in the presence of different iron particles like FeSO₄, colloidal iron, and zeolite iron. Hydroxyl radicals produced have the potential to degrade complex organic molecules. The production of hydroxyl radicals was indicated by the fluorescence produced as a result of the cleavage of aminophenyl rings in aminophenyl fluorescine (APF). The capability of diatoms to degrade the tetracycline antibiotic was also demonstrated in batch experiments and three consecutive runs of the sequence batch reactor. Batch experiments showed that the main removal mechanism is the bio-Fenton process; adsorption and iron complex formation also contributed to the overall removal of tetracycline by the diatoms.