Assessment of the biotic and abiotic elimination processes of five micropollutants during cultivation of the green microalgae Acutodesmus obliquus

The elimination by photolysis, microalgae and sorption of five persistent micropollutants Sulfamethoxazole (SMX), Ciprofloxacin (CIP), Quetiapine (QUT), Gabapentin (GAB) and 2-Phenyl-5-benzimidazolesulfonic acid (PBSA) was studied. Microalgae growth was not inhibited by the micropollutants. SMX, QUT, CIP were significantly eliminated during exposure with microalgae, while GAB and PBSA remained unaffected. SMX was eliminated by 43% only under optimal cultivation conditions at an elimination rate of 2.1 μg L⁻¹ h⁻¹. Sorption and photolysis were not involved in the elimination of SMX. QUT was eliminated by 99% with a rate of 4.6 μg L⁻¹ h⁻¹ during microalgae cultivation as a result of photolysis and microalgae activity. Microalgae cultivation produced a 52.8% higher elimination compared photolysis. CIP decreased by 86% at a rate of 1.78 μg L⁻¹ h⁻¹ which was mainly produced by photolysis with an impact of microalgae of 10%. Growth rates of the microalgae and elimination rates of the micropollutants were not correlating. While the underlying processes remained unclear, present study shows that biotic processes coupled to the growth of Acutodesmus obliquus removed most of the micropollutants under study at rates exceeding those of the abiotic removal processes.