Fast removal and detoxification of oxytetracycline, triazine and organophosphate pesticides in a biopurification system

Biopurification systems (BPS) are aimed at treating pesticide-containing wastewater. Since antibiotics employed in agriculture produce similar wastes, their treatment in BPS represents the logical disposal approach; nonetheless, antibiotics could hinder the biological removal of pesticides in BPS. This work aims at assessing the simultaneous removal of several pesticides (four organophosphates and four triazines) in a BPS biomixture during their co-disposal with the antibiotic oxytetracycline (OTC) at relevant concentrations (10 mg kg⁻¹ and 50 mg kg⁻¹). All pesticides were removed from the biomixture, regardless of the presence of OTC; among organophosphates, DT₅₀ values were among the lowest reported in BPS or soil, ranging from 1.1 d to 9.31 d; only cadusafos showed a similar removal than in soil (DT₅₀ 56–61 d). Successful and fast removal was also achieved for triazines, with DT₅₀ values ranging from 6.9 d to 11 d. Interestingly, co-application of OTC enhanced the removal of methamidophos; while in the case of triazines, OTC (at 50 mg L⁻¹) produced a slight increase in the DT₅₀ for every herbicide, an effect only evident for terbutryn at OTC 10 mg L⁻¹. The system also proved to be efficient in removing OTC itself, achieving DT₅₀ values from 8.0 to 12.3 d, the fastest so far reported in BPS. Important detoxification, over 90% towards D. magna and 26–37% on the germination index in L. sativa, provide additional support to suggest the co-disposal of OTC and the studied pesticides in the same BPS as a feasible agricultural practice at real on-farm conditions.