Removal of atrazine and 2,4-D pesticides from wastewater by anaerobic biological process using batch reactors

Biological treatment via anaerobic digestion (AD) represents a sustainable alternative for removing persistent organic contaminants, such as pesticides, from aqueous matrices while simultaneously enabling bioenergy production. This research aimed to evaluate the use of AD in anaerobic batch reactors to remove the pesticides atrazine (ATZ) and 2,4-D from wastewater at mesophilic temperatures (35 °C). The results demonstrated that the presence of the pesticides stimulated methane production and did not inhibit the overall anaerobic process. Total Chemical Oxygen Demand (COD) removal efficiencies exceeded 80% for all tested concentrations, with stable operational parameters including optimal pH and total alkalinity, and no accumulation of volatile fatty acids (VFAs). Pesticide removal kinetics revealed that ATZ achieved a maximum removal of 43.6% when applied alone. Conversely, the presence of ATZ in the mixed reactors served as a co-metabolic stimulant, significantly increasing the removal of 2,4-D to over 90% for all combined concentrations. This synergistic effect suggests that the presence of mixed pesticides can induce the necessary enzymatic activity (co-metabolism) required for the effective degradation of 2,4-D, thereby eliminating the need for a long acclimatization period. AD is thus presented as an efficient, stable, and sustainable approach for managing wastewater contaminated with these specific co-occurring pesticides.