Removal of Myclobutanil and Detoxification in Modified Biomixtures: Fungal Bioaugmentation and Biochar Amendment

Abstract

Biopurification systems are designed for the treatment of pesticide-containing agricultural wastewater; their biologically active matrix, the biomixture, can be modified to enhance the pesticide removal capacity. Two approaches, fungal bioaugmentation with Trametes versicolor and amendment with biochar, were applied for the potential improvement of biomixtures’ capacity to remediate myclobutanil-contaminated wastewater. The conventional biomixture (B) and its modifications, either bioaugmented with Trametes versicolor (biomixture BT) or supplemented with pineapple biochar (5% v/v) (biomixture BB), were spiked with myclobutanil at a very high concentration (10,000 mg/kg) to simulate extreme on-farm events such as the disposal or leakage of commercial formulations. The dissipation followed a bi-phasic behavior in every case. Both modifications of the conventional biomixture increased the dissipation rates, resulting in estimated DT50 values of 61.9 (BB) and >90 days (BT) compared to biomixture B (DT50 = 474 days). The assessment of biomixtures’ detoxification was carried out with two different bioindicators: a seed germination test in Lactuca sativa and an algal growth inhibition test. Some degree of detoxification was achieved for all biomixtures in both indicators, with the exception of the biochar-containing biomixture, which, despite showing the fastest myclobutanil dissipation, was unable to maintain a steady detoxification trend towards the algae over the course of the treatment, probably due to biochar adverse effects. This approach seems promising for removing persistent myclobutanil from agricultural wastewater and demonstrates the dissipation capacity of biomixtures at extremely high pesticide concentrations likely to take place at an on-farm level.