Oak wood provides suitable nutrients for long-term continuous pesticides removal by Trametes versicolor in a pilot plant trickle bed reactor

In the Catalan area (Spain), diuron and bentazon are extensively used to control weeds and are therefore abundant in agricultural drainage. White-rot fungi have a high potential for removing these contaminants because of a potent and nonsubstrate-specific lignin-degrading enzyme system. Unfortunately, bacterial contamination hinders practical application of fungal treatment. In this study, a trickle bed reactor (TBR) containing Trametes versicolor immobilized on oak wood was used to treat spiked nonsterile agricultural wastewater. The TBR was operated for 186 days in continuous mode at different recirculation rates. The TBR exhibited stable and promising performance, with an average removal of diuron and bentazon of up to 80% and 67%, respectively, at steady state. The lignocellulosic carrier was the only carbon resource used for the immobilized biomass throughout the entire operation period and effectively suppressed bacterial growth. Adsorption of the contaminants on oak wood was also an important contribution to pesticide removal. The constructed system exhibited persistent fungal activity and high robustness to adverse impacts regarding clogging, based on pesticides removal, laccase activity, ergosterol quantity and scanning electron microscopy analysis. This study demonstrates the concept of long-term fungal treatment and paves the way to full-scale application.