Substrate evaluation for biobeds in the degradation of ethylene bis-dithiocarbamate in wastewater from pesticide application in banana

The efficacy of biobeds was evaluated by testing three agricultural residues (sugarcane top, banana stem, and eucalyptus chip) as substrates for the degradation of ethylene bis-dithiocarbamate (EBDC) and ethylene thiourea (ETU) in wastewater from banana spraying. Acrylic columns with a capacity to treat 1 L/ea. of wastewater were used as experimental units. Each unit was filled with different proportions of the test substrate (30%, 50% and 70% v/v) and the difference in volume was made up of equal parts of sugar cane cachasse and Fluvisol soil. Subsequently, the units were contaminated with suspensions of 878 mgL −1 of EBDC, and the dose was repeated periodically. The ETU concentration and leachate toxicity were evaluated every month for six months. The mixtures with 30% sugarcane top and 50% eucalyptus chip gave the best results, with leachable ETU concentrations down to a level protective of the environment, and toxicity down to background levels or nearly so. This was only found in mixtures with a high C:N ratio (20–25), thus, the effectiveness of the biobeds appears to be related to high lignolytic activity. .