Biogeofilter with Hydrothermal Treated Stevensite Clay and Laccase Enzymes for Retention and Degradation of Tetracycline

The concentration of antibiotics in surface water is an issue of high concern. The present study aims to manufacture and evaluate a biogeofilter, with stevensite clay and enzymes immobilized on it, for the adsorption and degradation of tetracycline-based antibiotics. To retain the small particle aggregates of the clay in the filter, a hydrothermal treatment was applied to the stevensite, prior to compaction in pellets and its insertion into a cylindric cell, mixed with sand. The structure of the pellets avoids the loss of the clay material during the fluid transport through the porous medium. Several temperature treatments were applied to the pellets, but the treatment at 300 °C was revealed as the best option. Laccase enzymes were immobilized on the stevensite surface. Reactive transport experiments of tetracycline solutions were performed through the transport cells. The biogeofilter has a relevant adsorption capacity with a significant degradation factor. By modelling with STANMOD software, the hydrodynamic characteristics of the transport were determined and, therefore, the behaviour of a large-scale filter and transports of low tetracycline concentrations could be predicted. The results obtained are promising for irrigation systems at medium scale, as well as for the perspective of wastewater treatment plants at large scale.