Aplicação e imobilização de lacase em resíduos da construção civil para tratamento de águas de córrego urbano em wetlands construídos de fluxo vertical subsuperficial

Abstract

The application of oxidative enzymes in constructed wetlands has been investigated as a strategy to enhance the removal of recalcitrant compounds that conventional filter bed mechanisms do not efficiently degrade. In this study, the performance of vertical subsurface flow constructed wetlands (VSFCW) filled with red ceramic brick fragments and vegetated with Eichhornia crassipes was evaluated in the treatment of urban stream water from Ribeirão dos Müller, with and without the addition of laccase produced by Trametes villosa. Laccase was obtained by liquidstate fermentation using agroindustrial waste, reaching a maximum activity of 9,106.44 U L-1 on the 12th day of cultivation, and standardized to 500 U L-1. Two bench-scale systems with 2 L working volume and continuous aeration were operated in batch mode with 48 h cycles over 162 days: System A, with the addition of free laccase at 500 U L-1, and System B, an enzymefree control. Operation was divided into Phase I, without dye addition, and Phase II, with indigo carmine at 25 mg L-1 as a model contaminant. In Phase I, both systems achieved high removal efficiencies: COD of 91.8% and 85.3%, TKN of 87.4% and 88.8%, N-Ammon of 95.2% and 94.1%, and TP of 50.0% and 95.1% in Systems A and B, respectively. The lower TP removal efficiency in System A was attributed to residual KH2PO4 from the fungal growth medium in the influent. In Phase II, indigo carmine decolorization reached 86.32% in System A and 72.81% in System B (p-value = 0.0009), confirming the catalytic contribution of laccase to dye decolorization. Covalent immobilization of laccase on construction and demolition waste was evaluated on six support materials, of which red ceramic brick showed technical feasibility, with 17.21% recovered activity after protocol optimization. In bench-scale assays with three consecutive 48 h cycles, immobilized laccase achieved 19.3 to 25.5% decolorization of indigo carmine without enzyme renewal, retaining 75.7% of catalytic capacity between the first and the third cycle. When normalized by the number of enzymatic doses applied, immobilized laccase reached 67.1% decolorization per dose, a value 28% higher than that of free laccase (52.5%), indicating better enzymatic utilization in the immobilized form. The results demonstrate that the integration of laccase with constructed wetlands filled with red ceramic brick is a viable alternative for the removal of recalcitrant compounds from urban stream water.