Design of a Biocatalytic Filter for the Degradation of Diclofenac and Its Ozonation Products

Abstract

Posttreatment of the effluents from wastewater treatment plants is becoming increasingly important, as the conventional treatment cannot completely remove organic trace contaminants. Promising techniques like chemical oxidation methods, including ozonation, face the challenge of potentially generating more toxic transformation products than their parent substances due to incomplete oxidation. In this work, the laccase from Trametes versicolor was immobilized on a polyester textile to create a biocatalytic textile filter for the posttreatment of organic trace contaminants and their ozonation by-products. Different filter designs for reactive filtration with biocatalytic textiles were implemented on the laboratory scale and tested for their effectiveness in degrading the dye Remazol Brilliant Blue, the pharmaceutical diclofenac, and its ozonation products. The plate module, inspired by lamellar clarifiers and featuring the textile with covalently immobilized enzyme on the lamella surfaces, exhibited the best performance characteristics. Employing this module, a continuous process of diclofenac ozonation and subsequent posttreatment with the biocatalytic filter was conducted. This not only demonstrated the feasibility of continuous biocatalytic wastewater filtration but also highlighted improved degradation efficiencies of ozonation products compared to the batch process using laccase in solution.

Keywords: filter design; immobilized laccase; micropollutant; textile; wastewater treatment.

FIGURE 1

Proposed reaction mechanism of adsorptive (A) and covalent immobilization (B) of the laccase from T. versicolor [E].

FIGURE 2

UV‐Vis remission spectrum of textiles before and after adsorptive (blue) and covalent (green) immobilization of laccase T. versicolor. The inset provides the absorbance spectrum of laccase of T. versicolor.

FIGURE 3

SEM images of adsorptive (B2–B3) and covalent (C2–C3) immobilization of laccase T. versicolor. Blank: untreated polyester needle felt, B1: PET pre‐functionalized with Bayhydur and polyacrylic acid for adsorptive immobilization. B2 and B3: PET after adsorptive immobilization of the laccase at 100× and 2000× resolution, respectively. C1: PET treated with one‐pot PAA/Bayhydur solution without enzyme. C2 and C3: PET after covalent immobilization of laccase at 100× and 2000× resolution, respectively.

FIGURE 4

Design of the enzymatic filter in the form of a plate module (A) and a wound module (B) in the continuous process.

FIGURE 5

Degradation of RBB in the plate module (blue) and wound module (green) by adsorptive and covalently immobilized laccase T. versicolor at RT. The black dashed lines represent the fit according to the Gompertz function.

FIGURE 6

Degradation of DF in the plate module by adsorptive (orange) and covalently (purple and yellow) immobilized laccase T. versicolor at different flow rates, yellow: 2.5 mL/min, purple: 5.0 mL/min. The black dashed lines represent the fit according to the Gompertz function.

FIGURE 7

Comparison of the removal efficiencies of ozonation products in the continuous mode in the biocatalytic filter (light blue), and the adsorption (dark blue) with the degradation in the batch process by laccase in solution (orange). The degradation in continuous operation is compared with the degradation in batch operation after 3 h, as the residence time in continuous operation is approximately 2.75 h. Batch mode conditions: 250 U/L ± 10 U/L, 20°C, 100 rpm, continuous mode conditions: room temperature, 343 U/L ± 38 U/L.