Innovative laccase-based hollow packed-bed reactor for continuous treatment of hospital wastewater

Abstract

This study reports on laccase-mediated removal of trace organic compounds (TrOCs) from real hospital wastewater (HWW) in a packed-bed reactor (PBR). The reactor column consisted of a catalytic bed of amino-functionalized mesoporous silica microspheres attached to a hollow polyethylene packing on which a Trametes hirsuta laccase was immobilized. This bed material had the advantage of significantly limiting pressure drop, which is one of the major drawbacks of PBRs operating in continuous mode. The PBR was fed with HWW, previously filtered through a 0.45-µm PTFE filter. The HWW was used either unspiked or spiked at 1 µg L⁻¹ with acetaminophen, ibuprofen, naproxen, ketoprofen, mefenamic acid, indomethacin, and carbamazepine. A kinetic model combining the substrate conversion (1st-order kinetic) and the biocatalyst inactivation (1st-order kinetic) was developed and implemented, using acetaminophen as a model phenolic compound. After validation, the model showed good fit with experimental data and robustness regarding extended time operation with real HWW under uncontrolled conditions (pH, unbuffered media, ambient temperature). After 6 h of contact time, more than 95% of acetaminophen and mefenamic acid were removed in the PBR. In addition, toxicity tests showed that the laccase-based treatment resulted in a reduction in toxicity to Daphnia magna. The treated HWW did not significantly affect the mobility of Daphnia magna, unlike untreated HWW.