Membrane-based bioprocesses for polylactic acid recycling and pharmaceuticals biodegradation

This doctoral thesis investigates how membrane technologies can be integrated into biological processes to address two environmental challenges: valorization of post-consumer bioplastics and removal of pharmaceutical micropollutants from wastewater. In both cases, membranes are employed as multifunctional platforms that enable selective product recovery, biofilm support, and controlled oxygen delivery, rather than merely serving as separation media. First, a PLA enzymatic depolymerization system equipped with two ultrafiltration modules was developed to enable enzyme retention and continuous product removal. Membrane selectivity was tuned to extract or concentrate oligomers, enabling targeted recovery for downstream use. In addition, membrane-contactor liquid–liquid extraction was evaluated as an intensified method for selective lactic acid recovery. This integrated approach demonstrates the use of membranes to control reaction environment, steer product distribution, and enable continuous PLA depolymerization. The second section focuses on the development of a membrane-aerated biofilm reactor (MABR) for the continuous biodegradation of ibuprofen and paracetamol within an integrated adsorption–desorption treatment scheme. The MABR was initially adapted to degrade the target compounds under aqueous conditions, achieving complete and stable removal of both pharmaceuticals over several months. When pharmaceuticals were co-fed with ethanol, obtained by regeneration of the upstream adsorption step, the increased oxygen demand necessitated biofilm adaptation to mixed-substrate conditions. Stable pharmaceutical degradation was maintained once operating parameters were adjusted, showing that the limitation arose from oxygen transfer rather than biological inhibition. The study demonstrates that near-complete removal can be recovered by rebalancing oxygen supply and organic load, highlighting the novelty of sustained MABR operation under solvent-containing feeds representative of integrated treatment configurations. Overall, the thesis demonstrates that membrane-based technologies, when coupled with enzymatic and biological processes, represent versatile green platforms for selective product recovery, process intensification, and pollutant removal, extending their role from passive separation units to active drivers of sustainable reaction–separation systems.