Transient cavitation enables ultrafast fouling removal in mesh bioreactors for efficient sludge‒liquid separation during wastewater treatment

Effective sanitation requires sufficient wastewater treatment, and the total suspended solids (TSS) concentration is a key treatment performance indicator. Whereas membrane-based separation methods employing micro- or ultra-filtration achieve high TSS removal, they are costly and energy-intensive because of membrane fouling, and gravity-based separation methods often cannot consistently meet TSS discharge standards. Here we present a mesh bioreactor (MeBR) that combines a coarse-pore mesh with a piezoelectric fouling removal strategy for efficient sludge–liquid separation. Experiments revealed that irreversible mesh fouling was completely eliminated within 10 s when near-field transient cavitation, induced by piezoelectric ultrasound transducers, was the primary cleaning mechanism, rather than oscillation or reactive oxygen species generation. This ultrafast cleaning enabled continuous ultrahigh-flux MeBR operation (148–307 l m⁻² h⁻¹), which ensured rapid biocake formation (< 10 min) and globally regulation-compliant TSS levels. Overall, the transient cavitation-integrated MeBR offers a sustainable, reliable and energy-efficient solution for wastewater treatment. © The Author(s), under exclusive licence to Springer Nature Limited 2025.