Regulating composite fouling detachability in reclaimed water distribution systems under electromagnetic field-assisted hydraulic flushing

Abstract Composite fouling remains a major operational challenge for reclaimed water distribution systems. Conventional hydraulic flushing (HF) often fails over the long term not simply because of the amount of fouling accumulated, but because the deposits develop strong internal cohesion and tight interfacial adhesion that resist shear removal. Here, we present a non-chemical strategy that couples electromagnetic field (MF) with hydraulic flushing (HF) to regulate fouling detachability, defined here as the ease with which deposits are removed by shear, rather than merely attempting to reduce fouling mass. The approach was evaluated in a pilot-scale distribution system operated for 600 h under realistic reclaimed water conditions. The combination of electromagnetic field and hydraulic flushing (MF-HF) treatment substantially reduced total fouling accumulation (64.8–80.8%) and restored system flow rates (70.4–81.3%) relative to the control, outperforming electromagnetic field or hydraulic flushing applied individually. Multiscale analyses revealed that electromagnetic field conditioning altered the physicochemical state of composite fouling, including weakened mineral structures, reduced extracellular polymeric substances, and disruption of organic binding matrices. These changes collectively lowered fouling adhesion and rendered deposits more responsive to shear-induced removal during subsequent flushing, as independently supported by nanoscale adhesion measurements and flushing effluent characterization. The MF-HF strategy converted composite fouling from an adhesion-dominated state to a shear-responsive state, demonstrating that fouling detachability is a regulatable property rather than a passive consequence of fouling accumulation. This change led to markedly improved cleaning efficiency under identical hydraulic conditions and provides mechanistic support for low-energy, chemical-free fouling control in reclaimed water distribution systems.