Change in the fouling propensity of sludge in membrane bioreactors (MBR) in relation to the accumulation of biopolymer clusters

► MBR sludge liquor has a higher organic content and more BPC than activated sludge supernatant. ► MBR filtration transforms activated sludge to MBR sludge with more BPC and higher fouling propensity. ► Vast membrane surface in MBR allows the transformation of organic to more detrimental BPC foulant.