Pore blockage of organic fouling layer with highly heterogeneous structure in membrane filtration: Role of minor organic foulants

► We probed spatial distribution of EPS in fouling layer on membrane after filtration. ► The contributions of filtration resistances by individual foulants were identified. ► The β-d-glucopyranose polysaccharides occupied over 80% volume of the fouling layer. ► Blockage of large pore by minor pollutants determined the cake resistance in filtration.