This study investigated the microfiltration of microalgae, Chlorella sp., in the presence of polymethylmethacrylate (PMMA) under dead-end and cross-flow modes. The concentration of microalgae was 10 mg/L, while PMMA concentration varied from 10 to 40 mg/L. Flux increased with increasing concentration of PMMA in dead-end microfiltration, and the specific cake resistance decreased as PMMA concentration increased under three different trans-membrane pressure (TMP) of 20, 40, and 60 kPa. The cake compressibility decreased in the presence of PMMA. In cross-flow microfiltration of microalgae in the presence of PMMA, the flux increased as cross-flow velocity increased, and the effect became more pronounced as PMMA concentration increased. It was because the rigid PMMA particles rendered the distribution of local specific resistance more uniform along the cake thickness. In addition, the cake growth became more containable by increasing cross-flow velocity when more PMMA particles were present, and resulted in higher steady flux under both laminar and turbulent flow conditions. (C) 2016 Elsevier B.V. All rights reserved.