In this study, the effect of sludge concentration on the performance of an aerobic dynamic membrane bioreactor (DMBR) was investigated. Low-cost polyester hollow fiber support material was used for the formation of dynamic membrane (DM). Treatment and filtration performances of the DMBR were investigated at two different sludge concentrations (5 g/L; 10 g/L). Both DMBRs were operated at a flux of 18 L/m2 h The DM could be operated at steady conditions for 51 and 24 days at sludge concentrations of 5 and 10 g/L, respectively. High treatment performance and permeate quality were achieved at each sludge concentration. High chemical oxygen demand (COD) removal ( 88%), low total suspended solids (TSS) concentrations (<10 mg/L), and low turbidity values (<1.15 NTU) were achieved by both DMs. However, a shift to a relatively larger range in particle size distribution of permeate were observed at high sludge concentration. Furthermore, higher transmembrane pressure was observed at the sludge concentration of 10 g/L, resulting in a rapid clogging. At the tested conditions, overall results indicated that selection of the optimum sludge concentration played a significant role in achieving homogeneous and stable DM layer in DMBRs. ? 2021 Elsevier B.V. All rights reserved.