The results of a two-phase anaerobic system using anaerobic sequencing batch reactors (ASBRs), treating low-strength wastewater (COD similar to 500 mg/L) with a high fraction of particulate organic matter (70%, COD basis), are presented. Two reactors in series were used; the first one was hydrolytic-acidogenic while, the second one was methanogenic. This configuration was proposed to promote high efficiency solids removal. During the experiment, 69% and 50% efficiencies of total COD removal were obtained for OLRs of 0.63 and 1.22 kgCOD/(m(3) d), respectively. Values of the solubilized organic fraction (SOF) achieved in the hydrolytic-acidogenic reactor were within the range of 0.3-0.6gCOD(solubilized)/gpCOD(removed), and the average acidified organic fraction (AOF) was 0.6 g CODVFA-produced/gsCOD(fed). The methanogenic reactor had a VFA removal fraction (VFARF) between 0.4 and 0.6 g CODVFA-removed/gCOD(VFA-fed) for the OLR of 0.63 and 1.22. The two-phase ASBR system is suitable. and can be implemented, for the anaerobic treatment of this kind of wastewater. (C) 2008 Elsevier B.V. All rights reserved.