This paper is concerned with the capture and subsequent release of wastewater biomass using a high voidage filter. A semi-automated experimental rig was developed where both the hydraulic response of the filter and the capture of biomass were investigated as a function of throughput and filter voidage. The hydraulic response of the clean filter was found to correlate well with the Jackson-James permeability model for gas filtration, and the hydraulic measurements give information about the average shear stresses present during the initial stages of biomass deposition. Biomass capture in the filter was achieved for low Reynolds number throughput followed by a characteristic breakthrough of particles to the effluent stream. Subsequent release of biomass and regeneration of the filter was accomplished by high intensity oscillation of the fluid in the filter, causing the re-suspension of the biomass, which could then be drained from the column. The performance of the filter is evaluated in terms of its cycle and energy efficiency, and its potential for scale-up. (c) 2005 Elsevier Ltd. All rights reserved.