A novel technique is described that achieves particle concentration using inclined sedimentation via sludge accumulation and removal (CISSAR(1)). In contrast to a continuous inclined sedimentation process, in which clarification via sedimentation and recovery via sediment or sludge flow occur simultaneously, the CISSAR process consists of a long, particle-deposition and fluid-clarification step, followed by a short, sludge-resuspension and sludge-recovery step. The separation of the clarification and sludge-recovery processes removes design limitations necessary for sludge flow, enabling optimization of the clarification process. While commercial settlers are typically operated at about 55 from the horizontal to ensure sludge flow, the CISSAR process is operated at a shallow angle, resulting in 70% faster clarification per plate area. Using a high-aspect-ratio inclined settler (L/b=500) with the CISSAR process, a similar to 0.7 g/L, unflocculated algal suspension was concentrated over 80-fold to 59 g/L at a bulk-average clarification velocity of nearly 500-fold greater than the algal terminal settling velocity. The extent of concentration (below a maximum value) was shown to be proportional to the settling rate and the duration of clarification, inversely proportional to the plate spacing, and independent of settling area. (C) 2013 Elsevier Ltd. All rights reserved.