Dewatering of the dilute algal suspensions required to minimize light limitation in the bioreactor is recognized as a key challenge in large-scale algal processes. This is aggravated by small algal cell size and a density only slightly greater than that of water. An initial dewatering step is required to achieve a solids concentration of 1% to 2.5% by mass prior to concentration using an energy-intensive operation such as centrifugation to a solids concentration of 5% to 20% (Benemann and Oswald, 1996). Ideally, flocculation and sedimentation are used for the primary dewatering, facilitated by the algal species selected (Lardon 2009; Stephenson et al., 2010). Other options include natural settling (Collet et al., 2010), filtration (Yang et al., 2011), and dissolved air flotation (Campbell et al., 2010). The decanter centrifuge, spiral-plate centrifuge, and rotary press are most typically proposed for the second dewatering step (Lardon et al., 2009; Campbell et al., 2010; Clarens et al., 2010; Collet et al., 2010; Stephenson et al., 2010). Stephenson et al. (2010) report a relative electricity consumption for flocculation of 1 unit versus 4 units for centrifugation and 14.4 units for the cultivation. On using a more dilute algal culture, as typically found with the raceway, both pumping energy and the need to increase flocculant supplied to main­tain its volumetric concentration impact the process.