Active research and process development are still ongoing to improve the overall cost efficiency of DAF-related systems so that they can meet the economic thresholds imposed by the biofuel marketplace. Two recent examples of this are posiDAF and ballastDAF. The term posiDAF is used to describe DAF being run with a positive surfactant added to the bubble generation system. The 2007 thesis of Henderson (2007) applied this technology to algae and is under development as a commercial product by WaterInnovate Ltd. (http://waterinnovate. co. uk/). Another technology, termed ballastDAF, uses positively charged glass beads pushed through the system instead of air bubbles to provide separation of the cells from the medium (www. rachelwhitton. co. uk/uploads/1/9/4/5/…/whitton_poster. pdf). The glass beads are collected by low-speed centrifugation (e. g., cyclones), and then, the beads can be reused for further separation. Jefferson and colleagues claimed a reduction in energy to <20 % of that required by conventional DAF.