Development of a foam flotation system for harvesting microalgae biomass

High-pH-induced flocculation–flotation of the hypersaline microalga Dunaliella salina

“…The mechanism of pH-induced flocculation has been investigated in freshwater, seawater and wastewater (see background in Section 2) but no study has been reported on the hypersaline waters in which D. salina is cultivated, neither are there any studies on the coupling of pH-induced flocculation and flotation. Considering that gravitational drainage of the liquid in the flotation foam gives a better concentration of the algal biomass than is obtained by sedimentation (Coward et al, 2013), this coupling may be interesting. Savings made by reducing the volumes of suspension to be treated in downstream processes may be greater than the cost of bubble production.…”

Harvesting of microalgae within a biorefinery approach: A review of the developments and case studies from pilot-plants

“…A 10.2 L dispersed air flotation-foam fractionation was reported to achieve maximum biomass concentration of 14-24 g DCW/L with an energy consumption of 0.015 kWh/m 3 , using a limewood sparger. When combined with fluidic oscillation, the maximum biomass concentration increased to 28 g DCW/L, and the energy consumption was estimated to be 0.105 kWh/m 3 [25,106]. In other work, the same researchers demonstrated that harvesting algal biomass with cetyltrimethylammonium bromide (CTAB) aided foam flotation, gained higher lipid recoveries, and exhibited a lipid profile more suited to biodiesel conversion.…”

“…Dispersed air flotation was reported to operate at 15 psi and energy consumption was reported to be 3 kWh/m 3 [100]. Coward et al [25] reported a flotation device which combines dispersed air flotation with foam fractionation to allow harvesting, concentration and physical separation of algal biomass [25]. Foam fractionation uses low pressure spargers for the production of bubbles and may also be used in combination with fluidic oscillation [106].…”

“…This is largely due to the dilute nature of autotrophic microalgae cultures, to the order of 0.3-5 kg/m 3 [22,23], leading to time and energy intensive cell harvesting stages. Indeed, harvesting has often been cited as one of the major factors preventing a scalable industry [18,[24][25][26]. Consequently, the algal research community has shifted from a one-product focus to multiple-product extraction strategies [27][28][29][30].…”

Liquid culture of microalgae in a photobioreactor (PBR) based on oscillatory baffled reactor (OBR) technology – A feasibility study

“…However, there are several barriers to the development of economic bioprocesses for production of sustainable products based on microalgae. These include light penetration (Lee, 1999), oxygen removal (Richmond et al, 1993), CO 2 addition (Eriksen, 2008), contamination (Chen et al, 2011) and harvesting (Coward et al, 2013).…”