Patent ID: 8650798

Claim:
A method of algae cultivation including the removal of adhered algae from a bioreactor comprising the steps of: (a) circulating an algae slurry through a bioreactor in a first mode; wherein the bioreactor comprises a plurality of translucent bioreactor panels, vertically arranged, and a distribution system comprising connecting tubing for flowing the slurry; wherein, in the first mode the slurry is pumped in a first flow direction, through the distribution system, into the bioreactor panels through openings in the bottoms, into flow channels located within the panels, upward through the channels, out of the panels through an opening at the top, and back into the distribution system; (b) sensing a first light intensity sufficient to penetrate the translucent bioreactor panels using at least one sensor located within the flow channels and sensing a pH level of the slurry; (c) maintaining the first mode while the light intensity is at or above the first intensity level, thereby allowing the algae to photosynthesize; (d) adding gaseous carbon dioxide to the algae slurry to lower the pH level to a substantially optimum level for algae growth when the sensed pH level has increased above said optimum pH level, due to algae photosynthesis; (e) continuing to circulate in the first mode, regulating the optimum pH level, until a second light intensity level is sensed; wherein, the second intensity level is below the first intensity level and is insufficient to penetrate the translucent bioreactor panels to reach the algae slurry in order to allow the algae to photosynthesize; (f) switching to a second circulation mode, having a flow direction opposite the first mode, upon sensing the second intensity level; (g) adding gaseous carbon dioxide to the algae slurry to lower the pH level below the optimum level for algae growth; (h) removing algae adhered to the interior surfaces of the bioreactor panels by maintaining the second mode; wherein, the lowered pH and physical forces due to backwashing act to remove the adhered algae.