Preparing mixed microalgae­bacteria granules for waste water purification involves growing the microalgaeactive sludge inoculum in a bioreactor

Preparing mixed microalgae ­bacteria granules for purifying waste water comprises growing the microalgae­active sludge inoculum in a bioreactor, according to the following sequence: supply of bioreactor inoculated with a substrate­ containing liquid medium, periodically exposing the bioreactor to a light source, mechanically stirring the medium during substrate consumption, stopping the mechanical stirring, settling of the microalgae­ active sludge system and discharge of the active medium to obtain mixed microalgae­ active sludge granules having sizes of 200­300 and a settling rate of at least 10 m/h while ensuring, by settling, the microalgae recovery from the liquid medium at an efficiency of at least 99%.