The Cyanobactrium Phormidium fragile and the green alga Scenedesmus armatus are chosen in this study for treatment of synthetic wastewater. The growth rate and nutrient removal rates were investigated under different irradiance condition. The growth rate increased with increasing irradiance, reaching a saturation value at 2000 and 1500 Lux for P. fragile and S. armatus respectively. The organic acids removal rates by S. armatus were higher than those removed by P. fragile reaching the maximum values at 1500 and 2000 Lux. On the other hand phosphate, nitrate and ammonia removal rates by P. fragile were higher than those by S. armatus. A mixed culture of both P. fragile and S. armatus was therefore used for simultaneous removal of organic acids, nitrate, ammonia and phosphate. Both acetate and propionate removal rates increased with the increase in the concentration of S. armatus while removal rates of nitrate and phosphate increased with the increasing in the concentrations of P. fragile.
Key words: wastewater treatment, photosynthetic cells, Phprmidium fragile, Scenedesmus armatus.