Nitrogen budget in Scenedesmus obliquus cultures with artificial wastewater

Semicontinuous cultures of Scenedesmus obliquus in artificial wastewater. r ecycled into proteins about 33% and 25% of the dissolved nitrogen missing f rom the medium 24 h after harvesting 50% and 70% of the culture, and replac ing the volume harvested with fresh medium. The residual dissolved nitrogen concentrations were 25% and 43% of the initial, respectively, with an imba lance in the mass budget close to 17 and 20 mg N l(-1) dl. Most or all the nitrogen missing was found in an ammonia trap located at the air vent of th e closed cultures, showing that an important role of microalgae in wastewat er treatment is that of favouring NH3 stripping due to the photosynthesis-i nduced pH increases. (C) 2001 Elsevier Science Ltd. All rights reserved.