Alejandro Ruiz-Marín

Growth and nutrient removal in free and immobilized green algae in batch and semi-continuous cultures treating real wastewater

Two species of microalgae growing as immobilized and free-cells were compared to test its ability to remove N and P in batch cultures of urban wastewater. The best microalgae-cell growth configuration was selected to be tested in bioreactor operated in semi-continuous mode. Scenedesmus obliquus showed a higher N and P uptake rate in urban wastewater than Chlorella vulgaris. When tested in semi-continuous mode and with the re-calcification of beads, S. obliquus was more effective in removing N and P for longer periods (181 h) than batch cultures; fecal coliforms removal was good (95%) although the final concentration was still unsuitable for discharge to natural water bodies. Protein and lipids content analysis suggest that, from a practical point of view, immobilized systems could facilitate the separation of the biomass from the treated wastewater although in terms of nutritional value of the biomass, immobilized systems do not represent an advantage over free-cell systems.

A two-stage culture process using Chlorella vulgaris for urban wastewater nutrient removal and enhanced algal lipid accumulation under photoautotrophic and mixotrophic conditions

Microalgae such as Chlorella vulgaris contain sufficient fatty acids to suggest their use as feedstocks for biodiesel production. Their capacity to remove nitrogen, phosphate, and other nutrients from a culture medium makes them a potentially useful element in urban wastewater treatment systems. A two-stage process was used to grow Chlorella vulgaris under mixotrophic and autotrophic conditions in artificial wastewater and urban wastewater media. Growth rate, nutrient removal, and lipids accumulation were quantified. Initially, the media were nitrogen-enriched (90 mg−1; Stage I), and then nitrogen limited (30, 20, and 10 mg l−1; Stage II). Growth was not inhibited under either of the culture conditions, and nitrogen uptake rates were above 90%. Total organic carbon removal was higher (56.2%–86%) under mixotrophic conditions than under photoautotrophic conditions (15.2%–69%). Lipids productivity was 2.7 times higher under mixotrophic conditions and nitrogen limitation than under photoautotrophic conditions...

Productivity and Biodiesel Quality of Fatty Acids Contents from Scenedesmus obliquus in Domestic Wastewater Using Phototrophic and Mixotrophic Cultivation Systems

RESEARCH ARTICLE Productivity and Biodiesel Quality of Fatty Acids