Hyperconcentrated cultures of Scenedesmus obliquus: A new approach for wastewater biological tertiary treatment? |
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Authors: | A Lavoie J de la Noüe |
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Affiliation: | Département de biologie and Centre de recherche en nutrition, Université Laval, Québec, Canada G1K 7P4 |
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Abstract: | Algal cultures of Scenedesmus obliquus at low concentrations (0.1–0.2 g dry wt l−1) provide adequate biological tertiary treatment of wastewaters. This research was aimed at studying the possibility of increasing the system performance by using hyperconcentrated cultures of S. obliquus (up to 2.6 g dry wt l−1) at the laboratory scale. The algal culture grown on secondary effluent was first chemically flocculated with chitosan (30 mg l−1) and decanted; the sedimented culture (5 g dry wt l−1) was then resuspended in secondary effluent to obtain algal suspensions at various concentrations, the performance of which was compared to that of a control culture (0.13 g dry wt l−1). The rate of exhaustion of nitrogen (N-NH4+) was proportional to the algal concentration and a complete removal could be obtained within 15 min (at 2.6 g dry wt algae l−1); this result compares favorably to the 2.5 h or so required by the control culture. The unit uptake rate for nitrogen (N-NH4+) had a tendency to increase with the algal concentration, whereas that of phosphorus (P-PO43−) showed the opposite relationship. Considering the results obtained, it appears that hyperconcentrated algal cultures have a high potential for the tertiary treatment of wastewaters; a significant reduction of pond surface for large scale operations can be anticipated. |
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Keywords: | wastewater treatment Scenedesmus obliquus microalgae hyperconcentrated culture nitrogen uptake |
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