Effect of light/dark cycle on nitrate and phosphate removal from synthetic wastewater based on BG11 medium by Scenedesmus sp.

Abstract

In this study, microalgae growth in the synthetic wastewater and their ability to remove nutrients under different light levels was investigated. For this purpose, a comparative study was conducted on freshwater microalgae Scenedesmus sp. to evaluate their performance to remove nitrate and phosphate from both slaughterhouse and dairy synthetic treated wastewaters, under different light/dark cycles (12/12, 16/8 and 24/0h), in Erlenmeyer flasks. The best light/dark cycles in Erlenmeyer flasks for nitrate and phosphate removal and growth were obtained at 24/0h. Moreover, nitrate and phosphate removal under light conditions at 24/0h light/dark cycles were tested in a designed open raceway pond. The maximum nitrate removal in slaughterhouse and dairy synthetic wastewater was 78% and 99.7%, and the phosphate removal was 31% and 68%, respectively. Furthermore, the highest biomass productivity in dairy and slaughterhouse synthetic wastewater during 9days was 0.65gL-1 and 1.5gL-1, respectively. Thus, Scenedesmus sp. could be potential candidates by showing their intrinsic merit, for the reduction of nitrate and phosphate residue levels from dairy and slaughterhouse synthetic wastewaters in open raceway ponds.