Microalgae Strain Porphyridium purpureum for Nutrient Reduction in Dairy Wastewaters

Abstract

This paper has approached the study of dairy wastewater treatment and the simultaneous biocompound production by Porphyridium purpureum under continuous light and under a day–night cycle. The main goals were to achieve a reduction in the lactose content of the cheese wastewater that was tested and, at the same time, to obtain added value from the produced compounds, so as to increase the economic value of the process. The results show that biomass production increases proportionally with the concentration of lactose for both of the illumination options. The lactose concentration in the waste stream was reduced over 90% in just 7 days. The exopolysaccharide concentration in the growth medium increased with lactose availability. For the samples that were under constant light stress, the concentration of phycobiliproteins was highest when there was small amounts of lactose in the medium. The content of pigments was higher in the case of the day–night cycle of illumination; these being affected by stress factors such as continuous light and high lactose concentration. The results that were obtained prove that dairy wastewaters that are rich in lactose can be used efficiently for the growth of Porphyridium purpureum, achieving an increase in the biomass concentration and a large reduction of the lactose from this waste stream while obtaining a microalgae biomass that is rich in valuable compounds.