Fisheries wastewater as a sustainable media for the production of algae-based products

Colombian intensive fish production is concentrated mainly in the departments of the Andean Region, Amazon, and Orinoquía. These systems were characterized for being exploited mainly by family farming nuclei, which are dedicated exclusively to breeding and others with mixed systems. Currently, the sustainable development of this economic line depends on two factors: global warming and the consumption of resources (energy, fresh water, and protein). The rapid growth of this socio-economic line has led to the development of 3 critical restrictions: the demand for food for fish production, the high volume of fresh water needed and the high concentration of wastewater which must be disposed of safely. Sewage from closed fish farming systems has high levels of nitrogen and inorganic phosphorus dissolved in the systems. The primary responsibility for these high contents is the feed which contributes to the sustained increase in the concentration of organic waste and toxic compounds in aquatic systems. To make use of this wastewater, the use of these as a culture medium for microalgal production has been studied in order to generate metabolites of industrial interest from a low-cost culture medium. In this work, the necessary culture conditions for the biomass production of Scenedesmus obliquus, Chlorella vulgaris, Spirulina maxima, and Oscillatoria sp. in fish farming wastewater to produce pigments and total biomass are evaluated. The wastewater was obtained from an intensive fish farming company in El Zulia (Norte de Santander, Colombia). The medium was UV-sterilized (4 Lamps of 15W, 5 minutes). In order to optimize the production of biomass and pigments, the wastewater was adjusted with the addition of nitrogen, phosphorus, and carbon (K2HPO4 + NaNO3 + NaHCO3) According to the results, the residual water enriched with K2HPO4, NaNO3 and NaHCO3 presented the best culture conditions for obtaining carotenoids (in C. vulgaris and S. obliquus with values of 2.6 and 1.7% p/p respectively) and Phycobiliproteins in Spirulina maxima and Oscillatoria sp (10.9 and 11% p/p respectively). These results allow concluding that the residual water of fish systems is outlined as a suitable culture medium that can be used to produce metabolites of interest. Also, this culture medium must be enriched in order to increase the productivity of the system.