Data from: Treatment of aquaculture effluent with Chlorella vulgaris and Tetradesmus obliquus: the effect of pretreatment on microalgae growth and nutrient removal efficiency

The ongoing and increasing worldwide demand for fish has caused a steady
increase in aquaculture production during the last decades. This
emphasizes the importance of farming systems with a low ecological
footprint, like recirculating aquaculture systems (RAS), which are an
alternative to traditional open systems. Furthermore, implementing
microalgae treatments in RAS, sustainable water management and low
discharge of concentrated wastewater could be achieved, allowing its reuse
in the system. The influence of three factors on microalgae treatment
efficiency in RAS water were studied: i) microalgae species (Chlorella
vulgaris, Tetradesmus obliquus), ii) water pre-treatment (sterile
filtration), and iii) sampling location within the RAS (e.g. from fish
tank, after UV-disinfection, etc.). To this end, fully factorial,
replicated cultivations were carried out in 100-ml flasks, and nutrient
removal, microalgae growth, and density of bacteria and protozoa were
measured for up to 18 days. Results show that both species are able to
grow in RAS water and effectively remove nutrients in it, yet their
performance depended greatly on water quality. In sterile RAS water,
growth and nutrient removal efficiency of C. vulgaris surpassed that of T.
obliquus. In non-sterile RAS water, the pattern reversed because of
grazing proto- zoa. The location of sampling within the RAS had no
discernible effect on microalgae growth or nutrient removal efficiency.
The results confirm that a microalgae-based technology to treat and
valorise RAS water is technically feasible, yet caution that inferences
made can be reversed depending on the choice of the species and the pre-
treatment of the RAS water prior to cultivation.