Semi-continuous summer-season cultivation in a flat outdoor prototype of an autochthonous microalgae for the phytoremediation of urban wastewater at the Ferrara (Italy) plant

Nutrients, like nitrogen (N) and phosphorus (P), released in wastewaters (WW) due to anthropic activities are common pollutants for the environment, since they are usually responsible for the phenomenon of eutrophication of natural wetlands and superficial waters. Similarly WW, mainly urban ones, are often enriched in several micro-organisms, for example coliforms like Escherichia coli, which can cause a wide range of pathologies for humans and animals, beside being increasingly frequently resistant to common antibiotics. Because of their versatility, microalgae are excellent candidates for application in many biotechnological fields, including WW treatment. Results from laboratory-scale experiments on microalgae- based WW treatment are generally promising, while upscaling to outdoor conditions is still in early stages. So, further investigations are needed to improve the applicability of microalgae-based phytoremediation technologies on outdoor plants. This work is focussed on testing the phytoremediation effectiveness with respect to nutrients and E. coli of an autochthonous microalgae strain cultivated in semi- continuous conditions in an 800-L outdoor microalgae prototype placed at the HERA-Ferrara (Italy) WWTP. We assessed, during a summer period, the growth of algae and their potential in nutrients and E. coli removal efficiency (RE) from the effluent deriving from the thickening step of the sludge treatment.