Urban wastewater phytoremediation by autochthonous microalgae in winter season: indoor and outdoor trials

Pierluigi Giacò ¹, Elisa Benà ¹, Sara Demaria ¹, Costanza Baldisserotto ¹, Giulia Zanotti ², Simonetta Pancaldi ³

Department of Environmental and Prevention Sciences, University of Ferrara, C.so Ercole I d’Este, 32, 44121 Ferrara, Italy ¹, HERA SpA – Direzione Acqua, Via C. Diana, 40, 44044 Cassana (Ferrara), Italy ², Department of Environmental and Prevention Sciences, University of Ferrara, C.so Ercole I d’Este, 32, 44121 Ferrara, Italy; Terra&Acqua Tech Laboratory, Technopole of Ferrara University, Via Saragat, 13, 44122 Ferrara, Italy ³

Water scarcity and water pollution are two of the major problems that humanity is going to face shortly. Water is mostly consumed by agriculture, industry, and housing, which then release wastewater (WW) into the environment. These effluents generally are rich in organic matter, nitrogen (N), and phosphorus (P), and their release into the environment can bring to loss in river quality, sediment contamination, and even eutrophication. Even if depuration is performed, WW treatment plants (WWTPs) are still considered a point source of pollution. Microalgae are gaining increasing attention for WW depuration thanks to their ability to remove pollutants from the wastewater (WW) with simultaneous production of biomass enriched in nutrients and other molecules of interest. As environmental conditions change widely geographically and throughout the year, sites and seasons specific tests are needed. We performed two site-specific prototype-scale experiments to test the ability of a previously isolated microalga to efficiently depurate prototype-scale volumes of WW during winter, when the environmental conditions are not optimal for microalgal growth. Two different setups were tested, one indoor and one outdoor. For both cultivations, dry biomass production, photosystem II maximum quantum yield (Fv/Fm), pigments concentrations were monitored. N and P removals were evaluated along with nutrient concentration in biomass. In addition, Escherichia coli concentration was monitored to evaluate the microalgal disinfection potential of the effluent. Interestingly, cells grown outdoor underwent severe photoinhibition for the first days, but then they adapted to the new growth conditions. Despite the absence of significant growth in both indoor and outdoor conditions, N was largely removed from the medium with the highest result recorded outdoor (almost 70%). No P removal was recorded, although P content in biomass increased both indoor and outdoor, meaning that multiple processes could be happening at the same time. Moreover, a huge decrease in E. coli content was recorded in both conditions, suggesting potential for effluent disinfection. Project funded under PR-FESR EMILIA ROMAGNA 2021-2027 (CUP F37G22000200003).

Main author career stage: PhD student

Contribution type: Talk

First choice session: 4. Structure, physiology, and development

Second choice session: 3. Biodiversity and global change