Techno-economic analysis of a circular microalgal approach for enhanced wastewater treatment and resource recovery in Northern Portugal

Microalgae culturing in municipal wastewater treatment plants (WWTP) can be a solution to lower the effluent's nitrogen and phosphorus concentrations to comply with the new legislative limits. Microalgae can also promote a circular approach to WWTP by recycling material streams and reducing the energetic consumption of the treatment process. This study aims to perform a techno-economic assessment of the integration of microalgae culture (Chlorella vulgaris) as tertiary treatment at a WWTP in northern Portugal. This evaluation took into account information collected from the specific WWTP under study as well as relevant literature for each stage of the process. The major system flows: (i) a 7377 m3 d-1 treated water flow (ii) the treatment of 107,736 kg d -1 of sludge; (iii) a biosolids soil amendment production of 7580 kg d-1; and (iv) 10,874 kW h d-1 energy for selfconsumption. In this work, the integration of microalgae in WWTP achieved yearly gross earnings of approximately 619,100 euro.