Tertiary urban wastewater treatment with microalgae natural consortia in novel pilot photobioreactors

The aim of this work was to evaluate the efficiency of the new GreenDune photobioreactors for tertiary wastewater treatment, treated wastewater reuse and biomass application, using naturally occurring microalgae consortia. The study was conducted on a pilot installation in a wastewater treatment plant in Portugal and different operational conditions were tested. The system was capable to remove up to 95% of NH4+, the main pollutant in wastewater after secondary treatment using hydraulic retention times as low as 24 h. The application of a non-conservative scenario allowed the reuse of treated wastewater for seed production, and irrigation of naturally restricted use areas. The produced biomass was rich in proteins and carbohydrates with potential for biofuel production such as biogas or use as biofertilizers, closing the energy and nutrients cycle. Finally, the life cycle assessment of both the GreenDune and existing nitrification/denitrification systems were compared revealing that the operation of the GreenDune are more environmentally favourable than the existing system.