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With the aim of assessing the potential of microalgae cultivation for water resource recovery (WRR), the performance of three 0.55m(3) flat-plate photobioreactors (PBRs) was evaluated in terms of nutrient removal rate (NRR) and biomass production. The PBRs were operated outdoor (at ambient temperature and light intensity) using as growth media the nutrient-rich effluent from an AnMBR fed with pre-treated sewage. Solar irradiance was the most determining factor affecting NRR. Biomass productivity was significantly affected by temperatures below 20°C. The maximum biomass productivity (52.3mgVSS·L(-1)·d(-1)) and NRR (5.84mgNH4-N·L(-1)·d(-1) and 0.85mgPO4-P·L(-1)·d(-1)) were achieved at solar irradiance of 395μE·m(-2)·s(-1), temperature of 25.5°C, and HRT of 8days. Under these conditions, it was possible to comply with effluent nutrient standards (European Directive 91/271/CEE) when the nutrient content in the influent was in the range of 40-50mgN·L(-1) and 6-7mg P·L(-1).

The objective of this work was to evaluate the performance of a pilot scale membrane photobioreactor (MPBR) for treating the effluent of an anaerobic membrane bioreactor (AnMBR) system. In particular, new experimental data on microalgae productivity, nutrient recovery, CO2 biofixation and energy recovery potential was obtained under different operating conditions, which would facilitate moving towards cost-effective microalgae cultivation on wastewater. To this aim, a 2.2-m 3 MPBR equipped with two commercial-scale hollow-fibre ultrafiltration membrane modules was operated treating the nutrientloaded effluent from an AnMBR for sewage treatment. The influence of several design, environmental and operating parameters on MPBR performance was studied. Among the conditions evaluated, variations in solar irradiance significantly affected the nutrient recovery rate (NRR). Operating at temperatures above 25 ºC and high biomass concentrations, which increased light shading effect, negatively affected biomass production and NRR. Maximum biomass productivity of 66 mg VSS•L-1 •d-1 2 (areal productivity of 15.78 g VSS•m-2 •d-1) and NRR of 7.68 mg N•L-1 •d-1 and 1.17 mg P•L-1 •d-1 were achieved when operating at 4.5 days of biomass retention time. These results would outcome maximum theoretical energy recoveries and CO2 biofixations of about 0.43 kWh and 0.51 kg CO2 per m 3 of treated water, respectively. Moreover, the excellent quality permeate that was produced (i.e. negligible levels of pathogens and suspended solids) represents a reclaimed water source.