Microalgae cultivation in wastewater: Nutrient removal from anaerobic membrane bioreactor effluent

This study investigated the removal of nitrogen and phosphorus from the effluent of a submerged anaerobic membrane bioreactor (SAnMBR) by means of a lab-scale photobioreactor in which algae biomass was cultured in a semi-continuous mode for a period of 42 days. Solids retention time was 2 days and a stable pH value in the system was maintained by adding CO2. Nitrogen and phosphorus concentrations in the SAnMBR effluent fluctuated according to the operating performance of the bioreactor and the properties of its actual wastewater load. Despite these variations, the anaerobic effluent proved to be a suitable growth medium for microalgae (mean biomass productivity was 234 mg l−1 d−1), achieving a nutrient removal efficiency of 67.2% for ammonium (NH4+–N) and 97.8% for phosphate (PO4−3–P). When conditions were optimum, excellent water quality with very low ammonium and phosphate concentrations was obtained.

► A mixed microalgal culture is grown in anaerobically pretreated wastewater. ► Cultivation is in semi-continuous mode and biomass productivity is 234 mg l−1 d−1. ► High nutrient removal rates are maintained for 42 days. ► The water quality of the effluent is excellent in terms of soluble inorganic N and P.