Experiments were carried out at the laboratory of the GEMMA
Research Group (Universitat Politècnica de Catalunya·BarcelonaTech,
Barcelona, Spain). Microalgal biomass was grown in an experimental
plant that had been in continuous operation for more than 1 year.
Urban wastewater was pumped from a nearby municipal sewer and
conveyed to a primary settler. Following that, primary treatedwastewater
was continuously fed (60 L/day) to an experimental HRAP; a raceway
pond with a volume of 0.47 m3 and a nominal hydraulic
retention time of 8 days. Average loading rates of the HRAP were
24 g COD/m2·day and 4 g NH4-N/m2·day. Microalgal biomass grown
in the HRAP was separated in a clarifier connected in series with the
HRAP (without coagulation–flocculation). A detailed description of the
wastewater treatment system and its operation and performance may
be found elsewhere [18].