2.1. Preparation of an active microalgal-bacteria inoculum
The microbial biomass used in all batch experiments was obtained from a HRAP pilot plant in Pau (France). The microbial consortium (microalgae, bacteria and other microscopic organisms) collected was firstly allowed to settle for 2 h and the settled solids were used as an “enriched microbial biomass inoculum”. The wastewater collected from another similar pilot plant (Ouistreham − France) was clarified through centrifugation (2000g; 10 min) and used as the nutrient medium for batch experiments.
The enriched microbial biomass was used to inoculate (10% v/v) the clarified nutrient medium (2900 mL). This culture was continuously stirred (35 × 6 mm magnetic stirrer; 100 rpm) in an Erlenmeyer flask under continuous illumination (45 μmol s−1 m−2 at the culture surface with fluorescent lamps, Biolux OSRAMJ 30W/965) and was maintained at room temperature (approx. 20 °C). The constant mixing served to avoid sedimentation.