Nitrification by microalgal-bacterial consortia for ammonium removal in flat panel sequencing batch photo-bioreactors

- Nitrifiers present in the microalgal-bacterial consortia increase ammonium removal.
- Nitrification is the main mechanism that causes the increase in ammonium removal.
- Nitrifiers in the microalgal-bacterial system do not inhibit algal activity.
- The biomass retention is necessary to ensure higher nitrification rates.

Ammonium removal from artificial wastewater by microalgal-bacterial consortia in a flat-panel reactor (FPR1) was compared with a microalgae-only flat-panel reactor (FPR2). The microalgal-bacterial consortia removed ammonium at higher rates (100 ± 18 mg NH4+-N L−1 d−1) than the microalgae (44 ± 16 mg NH4+-N L−1 d−1), after the system achieved a stable performance at a 2 days hydraulic retention time. Nitrifiers present in the microalgae-bacteria consortia increased the ammonium removal: the ammonium removal rate by nitrifiers and by algae in FPR1 was, respectively, 50 (±18) and 49 (±22) mg NH4+-N L−1 d−1. Apparently ammonium removal by algae was not significantly different between FPR1 and FPR2. The activity of the nitrifiers did not negatively affect the nitrogen uptake by algae, but improved the total ammonium removal rate of FPR1.