Continuous flow aerobic granular sludge reactor for dairy wastewater treatment

The focus of this study was to assess the treatment performance and granule progression over
time within a continuous flow reactor. A continuous flow airlift reactor was seeded with aerobic
granules from a laboratory scale sequencing batch reactor (SBR) and fed with dairy wastewater.
Stereomicroscopic investigations showed that the granules maintained their integrity during the
experimental period. Laser diffraction investigation showed proof of new granules formation with
100–500 μm diameter after only 2 weeks of operation. The treatment performances were satisfactory
and more or less similar to the ones obtained from the SBR. Thus, removal efficiencies of 81–93% and
85–94% were observed for chemical oxygen demand and biological oxygen demand, respectively.
The N-NHþ
4 was nitrified with removal efficiencies of 83–99% while the nitrate produced was
simultaneously denitrified – highest nitrate concentration determined in the effluent was 4.2 mg/L.
The removal efficiency of total nitrogen was between 52 and 80% depending on influent nitrogen
load (39.3–76.2 mg/L). Phosphate removal efficiencies ranged between 65 and above 99% depending
on the influent phosphate concentration, which varied between 11.2 and 28.3 mg/L.