An SBR was employed for nitrogen removal via nitrite from wastewater and the selection of PHA storing biomass. The strategy applied consisted of the simultaneous PHA storing biomass selection
and nitritation/denitritation driven by the stored PHA by adding carbon source during aerobic phase for PHA storage.
The scSBR was made of Plexiglas and had a reaction volume of 20 L. The activated sludge inoculum was taken from a pilot SBR treating sludge reject water in the municipal WWTP of Carbonera.
During the start-up, the SBR operated without any biomass wasting for 10 days (volatile suspended solids (VSS) in the mixed liquor increased up to 2 g L1); subsequently, activated sludge was wasted to achieve a sludge retention time (SRT) of 25 days(VSS 2.5 g L1).
Once pseudo-steady state conditions were established the normal SBR operation initiated, which consisted of two experimental periods. The first experimental period (Period I) lasted 45 days and the second experimental period (Period II) lasted 30 days. In Period II, the pseudo-steady state conditions were established within the first 10 days operation since the only major change that was imposed was the change in carbon source.
Details concerning the two experimental periods are given below: