The addition of an external carbon source was necessary due to a lack of significant concentrations of VFA in the influent wastewater. 
Two types of external carbon source were tested in the process; OFMSW FL and combined PS & OFMSW FL (Table 1). 
The carbon source was added at a ratio of 2.3–2.5 kg COD/N. The fermentation process is described in Section 2.3. Wastewater was collected from the municipal WWTP of Verona (Italy) and was fed into the SBR. 
The feast conditions were established in aerobic environment, by feeding the reactor with fermentation liquid. 
The oxidation of ammonium to nitrite occurred during, aerobic conditions, while denitritation occurred under famine, anoxic conditions. 
In situ and ex situ biomass activity tests were carried out to evaluate the rate of nitrogen removal and VFA uptake (Katsou et al., 2015).