Since biomass was rich in PHA storing bacteria, PHA was rapidly accumulated up to 6.2% during the feast phase (first 10 min) and it was progressively consumed before the initiation of the anoxic phase to 2.3%, which was enough to complete the subsequent denitritation.
Following the sOUR profile, it seems that sCOD was oxidised during the first 40 min; however, the PHA content did not increase. Therefore, non-VFA COD did not to contribute to PHA storage.
Albuquerque et al. (2010) demonstrated that the residual sCOD favoured the growth of non-storing biomass that consumed this COD fraction during famine phase, resulting in a loss of PHA storage
capacity.
The feast and famine ratio was calculated based on the VFA basis and was 0.05 for the cycle shown in Fig. 3c and d, considering that within 10 min VFAs were consumed followed by
190 min under famine conditions.
The non-VFA COD present in the system resulted in a sOUR was around 40 mgO2 (gVSS h)1 due to its oxidation. Then, sOUR decreased to 10 mgO2 (gVSS h)1.
The feast and famine ratio calculated based on sCOD was 0.25 that was adequate to favour the selection of biomass.
During the SBR cycle presented in Fig. 3c and d, the overall nitrogen removal was 84%, resulting in an effluent with 7.2 mgNH4-N L1 and 2.4 mgNO2-N L1, accomplishing the limit of 10 mgN L1. In this cycle, the sAUR observed during the first 40 min was 1.7 mgNH4-N (gVSS h)1 and then it increased to 3.4 mgNH4-N (gVSS h)1.