Figure legends
Figure 1. Operational settings chosen, with the measured feast length during the start-up period for obtaining granules.
Figure 2. Visual impression of the sludge bed during the different operational periods in this study. From left to right, Start-up phase, 40-50 d SRT, 10-20 d SRT, and 1-2 d SRT.
Figure 3. Upper picture is an overview of the reactor performance in terms of VFA, VSS production and the compactness of the culture expressed as SVI60. The bottom picture is the evolution of the product spectrum obtained during each enrichment. Day 0-136 is the 40-50 d SRT, day 137-192 is the 10-20 d SRT and finally day 193-212 is the 1-2 d SRT system.
Figure 4. All system characterisations performed in this study. From top to bottom the 40-50 d SRT, 10-20 d SRT and finally the 1-2 d SRT is depicted. Markers reflect measurements and lines are modelled. Soluble COD concentrations (sCOD) were calculated as the sum of the individual substrate and product concentrations. All cycle measurements were performed on the last day of the enrichment thus on days: 136, 192 and 212 for respectively 40-50 d, 10-20 d and 1-2 d SRT.

Appendix A

The mathematical model made in this study was aimed to derive characteristic parameters from the experimental data. The model was based upon 3 reactions: (i) the direct conversion of glucose to organic acids, storage polymers, and biomass; (ii) the conversion of storage polymers to organic acids and biomass; (iii) when lactate was one of the organic acids produced a third reaction was used describing the conversion of lactate to acetate, propionate and biomass. Glucose and lacatate conversions occurred in parallel and resulting in (partial) similar products thus these could not be calibrated separately. For this reason the reaction stoichiometry for lactate was fixed and similar to that used by (J. Tamis et al., 2015) and shown in table A.1. The reaction stoichiometry for reaction (i) and (ii) are given in table A.1
Table A.1. The reaction stoichiometries used to calibrate the model to the measured data