Fig. 5

Conductivity (a), total COD (b), and COD conversion (c) and removal (d) rates in terrestrial and marine PBBRs. Terrestrial (T) and marine (M) PBBRs were operated at a controlled pH equal to 7, temperature was set to 34 °C. Following 7 days of recirculation to allow biomass development in the PBBRs, both reactors were continuously fed with molasses with a hydraulic retention time (HRT) of 10 days. Time zero represents the first day that PBBRs were operated continuously. Hence, the startup period refers to almost entire 2 retention times (day 19) where PBBRs were continuously fed before observing constant productivity in VFAs and other related parameters. PBBRs were fed with an OLR equal to 5 g L⁻¹ d⁻¹ until day 47, after which the OLR was increased to 10 g L⁻¹ d⁻¹ by reducing the dilution rate of molasses. Operational parameters reached a renewed stability at day 63, although this did not apply to conductivities values (a). Marine cultures were provided with 23 g L⁻¹ NaCl to maintain a higher salinity with respect to terrestrial cultures. Error bars only refer to the influent COD (Feed_T&M) and represent standard deviations of 2 independent replicates. Keys reported in the graph