COD concentration was measured with Hach COD analysis kits (reagent 20–1,500 mg/L COD range, Hach Company, USA). After filtration of MXC effluent with 0.45 μm membrane (RK-02915-14, Cole-Parmer, USA) SCOD concentration was quantified. Total suspended solids (TSS), volatile suspended solids (VSS), and alkalinity concentrations

were measured, according to the Standard Methods (APHA, 1998). The pH in acetate medium, the wastewater and MXC effluent this website were measured with a pH benchtop meter (PHB-600R, OMEGA, Canada) connected with a microprobe pH electrode (RK-55500-40, Accumet® MicroProbe™ combination electrode, Cole-Parmer, Canada). Volatile fatty acids (VFAs) which includes acetate, propionate, n-butyrate, n-valerate, iso-butyrate, and iso-valerate were analyzed using a gas chromatography (GC) (Model: Hewlett Packard

HP 5890 Series II) equipped with a Nukol fused-silica capillary column and flame ionization detector (FID). Helium gas was used as a carrier gas. The initial temperature of the column was 110 °C, increasing to 195 °C at the rate of 8 °C/min, and then held constant at the final temperature of 195 °C for 9 min. Injector and detector temperatures were 220 °C and 280 °C, respectively. Prior to GC-FID analyses, liquid samples were acidified to pH ∼2 using 1 N phosphoric acid, and then filtered using 0.2 μm membrane filter (DISMIC-25HP, Toyo Roshi Kaisha Ltd., Japan). All samples were analyzed in triplicates. Fig. 1 shows current density at various acetate concentrations, which follows a typical Monod pattern. The maximum current density (jmax) was 6.43 A/m2 of membrane, PLX3397 and the best-fit of Ks was estimated at 17.3 mg COD/L. The simulated curve with the estimated Ks, measured jmax, and measured acetate concentration well fitted into experimental data ( Fig. 1). The pseudo, apparent Ks does not represent the half-maximum substrate concentration Gefitinib of ARB for acetate because current density was expressed per the projected area of membrane, instead of anode surface

area; the literature provides more detailed information on this aspect [17] and [35]. However, this pseudo, apparent Ks is able to provide useful information on the relationship between substrate concentration and current density in the MXC. For instance, the simulation with Eq. (1) predicts 3.9 A/m2 for effluent SCOD of 26 mg/L (only 9% error). Hence, this pseudo, apparent Ks can be used for a design parameter of MXCs. Table 2 shows an average of the maximum current density observed in the MXC at different feed conditions. The maximum current density was small at 1.2 ± 0.25 A/m2 for Run 1 (bicarbonate buffer 50 mM), due to substrate limitation (acetate 2.7 ± 0.2 mM and 175 ± 10 mg COD/L); in comparison, the maximum current density was 18 ± 2 A/m2 at 25 mM acetate during acclimation.