2.1. Reactor operation and monitoring
2.2. Analytical methods
TS, VS, TCOD, and SCOD were determined according to standard methods (Clesceri et al., 1998). NH4+-N concentration was measured using an ion chromatography (ICS-1100, Dionex, USA). Soluble protein and carbohydrate were analyzed using Lowry-Folin method and phenol–sulfuric RG7112 method, respectively (Cho et al., 2013 and Dubois et al., 1956). Soluble samples were filtered through syringe filters (0.45 μm) produced from Merck Millipore in USA. pH values of broths were measured using a pH electrode connected to a pH measuring instrument (Mettler Toledo, Switzerland). Quantification of VFAs was performed operating a high performance liquid chromatography (HPLC-1100, Agilent Technology, USA) connected with a column (Aminex HPX-87H, Biorad Inc., USA), diode array detector (DAD), and refractive index detector (RID). The flow rate of eluent (0.6 mL/min) and column temperature (50 °C) were maintained based on a previously described method (Cho et al., 2013).