2.3 Chemical analyses
Effluent samples were taken from the reactor every 1-3 days under different stages. The total solids (TS), volatile solids (VS) of the substrates and effluent were measured with dry methods to a constant weight at 105°C for 24 h in an electric heating air-blowing drier and at 600°C for 2 h in a muffle stove, respectively (Sluiter et al., 2005). Total and soluble chemical oxygen demand (TCOD and SCOD), and ammonium nitrogen were sampled every three days, and then measured with standard methods (APHA 2005). Contents of C, H, O, N, S were measured through a Macro Element Analyzer. The biogas (CH4 and CO2) composition, volume, VFAs and pH were determined as previously described (Mahdy et al., 2019b). One-way analysis of variance (ANOVA, p<0.05) was applied to identify the statistical significance.