Comprehensive Anaerobic Digestion Monitoring

Daily pH measurements were performed on the digestate from each reactor. In addition, the total alkalinity (IA/PA) ratio, the total ammonia nitrogen (TAN), and the volatile solids (VS) removal were measured twice each week. The amount of biogas was measured everyday using the water displacement method described in Section 2.3. The TDS, pH, and salinity were measured using a Meter tabletop with a stirrer from ISOLAB, Eschau, Germany. Meanwhile, the VS and VSS were calculated utilizing the standard method for the examination of water and wastewater [49 ] and in accordance with the protocol outlined in [36 (link),50 (link)]. The salicylate powder pillow technique 8155 was implemented to measure the TAN using a spectrophotometer (HACH 157 DR 900, Agilent, Santa Clara, CA, USA). In the meantime, 0.02 N sulfuric acid (H₂SO₄) was employed with the titrimetric technique to assess the IA/PA ratio. A gas chromatograph (Agilent HP 6890 N, Santa Clara, CA, USA) fitted with a thermal conductivity detector (TCD) and a capillary column (30 mm × 0.5 mm × 40 m) was utilized to quantify the biogas generated composition. The VFAs were measured using a Shi-madzu GC 2010 gas chromatograph, Kyoto, Japan. The machine is equipped with a flame ionization detector (FID) and a FameWax capillary column (30 m × 0.32 mm × 0.25 µm).