EFFECTS OF PARTICULATE SIZE IN ANAEROBIC ACIDOGENESIS USING CELLULOSEAS A SOLE CARBON SOURCE

Pure cellulose with average diameters of 20 and 50 mum were treated in laboratory-scale CSTRs to study the effect of pH, reactor hydraulic r etention time (HRT), and substrate concentration on the rate of anaero bic acidogenesis for those two cellulose particle sizes. The pH effect was studied using a particle size of 20 mum at an HRT of 48 hours whi le controlling the pH at levels of 5.2, 5.6, 6.0, 6.4, and 6.8. After determining that a pH of 5.6 was optimum, the effect of HRT was evalua ted by operating the reactors at HRTs of 24, 36, 48, 60, and 72 hours for both the 20 and 50 mum cellulose sizes. After finding that an HRT of 48 hours was sufficient for acidogenesis, the effect of organic loa ding rate (OLR) was studied by varying the OLR between 2 and 8 g/L/day . The results of the research indicate that the conversion of particul ate cellulose to soluble chemical oxygen demand (SCOD) ranged from 31% (pH 6.8) to 44% (pH 5.6). The HRT studies illustrated that a substrat e with a smaller particle size (20 mum) and operation at a longer HRT resulted in a higher conversion to SCOD compared with a larger particl e size (50 mum) and operation at a shorter HRT. It was also observed t hat the effluent SCOD increased proportionally with increases in the i nfluent particulate COD.