Abstract
Influences of temperature (25–35 °C) and substrate particulate content (3.0–9.4 g total suspended solids (TSS)/L) on granular sludge bed anaerobic digestion (AD) were analyzed in lab-scale reactors using manure as a substrate and through modeling. Two particle levels were tested using raw (RF) and centrifuged (CF) swine manure slurries, fed into a 1.3-L lab-scale up-flow anaerobic sludge bed reactor (UASB) at temperatures of 25 °C and 35 °C. Biogas production increased with temperature in both high- and low-particle-content substrates; however, the temperature effect was stronger on high-particle-content substrate. RF and CF produced a comparable amount of biogas at 25 °C, suggesting that biogas at this temperature came mainly from the digestion of small particles and soluble components present in similar quantities in both substrates. At 35 °C, RF showed significantly higher biogas production than CF, which was attributed to increased (temperature-dependent) disintegration of larger solid particulates. Anaerobic Digestion Model No.1 (ADM1) based modeling was carried out by separating particulates into fast and slow disintegrating fractions and introducing temperature-dependent disintegration constants. Simulations gave a better fit for the experimental data than the conventional ADM1 model.
Highlights
Up-flow anaerobic sludge bed reactors (UASBs) are normally used for the treatment of substrates with a low level of suspended solids such as industrial wastewater
Solid accumulation and granular sludge floatation leading to losses of biomass are known challenges in the treatment of wastewater with a high level of suspended solids [2], but high anaerobic digestion (AD) efficiency was reported for particle-rich substrates [3]
We investigate the effect of temperature variation on anaerobic digestion of particle-rich and particle-“free” substrates by varying temperature between 25 ◦ C and 35 ◦ C
Summary
Up-flow anaerobic sludge bed reactors (UASBs) are normally used for the treatment of substrates with a low level of suspended solids such as industrial wastewater. Their attributes, such as low cost, high efficiency, and low footprint, make them attractive for the treatment of particle-rich substrates such as sludge and manure slurries that are available in large quantities worldwide [1]. The interaction of solid particles with microorganisms in the sludge bed, as well as the extent of the contribution of solid particulates to biogas production, is not clear Due to these reasons, high-rate reactors are mostly used for the treatment of substrates with low solid content, mostly industrial wastes
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