Evaluation of different types of anaerobic seed sludge for the high rate anaerobic digestion of pig slurry in UASB reactors

• Published in: Bioresource technology Vol. 238; pp. 147 - 156
• Main Authors: Rico, Carlos, Montes, Jesús A., Rico, José Luis
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2017
• Subjects: Anaerobic sewage sludge; Anaerobiosis; Animals; Bioreactors; Digestion; Granular sludge; Methane; Sewage; Supernatant; Swine; Thickened digestate; Volumetric methane production rate; Thickened digestate; Granular sludge; Anaerobic sewage sludge; Supernatant; Volumetric methane production rate
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2017.04.014

•Supernatant pig slurry is suitable for UASB at stable high process performance.•Thickened digestate sludge was inappropriate as seed inoculum source.•Granular biomass inoculum reactor yielded 248mLCH4g−1COD at 1.5days HRT.•Anaerobic sewage sludge inoculum reactor yielded 236mLCH4g−1COD at 3days HRT. Three different types of anaerobic sludge (granular, thickened digestate and anaerobic sewage) were evaluated as seed inoculum sources for the high rate anaerobic digestion of pig slurry in UASB reactors. Granular sludge performance was optimal, allowing a high efficiency process yielding a volumetric methane production rate of 4.1LCH4L−1d−1 at 1.5days HRT (0.248LCH4g−1COD) at an organic loading rate of 16.4gCODL−1d−1. The thickened digestate sludge experimented flotation problems, thus resulting inappropriate for the UASB process. The anaerobic sewage sludge reactor experimented biomass wash-out, but allowed high process efficiency operation at 3days HRT, yielding a volumetric methane production rate of 1.7LCH4L−1d−1 (0.236LCH4g−1COD) at an organic loading rate of 7.2gCODL−1d−1. To guarantee the success of the UASB process, the settleable solids of the slurry must be previously removed.