Start-up and steady-state results of a full-scale UASB reactor treating malting wastewater

An Imhoff tank was reconstructed into a 250 m³ UASB reactor in order to treat a malting plant wastewater. The UASB was inoculated with sludge from an anaerobic lagoon used for slaughterhouse wastewater treatment. After two months of operation the reactor achieved full load with an HRT of 17 h, a COD removal higher than 80% and a biogas production of 300 m³/day (77% average methane content), with an organic loading rate of 3.6 kgCOD/m³.d (0.24 kgCOD/kgVSS.d). A yield coefficient of 0.09 gVSS/gCOD_rem was found from a mass balance. The fat present in the inoculated sludge (48 mg/gSSV) did not affect the start up performance. Sludge from the inoculum with high content of fat (270 mg/gSSV), was separated by flotation in the first week of operation. The COD removal efficiency was scarcely influenced by the reactor operation temperature (17–25 °C).