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Performance parameters were studied in an alternative full-scale dairy effluent treatment system comprising two anaerobic sludge-blanket reactors in parallel arrangement with upward flow, internal fat-separation by flotation, external lamella settler and floated material digester. Reactors were initially inoculated with flocculent sludge and granulated in a high-load stage. Using loading rates up to a maximum 5.5 kg COD/m(3) x d-hydraulic residence time of 17 hours- reactor efficiency was found to remain stable around 90% of COD. Average sludge digester efficiency using a loading rate of 3.5 kgVS/m(3) x d with a lipid content of 47% of COD amounted to 78% of VS (87% of lipid removal). LCFA inhibition as assayed using palmitate was found to depend not only on the palmitate concentration but also on the palmitate-to-biomass concentration ratio.

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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/gCODrem 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 degrees C).

BACKGROUND Vinasse is a wastewater from bioethanol production with a very high concentration of organic matter, usually from 40 to 80 gCOD L‐1. These features make this wastewater attractive for treatment in an anaerobic system. Anaerobic processes allow the valorisation of this highly polluting wastewater as an energy resource in an environmentally friendly way. RESULTS A multiscale approach was followed, using batch tests, continuous bench scale reactors, and a full‐scale upflow anaerobic sludge bed (UASB) reactor. Potential inhibition due to high potassium concentrations was evaluated. Using batch tests, the IC50 potassium concentration was determined to be around 6 g L‐1, but continuous reactors could adapt the biomass to this concentration level without removal efficiency decay. A load of 20 gCOD L‐1 d with chemical oxygen demand (COD) removal efficiencies between 60% and 80% were reached in bench scale UASB and expanded granular sludge bed (EGSB) reactors. Finally, a 100 m3 UASB reactor located in a distillery was tested under industrial conditions. A load of 0.6 kgCOD kg‐1VSS d‐1 was achieved with a COD removal efficiency of 78%. CONCLUSION Although potassium was inhibitory for the inoculum, the sludge from a continuously operated reactor can be adapted to high potassium concentrations without affecting its performance. The real possibility of working with undiluted vinasse was also verified. For distilleries like the Uruguayan case, which produces 18 000 m3 of bioethanol per year, 5x10 m3 of biogas per year, with 68% methane, could be expected, representing an energy potential of about one‐third of the main fuel produced. © 2017 Society of Chemical Industry