Abstract Two UASB reactors of 9 and 220 liters capacity and one AFB reactor of 9 liters capacity are described. The reactors operated with currant-finishing wastewater. Acclimation period was short provided that the reactors were seeded with active granular sludge. Performance of the AFB reactor was higher than the UASB reactor. Loadings of 16 and 21 kg/m 3 day in AFB resulted in COD removals of 95 and 85%, respectively. Loadings of 12·5 and 10·2 kg/m 3 day in the 220 and 9 liter UASB reactors resulted in COD removals of 93·5 and 95%, respectively.