The system was inoculated by an anaerobic sludge taken from the stock anaerobic sequencing batch reactor treating a synthetic substrate with a total Chemical Oxygen Demand (COD) of 4400 mg/L and including the following ingredients: starch, 2090mg COD/L; glucose, 1350 mg COD/L; sodiumacetate, 240mgCOD/L; sodiumbutyrate, 330mgCOD/L; and sodium propionate, 490 mg COD/L in an 8-liter active volume.