Pre-acidification in anaerobic sludge bed process treating brewery wastewater

The effect of pre-acidification on anaerobic granule bed processes treating brewery wastewater was the focus of a comparison study employing two confi gurations, (a) a single stage upflow anaerobic sludge bed (UASB) and (b) an upflow acidification reactor in series with a methanogenic UASB. The pre-a cidification reactor achieved 20 +/- 4% SCOD removal and 0.08 +/- 0.003 L o f methane produced per gram of SCOD removal at a hydraulic retention time ( HRT) of 0.75-4 h. Butyric acid was not detected and short chain fatty acids (SCFAs) were mainly acetic and propionic acids. The acidification ratio wa s about 0.42 +/- 0.02g SCFAs as COD/g of influent COD. Both systems' critical loading rate to achieve 80% COD removal was establis hed at 34-39 kg COD/m(3) of total sludge bed volume per day. SCOD removal e fficiency of 90 +/-3% was achieved by both systems at an organic loading ra te of 25 +/-1 kg COD/m(3) of total sludge bed volume per day, indicating th at the installation of an acidification reactor had no effect in terms of t he maximum granular activity, biomass granulation and the settleability of granules. At an organic loading rate of 67 kg COD/m(3) of total sludge bed volume per day at an HRT of I h, the series system outperformed the single UASB by a removal of 62 compared to 57%. (C) 2001 Elsevier Science Ltd. All rights reserved.