Evaluation of Process Performance and Sludge Properties of an up-flow staged Sludge Blanket (USSB) reactor for Treatment of Molasses Wastewater

Document Type: Original Research Paper

Authors

1 Center for Regional Environmental Research, National Institute for Environmental Studies, Ibaraki 305-8506, Japan

2 Center for Regional Environmental Research, National Institute for Environmental Studies, Ibaraki 305-8506, Japan- Department of Civil and Environmental Engineering, Nagaoka University of Technology, Niigata 940-2188, Japan

3 Department of Environmental Engineering, Khon Kaen University, Khon Kaen 40002, Thailand

4 Department of Environmental Engineering, King Mongkut’s University of Technology Thonburi, Thailand

5 Department of Civil Engineering, Gifu National College of Technology, Gifu 501-0495, Japan

6 Department of Civil and Environmental Engineering, Nagaoka University of Technology, Niigata 940-2188, Japan

7 Center for Material Cycles and Waste Management Research, National Institute for Environmental Studies, Ibaraki 305-8506, Japan

Abstract

A combination of an acidification reactor and an up-flow staged sludge bed (USSB) reactor was
applied to treatment of molasses wastewater. The USSB, equipped with three gas solid separators, was
selected because of superior organic removal by means of good retention of granular sludge. The combined
system was continuously operated at mesophilic (35°C) conditions for 600 days. The USSB achieved a high
organic removal rate of 37 kgCOD/m3 day (organic loading rate of 43 kgCOD/m3 day with 86.2% COD
removal). The USSB retained high sludge concentration of approximately 58 gVSS/L based on the reactor
volume. The retained granular sludge had good settle-ability with a sludge volume index (SVI) of 4 to 20 ml/gSS. The retained sludge possessed a sufficient level of methanogenic activities for acetate (1.2 gCOD/gVSS day) and for hydrogen (1.7 gCOD/gVSS day). Analysis of microbial community revealed that genus Methanobacterium as hydrogen utilizing methanogen and order Methanosarcinales as acetate utilizing
methanogen were detected in the retained sludge of the USSB reactor. The superior performance of the USSB was attributed to good retention of a large amount of granular sludge with high methanogenic activity.

Keywords