Characteristics of anaerobic granular sludges and operation of pilot-scale UASB reactor

Abstract

In this research, the comprehensive characteristics of anaerobic granular sludges and the scale-up effect of UASB reactor were studied. The morphological and microbial characteristics of both acidogenic and methanogenic granules cultivated on distillery wastewater were investigated, and the preservation and re-activation characteristics of granules formed on synthetic glucose wastewater were quantified in terms of storing period and temperature. And the scale-up effect of UASB reactor was examined by using a pilot-scale reactor of 3.3 m height. The acidogenic granular sludge, formed in the acidogenic UASB reactor treating raw distillery wastewater for 90 days of operation, consisted of long chains of large rods, short plump rods, and cocci of various sizes, which have different shapes and cytoplasmic appearances from common methanogenic bacteria. In the methanogenic granule, which cultivated in the methanogenic reactor treating acidified distillery wastewater for 120th day, long multicellular filaments of Methanothrix spp. with diverse entrapped bacteria were prevalent. It is expected that extensive microscopic studies on acidogenic granular sludges should help in understanding the granulation process. During 10 months of storage without feeding, specific acidogenic activity(SAA) reduced to about 30% of an initial value regardless of the storage condition, however the extent of the decrease in specific methanogenic activity(SMA) was quite different. In case in the room condition, SMA decreased to 60%, whereas 80% of SMA was decreased at 4℃. Room temperature seemed more beneficial than 4℃ in maintaining the methanogenic activity. In the microscopic study of granular sludges, although some debris formed on the surface of granular sludges and dead cells were observed by transmission electron micrography, no remarkable change in the overall configuration of granular sludges was observed in 8-month storage. In spite of 10 months storage without feeding, anaerobic ...