Formation of Denitrifying Granular Sludge in USB Reactor with Municipal Sewage as Carbon Source

摘要

An upflow sludge blanket (USB) reactor is capable to perform under the high nitrogen loading rate due to high biomass concentration from denitrifying granular sludge formation. In this study, the formation of denitrifying granular sludge with feeding sewage as a carbon source was studied by operating laboratory scale USB reactor. In addition, microbial community of granular sludge was investigated to understand the key organisms of granular sludge formation. The USB reactor (height: 137cm, volume: 11.4L) was operated by the upflow velocity of 50cm·h~(-1), hydridic retention time (HRT) of 2.9hours and under the ambient temperature. The returned activated sludge obtained from Nagaoka Sewage Center was inoculated to USB reactor. The raw sewage was fed to USB reactor with sodium nitrate. The nitrate removal rate of retained sludge was significantly increased to 42mgNO_3~--N·gMLVSS~(-1)·h~(-1) within 12days of operation. Furthermore, granular sludge formation was observed on day 15. Cloacibacterium sp. which represents as the key organisms for granulation was highly detected. Therefore, denitrifying granular sludge was successfully cultivated in a USB reactor with municipal wastewater and sodium nitrate. Also, propionate-producing bacteria Paludibacter sp., acetate-utilizing denitrifying bacteria Acidovorax sp. and Dechloromonas sp. were highly founded in the granular sludge.