Effects of up-flow velocity on the community of anaerobic protozoa in UASB fed with municipal sewage

Abstract

 In this study, the up-flow velocity in the UASB reactor fed with municipal sewage was changed stepwise, and the influence on number of anaerobic protozoan cells and protozoan community was measured. Number of protozoan cells increased by rising the up-flow velocity in the range of 2.4 to 14.4 m/day, but the number of the ciliates decreased sharply due to a washout occurred at 22.4 m/day. Predominant species of anaerobic protozoa present in UASB were Metopus palaeformis, Metopus contortus, Chaenomorpha sp., and Plagiopyla sp, which accounted for about 60% of all 18S rRNA genes. Dominant species of protozoa changed in a short period of time under higher up-flow velocity conditions.