The allocation of the ciliate Drepanomonas revoluta to its correct functional group in evaluating the sludge biotic index

The position of the ciliate Drepanomonas revoluta Penard 1922 in the functional groups of the protistan community of the activated-sludge process was investigated. The protists colonizing three different activated-sludge plants receiving domestic and industrial wastewater were monitored for about four months. The sludge biotic index (SBI) method was applied to the observed protistan community and the results were compared with chemical and operational parameters. Statistical analysis revealed a negative correlation between D. revoluta and crawling ciliates such as Aspidisca cicada and Acineria uncinata, possibly due to competition. Thus, the hypothesis was put forward that D. revoluta is a crawling form rather a free-swimming form in the activated sludge.