A COMPARATIVE-STUDY OF CILIATED PROTOZOA COMMUNITIES IN ACTIVATED-SLUDGE PLANTS

Ciliated protozoa present in ten activated sludge plants at Madrid (Sp ain) were identified. The abundance of key groups of ciliates was dete rmined at each plant; attached ciliates made up the most abundant and representative group. Multivariate statistical analysis was employed t o study relationships between ciliates and both the physico-chemical a nd operational parameters of the plants. Partial correlation analysis revealed: (1) The indicator value of attached ciliates in assessing ma nagement and performance of the activated sludge process, (2) the rela tionship of swimming ciliates with short-aged sludges and lower qualit y effluents and (3) the direct association between swimming-crawling c iliates and bad settlement conditions of the sludge. Factor analysis s howed the associations of the most frequent species of ciliates with t he operational parameters of the plants, suggesting the indicator valu e of some of the species: Vorticella striata was related with poor qua lity of effluent; Aspidisca cicada with stable plant conditions, and L itonotus lamella with a deficiently settling sludge.