The derived toxicity values obtained in this study are of
potential relevance for microbial food web in water bodies
receiving effluent or in wastewater treatment plants, since
two out of four of the tested ciliate species (Colpidium colpoda
and Euplotes aediculatus) are common in activated sludges
and other biological treatment processes (Madoni, 1994;
Amann et al., 1998).