Ciliated protozoa are one of the most relevant biological communities in the reactors of wastewater treatment plants. These organisms are excellent tools to assess the biological status of the reactor being used to monitor wastewater treatment plants performance. This book has been designed to simplify identification of ciliates, bearing in mind the difficulties on the manipulation and proper identification of these species. The specific role of ciliates in WWTP is discussed; methods for observation together with a glossary of scientific words and a simple and easy key to the taxonomic groups...