[Comparison of ciliate diversity in biodisc reactors which purify industrial wastewater].

The comparative study of the ciliate populations present in rotating biological reactors (biodiscs reactors) of 20 l working volume, treating three different wastewaters is the aim of this project. Wastewaters chosen were those of a maize mill, of a sugarcane/ethyl alcohol plant, and of a recycled paper mill. Its dissolved organic contents, measured as soluble chemical oxygen demand (COD) and five-day biochemical oxygen demand (BOD5), were 2040 mg COD/l and 585 mg BOD5/l for maize mill effluents (nejayote), 2000 mg COD/l and 640 mg BOD5/l for sugarcane/ethanol effluents (vinasses), and 960 mg COD/l and 120 mg BOD5/l for whitewaters of the paper industry. Results obtained indicate that ciliate proliferate in all chambers of reactors treating these wastewaters. The ciliates were more abundant in vinasses, followed by nejayote, and then whitewaters. Among protozoa, ciliates were present as follows: 19 species in total. Three of them were common for the three systems. Free swimming ciliates were in higher proportion than pedunculated ones. Its diversity was higher for the whitewaters system, next for nejayote, and the lesser, for vinasses, corroborating the fact that less polluted waters have higher organisms' diversity.