Brazilian Archives of Biology and Technology

p. 311-319The treatment efficiency of industrial effluents, after biological treatment by activated sludge in aeration tanks (AT), was assessed through the utilisation of respirometry tests at the Cetrel's-wastewater treatment plant (WTP). Samples of the equalised effluent (EE), prior to treatment, and of the treated effluent (TE), after treatment, were analysed. Twenty bioassays batch were carried out to AT (AT-2, AT-3 and AT-4). Each test consisted of: a basic test, a basic test with peptone added, a test using EE and a test using TE. The data showed that there was no statistically significant difference (p>0.05) in the respiration activity between the aeration tanks. Regarding the specific oxygen uptake rate there was a mean reduction of 70.8% between the tests performed with EE and TE. The results demonstratd that respirometry tests could successfully assess the efficiency of the activated sludge process and, therefore, be adopted as tool for the monitoring from the WTP