The environment pollution is an important issue influencing on human health and environmental equilibrium. The range of pollutants is very wide due to the industrialization and population growth and the surfactants are one of the most common organic pollutants due to their extensive use and ubiquitous presence from industry to households. Their massive presence in the domestic and industrial wastewater could affect the Wastewater treatment plants by inhibit the activated sludge used in pollutants biodegradation treatment step. This paper aimed to study the inhibition effect of three classes of surfactants (nonionic, anionic and cationic) by measuring of the respiratory activity of microorganisms with the application of the Oxygen Uptake Rate (OUR) test. This study established that the surfactants can activate or inhibit microorganisms activity, depending on surfactant concentration.