Avaliação da toxicidade de surfactantes ao lodo ativado de indústrias de alimentos, utilizando o método respirométrico.

Abstract

Treatment of industrial wastewater by activated sludge is widely used throughout the world due its high efficiency and affordable technology. However, in certain industries such as food, which needs to meet strict hygiene standards, the effluent is composed of many chemical cleaners such as surfactants. The presence of potentially toxic surfactants can compromise bacterial metabolism necessary for the stabilization of organic matter and thus decrease the efficiency of the biological treatment. To better understand this impact on the activated sludge process, the present study aimed to evaluate the influence of high surfactant concentrations in biological activity of activated sludge using respirometric method, which consists in measuring the specific oxygen consumption rate (TCOe ) by microbial biomass. The surfactants investigated in this study were lauryl ether sodium sulfate and linear alkylbenzene sulfonate. Lauryl ether sodium sulfate was applied to an activated sludge of a food industry and to an activated sludge acclimated with synthetic effluent in a bench reactor. While the linear alkyl benzene sulfonate was applied only in activated sludge from the food industry. The results of respirometry show that lauryl ether sodium sulfate caused no toxic effect on the microorganisms in the activated sludge. While the linear alkyl benzene sulfonate showed remarkable toxic effect to the microorganisms of the activated sludge. In acute toxicity tests using Microtox, the linear alkylbenzene sulfonate also showed a higher toxic effect to a Aliivibrio fischeri bacteria that lauryl ether sodium sulfate. The results even suggest that respirometry tests are applicable and efficient on detecting effects of surfactants on the activated sludge process.