Estequiometria e cinética da remoção de fósforo em sistemas de lodo ativado.

Abstract

Discharge of effluents from waste water treatment plants in water bodies causes eutrophication of these, leading to degradation and resulting, as a consequence, in excessive algae growth. To avoid the eutrophication of the receiving water bodies it is necessary to design, construct and operate waste water treatment plants that, along with removal of organic material and suspended solids, are also capable of removing nutrients, particularly nitrogen and phosphorus. In order to design rationally waste water treatment plants for efficient nutrient removal it is necessary to know the stoichiometry and kinetics of the bacterial populations that develop in those systems. In this work an experimental investigation is described in which several activated sludge systems were operated with the aim to evaluate the stoichiometry and kinetics of the phosphorus removal mechanisms. Respirometry was used in combination with laboratorial testes to evaluate the phosphorus release by activated sludge batches and the consequential sequester of organic material (acetate) in an anaerobic environment as well as the kinetics of the utilization of the sequestered material in a subsequent aerobic environment. The results indicated that phosphorus removal did not occur at and that nitrogen and phosphorus removal did not occur simultaneously in systems designed for nitrogen removal. The composition of the waste water notably the P/COD and TKN/COD ratios and the readily biodegradable fraction of the organic material in the influent and the operational sludge age are important factors. It was also shown that respirometry is a fundamental tool to evaluate the stoichiometric and kinetic aspects of biological nitrogen removal.