Sedimentação de lodo ativado.

Abstract

In this work, we interpret a mathematical model to size Secondary Decanters, taking; taking into account sedimentation characteristics, sludge and sludge recirculation within the main treatment system. For this, the continuous operation of a Secondary Decanter is analyzed, which receives a mixed liquor flow from the Biological Reactor. Part of this flow comes out as clarified effluent (free of suspended solids), and the remaining part returns to the Biological Reactor as decanted sludge. According to sedimentation characteristics of the sludge and the operating conditions defined by the recirculation flow, the solids are distributed inside the decanter forming three distinct regions, uniform sedimentation zone, transition zone and compression region. These regions are important in establishing criteria that consist of the ability to transmit solids and in the withdrawal of solids from the background of the singer. For the evaluation of such criteria, the concept of Solid Flow is studied, which is studied from the flow curves (Sedimentation Flow Curve - and Recirculation Flow Curve). The mathematical formulation of the model involves the use of the Vesilind Equation that expresses the zone sedimentation velocity as an exponential function of the concentration of suspended solids. Chapter 5 discusses the use of the model to optimize the design of the main treatment system. In order to justify the use of Vesilind's equation, sedimentation tests are performed, which consist of determining the in-zone sedimentation rate, varying the concentration of total suspended solids within a range of 2 to 7 g / t, the sludge tested was generated from domestic sewage of the city of Campina Grande, with mud age of five days at an average ambient temperature of 28C. The assays were repeated for the sludge digested aerobically for one, three and five days. In order to carry out the tests, a system was built consisting of a Sedimentation Cylinder (for the purpose of the test), an Aerada Lagoon intermittently fed (for the generation of the sludge), and an Aerobic Digester (for the stabilization of the sludge) . The experimental work was developed in the facilities of the Sanitation Laboratory of the Science and Technology Center of the UFPb. - Campus I I, in the city of Campina Grande - Pb.