Caracterização do lodo autotrófico de sistemas de lodo ativado gerado a partir de diferentes substratos.

Abstract

The association of anaerobic pre-treatment, for example, in a UASB reactor with activated sludge systems for post treatment has been an object of several studies and is being applied in practice of waste water treatment systems. However, activated sludge systems fed with different substrates (for example raw or digested sewage) tend to produce sludges with different mechanical and biological characteristics. In order to evaluate the characteristics of the autotrophic fraction of sludge generated from different substrates an experimental investigation was carried out, where three activated sludge systems of the sequencing batch reactor (SBR) type, were operated with raw sewage, digested sewage an ammonium solution as substrates. The systems were evaluated with respect to the suspended solids and organic material and ammonium removal efficiencies, as well as the settleability and activity of the sludges. The Volumetric Sludge Index (VSI) and the Oxygen Uptake Rate (OUR) were used for the assessment of the mechanical and biological characteristics. The obtained results during the experimental investigation showed that the systems were equally efficient in the removal of organic material and suspended solids with efficiencies of 83% for COD and 91% for TSS. The settleability of the sludge was considered good for the system operated with digested sludge and fair with the system operated with raw sewage. However, the autotrophic sludge did not exhibit high biological activity having values of the specific growth rate constant for Nitrossomonas (p*,) in the range of 0,31 d"1 for the system fed with raw sewage and 0,21 d"1 for the system fed with ammonium substrate, whereas no activity was detected in the system fed with digested sewage.