Granulação de lodo aeróbio em reator de batelada sequencial utilizando fração líquida de esterco proveniente de atividade leiteira

Abstract

The granular sludge technology is used in anaerobic conditions, through UASB reactors, and more recently in aerobic conditions, mainly in batch reactors. Granular aerobic sludge is classified as a special case of biofilm where the union of cells to form a stable, continuous structure and composed of multicellular associations under specific physiological conditions. Its composition is defined as a package of consortia of different bacterial strains containing millions of units per gram of biomass that do not coagulate in reduced hydrodynamic forces . Unlike activated sludge, presents a regular structure, dense and strong, with different rates of oxygen diffusion within its structure. These characteristics represents, mainly, an excellent sedimentation capacity and possibility of several metabolic processes in a single reactor. In the present study, a systems of sequence batch reactors (RBS1 and RBS2) were developed at the laboratory level for the application of this technology in the sewage treatment plant of the Lorena Engineering School of the Universisty of São Paulo. Initially, preliminary studies with synthetic substrates was realized to observe the operational conditions of the reactor and the first transformations of the inoculated activated sludge in relation to the granulation process. In the experiment with real effluent, it was decided to use the liquid fraction of dairy manure. The design of the experiment was based on the reduction of the sedimentation time along its phases in the cycle of a sequential batch reactor. This represents an increase in dense biomass selection pressure with a high sedimentation rate. The hydraulic retention rate of the two reactors (RBS1 and RBS2) were initially 12 and 24 hours, respectively. The duration of the experiment was 2 months of acclimatization, without use of inoculation, with Vs(min) ranging from 1m/h to 2.5m/h and 3 months of operation with (Vs) min of 3.75m/h, 5m/h and 7.5m/h. respectively. Physical and chemical analysis of both reactors was performed. The granulation process was successfully performed at RBS2 in the second month of operation, showing dominance in the granular biomass reactor up to 1.5mm from the seventh week. An increase of the inorganic portion in granular biomass present in RBS2 was observed in relation to flocular biomass in RBS1. Toxicity tests using Daphnia similis indicated high acute toxicity of crude effluent prepared from high dilution of cattle manure. The treatments performed by both reactors reduced the EC50 (%), but the treated effluents did not reduce their toxicological classification The treatments performed by both reactors reduced the EC50 (%), but the treated effluents did not reduce their toxicological classification according to the toxic unit.