Pós-tratamento físico-químico por flotação FAD em efluentes de laticínios

Abstract

The dairy industry is a sector of great relevance worldwide and, uses billions of liters of water in its production. Linked to the large production, there is a large generation of effluents that without adequate treatment end up becoming an environmental problem due to its great polluting potential and, mainly to the increase of organic loads in these effluents. Additional to the conventional treatment, in some cases, the application of a post-treatment aims at a better quality of effluent output, and to comply with the current legislation. The choice of the treatment system should be made accordingly to the physical-chemical characteristics of the effluents. One of the methods used is flotation preceded by coagulation/flocculation. This method, through coagulating and flocculating agents, allows the agglomeration of particles and the making flotation possible. These substances generally use chemical products based on aluminum or iron, resulting in the generation of sludge with high concentrations of metallic ions. Also, it makes the disposal of sludge more expensive. Considering the problems mentioned, coagulants and organic based flocculants have been studied and used, once they generate biodegradable sludge that can be destined to fertilize the soil. Thus, the purpose of this work is to compare the efficiency of inorganic coagulants and flocculants with organic bases, to the bench scale flotation process, in the treatment of effluent from an agroindustry. It was studied the coagulants NOVFLOC, and the floculant POLFLOC from NOVTEC, and the coagulant KLARAID 1176 from GE. It was applied the experimental design methodology and process optimization, using, as independent variables, the concentration of coagulants and flocculants, with the response variable the removal of turbidity. As a first step, the initial factorial 22 planning of sedimentation and flotation was done aiming to adjust the application ranges, followed by a central rotational compound design – DCCR aiming at the optimization of sedimentation and flotation processes. With the use of the Klaraid 1176L coagulant aided by the Polfloc flocculant, a sedimentation turbidity removal of up to 78,93% was obtained, with 390 to 427 ppm of coagulant and 9 to 12 ppm of flocculant. For flotation the best results obtained up to 74,92% removal, with 390 to 427 ppm of coagulant and 10 to 13 ppm of flocculant. However, with the Novfloc organic base coagulant assisted by the Polfloc flocculant, the sedimentation efficiency reached up to 78,09% with the range of 390 to 427 ppm of coagulant and 7 to 10 ppm of flocculant, in the flotation the result was up to 72,11% with 390 to 427 ppm of coagulant and 10 to 13 ppm of flocculant.