Estudo da viabilidade de utilização de um polímero de base orgânica em substituição ao cloreto férrico no tratamento de efluente industrial

Abstract

In some cases, in wastewater treatment, it is necessary a post-treatment in order to ensure legal compliance. A way to do this is through the coagulation/flocculation process, which uses chemical products, mainly iron and aluminum salts. However, the use of these products brings some difficulties to the company, such as sludge destination, given that it contains metal substances and that it is not biodegradable. Thereby, the purpose of this paper was to evaluate the technical and economical feasibility related to the exchange of a inorganic coagulant for a organic based one, and also, to propose the utilization of another, plant based coagulant, in the wastewater treatment of an agro-industry. The coagulants Moringa oleifera (MO) and NOVFLOC, and the flocculant POLFLOC by NOVTEC® were studied. It was applied the experimental design and process optimization method, in which in one experiment, the independent variables were the NOVFLOC and POLFLOC concentration, and in another, the MO and POLFLOC concentration in the wastewater, whereas in both cases, the response variable was the turbidity removal. There were also evaluation parameters the COD, pH, total dissolved solids and electrical conductivity. Firstly, it was carried out a initial factorial 22 experimental design, followed by a Composite Central Rotatable Design (CCRD). Economically, the substitution was not feasible, given that the initial R$ 0,44 cost for treated wastewater cubic meter became R$ 0,76. However, it proved to be technically feasible, because the substitution did not significantly change the treatment efficiency and allowed the effluent release legal compliance, not to mention many other advantages for the company and the environment. For NOVFLOC, the optimization was obtained at the 500 to 700 ppm range of coagulant concentration, presenting a 100% turbidity efficiency removal, whereas the POLFLOC concentration did not prove to be statistically significant. The COD removal was of 56,93%, when it was applied a 120 ppm coagulant concentration and a 6 ppm flocculant concentration. The optimization was not obtained with the MO experiment, but there were obtained turbidity removal results up to 61,11%, with a 200 to 250 ppm range of coagulant concentration and 4 to 6 of flocculant concentration, and also, a COD removal of 99%, when using 95,2 ppm of coagulant and 4 ppm of flocculant.