Tratamento de efluente do processamento de peixe utilizando coagulação / sedimentação e flotação

Abstract

Fish processing contributes voluminous amounts of effluent with a high content of organic matter, which demands an effective treatment for release into water bodies. In this sense, the objective of this study was to evaluate the performance of coagulation / flocculation (C/F) by applying sedimentation (C/F/S) and flotation (C/F/F) to separate sludge in the treatment of effluents from slaughter, using a natural coagulant (Tanfloc SH) and an inorganic coagulant (FeCl3). Preliminary C/F/S and C/F/F tests were performed in a Jar-Test adapted to a flotation module to investigate the dosage of coagulant agents (ferric chloride and Tanfloc SH), air flow, pH, flotation and sedimentation in order to determine the best operating ranges for further optimization through Doehlert experimental design. The flotation kinetics were also obtained and the first and second order models applied. The experimental design showed in the best operating conditions that C/F/S (Tanfloc SH) and C/F/F (FeCl3) had the best performance in the clarification parameters (color removal and turbidity), with the validation of the Quadratic empirical model for statistical and predictive purposes with coefficients of determination (R2) above 0,97 for the responses (color and turbidity). For C/F/S the best operating conditions were 143,30 mg L-1 Tanfloc SH at pH 5,91; and in C/F/F 65,39 mg L-1 FeCl3, air flow 0,20 L min -1 at pH 6,58. Under these conditions, C/F/S (Tanfloc SH) had 88,27% color removal and 97,19% turbidity, while for C/F/F (FeCl3) turbidity removal was 92,69 % and 72,85% color. Although C/F/S with Tanfloc SH had the best clarification results, C/F/F (FeCl3) had the best performance in removing COD (87,25%), BOD (86,71%), oils and greases (88,06%), total phosphorus (20,72%) and ammonia nitrogen (35,68%). The flotation kinetics for turbidity removal using ferric chloride was represented by the first order model with determination coefficient (R2) of 0,98 under optimized conditions. The main advantage of the primary C/F/F (FeCl3) process is the reduced time for removal of physicochemical parameters, and a disadvantage due to the use of ferric chloride is the insertion of 1,67 mg L-1 iron. in treated effluent. Luminescent bacteria ecotoxicity assays (Vibrio fischeri) showed that both treatment processes (C/F/S Tanfloc SH and C/F/F FeCl3) promoted toxicity reduction (FT = 4). Both processes can be used as primary treatment, considering that the effluent has a high polluting load, requiring a sequential process to meet the limits established in current regulations for effluent discharge.