Remoção de fósforo de águas residuárias da suinocultura em sistema phoredox A2/O submetidos a diferentes carregamentos orgânicos

Abstract

Pig farming is an activity of social and economic importance. However, it can cause volumes of wastewater rich in organic matter and nutrients which, if left untreated, cause environmental pollution. In this context, the removal of phosphorus (P) is a challenge, given that chemical processes are more costly; and the biological systems traditionally used have low removal efficiency, or require a control that is often not applied. It is therefore important to establish parameters and criteria for P removal in biological reactors in which organic matter is also removed. The aim of this research was to evaluate different organic loadings in the operational configurations of pig farm wastewater treatment in a phoredox system (A2/O) with a view to increasing phosphorus removal efficiency. The wastewater came from UFLA's pig facilities. The anaerobic reactor - R1, anoxic reactor - R2 had a height and useful volume of 0.30 m and 18 L, the aerobic reactor - R3 had a height and useful volume of 0.40 m and 49 L and the secondary decanter - DS had a height and useful volume of 0.25 m and 4.0 L. The system was fed (0.049 m-3 d -1 ) and the effluent was recirculated to R2 (0.025 m-3 d -1 ) using peristaltic pumps, resulting in hydraulic detention times of 8.8 h (R1), 6.0 h (R2), 24.0 h (R3) and 2.0 h (DS). Nine organic loads were applied (4.21, 2.85 and 1.59; 1.50, 0.76, and 0.25; 1.26, 0.60 and 0,23 kg m-3 d -1 COD) for reactors R1, R2 and R3 corresponding to three phases (F1 - 90 days, F2 - 110 days and F3 - 45 days), the conditions were modified based on the COD present in the raw ARS. The average aeration rate provided was between 0.7 and 3.5 mg L-1 in each operational phase. The characterization of the effluent and effluent of each reactor was carried out by weekly analyses of pH, COD, ST, SV, AB, AVT and PT, P-PO4 3- . The variables were assessed for normality using the Shapiro-Wilk test, submitted to the Kruskal-Wallis test at 5% probability using the Jamovi software and Sperman's correlation. Average effluent pHs of 7.7 and 7.9 were obtained in F2 and F3, corroborating the best stability conditions that occurred with AI/AP between 0.19 and 0.17, generation of bicarbonate alkalinity and consumption of total volatile acids during the F2 and F3 phases indicated satisfactory stabilization of the anaerobic reactor, thus the COD removal efficiencies were 58 and 61%. The removal efficiencies of PT and P-PO4

3- were 88 and 57% in phase 1 (p<0.05), when organic loads were

applied (4.21, 2.85 and 1.59 kg m-3 d -1 COD) operated with an average DO of 2.8 mg L-1 in R3, under these conditions the efficiencies were mainly provided by the anoxic reactor and the sedimentation of solids. Sperman's correlation indicated a strong positive correlation between PT and COD in the anoxic and aerobic reactors, with values of 0.78 and 0.80. In addition, in F3 the COD concentration of the effluent met the standard for discharge into a watercourse established by the State of Minas Gerais. It was found that the A2/O phoredox system, combined with the appropriate operating conditions for the reactors, is a promising alternative for removing organic matter and phosphorus from pig farm wastewater.