Reatores biológicos submetidos a diferentes carregamentos de água residuária de suinocultura: remoção de compostos orgânicos emergentes, matéria orgânica e nutrientes

Abstract

The pig agroindustrial are present in the economics of many countries with intensive agricultural activity, such as Brazil, however, the unsustainable practices used have provided pressures on natural resources and, consequently, increased water consumption and effluent volumes produced with high concentrations of organic matter, nutrients and emerging contaminants, thus becoming a point of inflection on the decisions to be made to maintain the desired environmental quality for the future.In this context, this research aimed to evaluate a sequential system of swine wastewater treatment through conventional and multivariate analyzes, associating the presence of emerging contaminants, organic matter, nutrients and ecological risks throughout the treatment.The experiment was conducted at the Federal University of Lavras, using a sequential system composed of reactors:UASB (Upflow anaerobic sludge blanket reactor), SABF (submerged aerated biological filter) and HFCW(horizontal subsurface flow constructed wetlands)cultivated with Tifton 85 grass, laboratory scale, swine wastewater treatment (SW) produced in Lavras-MG.Four phases were monitored in 420 days, applying organic loads of 1 (phase I), 2 (phase II), 3 (phase III) and 4 kg m-3 d-1 COD (phase IV).Thirteen emerging contaminants were analyzed (genfibrozil, caffeine, ibuprofen, paracetamol, naproxen, diclofenac, estrone, 17β-estradiol, ethinylestradiol, bisphenol A, 4-octylphenol and 4-nonylphenol), beyond the variables organic matter, solids and nutrients in all reactors.It was evidenced in the UASB reactor that the best stability conditions occurred with the maintenance of the intermediate alkalinity and partial alkalinity (IA/PA) ratio between 0.24 and 0.25, observed in phases I and II, respectively, with an average COD removal of 47. at 57% and pH values between 6 and 8.Despite the increase in the AI/AP ratio (average 0.57), in phases III and IV, the organic matter removal efficiencies increased with the application of organic loads, showing averages of 45 to 67% in phases I and IV, respectively, for COD and BOD in all reactors.The interactions of the results showed strong correlations between the organic variables, indicating that the quality of the input SW in the anaerobic reactor provided considerable influences on the efficiency dynamics throughout the system.The study with multivariate analysis found a reduction of 13 original variables to 5, 8 and 5 main components in the UASB, SABF and HFCW reactors, respectively, with variability between 58 and 64% in the first two components.The complete system provided maximum TKN and PT efficiencies greater than 85 and 65%, respectively, which show the nutritional removal capacity in aerated and plant systems.Dissolved oxygen concentrations provided increments of more than 50 mg L-1 of N-NO3- between phases I and IV, while the ability of SAC to N-NO3- assimilate was an 82.9%, observed with reduction reactor output.The data dimensionality of the nutritional variables was reduced for two main components in the UASB and SABF reactors, and three components with the HFCW variables, maintaining between 60 and 81% of the variability of the original data with the first two components.The performance of Tifton 85 grass in HFCW was verified with increase of productivity and crude protein from 13.2 t ha-1 and 8.4% in cut 1 to 52.0 t ha-1 and 24%, respectively.Moreover, nitrate concentrations increased the height of Tifton 85 grass, showing average growth of 2 cm per day and maximum height of 84 cm with application of 30.9 kg ha-1 d-1 of N - NO3- in the cut 8.Similarly, the last cuts were responsible for the largest nutritional assimilations, with 1996.8, 260.1 and 2220.4 kg ha-1 of TKN, PT and K, respectively, absorbed by Tifton 85 grass with application of 630, 4 kg ha-1 d-1 of COD.Among the emerging contaminants, it was emphasized that bisphenol A presented removal of more than 1.8 μg L-1 in the UASB, SABF and HFCW reactors, but it was also configured as the most persistent compound in the system.There was an overall efficiency of 99.2%, increasing total mass flow of 348.5 μg d-1 of emerging phase IV contaminants.It was found that 21.3% of the ecological risk quotient (RQs) data presented values higher than 1 for the aquatic environment species with the UASB effluent swine wastewater,highlighting E2 with a risk of 24.6, besides confirming that part of the emerging contaminants, even after aerated treatment, presented moderate ecological risks for bisphenol A (RQ = 0.3) and NAP (RQ = 0.2 ) on zebrafish (Danio rerio) and cnidarian (Hydra attenuata) species.It was concluded that the system was efficient in removing emerging compounds, nutrients and organic matter, but further efforts should be made in future research to evaluate the actions of bacteria that potentiate the biodegradation of emerging and organic compoundsmonitoring their conjugates linked to external factors that promote the reformulation in their active compounds, contributing,therefore, for decision making in water treatment plants and reduction of possible environmental risks to aquatic ecosystems.